Fix upper limit of superuser_reserved_connections, add limit for wal_senders

Should be limited to the maximum number of connections excluding
autovacuum workers, not including.

Add similar check for max_wal_senders, which should never be higher than
max_connections.

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index d8bc344b15db7a7431ae22b10d3fa1f0745a61e0..b8eaac39eaf7c587d8972571a32d9134248c2069 100644 (file)
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1908,11 +1908,16 @@ SET ENABLE_SEQSCAN TO OFF;
        </indexterm>
        <listitem>
        <para>
-        Specifies the maximum number of concurrent connections from standby
-        servers (i.e., the maximum number of simultaneously running WAL sender
-        processes). The default is zero. This parameter can only be set at
-        server start. <varname>wal_level</> must be set to <literal>archive</>
-        or <literal>hot_standby</> to allow connections from standby servers.
+        Specifies the maximum number of concurrent connections from
+        standby servers (i.e., the
+        maximum number of simultaneously running WAL sender
+        processes). The default is zero, meaning replication is
+        disabled. WAL sender processes count towards the total number
+        of connections, so the parameter cannot be set higher than
+        <xref linkend="guc-max-connections">.  This parameter can only
+        be set at server start. <varname>wal_level</> must be set
+        to <literal>archive</> or <literal>hot_standby</> to allow
+        connections from standby servers.
        </para>
        </listitem>
       </varlistentry>

diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index 5ae92d714005c78757127b214fa5cbb7dc129299..657dc088594b8f8fe69306cb2180140dc7e6001b 100644 (file)
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -724,11 +724,16 @@ PostmasterMain(int argc, char *argv[])
        /*
         * Check for invalid combinations of GUC settings.
         */
-       if (ReservedBackends >= MaxBackends)
+       if (ReservedBackends >= MaxConnections)
        {
                write_stderr("%s: superuser_reserved_connections must be less than max_connections\n", progname);
                ExitPostmaster(1);
        }
+       if (max_wal_senders >= MaxConnections)
+       {
+               write_stderr("%s: max_wal_senders must be less than max_connections\n", progname);
+               ExitPostmaster(1);
+       }
        if (XLogArchiveMode && wal_level == WAL_LEVEL_MINIMAL)
                ereport(ERROR,
                                (errmsg("WAL archival (archive_mode=on) requires wal_level \"archive\" or \"hot_standby\"")));