I wrote:
> Therefore, the condition that actually ought to be getting enforced here
> is either "ReservedBackends + max_wal_senders < MaxConnections", or
> "ReservedBackends + max_wal_senders <= MaxConnections", depending on
> whether you think it's appropriate to require at least one not-reserved-
> for-superusers connection slot to remain available if the walsenders
> slots are fully populated.
I propose the first attached patch to do that. (I failed to resist the
temptation to copy-edit some nearby docs and comments, too.)
> My proposal is to default max_wal_senders to perhaps 3, and leave
> initdb's logic alone.
... and then the second attached patch to do that.
I noticed that a lot of our TAP tests are setting max_wal_senders
and max_replication_slots to random values around 4 or 5. Probably
we could drop all that now, and let them just use the defaults.
I've not done that here, except for adjusting 010_pg_basebackup.pl
which would fail for no very good reason with minimal max_connections.
regards, tom lane
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 259a2d8..3a8fc7d 100644
*** a/doc/src/sgml/config.sgml
--- b/doc/src/sgml/config.sgml
*************** include_dir 'conf.d'
*** 696,703 ****
<para>
The default value is three connections. The value must be less
! than the value of <varname>max_connections</varname>. This
! parameter can only be set at server start.
</para>
</listitem>
</varlistentry>
--- 696,704 ----
<para>
The default value is three connections. The value must be less
! than <varname>max_connections</varname> minus
! <xref linkend="guc-max-wal-senders"/>.
! This parameter can only be set at server start.
</para>
</listitem>
</varlistentry>
*************** include_dir 'conf.d'
*** 2982,2994 ****
maximum number of simultaneously running WAL sender
processes). The default is 10. The value 0 means 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"/>. Abrupt streaming client
! disconnection might cause an orphaned connection slot until
a timeout is reached, so this parameter should be set slightly
higher than the maximum number of expected clients so disconnected
clients can immediately reconnect. This parameter can only
! be set at server start. <varname>wal_level</varname> must be set to
<literal>replica</literal> or higher to allow connections from standby
servers.
</para>
--- 2983,2998 ----
maximum number of simultaneously running WAL sender
processes). The default is 10. The value 0 means replication is
disabled. WAL sender processes count towards the total number
! of connections, so this parameter's value must be less than
! <xref linkend="guc-max-connections"/> minus
! <xref linkend="guc-superuser-reserved-connections"/>.
! Abrupt streaming client disconnection might leave an orphaned
! connection slot behind until
a timeout is reached, so this parameter should be set slightly
higher than the maximum number of expected clients so disconnected
clients can immediately reconnect. This parameter can only
! be set at server start.
! Also, <varname>wal_level</varname> must be set to
<literal>replica</literal> or higher to allow connections from standby
servers.
</para>
*************** include_dir 'conf.d'
*** 3007,3016 ****
(see <xref linkend="streaming-replication-slots"/>) that the server
can support. The default is 10. This parameter can only be set at
server start.
! <varname>wal_level</varname> must be set
! to <literal>replica</literal> or higher to allow replication slots to
! be used. Setting it to a lower value than the number of currently
existing replication slots will prevent the server from starting.
</para>
</listitem>
</varlistentry>
--- 3011,3021 ----
(see <xref linkend="streaming-replication-slots"/>) that the server
can support. The default is 10. This parameter can only be set at
server start.
! Setting it to a lower value than the number of currently
existing replication slots will prevent the server from starting.
+ Also, <varname>wal_level</varname> must be set
+ to <literal>replica</literal> or higher to allow replication slots to
+ be used.
</para>
</listitem>
</varlistentry>
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index f3ddf82..660f318 100644
*** a/src/backend/postmaster/postmaster.c
--- b/src/backend/postmaster/postmaster.c
*************** char *ListenAddresses;
*** 202,210 ****
/*
* ReservedBackends is the number of backends reserved for superuser use.
! * This number is taken out of the pool size given by MaxBackends so
* number of backend slots available to non-superusers is
! * (MaxBackends - ReservedBackends). Note what this really means is
* "if there are <= ReservedBackends connections available, only superusers
* can make new connections" --- pre-existing superuser connections don't
* count against the limit.
--- 202,210 ----
/*
* ReservedBackends is the number of backends reserved for superuser use.
! * This number is taken out of the pool size given by MaxConnections so
* number of backend slots available to non-superusers is
! * (MaxConnections - ReservedBackends). Note what this really means is
* "if there are <= ReservedBackends connections available, only superusers
* can make new connections" --- pre-existing superuser connections don't
* count against the limit.
*************** PostmasterMain(int argc, char *argv[])
*** 882,895 ****
/*
* Check for invalid combinations of GUC settings.
*/
! 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 > ARCHIVE_MODE_OFF && wal_level == WAL_LEVEL_MINIMAL)
--- 882,892 ----
/*
* Check for invalid combinations of GUC settings.
*/
! if (ReservedBackends + max_wal_senders >= MaxConnections)
{
! write_stderr("%s: superuser_reserved_connections (%d) plus max_wal_senders (%d) must be less than max_connections (%d)\n",
! progname,
! ReservedBackends, max_wal_senders, MaxConnections);
ExitPostmaster(1);
}
if (XLogArchiveMode > ARCHIVE_MODE_OFF && wal_level == WAL_LEVEL_MINIMAL)
diff --git a/src/backend/utils/init/postinit.c b/src/backend/utils/init/postinit.c
index 4846289..d8f45b3 100644
*** a/src/backend/utils/init/postinit.c
--- b/src/backend/utils/init/postinit.c
*************** InitPostgres(const char *in_dbname, Oid
*** 778,784 ****
}
/*
! * The last few connections slots are reserved for superusers. Although
* replication connections currently require superuser privileges, we
* don't allow them to consume the reserved slots, which are intended for
* interactive use.
--- 778,784 ----
}
/*
! * The last few connection slots are reserved for superusers. Although
* replication connections currently require superuser privileges, we
* don't allow them to consume the reserved slots, which are intended for
* interactive use.
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 1db7845..d91ba05 100644
*** a/src/backend/utils/misc/guc.c
--- b/src/backend/utils/misc/guc.c
*************** static struct config_int ConfigureNamesI
*** 1873,1878 ****
--- 1873,1879 ----
},
{
+ /* see max_connections and max_wal_senders */
{"superuser_reserved_connections", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
gettext_noop("Sets the number of connection slots reserved for superusers."),
NULL
*************** static struct config_int ConfigureNamesI
*** 2375,2381 ****
},
{
! /* see max_connections */
{"max_wal_senders", PGC_POSTMASTER, REPLICATION_SENDING,
gettext_noop("Sets the maximum number of simultaneously running WAL sender processes."),
NULL
--- 2376,2382 ----
},
{
! /* see max_connections and superuser_reserved_connections */
{"max_wal_senders", PGC_POSTMASTER, REPLICATION_SENDING,
gettext_noop("Sets the maximum number of simultaneously running WAL sender processes."),
NULL
*************** static struct config_int ConfigureNamesI
*** 2386,2392 ****
},
{
! /* see max_connections */
{"max_replication_slots", PGC_POSTMASTER, REPLICATION_SENDING,
gettext_noop("Sets the maximum number of simultaneously defined replication slots."),
NULL
--- 2387,2393 ----
},
{
! /* see max_wal_senders */
{"max_replication_slots", PGC_POSTMASTER, REPLICATION_SENDING,
gettext_noop("Sets the maximum number of simultaneously defined replication slots."),
NULL
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 3a8fc7d..db43caf 100644
*** a/doc/src/sgml/config.sgml
--- b/doc/src/sgml/config.sgml
*************** include_dir 'conf.d'
*** 2981,2987 ****
Specifies the maximum number of concurrent connections from
standby servers or streaming base backup clients (i.e., the
maximum number of simultaneously running WAL sender
! processes). The default is 10. The value 0 means replication is
disabled. WAL sender processes count towards the total number
of connections, so this parameter's value must be less than
<xref linkend="guc-max-connections"/> minus
--- 2981,2987 ----
Specifies the maximum number of concurrent connections from
standby servers or streaming base backup clients (i.e., the
maximum number of simultaneously running WAL sender
! processes). The default is 3. The value 0 means replication is
disabled. WAL sender processes count towards the total number
of connections, so this parameter's value must be less than
<xref linkend="guc-max-connections"/> minus
*************** include_dir 'conf.d'
*** 3009,3015 ****
<para>
Specifies the maximum number of replication slots
(see <xref linkend="streaming-replication-slots"/>) that the server
! can support. The default is 10. This parameter can only be set at
server start.
Setting it to a lower value than the number of currently
existing replication slots will prevent the server from starting.
--- 3009,3015 ----
<para>
Specifies the maximum number of replication slots
(see <xref linkend="streaming-replication-slots"/>) that the server
! can support. The default is 3. This parameter can only be set at
server start.
Setting it to a lower value than the number of currently
existing replication slots will prevent the server from starting.
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index d91ba05..85507d5 100644
*** a/src/backend/utils/misc/guc.c
--- b/src/backend/utils/misc/guc.c
*************** static struct config_int ConfigureNamesI
*** 2382,2388 ****
NULL
},
&max_wal_senders,
! 10, 0, MAX_BACKENDS,
NULL, NULL, NULL
},
--- 2382,2388 ----
NULL
},
&max_wal_senders,
! 3, 0, MAX_BACKENDS,
NULL, NULL, NULL
},
*************** static struct config_int ConfigureNamesI
*** 2393,2399 ****
NULL
},
&max_replication_slots,
! 10, 0, MAX_BACKENDS /* XXX? */ ,
NULL, NULL, NULL
},
--- 2393,2399 ----
NULL
},
&max_replication_slots,
! 3, 0, MAX_BACKENDS,
NULL, NULL, NULL
},
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 3927292..15f257b 100644
*** a/src/backend/utils/misc/postgresql.conf.sample
--- b/src/backend/utils/misc/postgresql.conf.sample
***************
*** 234,245 ****
# Set these on the master and on any standby that will send replication data.
! #max_wal_senders = 10 # max number of walsender processes
# (change requires restart)
#wal_keep_segments = 0 # in logfile segments; 0 disables
#wal_sender_timeout = 60s # in milliseconds; 0 disables
! #max_replication_slots = 10 # max number of replication slots
# (change requires restart)
#track_commit_timestamp = off # collect timestamp of transaction commit
# (change requires restart)
--- 234,245 ----
# Set these on the master and on any standby that will send replication data.
! #max_wal_senders = 3 # max number of walsender processes
# (change requires restart)
#wal_keep_segments = 0 # in logfile segments; 0 disables
#wal_sender_timeout = 60s # in milliseconds; 0 disables
! #max_replication_slots = 3 # max number of replication slots
# (change requires restart)
#track_commit_timestamp = off # collect timestamp of transaction commit
# (change requires restart)
diff --git a/src/bin/pg_basebackup/t/010_pg_basebackup.pl b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
index cdf4f5b..29cd928 100644
*** a/src/bin/pg_basebackup/t/010_pg_basebackup.pl
--- b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
*************** $node->command_fails([ 'pg_basebackup',
*** 45,52 ****
ok(-d "$tempdir/backup", 'backup directory was created and left behind');
open my $conf, '>>', "$pgdata/postgresql.conf";
! print $conf "max_replication_slots = 10\n";
! print $conf "max_wal_senders = 10\n";
print $conf "wal_level = replica\n";
close $conf;
$node->restart;
--- 45,52 ----
ok(-d "$tempdir/backup", 'backup directory was created and left behind');
open my $conf, '>>', "$pgdata/postgresql.conf";
! print $conf "max_replication_slots = 5\n";
! print $conf "max_wal_senders = 5\n";
print $conf "wal_level = replica\n";
close $conf;
$node->restart;
