5 files changed, 793 insertions, 299 deletions

diff --git a/bitbake/lib/prserv/__init__.py b/bitbake/lib/prserv/__init__.py
index 0e0aa34d0e..ffc5a40a28 100644
--- a/bitbake/lib/prserv/__init__.py
+++ b/bitbake/lib/prserv/__init__.py
@@ -4,17 +4,92 @@
 # SPDX-License-Identifier: GPL-2.0-only
 #
 
-__version__ = "1.0.0"
 
-import os, time
-import sys, logging
+__version__ = "2.0.0"
 
-def init_logger(logfile, loglevel):
-    numeric_level = getattr(logging, loglevel.upper(), None)
-    if not isinstance(numeric_level, int):
-        raise ValueError("Invalid log level: %s" % loglevel)
-    FORMAT = "%(asctime)-15s %(message)s"
-    logging.basicConfig(level=numeric_level, filename=logfile, format=FORMAT)
+import logging
+logger = logging.getLogger("BitBake.PRserv")
 
-class NotFoundError(Exception):
-    pass
+from bb.asyncrpc.client import parse_address, ADDR_TYPE_UNIX, ADDR_TYPE_WS
+
+def create_server(addr, dbpath, upstream=None, read_only=False):
+    from . import serv
+
+    s = serv.PRServer(dbpath, upstream=upstream, read_only=read_only)
+    host, port = addr.split(":")
+    s.start_tcp_server(host, int(port))
+
+    return s
+
+def increase_revision(ver):
+    """Take a revision string such as "1" or "1.2.3" or even a number and increase its last number
+    This fails if the last number is not an integer"""
+
+    fields=str(ver).split('.')
+    last = fields[-1]
+
+    try:
+         val = int(last)
+    except Exception as e:
+         logger.critical("Unable to increase revision value %s: %s" % (ver, e))
+         raise e
+
+    return ".".join(fields[0:-1] + [ str(val + 1) ])
+
+def _revision_greater_or_equal(rev1, rev2):
+    """Compares x.y.z revision numbers, using integer comparison
+    Returns True if rev1 is greater or equal to rev2"""
+
+    fields1 = rev1.split(".")
+    fields2 = rev2.split(".")
+    l1 = len(fields1)
+    l2 = len(fields2)
+
+    for i in range(l1):
+       val1 = int(fields1[i])
+       if i < l2:
+           val2 = int(fields2[i])
+           if val2 < val1:
+              return True
+           elif val2 > val1:
+              return False
+       else:
+          return True
+    return True
+
+def revision_smaller(rev1, rev2):
+    """Compares x.y.z revision numbers, using integer comparison
+    Returns True if rev1 is strictly smaller than rev2"""
+    return not(_revision_greater_or_equal(rev1, rev2))
+
+def revision_greater(rev1, rev2):
+    """Compares x.y.z revision numbers, using integer comparison
+    Returns True if rev1 is strictly greater than rev2"""
+    return _revision_greater_or_equal(rev1, rev2) and (rev1 != rev2)
+
+def create_client(addr):
+    from . import client
+
+    c = client.PRClient()
+
+    try:
+        (typ, a) = parse_address(addr)
+        c.connect_tcp(*a)
+        return c
+    except Exception as e:
+        c.close()
+        raise e
+
+async def create_async_client(addr):
+    from . import client
+
+    c = client.PRAsyncClient()
+
+    try:
+        (typ, a) = parse_address(addr)
+        await c.connect_tcp(*a)
+        return c
+
+    except Exception as e:
+        await c.close()
+        raise e
diff --git a/bitbake/lib/prserv/client.py b/bitbake/lib/prserv/client.py
index 8471ee3046..9f5794c433 100644
--- a/bitbake/lib/prserv/client.py
+++ b/bitbake/lib/prserv/client.py
@@ -6,6 +6,7 @@
 
 import logging
 import bb.asyncrpc
+from . import create_async_client
 
 logger = logging.getLogger("BitBake.PRserv")
 
@@ -13,16 +14,16 @@ class PRAsyncClient(bb.asyncrpc.AsyncClient):
     def __init__(self):
         super().__init__("PRSERVICE", "1.0", logger)
 
-    async def getPR(self, version, pkgarch, checksum):
+    async def getPR(self, version, pkgarch, checksum, history=False):
         response = await self.invoke(
-            {"get-pr": {"version": version, "pkgarch": pkgarch, "checksum": checksum}}
+            {"get-pr": {"version": version, "pkgarch": pkgarch, "checksum": checksum, "history": history}}
         )
         if response:
             return response["value"]
 
-    async def test_pr(self, version, pkgarch, checksum):
+    async def test_pr(self, version, pkgarch, checksum, history=False):
         response = await self.invoke(
-            {"test-pr": {"version": version, "pkgarch": pkgarch, "checksum": checksum}}
+            {"test-pr": {"version": version, "pkgarch": pkgarch, "checksum": checksum, "history": history}}
         )
         if response:
             return response["value"]
@@ -48,9 +49,9 @@ class PRAsyncClient(bb.asyncrpc.AsyncClient):
         if response:
             return response["value"]
 
-    async def export(self, version, pkgarch, checksum, colinfo):
+    async def export(self, version, pkgarch, checksum, colinfo, history=False):
         response = await self.invoke(
-            {"export": {"version": version, "pkgarch": pkgarch, "checksum": checksum, "colinfo": colinfo}}
+            {"export": {"version": version, "pkgarch": pkgarch, "checksum": checksum, "colinfo": colinfo, "history": history}}
         )
         if response:
             return (response["metainfo"], response["datainfo"])
@@ -65,7 +66,7 @@ class PRAsyncClient(bb.asyncrpc.AsyncClient):
 class PRClient(bb.asyncrpc.Client):
     def __init__(self):
         super().__init__()
-        self._add_methods("getPR", "test_pr", "test_package", "importone", "export", "is_readonly")
+        self._add_methods("getPR", "test_pr", "test_package", "max_package_pr", "importone", "export", "is_readonly")
 
     def _get_async_client(self):
         return PRAsyncClient()
diff --git a/bitbake/lib/prserv/db.py b/bitbake/lib/prserv/db.py
index eb41508198..2da493ddf5 100644
--- a/bitbake/lib/prserv/db.py
+++ b/bitbake/lib/prserv/db.py
@@ -8,19 +8,13 @@ import logging
 import os.path
 import errno
 import prserv
-import time
+import sqlite3
 
-try:
-    import sqlite3
-except ImportError:
-    from pysqlite2 import dbapi2 as sqlite3
+from contextlib import closing
+from . import increase_revision, revision_greater, revision_smaller
 
 logger = logging.getLogger("BitBake.PRserv")
 
-sqlversion = sqlite3.sqlite_version_info
-if sqlversion[0] < 3 or (sqlversion[0] == 3 and sqlversion[1] < 3):
-    raise Exception("sqlite3 version 3.3.0 or later is required.")
-
 #
 # "No History" mode - for a given query tuple (version, pkgarch, checksum),
 # the returned value will be the largest among all the values of the same
@@ -29,287 +23,232 @@ if sqlversion[0] < 3 or (sqlversion[0] == 3 and sqlversion[1] < 3):
 # "History" mode - Return a new higher value for previously unseen query
 # tuple (version, pkgarch, checksum), otherwise return historical value.
 # Value can decrement if returning to a previous build.
-#
 
 class PRTable(object):
-    def __init__(self, conn, table, nohist, read_only):
+    def __init__(self, conn, table, read_only):
         self.conn = conn
-        self.nohist = nohist
         self.read_only = read_only
-        self.dirty = False
-        if nohist:
-            self.table = "%s_nohist" % table
-        else:
-            self.table = "%s_hist" % table
-
-        if self.read_only:
-            table_exists = self._execute(
-                        "SELECT count(*) FROM sqlite_master \
-                        WHERE type='table' AND name='%s'" % (self.table))
-            if not table_exists:
-                raise prserv.NotFoundError
-        else:
-            self._execute("CREATE TABLE IF NOT EXISTS %s \
+        self.table = table
+
+        # Creating the table even if the server is read-only.
+        # This avoids a race condition if a shared database
+        # is accessed by a read-only server first.
+
+        with closing(self.conn.cursor()) as cursor:
+            cursor.execute("CREATE TABLE IF NOT EXISTS %s \
                         (version TEXT NOT NULL, \
                         pkgarch TEXT NOT NULL,  \
                         checksum TEXT NOT NULL, \
-                        value INTEGER, \
-                        PRIMARY KEY (version, pkgarch, checksum));" % self.table)
-
-    def _execute(self, *query):
-        """Execute a query, waiting to acquire a lock if necessary"""
-        start = time.time()
-        end = start + 20
-        while True:
-            try:
-                return self.conn.execute(*query)
-            except sqlite3.OperationalError as exc:
-                if "is locked" in str(exc) and end > time.time():
-                    continue
-                raise exc
-
-    def sync(self):
-        if not self.read_only:
+                        value TEXT, \
+                        PRIMARY KEY (version, pkgarch, checksum, value));" % self.table)
             self.conn.commit()
-            self._execute("BEGIN EXCLUSIVE TRANSACTION")
 
-    def sync_if_dirty(self):
-        if self.dirty:
-            self.sync()
-            self.dirty = False
+    def _extremum_value(self, rows, is_max):
+        value = None
+
+        for row in rows:
+            current_value = row[0]
+            if value is None:
+                value = current_value
+            else:
+                if is_max:
+                    is_new_extremum = revision_greater(current_value, value)
+                else:
+                    is_new_extremum = revision_smaller(current_value, value)
+                if  is_new_extremum:
+                    value = current_value
+        return value
+
+    def _max_value(self, rows):
+        return self._extremum_value(rows, True)
+
+    def _min_value(self, rows):
+        return self._extremum_value(rows, False)
 
     def test_package(self, version, pkgarch):
         """Returns whether the specified package version is found in the database for the specified architecture"""
 
         # Just returns the value if found or None otherwise
-        data=self._execute("SELECT value FROM %s WHERE version=? AND pkgarch=?;" % self.table,
-                           (version, pkgarch))
-        row=data.fetchone()
-        if row is not None:
-            return True
-        else:
-            return False
+        with closing(self.conn.cursor()) as cursor:
+            data=cursor.execute("SELECT value FROM %s WHERE version=? AND pkgarch=?;" % self.table,
+                               (version, pkgarch))
+            row=data.fetchone()
+            if row is not None:
+                return True
+            else:
+                return False
+
+    def test_checksum_value(self, version, pkgarch, checksum, value):
+        """Returns whether the specified value is found in the database for the specified package, architecture and checksum"""
+
+        with closing(self.conn.cursor()) as cursor:
+            data=cursor.execute("SELECT value FROM %s WHERE version=? AND pkgarch=? and checksum=? and value=?;" % self.table,
+                               (version, pkgarch, checksum, value))
+            row=data.fetchone()
+            if row is not None:
+                return True
+            else:
+                return False
 
     def test_value(self, version, pkgarch, value):
         """Returns whether the specified value is found in the database for the specified package and architecture"""
 
         # Just returns the value if found or None otherwise
-        data=self._execute("SELECT value FROM %s WHERE version=? AND pkgarch=? and value=?;" % self.table,
-                           (version, pkgarch, value))
-        row=data.fetchone()
-        if row is not None:
-            return True
-        else:
-            return False
+        with closing(self.conn.cursor()) as cursor:
+            data=cursor.execute("SELECT value FROM %s WHERE version=? AND pkgarch=? and value=?;" % self.table,
+                               (version, pkgarch, value))
+            row=data.fetchone()
+            if row is not None:
+                return True
+            else:
+                return False
 
-    def find_value(self, version, pkgarch, checksum):
+
+    def find_package_max_value(self, version, pkgarch):
+        """Returns the greatest value for (version, pkgarch), or None if not found. Doesn't create a new value"""
+
+        with closing(self.conn.cursor()) as cursor:
+            data = cursor.execute("SELECT value FROM %s where version=? AND pkgarch=?;" % (self.table),
+                                 (version, pkgarch))
+            rows = data.fetchall()
+            value = self._max_value(rows)
+            return value
+
+    def find_value(self, version, pkgarch, checksum, history=False):
         """Returns the value for the specified checksum if found or None otherwise."""
 
-        data=self._execute("SELECT value FROM %s WHERE version=? AND pkgarch=? AND checksum=?;" % self.table,
-                           (version, pkgarch, checksum))
-        row=data.fetchone()
-        if row is not None:
-            return row[0]
+        if history:
+            return self.find_min_value(version, pkgarch, checksum)
         else:
-            return None
+            return self.find_max_value(version, pkgarch, checksum)
 
-    def find_max_value(self, version, pkgarch):
-        """Returns the greatest value for (version, pkgarch), or None if not found. Doesn't create a new value"""
 
-        data = self._execute("SELECT max(value) FROM %s where version=? AND pkgarch=?;" % (self.table),
-                             (version, pkgarch))
-        row = data.fetchone()
-        if row is not None:
-            return row[0]
-        else:
-            return None
-
-    def _get_value_hist(self, version, pkgarch, checksum):
-        data=self._execute("SELECT value FROM %s WHERE version=? AND pkgarch=? AND checksum=?;" % self.table,
-                           (version, pkgarch, checksum))
-        row=data.fetchone()
-        if row is not None:
-            return row[0]
-        else:
-            #no value found, try to insert
-            if self.read_only:
-                data = self._execute("SELECT ifnull(max(value)+1, 0) FROM %s where version=? AND pkgarch=?;" % (self.table),
-                                   (version, pkgarch))
-                row = data.fetchone()
-                if row is not None:
-                    return row[0]
-                else:
-                    return 0
+    def _find_extremum_value(self, version, pkgarch, checksum, is_max):
+        """Returns the maximum (if is_max is True) or minimum (if is_max is False) value
+           for (version, pkgarch, checksum), or None if not found. Doesn't create a new value"""
 
-            try:
-                self._execute("INSERT INTO %s VALUES (?, ?, ?, (select ifnull(max(value)+1, 0) from %s where version=? AND pkgarch=?));"
-                           % (self.table, self.table),
-                           (version, pkgarch, checksum, version, pkgarch))
-            except sqlite3.IntegrityError as exc:
-                logger.error(str(exc))
+        with closing(self.conn.cursor()) as cursor:
+            data = cursor.execute("SELECT value FROM %s where version=? AND pkgarch=? AND checksum=?;" % (self.table),
+                                 (version, pkgarch, checksum))
+            rows = data.fetchall()
+            return self._extremum_value(rows, is_max)
 
-            self.dirty = True
+    def find_max_value(self, version, pkgarch, checksum):
+        return self._find_extremum_value(version, pkgarch, checksum, True)
 
-            data=self._execute("SELECT value FROM %s WHERE version=? AND pkgarch=? AND checksum=?;" % self.table,
-                               (version, pkgarch, checksum))
-            row=data.fetchone()
-            if row is not None:
-                return row[0]
-            else:
-                raise prserv.NotFoundError
-
-    def _get_value_no_hist(self, version, pkgarch, checksum):
-        data=self._execute("SELECT value FROM %s \
-                            WHERE version=? AND pkgarch=? AND checksum=? AND \
-                            value >= (select max(value) from %s where version=? AND pkgarch=?);"
-                            % (self.table, self.table),
-                            (version, pkgarch, checksum, version, pkgarch))
-        row=data.fetchone()
-        if row is not None:
-            return row[0]
-        else:
-            #no value found, try to insert
-            if self.read_only:
-                data = self._execute("SELECT ifnull(max(value)+1, 0) FROM %s where version=? AND pkgarch=?;" % (self.table),
-                                   (version, pkgarch))
-                return data.fetchone()[0]
-
-            try:
-                self._execute("INSERT OR REPLACE INTO %s VALUES (?, ?, ?, (select ifnull(max(value)+1, 0) from %s where version=? AND pkgarch=?));"
-                               % (self.table, self.table),
-                               (version, pkgarch, checksum, version, pkgarch))
-            except sqlite3.IntegrityError as exc:
-                logger.error(str(exc))
-                self.conn.rollback()
-
-            self.dirty = True
-
-            data=self._execute("SELECT value FROM %s WHERE version=? AND pkgarch=? AND checksum=?;" % self.table,
-                               (version, pkgarch, checksum))
-            row=data.fetchone()
-            if row is not None:
-                return row[0]
+    def find_min_value(self, version, pkgarch, checksum):
+        return self._find_extremum_value(version, pkgarch, checksum, False)
+
+    def find_new_subvalue(self, version, pkgarch, base):
+        """Take and increase the greatest "<base>.y" value for (version, pkgarch), or return "<base>.0" if not found.
+        This doesn't store a new value."""
+
+        with closing(self.conn.cursor()) as cursor:
+            data = cursor.execute("SELECT value FROM %s where version=? AND pkgarch=? AND value LIKE '%s.%%';" % (self.table, base),
+                                 (version, pkgarch))
+            rows = data.fetchall()
+            value = self._max_value(rows)
+
+            if value is not None:
+                return increase_revision(value)
             else:
-                raise prserv.NotFoundError
+                return base + ".0"
 
-    def get_value(self, version, pkgarch, checksum):
-        if self.nohist:
-            return self._get_value_no_hist(version, pkgarch, checksum)
-        else:
-            return self._get_value_hist(version, pkgarch, checksum)
-
-    def _import_hist(self, version, pkgarch, checksum, value):
-        if self.read_only:
-            return None
-
-        val = None
-        data = self._execute("SELECT value FROM %s WHERE version=? AND pkgarch=? AND checksum=?;" % self.table,
-                           (version, pkgarch, checksum))
-        row = data.fetchone()
-        if row is not None:
-            val=row[0]
-        else:
-            #no value found, try to insert
-            try:
-                self._execute("INSERT INTO %s VALUES (?, ?, ?, ?);"  % (self.table),
+    def store_value(self, version, pkgarch, checksum, value):
+        """Store value in the database"""
+
+        if not self.read_only and not self.test_checksum_value(version, pkgarch, checksum, value):
+            with closing(self.conn.cursor()) as cursor:
+                cursor.execute("INSERT INTO %s VALUES (?, ?, ?, ?);"  % (self.table),
                            (version, pkgarch, checksum, value))
-            except sqlite3.IntegrityError as exc:
-                logger.error(str(exc))
+                self.conn.commit()
 
-            self.dirty = True
+    def _get_value(self, version, pkgarch, checksum, history):
 
-            data = self._execute("SELECT value FROM %s WHERE version=? AND pkgarch=? AND checksum=?;" % self.table,
-                           (version, pkgarch, checksum))
-            row = data.fetchone()
-            if row is not None:
-                val = row[0]
-        return val
+        max_value = self.find_package_max_value(version, pkgarch)
 
-    def _import_no_hist(self, version, pkgarch, checksum, value):
-        if self.read_only:
-            return None
+        if max_value is None:
+            # version, pkgarch completely unknown. Return initial value.
+            return "0"
 
-        try:
-            #try to insert
-            self._execute("INSERT INTO %s VALUES (?, ?, ?, ?);"  % (self.table),
-                           (version, pkgarch, checksum, value))
-        except sqlite3.IntegrityError as exc:
-            #already have the record, try to update
-            try:
-                self._execute("UPDATE %s SET value=? WHERE version=? AND pkgarch=? AND checksum=? AND value<?"
-                              % (self.table),
-                               (value, version, pkgarch, checksum, value))
-            except sqlite3.IntegrityError as exc:
-                logger.error(str(exc))
-
-        self.dirty = True
-
-        data = self._execute("SELECT value FROM %s WHERE version=? AND pkgarch=? AND checksum=? AND value>=?;" % self.table,
-                            (version, pkgarch, checksum, value))
-        row=data.fetchone()
-        if row is not None:
-            return row[0]
+        value = self.find_value(version, pkgarch, checksum, history)
+
+        if value is None:
+            # version, pkgarch found but not checksum. Create a new value from the maximum one
+            return increase_revision(max_value)
+
+        if history:
+            return value
+
+        # "no history" mode - If the value is not the maximum value for the package, need to increase it.
+        if max_value > value:
+            return increase_revision(max_value)
         else:
-            return None
+            return value
+
+    def get_value(self, version, pkgarch, checksum, history):
+        value = self._get_value(version, pkgarch, checksum, history)
+        if not self.read_only:
+            self.store_value(version, pkgarch, checksum, value)
+        return value
 
     def importone(self, version, pkgarch, checksum, value):
-        if self.nohist:
-            return self._import_no_hist(version, pkgarch, checksum, value)
-        else:
-            return self._import_hist(version, pkgarch, checksum, value)
+        self.store_value(version, pkgarch, checksum, value)
+        return value
 
-    def export(self, version, pkgarch, checksum, colinfo):
+    def export(self, version, pkgarch, checksum, colinfo, history=False):
         metainfo = {}
-        #column info
-        if colinfo:
-            metainfo["tbl_name"] = self.table
-            metainfo["core_ver"] = prserv.__version__
-            metainfo["col_info"] = []
-            data = self._execute("PRAGMA table_info(%s);" % self.table)
+        with closing(self.conn.cursor()) as cursor:
+            #column info
+            if colinfo:
+                metainfo["tbl_name"] = self.table
+                metainfo["core_ver"] = prserv.__version__
+                metainfo["col_info"] = []
+                data = cursor.execute("PRAGMA table_info(%s);" % self.table)
+                for row in data:
+                    col = {}
+                    col["name"] = row["name"]
+                    col["type"] = row["type"]
+                    col["notnull"] = row["notnull"]
+                    col["dflt_value"] = row["dflt_value"]
+                    col["pk"] = row["pk"]
+                    metainfo["col_info"].append(col)
+
+            #data info
+            datainfo = []
+
+            if history:
+                sqlstmt = "SELECT * FROM %s as T1 WHERE 1=1 " % self.table
+            else:
+                sqlstmt = "SELECT T1.version, T1.pkgarch, T1.checksum, T1.value FROM %s as T1, \
+                        (SELECT version, pkgarch, max(value) as maxvalue FROM %s GROUP BY version, pkgarch) as T2 \
+                        WHERE T1.version=T2.version AND T1.pkgarch=T2.pkgarch AND T1.value=T2.maxvalue " % (self.table, self.table)
+            sqlarg = []
+            where = ""
+            if version:
+                where += "AND T1.version=? "
+                sqlarg.append(str(version))
+            if pkgarch:
+                where += "AND T1.pkgarch=? "
+                sqlarg.append(str(pkgarch))
+            if checksum:
+                where += "AND T1.checksum=? "
+                sqlarg.append(str(checksum))
+
+            sqlstmt += where + ";"
+
+            if len(sqlarg):
+                data = cursor.execute(sqlstmt, tuple(sqlarg))
+            else:
+                data = cursor.execute(sqlstmt)
             for row in data:
-                col = {}
-                col["name"] = row["name"]
-                col["type"] = row["type"]
-                col["notnull"] = row["notnull"]
-                col["dflt_value"] = row["dflt_value"]
-                col["pk"] = row["pk"]
-                metainfo["col_info"].append(col)
-
-        #data info
-        datainfo = []
-
-        if self.nohist:
-            sqlstmt = "SELECT T1.version, T1.pkgarch, T1.checksum, T1.value FROM %s as T1, \
-                    (SELECT version, pkgarch, max(value) as maxvalue FROM %s GROUP BY version, pkgarch) as T2 \
-                    WHERE T1.version=T2.version AND T1.pkgarch=T2.pkgarch AND T1.value=T2.maxvalue " % (self.table, self.table)
-        else:
-            sqlstmt = "SELECT * FROM %s as T1 WHERE 1=1 " % self.table
-        sqlarg = []
-        where = ""
-        if version:
-            where += "AND T1.version=? "
-            sqlarg.append(str(version))
-        if pkgarch:
-            where += "AND T1.pkgarch=? "
-            sqlarg.append(str(pkgarch))
-        if checksum:
-            where += "AND T1.checksum=? "
-            sqlarg.append(str(checksum))
-
-        sqlstmt += where + ";"
-
-        if len(sqlarg):
-            data = self._execute(sqlstmt, tuple(sqlarg))
-        else:
-            data = self._execute(sqlstmt)
-        for row in data:
-            if row["version"]:
-                col = {}
-                col["version"] = row["version"]
-                col["pkgarch"] = row["pkgarch"]
-                col["checksum"] = row["checksum"]
-                col["value"] = row["value"]
-                datainfo.append(col)
+                if row["version"]:
+                    col = {}
+                    col["version"] = row["version"]
+                    col["pkgarch"] = row["pkgarch"]
+                    col["checksum"] = row["checksum"]
+                    col["value"] = row["value"]
+                    datainfo.append(col)
         return (metainfo, datainfo)
 
     def dump_db(self, fd):
@@ -322,9 +261,8 @@ class PRTable(object):
 
 class PRData(object):
     """Object representing the PR database"""
-    def __init__(self, filename, nohist=True, read_only=False):
+    def __init__(self, filename, read_only=False):
         self.filename=os.path.abspath(filename)
-        self.nohist=nohist
         self.read_only = read_only
         #build directory hierarchy
         try:
@@ -334,14 +272,15 @@ class PRData(object):
                 raise e
         uri = "file:%s%s" % (self.filename, "?mode=ro" if self.read_only else "")
         logger.debug("Opening PRServ database '%s'" % (uri))
-        self.connection=sqlite3.connect(uri, uri=True, isolation_level="EXCLUSIVE", check_same_thread = False)
+        self.connection=sqlite3.connect(uri, uri=True)
         self.connection.row_factory=sqlite3.Row
-        if not self.read_only:
-            self.connection.execute("pragma synchronous = off;")
-            self.connection.execute("PRAGMA journal_mode = MEMORY;")
+        self.connection.execute("PRAGMA synchronous = OFF;")
+        self.connection.execute("PRAGMA journal_mode = WAL;")
+        self.connection.commit()
         self._tables={}
 
     def disconnect(self):
+        self.connection.commit()
         self.connection.close()
 
     def __getitem__(self, tblname):
@@ -351,7 +290,7 @@ class PRData(object):
         if tblname in self._tables:
             return self._tables[tblname]
         else:
-            tableobj = self._tables[tblname] = PRTable(self.connection, tblname, self.nohist, self.read_only)
+            tableobj = self._tables[tblname] = PRTable(self.connection, tblname, self.read_only)
             return tableobj
 
     def __delitem__(self, tblname):
@@ -359,3 +298,4 @@ class PRData(object):
             del self._tables[tblname]
         logger.info("drop table %s" % (tblname))
         self.connection.execute("DROP TABLE IF EXISTS %s;" % tblname)
+        self.connection.commit()
diff --git a/bitbake/lib/prserv/serv.py b/bitbake/lib/prserv/serv.py
index dc4be5b620..e175886308 100644
--- a/bitbake/lib/prserv/serv.py
+++ b/bitbake/lib/prserv/serv.py
@@ -12,6 +12,7 @@ import sqlite3
 import prserv
 import prserv.db
 import errno
+from . import create_async_client, revision_smaller, increase_revision
 import bb.asyncrpc
 
 logger = logging.getLogger("BitBake.PRserv")
@@ -41,18 +42,16 @@ class PRServerClient(bb.asyncrpc.AsyncServerConnection):
         try:
             return await super().dispatch_message(msg)
         except:
-            self.server.table.sync()
             raise
-        else:
-            self.server.table.sync_if_dirty()
 
     async def handle_test_pr(self, request):
         '''Finds the PR value corresponding to the request. If not found, returns None and doesn't insert a new value'''
         version = request["version"]
         pkgarch = request["pkgarch"]
         checksum = request["checksum"]
+        history = request["history"]
 
-        value = self.server.table.find_value(version, pkgarch, checksum)
+        value = self.server.table.find_value(version, pkgarch, checksum, history)
         return {"value": value}
 
     async def handle_test_package(self, request):
@@ -68,22 +67,110 @@ class PRServerClient(bb.asyncrpc.AsyncServerConnection):
         version = request["version"]
         pkgarch = request["pkgarch"]
 
-        value = self.server.table.find_max_value(version, pkgarch)
+        value = self.server.table.find_package_max_value(version, pkgarch)
         return {"value": value}
 
     async def handle_get_pr(self, request):
         version = request["version"]
         pkgarch = request["pkgarch"]
         checksum = request["checksum"]
+        history = request["history"]
 
-        response = None
-        try:
-            value = self.server.table.get_value(version, pkgarch, checksum)
-            response = {"value": value}
-        except prserv.NotFoundError:
-            self.logger.error("failure storing value in database for (%s, %s)",version, checksum)
+        if self.upstream_client is None:
+            value = self.server.table.get_value(version, pkgarch, checksum, history)
+            return {"value": value}
 
-        return response
+        # We have an upstream server.
+        # Check whether the local server already knows the requested configuration.
+        # If the configuration is a new one, the generated value we will add will
+        # depend on what's on the upstream server. That's why we're calling find_value()
+        # instead of get_value() directly.
+
+        value = self.server.table.find_value(version, pkgarch, checksum, history)
+        upstream_max = await self.upstream_client.max_package_pr(version, pkgarch)
+
+        if value is not None:
+
+            # The configuration is already known locally.
+
+            if history:
+                value = self.server.table.get_value(version, pkgarch, checksum, history)
+            else:
+                existing_value = value
+                # In "no history", we need to make sure the value doesn't decrease
+                # and is at least greater than the maximum upstream value
+                # and the maximum local value
+
+                local_max = self.server.table.find_package_max_value(version, pkgarch)
+                if revision_smaller(value, local_max):
+                    value = increase_revision(local_max)
+
+                if revision_smaller(value, upstream_max):
+                    # Ask upstream whether it knows the checksum
+                    upstream_value = await self.upstream_client.test_pr(version, pkgarch, checksum)
+                    if upstream_value is None:
+                        # Upstream doesn't have our checksum, let create a new one
+                        value = upstream_max + ".0"
+                    else:
+                        # Fine to take the same value as upstream
+                        value = upstream_max
+
+                if not value == existing_value and not self.server.read_only:
+                    self.server.table.store_value(version, pkgarch, checksum, value)
+
+            return {"value": value}
+
+        # The configuration is a new one for the local server
+        # Let's ask the upstream server whether it knows it
+
+        known_upstream = await self.upstream_client.test_package(version, pkgarch)
+
+        if not known_upstream:
+
+            # The package is not known upstream, must be a local-only package
+            # Let's compute the PR number using the local-only method
+
+            value = self.server.table.get_value(version, pkgarch, checksum, history)
+            return {"value": value}
+
+        # The package is known upstream, let's ask the upstream server
+        # whether it knows our new output hash
+
+        value = await self.upstream_client.test_pr(version, pkgarch, checksum)
+
+        if value is not None:
+
+            # Upstream knows this output hash, let's store it and use it too.
+
+            if not self.server.read_only:
+                self.server.table.store_value(version, pkgarch, checksum, value)
+            # If the local server is read only, won't be able to store the new
+            # value in the database and will have to keep asking the upstream server
+            return {"value": value}
+
+        # The output hash doesn't exist upstream, get the most recent number from upstream (x)
+        # Then, we want to have a new PR value for the local server: x.y
+
+        upstream_max = await self.upstream_client.max_package_pr(version, pkgarch)
+        # Here we know that the package is known upstream, so upstream_max can't be None
+        subvalue = self.server.table.find_new_subvalue(version, pkgarch, upstream_max)
+
+        if not self.server.read_only:
+            self.server.table.store_value(version, pkgarch, checksum, subvalue)
+
+        return {"value": subvalue}
+
+    async def process_requests(self):
+        if self.server.upstream is not None:
+            self.upstream_client = await create_async_client(self.server.upstream)
+        else:
+            self.upstream_client = None
+
+        try:
+            await super().process_requests()
+        finally:
+            if self.upstream_client is not None:
+                await self.upstream_client.close()
 
     async def handle_import_one(self, request):
         response = None
@@ -104,9 +191,10 @@ class PRServerClient(bb.asyncrpc.AsyncServerConnection):
         pkgarch = request["pkgarch"]
         checksum = request["checksum"]
         colinfo = request["colinfo"]
+        history = request["history"]
 
         try:
-            (metainfo, datainfo) = self.server.table.export(version, pkgarch, checksum, colinfo)
+            (metainfo, datainfo) = self.server.table.export(version, pkgarch, checksum, colinfo, history)
         except sqlite3.Error as exc:
             self.logger.error(str(exc))
             metainfo = datainfo = None
@@ -117,11 +205,12 @@ class PRServerClient(bb.asyncrpc.AsyncServerConnection):
         return {"readonly": self.server.read_only}
 
 class PRServer(bb.asyncrpc.AsyncServer):
-    def __init__(self, dbfile, read_only=False):
+    def __init__(self, dbfile, read_only=False, upstream=None):
         super().__init__(logger)
         self.dbfile = dbfile
         self.table = None
         self.read_only = read_only
+        self.upstream = upstream
 
     def accept_client(self, socket):
         return PRServerClient(socket, self)
@@ -134,27 +223,25 @@ class PRServer(bb.asyncrpc.AsyncServer):
         self.logger.info("Started PRServer with DBfile: %s, Address: %s, PID: %s" %
                      (self.dbfile, self.address, str(os.getpid())))
 
+        if self.upstream is not None:
+            self.logger.info("And upstream PRServer: %s " % (self.upstream))
+
         return tasks
 
     async def stop(self):
-        self.table.sync_if_dirty()
         self.db.disconnect()
         await super().stop()
 
-    def signal_handler(self):
-        super().signal_handler()
-        if self.table:
-            self.table.sync()
-
 class PRServSingleton(object):
-    def __init__(self, dbfile, logfile, host, port):
+    def __init__(self, dbfile, logfile, host, port, upstream):
         self.dbfile = dbfile
         self.logfile = logfile
         self.host = host
         self.port = port
+        self.upstream = upstream
 
     def start(self):
-        self.prserv = PRServer(self.dbfile)
+        self.prserv = PRServer(self.dbfile, upstream=self.upstream)
         self.prserv.start_tcp_server(socket.gethostbyname(self.host), self.port)
         self.process = self.prserv.serve_as_process(log_level=logging.WARNING)
 
@@ -233,7 +320,7 @@ def run_as_daemon(func, pidfile, logfile):
     os.remove(pidfile)
     os._exit(0)
 
-def start_daemon(dbfile, host, port, logfile, read_only=False):
+def start_daemon(dbfile, host, port, logfile, read_only=False, upstream=None):
     ip = socket.gethostbyname(host)
     pidfile = PIDPREFIX % (ip, port)
     try:
@@ -249,7 +336,7 @@ def start_daemon(dbfile, host, port, logfile, read_only=False):
 
     dbfile = os.path.abspath(dbfile)
     def daemon_main():
-        server = PRServer(dbfile, read_only=read_only)
+        server = PRServer(dbfile, read_only=read_only, upstream=upstream)
         server.start_tcp_server(ip, port)
         server.serve_forever()
 
@@ -336,6 +423,9 @@ def auto_start(d):
 
     host = host_params[0].strip().lower()
     port = int(host_params[1])
+
+    upstream = d.getVar("PRSERV_UPSTREAM") or None
+
     if is_local_special(host, port):
         import bb.utils
         cachedir = (d.getVar("PERSISTENT_DIR") or d.getVar("CACHE"))
@@ -350,7 +440,7 @@ def auto_start(d):
                auto_shutdown()
         if not singleton:
             bb.utils.mkdirhier(cachedir)
-            singleton = PRServSingleton(os.path.abspath(dbfile), os.path.abspath(logfile), host, port)
+            singleton = PRServSingleton(os.path.abspath(dbfile), os.path.abspath(logfile), host, port, upstream)
             singleton.start()
     if singleton:
         host = singleton.host
diff --git a/bitbake/lib/prserv/tests.py b/bitbake/lib/prserv/tests.py
new file mode 100644
index 0000000000..df0c003003
--- /dev/null
+++ b/bitbake/lib/prserv/tests.py
@@ -0,0 +1,388 @@
+#! /usr/bin/env python3
+#
+# Copyright (C) 2024 BitBake Contributors
+#
+# SPDX-License-Identifier: GPL-2.0-only
+#
+
+from . import create_server, create_client, increase_revision, revision_greater, revision_smaller, _revision_greater_or_equal
+import prserv.db as db
+from bb.asyncrpc import InvokeError
+import logging
+import os
+import sys
+import tempfile
+import unittest
+import socket
+import subprocess
+from pathlib import Path
+
+THIS_DIR = Path(__file__).parent
+BIN_DIR = THIS_DIR.parent.parent / "bin"
+
+version = "dummy-1.0-r0"
+pkgarch = "core2-64"
+other_arch = "aarch64"
+
+checksumX = "51bf8189dbe9ea81fa6dd89608bf19380c437a9cf12f6c6239887801ba4ab4f0"
+checksum0 = "51bf8189dbe9ea81fa6dd89608bf19380c437a9cf12f6c6239887801ba4ab4a0"
+checksum1 = "51bf8189dbe9ea81fa6dd89608bf19380c437a9cf12f6c6239887801ba4ab4a1"
+checksum2 = "51bf8189dbe9ea81fa6dd89608bf19380c437a9cf12f6c6239887801ba4ab4a2"
+checksum3 = "51bf8189dbe9ea81fa6dd89608bf19380c437a9cf12f6c6239887801ba4ab4a3"
+checksum4 = "51bf8189dbe9ea81fa6dd89608bf19380c437a9cf12f6c6239887801ba4ab4a4"
+checksum5 = "51bf8189dbe9ea81fa6dd89608bf19380c437a9cf12f6c6239887801ba4ab4a5"
+checksum6 = "51bf8189dbe9ea81fa6dd89608bf19380c437a9cf12f6c6239887801ba4ab4a6"
+checksum7 = "51bf8189dbe9ea81fa6dd89608bf19380c437a9cf12f6c6239887801ba4ab4a7"
+checksum8 = "51bf8189dbe9ea81fa6dd89608bf19380c437a9cf12f6c6239887801ba4ab4a8"
+checksum9 = "51bf8189dbe9ea81fa6dd89608bf19380c437a9cf12f6c6239887801ba4ab4a9"
+checksum10 = "51bf8189dbe9ea81fa6dd89608bf19380c437a9cf12f6c6239887801ba4ab4aa"
+
+def server_prefunc(server, name):
+    logging.basicConfig(level=logging.DEBUG, filename='prserv-%s.log' % name, filemode='w',
+                        format='%(levelname)s %(filename)s:%(lineno)d %(message)s')
+    server.logger.debug("Running server %s" % name)
+    sys.stdout = open('prserv-stdout-%s.log' % name, 'w')
+    sys.stderr = sys.stdout
+
+class PRTestSetup(object):
+
+    def start_server(self, name, dbfile, upstream=None, read_only=False, prefunc=server_prefunc):
+
+        def cleanup_server(server):
+            if server.process.exitcode is not None:
+                return
+            server.process.terminate()
+            server.process.join()
+
+        server = create_server(socket.gethostbyname("localhost") + ":0",
+                               dbfile,
+                               upstream=upstream,
+                               read_only=read_only)
+
+        server.serve_as_process(prefunc=prefunc, args=(name,))
+        self.addCleanup(cleanup_server, server)
+
+        return server
+
+    def start_client(self, server_address):
+        def cleanup_client(client):
+            client.close()
+
+        client = create_client(server_address)
+        self.addCleanup(cleanup_client, client)
+
+        return client
+
+class FunctionTests(unittest.TestCase):
+
+    def setUp(self):
+        self.temp_dir = tempfile.TemporaryDirectory(prefix='bb-prserv')
+        self.addCleanup(self.temp_dir.cleanup)
+
+    def test_increase_revision(self):
+        self.assertEqual(increase_revision("1"), "2")
+        self.assertEqual(increase_revision("1.0"), "1.1")
+        self.assertEqual(increase_revision("1.1.1"), "1.1.2")
+        self.assertEqual(increase_revision("1.1.1.3"), "1.1.1.4")
+        self.assertEqual(increase_revision("9"), "10")
+        self.assertEqual(increase_revision("1.9"), "1.10")
+        self.assertRaises(ValueError, increase_revision, "1.a")
+        self.assertRaises(ValueError, increase_revision, "1.")
+        self.assertRaises(ValueError, increase_revision, "")
+
+    def test_revision_greater_or_equal(self):
+        self.assertTrue(_revision_greater_or_equal("2", "2"))
+        self.assertTrue(_revision_greater_or_equal("2", "1"))
+        self.assertTrue(_revision_greater_or_equal("10", "2"))
+        self.assertTrue(_revision_greater_or_equal("1.10", "1.2"))
+        self.assertFalse(_revision_greater_or_equal("1.2", "1.10"))
+        self.assertTrue(_revision_greater_or_equal("1.10", "1"))
+        self.assertTrue(_revision_greater_or_equal("1.10.1", "1.10"))
+        self.assertFalse(_revision_greater_or_equal("1.10.1", "1.10.2"))
+        self.assertTrue(_revision_greater_or_equal("1.10.1", "1.10.1"))
+        self.assertTrue(_revision_greater_or_equal("1.10.1", "1"))
+        self.assertTrue(revision_greater("1.20", "1.3"))
+        self.assertTrue(revision_smaller("1.3", "1.20"))
+
+    # DB tests
+
+    def test_db(self):
+        dbfile = os.path.join(self.temp_dir.name, "testtable.sqlite3")
+
+        self.db = db.PRData(dbfile)
+        self.table = self.db["PRMAIN"]
+
+        self.table.store_value(version, pkgarch, checksum0, "0")
+        self.table.store_value(version, pkgarch, checksum1, "1")
+        # "No history" mode supports multiple PRs for the same checksum
+        self.table.store_value(version, pkgarch, checksum0, "2")
+        self.table.store_value(version, pkgarch, checksum2, "1.0")
+
+        self.assertTrue(self.table.test_package(version, pkgarch))
+        self.assertFalse(self.table.test_package(version, other_arch))
+
+        self.assertTrue(self.table.test_value(version, pkgarch, "0"))
+        self.assertTrue(self.table.test_value(version, pkgarch, "1"))
+        self.assertTrue(self.table.test_value(version, pkgarch, "2"))
+
+        self.assertEqual(self.table.find_package_max_value(version, pkgarch), "2")
+
+        self.assertEqual(self.table.find_min_value(version, pkgarch, checksum0), "0")
+        self.assertEqual(self.table.find_max_value(version, pkgarch, checksum0), "2")
+
+        # Test history modes
+        self.assertEqual(self.table.find_value(version, pkgarch, checksum0, True), "0")
+        self.assertEqual(self.table.find_value(version, pkgarch, checksum0, False), "2")
+
+        self.assertEqual(self.table.find_new_subvalue(version, pkgarch, "3"), "3.0")
+        self.assertEqual(self.table.find_new_subvalue(version, pkgarch, "1"), "1.1")
+
+        # Revision comparison tests
+        self.table.store_value(version, pkgarch, checksum1, "1.3")
+        self.table.store_value(version, pkgarch, checksum1, "1.20")
+        self.assertEqual(self.table.find_min_value(version, pkgarch, checksum1), "1")
+        self.assertEqual(self.table.find_max_value(version, pkgarch, checksum1), "1.20")
+
+class PRBasicTests(PRTestSetup, unittest.TestCase):
+
+    def setUp(self):
+        self.temp_dir = tempfile.TemporaryDirectory(prefix='bb-prserv')
+        self.addCleanup(self.temp_dir.cleanup)
+
+        dbfile = os.path.join(self.temp_dir.name, "prtest-basic.sqlite3")
+
+        self.server1 = self.start_server("basic", dbfile)
+        self.client1 = self.start_client(self.server1.address)
+
+    def test_basic(self):
+
+        # Checks on non existing configuration
+
+        result = self.client1.test_pr(version, pkgarch, checksum0)
+        self.assertIsNone(result, "test_pr should return 'None' for a non existing PR")
+
+        result = self.client1.test_package(version, pkgarch)
+        self.assertFalse(result, "test_package should return 'False' for a non existing PR")
+
+        result = self.client1.max_package_pr(version, pkgarch)
+        self.assertIsNone(result, "max_package_pr should return 'None' for a non existing PR")
+
+        # Add a first configuration
+
+        result = self.client1.getPR(version, pkgarch, checksum0)
+        self.assertEqual(result, "0", "getPR: initial PR of a package should be '0'")
+
+        result = self.client1.test_pr(version, pkgarch, checksum0)
+        self.assertEqual(result, "0", "test_pr should return '0' here, matching the result of getPR")
+
+        result = self.client1.test_package(version, pkgarch)
+        self.assertTrue(result, "test_package should return 'True' for an existing PR")
+
+        result = self.client1.max_package_pr(version, pkgarch)
+        self.assertEqual(result, "0", "max_package_pr should return '0' in the current test series")
+
+        # Check that the same request gets the same value
+
+        result = self.client1.getPR(version, pkgarch, checksum0)
+        self.assertEqual(result, "0", "getPR: asking for the same PR a second time in a row should return the same value.")
+
+        # Add new configurations
+
+        result = self.client1.getPR(version, pkgarch, checksum1)
+        self.assertEqual(result, "1", "getPR: second PR of a package should be '1'")
+
+        result = self.client1.test_pr(version, pkgarch, checksum1)
+        self.assertEqual(result, "1", "test_pr should return '1' here, matching the result of getPR")
+
+        result = self.client1.max_package_pr(version, pkgarch)
+        self.assertEqual(result, "1", "max_package_pr should return '1' in the current test series")
+
+        result = self.client1.getPR(version, pkgarch, checksum2)
+        self.assertEqual(result, "2", "getPR: second PR of a package should be '2'")
+
+        result = self.client1.test_pr(version, pkgarch, checksum2)
+        self.assertEqual(result, "2", "test_pr should return '2' here, matching the result of getPR")
+
+        result = self.client1.max_package_pr(version, pkgarch)
+        self.assertEqual(result, "2", "max_package_pr should return '2' in the current test series")
+
+        result = self.client1.getPR(version, pkgarch, checksum3)
+        self.assertEqual(result, "3", "getPR: second PR of a package should be '3'")
+
+        result = self.client1.test_pr(version, pkgarch, checksum3)
+        self.assertEqual(result, "3", "test_pr should return '3' here, matching the result of getPR")
+
+        result = self.client1.max_package_pr(version, pkgarch)
+        self.assertEqual(result, "3", "max_package_pr should return '3' in the current test series")
+
+        # Ask again for the first configuration
+
+        result = self.client1.getPR(version, pkgarch, checksum0)
+        self.assertEqual(result, "4", "getPR: should return '4' in this configuration")
+
+        # Ask again with explicit "no history" mode
+
+        result = self.client1.getPR(version, pkgarch, checksum0, False)
+        self.assertEqual(result, "4", "getPR: should return '4' in this configuration")
+
+        # Ask again with explicit "history" mode. This should return the first recorded PR for checksum0
+
+        result = self.client1.getPR(version, pkgarch, checksum0, True)
+        self.assertEqual(result, "0", "getPR: should return '0' in this configuration")
+
+        # Check again that another pkgarg resets the counters
+
+        result = self.client1.test_pr(version, other_arch, checksum0)
+        self.assertIsNone(result, "test_pr should return 'None' for a non existing PR")
+
+        result = self.client1.test_package(version, other_arch)
+        self.assertFalse(result, "test_package should return 'False' for a non existing PR")
+
+        result = self.client1.max_package_pr(version, other_arch)
+        self.assertIsNone(result, "max_package_pr should return 'None' for a non existing PR")
+
+        # Now add the configuration
+
+        result = self.client1.getPR(version, other_arch, checksum0)
+        self.assertEqual(result, "0", "getPR: initial PR of a package should be '0'")
+
+        result = self.client1.test_pr(version, other_arch, checksum0)
+        self.assertEqual(result, "0", "test_pr should return '0' here, matching the result of getPR")
+
+        result = self.client1.test_package(version, other_arch)
+        self.assertTrue(result, "test_package should return 'True' for an existing PR")
+
+        result = self.client1.max_package_pr(version, other_arch)
+        self.assertEqual(result, "0", "max_package_pr should return '0' in the current test series")
+
+        result = self.client1.is_readonly()
+        self.assertFalse(result, "Server should not be described as 'read-only'")
+
+class PRUpstreamTests(PRTestSetup, unittest.TestCase):
+
+    def setUp(self):
+
+        self.temp_dir = tempfile.TemporaryDirectory(prefix='bb-prserv')
+        self.addCleanup(self.temp_dir.cleanup)
+
+        dbfile2 = os.path.join(self.temp_dir.name, "prtest-upstream2.sqlite3")
+        self.server2 = self.start_server("upstream2", dbfile2)
+        self.client2 = self.start_client(self.server2.address)
+
+        dbfile1 = os.path.join(self.temp_dir.name, "prtest-upstream1.sqlite3")
+        self.server1 = self.start_server("upstream1", dbfile1, upstream=self.server2.address)
+        self.client1 = self.start_client(self.server1.address)
+
+        dbfile0 = os.path.join(self.temp_dir.name, "prtest-local.sqlite3")
+        self.server0 = self.start_server("local", dbfile0, upstream=self.server1.address)
+        self.client0 = self.start_client(self.server0.address)
+        self.shared_db = dbfile0
+
+    def test_upstream_and_readonly(self):
+
+        # For identical checksums, all servers should return the same PR
+
+        result = self.client2.getPR(version, pkgarch, checksum0)
+        self.assertEqual(result, "0", "getPR: initial PR of a package should be '0'")
+
+        result = self.client1.getPR(version, pkgarch, checksum0)
+        self.assertEqual(result, "0", "getPR: initial PR of a package should be '0' (same as upstream)")
+
+        result = self.client0.getPR(version, pkgarch, checksum0)
+        self.assertEqual(result, "0", "getPR: initial PR of a package should be '0' (same as upstream)")
+
+        # Now introduce new checksums on server1 for, same version
+
+        result = self.client1.getPR(version, pkgarch, checksum1)
+        self.assertEqual(result, "0.0", "getPR: first PR of a package which has a different checksum upstream should be '0.0'")
+
+        result = self.client1.getPR(version, pkgarch, checksum2)
+        self.assertEqual(result, "0.1", "getPR: second PR of a package that has a different checksum upstream should be '0.1'")
+
+        # Now introduce checksums on server0 for, same version
+
+        result = self.client1.getPR(version, pkgarch, checksum1)
+        self.assertEqual(result, "0.2", "getPR: can't decrease for known PR")
+
+        result = self.client1.getPR(version, pkgarch, checksum2)
+        self.assertEqual(result, "0.3")
+
+        result = self.client1.max_package_pr(version, pkgarch)
+        self.assertEqual(result, "0.3")
+
+        result = self.client0.getPR(version, pkgarch, checksum3)
+        self.assertEqual(result, "0.3.0", "getPR: first PR of a package that doesn't exist upstream should be '0.3.0'")
+
+        result = self.client0.getPR(version, pkgarch, checksum4)
+        self.assertEqual(result, "0.3.1", "getPR: second PR of a package that doesn't exist upstream should be '0.3.1'")
+
+        result = self.client0.getPR(version, pkgarch, checksum3)
+        self.assertEqual(result, "0.3.2")
+
+        # More upstream updates
+        # Here, we assume no communication between server2 and server0. server2 only impacts server0
+        # after impacting server1
+
+        self.assertEqual(self.client2.getPR(version, pkgarch, checksum5), "1")
+        self.assertEqual(self.client1.getPR(version, pkgarch, checksum6), "1.0")
+        self.assertEqual(self.client1.getPR(version, pkgarch, checksum7), "1.1")
+        self.assertEqual(self.client0.getPR(version, pkgarch, checksum8), "1.1.0")
+        self.assertEqual(self.client0.getPR(version, pkgarch, checksum9), "1.1.1")
+
+        # "history" mode tests
+
+        self.assertEqual(self.client2.getPR(version, pkgarch, checksum0, True), "0")
+        self.assertEqual(self.client1.getPR(version, pkgarch, checksum2, True), "0.1")
+        self.assertEqual(self.client0.getPR(version, pkgarch, checksum3, True), "0.3.0")
+
+        # More "no history" mode tests
+
+        self.assertEqual(self.client2.getPR(version, pkgarch, checksum0), "2")
+        self.assertEqual(self.client1.getPR(version, pkgarch, checksum0), "2") # Same as upstream
+        self.assertEqual(self.client0.getPR(version, pkgarch, checksum0), "2") # Same as upstream
+        self.assertEqual(self.client1.getPR(version, pkgarch, checksum7), "3") # This could be surprising, but since the previous revision was "2", increasing it yields "3".
+                                                                               # We don't know how many upstream servers we have
+        # Start read-only server with server1 as upstream
+        self.server_ro = self.start_server("local-ro", self.shared_db, upstream=self.server1.address, read_only=True)
+        self.client_ro = self.start_client(self.server_ro.address)
+
+        self.assertTrue(self.client_ro.is_readonly(), "Database should be described as 'read-only'")
+
+        # Checks on non existing configurations
+        self.assertIsNone(self.client_ro.test_pr(version, pkgarch, checksumX))
+        self.assertFalse(self.client_ro.test_package("unknown", pkgarch))
+
+        # Look up existing configurations
+        self.assertEqual(self.client_ro.getPR(version, pkgarch, checksum0), "3") # "no history" mode
+        self.assertEqual(self.client_ro.getPR(version, pkgarch, checksum0, True), "0") # "history" mode
+        self.assertEqual(self.client_ro.getPR(version, pkgarch, checksum3), "3")
+        self.assertEqual(self.client_ro.getPR(version, pkgarch, checksum3, True), "0.3.0")
+        self.assertEqual(self.client_ro.max_package_pr(version, pkgarch), "2") # normal as "3" was never saved
+
+        # Try to insert a new value. Here this one is know upstream.
+        self.assertEqual(self.client_ro.getPR(version, pkgarch, checksum7), "3")
+        # Try to insert a completely new value. As the max upstream value is already "3", it should be "3.0"
+        self.assertEqual(self.client_ro.getPR(version, pkgarch, checksum10), "3.0")
+        # Same with another value which only exists in the upstream upstream server
+        # This time, as the upstream server doesn't know it, it will ask its upstream server. So that's a known one.
+        self.assertEqual(self.client_ro.getPR(version, pkgarch, checksum9), "3")
+
+class ScriptTests(unittest.TestCase):
+
+    def setUp(self):
+
+        self.temp_dir = tempfile.TemporaryDirectory(prefix='bb-prserv')
+        self.addCleanup(self.temp_dir.cleanup)
+        self.dbfile = os.path.join(self.temp_dir.name, "prtest.sqlite3")
+
+    def test_1_start_bitbake_prserv(self):
+        try:
+            subprocess.check_call([BIN_DIR / "bitbake-prserv", "--start", "-f", self.dbfile])
+        except subprocess.CalledProcessError as e:
+            self.fail("Failed to start bitbake-prserv: %s" % e.returncode)
+
+    def test_2_stop_bitbake_prserv(self):
+        try:
+            subprocess.check_call([BIN_DIR / "bitbake-prserv", "--stop"])
+        except subprocess.CalledProcessError as e:
+            self.fail("Failed to stop bitbake-prserv: %s" % e.returncode)