diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 7e208a4b812..07b847a8e96 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -697,8 +697,7 @@ include_dir 'conf.d'
<para>
The default value is three connections. The value must be less
- than <varname>max_connections</varname> minus
- <xref linkend="guc-max-wal-senders"/>.
+ than <varname>max_connections</varname>.
This parameter can only be set at server start.
</para>
</listitem>
@@ -3495,24 +3494,25 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"' # Windows
</term>
<listitem>
<para>
- 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
- <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
+ 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
+ <literal>10</literal>. The value <literal>0</literal> means
+ replication is disabled. 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>
+
+ <para>
+ When running a standby server, you must set this parameter to the
+ same or higher value than on the master server. Otherwise, queries
+ will not be allowed in the standby server.
+ </para>
</listitem>
</varlistentry>
diff --git a/doc/src/sgml/high-availability.sgml b/doc/src/sgml/high-availability.sgml
index bbab7395a21..2b4dcd03c87 100644
--- a/doc/src/sgml/high-availability.sgml
+++ b/doc/src/sgml/high-availability.sgml
@@ -2177,6 +2177,11 @@ LOG: database system is ready to accept read only connections
<varname>max_locks_per_transaction</varname>
</para>
</listitem>
+ <listitem>
+ <para>
+ <varname>max_wal_senders</varname>
+ </para>
+ </listitem>
<listitem>
<para>
<varname>max_worker_processes</varname>
diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index 1f78f6c9569..7de26e98ad8 100644
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -720,13 +720,13 @@ psql: could not connect to server: No such file or directory
<row>
<entry><varname>SEMMNI</varname></entry>
<entry>Maximum number of semaphore identifiers (i.e., sets)</entry>
- <entry>at least <literal>ceil((max_connections + autovacuum_max_workers + max_worker_processes + 5) / 16)</literal> plus room for other applications</entry>
+ <entry>at least <literal>ceil((max_connections + autovacuum_max_workers + wax_wal_senders + max_worker_processes + 5) / 16)</literal> plus room for other applications</entry>
</row>
<row>
<entry><varname>SEMMNS</varname></entry>
<entry>Maximum number of semaphores system-wide</entry>
- <entry><literal>ceil((max_connections + autovacuum_max_workers + max_worker_processes + 5) / 16) * 17</literal> plus room for other applications</entry>
+ <entry><literal>ceil((max_connections + autovacuum_max_workers + max_wal_senders + max_worker_processes + 5) / 16) * 17</literal> plus room for other applications</entry>
</row>
<row>
@@ -785,13 +785,13 @@ psql: could not connect to server: No such file or directory
other applications. The maximum number of semaphores in the system
is set by <varname>SEMMNS</varname>, which consequently must be at least
as high as <varname>max_connections</varname> plus
- <varname>autovacuum_max_workers</varname> plus <varname>max_worker_processes</varname>,
- plus one extra for each 16
+ <varname>autovacuum_max_workers</varname> plus <varname>max_wal_senders</varname>,
+ plus <varname>max_worker_processes</varname>, plus one extra for each 16
allowed connections plus workers (see the formula in <xref
linkend="sysvipc-parameters"/>). The parameter <varname>SEMMNI</varname>
determines the limit on the number of semaphore sets that can
exist on the system at one time. Hence this parameter must be at
- least <literal>ceil((max_connections + autovacuum_max_workers + max_worker_processes + 5) / 16)</literal>.
+ least <literal>ceil((max_connections + autovacuum_max_workers + max_wal_senders + max_worker_processes + 5) / 16)</literal>.
Lowering the number
of allowed connections is a temporary workaround for failures,
which are usually confusingly worded <quote>No space
diff --git a/src/backend/access/rmgrdesc/xlogdesc.c b/src/backend/access/rmgrdesc/xlogdesc.c
index 7f732516963..0ad4454a8c6 100644
--- a/src/backend/access/rmgrdesc/xlogdesc.c
+++ b/src/backend/access/rmgrdesc/xlogdesc.c
@@ -110,10 +110,11 @@ xlog_desc(StringInfo buf, XLogReaderState *record)
}
appendStringInfo(buf, "max_connections=%d max_worker_processes=%d "
- "max_prepared_xacts=%d max_locks_per_xact=%d "
- "wal_level=%s wal_log_hints=%s "
- "track_commit_timestamp=%s",
+ "max_wal_senders=%d max_prepared_xacts=%d "
+ "max_locks_per_xact=%d wal_level=%s "
+ "wal_log_hints=%s track_commit_timestamp=%s",
xlrec.MaxConnections,
+ xlrec.max_wal_senders,
xlrec.max_worker_processes,
xlrec.max_prepared_xacts,
xlrec.max_locks_per_xact,
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index a9f32728495..ecd12fc53ae 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -5257,6 +5257,7 @@ BootStrapXLOG(void)
/* Set important parameter values for use when replaying WAL */
ControlFile->MaxConnections = MaxConnections;
ControlFile->max_worker_processes = max_worker_processes;
+ ControlFile->max_wal_senders = max_wal_senders;
ControlFile->max_prepared_xacts = max_prepared_xacts;
ControlFile->max_locks_per_xact = max_locks_per_xact;
ControlFile->wal_level = wal_level;
@@ -6170,6 +6171,9 @@ CheckRequiredParameterValues(void)
RecoveryRequiresIntParameter("max_worker_processes",
max_worker_processes,
ControlFile->max_worker_processes);
+ RecoveryRequiresIntParameter("max_wal_senders",
+ max_wal_senders,
+ ControlFile->max_wal_senders);
RecoveryRequiresIntParameter("max_prepared_transactions",
max_prepared_xacts,
ControlFile->max_prepared_xacts);
@@ -9460,6 +9464,7 @@ XLogReportParameters(void)
wal_log_hints != ControlFile->wal_log_hints ||
MaxConnections != ControlFile->MaxConnections ||
max_worker_processes != ControlFile->max_worker_processes ||
+ max_wal_senders != ControlFile->max_wal_senders ||
max_prepared_xacts != ControlFile->max_prepared_xacts ||
max_locks_per_xact != ControlFile->max_locks_per_xact ||
track_commit_timestamp != ControlFile->track_commit_timestamp)
@@ -9478,6 +9483,7 @@ XLogReportParameters(void)
xlrec.MaxConnections = MaxConnections;
xlrec.max_worker_processes = max_worker_processes;
+ xlrec.max_wal_senders = max_wal_senders;
xlrec.max_prepared_xacts = max_prepared_xacts;
xlrec.max_locks_per_xact = max_locks_per_xact;
xlrec.wal_level = wal_level;
@@ -9493,6 +9499,7 @@ XLogReportParameters(void)
ControlFile->MaxConnections = MaxConnections;
ControlFile->max_worker_processes = max_worker_processes;
+ ControlFile->max_wal_senders = max_wal_senders;
ControlFile->max_prepared_xacts = max_prepared_xacts;
ControlFile->max_locks_per_xact = max_locks_per_xact;
ControlFile->wal_level = wal_level;
@@ -9896,6 +9903,7 @@ xlog_redo(XLogReaderState *record)
LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
ControlFile->MaxConnections = xlrec.MaxConnections;
ControlFile->max_worker_processes = xlrec.max_worker_processes;
+ ControlFile->max_wal_senders = xlrec.max_wal_senders;
ControlFile->max_prepared_xacts = xlrec.max_prepared_xacts;
ControlFile->max_locks_per_xact = xlrec.max_locks_per_xact;
ControlFile->wal_level = xlrec.wal_level;
@@ -9927,7 +9935,7 @@ xlog_redo(XLogReaderState *record)
UpdateControlFile();
LWLockRelease(ControlFileLock);
- /* Check to see if any changes to max_connections give problems */
+ /* Check to see if any parameter change gives a problem on recovery */
CheckRequiredParameterValues();
}
else if (info == XLOG_FPW_CHANGE)
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index 40a0222220d..ccea231e985 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -885,11 +885,11 @@ PostmasterMain(int argc, char *argv[])
/*
* Check for invalid combinations of GUC settings.
*/
- if (ReservedBackends + max_wal_senders >= MaxConnections)
+ if (ReservedBackends >= MaxConnections)
{
- write_stderr("%s: superuser_reserved_connections (%d) plus max_wal_senders (%d) must be less than max_connections (%d)\n",
+ write_stderr("%s: superuser_reserved_connections (%d) must be less than max_connections (%d)\n",
progname,
- ReservedBackends, max_wal_senders, MaxConnections);
+ ReservedBackends, MaxConnections);
ExitPostmaster(1);
}
if (XLogArchiveMode > ARCHIVE_MODE_OFF && wal_level == WAL_LEVEL_MINIMAL)
@@ -5532,7 +5532,7 @@ int
MaxLivePostmasterChildren(void)
{
return 2 * (MaxConnections + autovacuum_max_workers + 1 +
- max_worker_processes);
+ max_wal_senders + max_worker_processes);
}
/*
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 2d2eb23eb73..9b143f361b8 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -2273,8 +2273,8 @@ InitWalSenderSlot(void)
Assert(MyWalSnd == NULL);
/*
- * Find a free walsender slot and reserve it. If this fails, we must be
- * out of WalSnd structures.
+ * Find a free walsender slot and reserve it. This must not fail due to
+ * the prior check for free WAL senders in InitProcess().
*/
for (i = 0; i < max_wal_senders; i++)
{
@@ -2310,12 +2310,8 @@ InitWalSenderSlot(void)
break;
}
}
- if (MyWalSnd == NULL)
- ereport(FATAL,
- (errcode(ERRCODE_TOO_MANY_CONNECTIONS),
- errmsg("number of requested standby connections "
- "exceeds max_wal_senders (currently %d)",
- max_wal_senders)));
+
+ Assert(MyWalSnd != NULL);
/* Arrange to clean up at walsender exit */
on_shmem_exit(WalSndKill, 0);
diff --git a/src/backend/storage/lmgr/proc.c b/src/backend/storage/lmgr/proc.c
index 89c80fb6874..0da5b19719f 100644
--- a/src/backend/storage/lmgr/proc.c
+++ b/src/backend/storage/lmgr/proc.c
@@ -43,6 +43,7 @@
#include "postmaster/autovacuum.h"
#include "replication/slot.h"
#include "replication/syncrep.h"
+#include "replication/walsender.h"
#include "storage/condition_variable.h"
#include "storage/standby.h"
#include "storage/ipc.h"
@@ -147,8 +148,9 @@ ProcGlobalSemas(void)
* running out when trying to start another backend is a common failure.
* So, now we grab enough semaphores to support the desired max number
* of backends immediately at initialization --- if the sysadmin has set
- * MaxConnections, max_worker_processes, or autovacuum_max_workers higher
- * than his kernel will support, he'll find out sooner rather than later.
+ * MaxConnections, max_worker_processes, max_wal_senders, or
+ * autovacuum_max_workers higher than his kernel will support, he'll
+ * find out sooner rather than later.
*
* Another reason for creating semaphores here is that the semaphore
* implementation typically requires us to create semaphores in the
@@ -180,6 +182,7 @@ InitProcGlobal(void)
ProcGlobal->freeProcs = NULL;
ProcGlobal->autovacFreeProcs = NULL;
ProcGlobal->bgworkerFreeProcs = NULL;
+ ProcGlobal->walsenderFreeProcs = NULL;
ProcGlobal->startupProc = NULL;
ProcGlobal->startupProcPid = 0;
ProcGlobal->startupBufferPinWaitBufId = -1;
@@ -253,13 +256,20 @@ InitProcGlobal(void)
ProcGlobal->autovacFreeProcs = &procs[i];
procs[i].procgloballist = &ProcGlobal->autovacFreeProcs;
}
- else if (i < MaxBackends)
+ else if (i < MaxConnections + autovacuum_max_workers + 1 + max_worker_processes)
{
/* PGPROC for bgworker, add to bgworkerFreeProcs list */
procs[i].links.next = (SHM_QUEUE *) ProcGlobal->bgworkerFreeProcs;
ProcGlobal->bgworkerFreeProcs = &procs[i];
procs[i].procgloballist = &ProcGlobal->bgworkerFreeProcs;
}
+ else if (i < MaxBackends)
+ {
+ /* PGPROC for walsender, add to walsenderFreeProcs list */
+ procs[i].links.next = (SHM_QUEUE *) ProcGlobal->walsenderFreeProcs;
+ ProcGlobal->walsenderFreeProcs = &procs[i];
+ procs[i].procgloballist = &ProcGlobal->walsenderFreeProcs;
+ }
/* Initialize myProcLocks[] shared memory queues. */
for (j = 0; j < NUM_LOCK_PARTITIONS; j++)
@@ -311,6 +321,8 @@ InitProcess(void)
procgloballist = &ProcGlobal->autovacFreeProcs;
else if (IsBackgroundWorker)
procgloballist = &ProcGlobal->bgworkerFreeProcs;
+ else if (am_walsender)
+ procgloballist = &ProcGlobal->walsenderFreeProcs;
else
procgloballist = &ProcGlobal->freeProcs;
@@ -341,6 +353,11 @@ InitProcess(void)
* in the autovacuum case?
*/
SpinLockRelease(ProcStructLock);
+ if (am_walsender)
+ ereport(FATAL,
+ (errcode(ERRCODE_TOO_MANY_CONNECTIONS),
+ errmsg("number of requested standby connections exceeds max_wal_senders (currently %d)",
+ max_wal_senders)));
ereport(FATAL,
(errcode(ERRCODE_TOO_MANY_CONNECTIONS),
errmsg("sorry, too many clients already")));
diff --git a/src/backend/utils/init/postinit.c b/src/backend/utils/init/postinit.c
index c0b62314580..a5ee209f910 100644
--- a/src/backend/utils/init/postinit.c
+++ b/src/backend/utils/init/postinit.c
@@ -527,7 +527,7 @@ InitializeMaxBackends(void)
/* the extra unit accounts for the autovacuum launcher */
MaxBackends = MaxConnections + autovacuum_max_workers + 1 +
- max_worker_processes;
+ max_worker_processes + max_wal_senders;
/* internal error because the values were all checked previously */
if (MaxBackends > MAX_BACKENDS)
@@ -811,12 +811,11 @@ InitPostgres(const char *in_dbname, Oid dboid, const char *username,
}
/*
- * 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.
+ * The last few connection slots are reserved for superusers. Replication
+ * connections are drawn from slots reserved with max_wal_senders and not
+ * limited by max_connections or superuser_reserved_connections.
*/
- if ((!am_superuser || am_walsender) &&
+ if (!am_superuser && !am_walsender &&
ReservedBackends > 0 &&
!HaveNFreeProcs(ReservedBackends))
ereport(FATAL,
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index ea5444c6f15..41d477165cd 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -187,6 +187,7 @@ static const char *show_tcp_keepalives_count(void);
static bool check_maxconnections(int *newval, void **extra, GucSource source);
static bool check_max_worker_processes(int *newval, void **extra, GucSource source);
static bool check_autovacuum_max_workers(int *newval, void **extra, GucSource source);
+static bool check_max_wal_senders(int *newval, void **extra, GucSource source);
static bool check_autovacuum_work_mem(int *newval, void **extra, GucSource source);
static bool check_effective_io_concurrency(int *newval, void **extra, GucSource source);
static void assign_effective_io_concurrency(int newval, void *extra);
@@ -2090,7 +2091,7 @@ static struct config_int ConfigureNamesInt[] =
},
{
- /* see max_connections and max_wal_senders */
+ /* see max_connections */
{"superuser_reserved_connections", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
gettext_noop("Sets the number of connection slots reserved for superusers."),
NULL
@@ -2608,14 +2609,13 @@ static struct config_int ConfigureNamesInt[] =
},
{
- /* 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
},
&max_wal_senders,
10, 0, MAX_BACKENDS,
- NULL, NULL, NULL
+ check_max_wal_senders, NULL, NULL
},
{
@@ -10911,7 +10911,7 @@ static bool
check_maxconnections(int *newval, void **extra, GucSource source)
{
if (*newval + autovacuum_max_workers + 1 +
- max_worker_processes > MAX_BACKENDS)
+ max_worker_processes + max_wal_senders > MAX_BACKENDS)
return false;
return true;
}
@@ -10919,7 +10919,17 @@ check_maxconnections(int *newval, void **extra, GucSource source)
static bool
check_autovacuum_max_workers(int *newval, void **extra, GucSource source)
{
- if (MaxConnections + *newval + 1 + max_worker_processes > MAX_BACKENDS)
+ if (MaxConnections + *newval + 1 +
+ max_worker_processes + max_wal_senders > MAX_BACKENDS)
+ return false;
+ return true;
+}
+
+static bool
+check_max_wal_senders(int *newval, void **extra, GucSource source)
+{
+ if (MaxConnections + autovacuum_max_workers + 1 +
+ max_worker_processes + *newval > MAX_BACKENDS)
return false;
return true;
}
@@ -10950,7 +10960,8 @@ check_autovacuum_work_mem(int *newval, void **extra, GucSource source)
static bool
check_max_worker_processes(int *newval, void **extra, GucSource source)
{
- if (MaxConnections + autovacuum_max_workers + 1 + *newval > MAX_BACKENDS)
+ if (MaxConnections + autovacuum_max_workers + 1 +
+ *newval + max_wal_senders > MAX_BACKENDS)
return false;
return true;
}
diff --git a/src/bin/pg_controldata/pg_controldata.c b/src/bin/pg_controldata/pg_controldata.c
index 1e1fd85b0ba..1aa1db218ac 100644
--- a/src/bin/pg_controldata/pg_controldata.c
+++ b/src/bin/pg_controldata/pg_controldata.c
@@ -304,6 +304,8 @@ main(int argc, char *argv[])
ControlFile->MaxConnections);
printf(_("max_worker_processes setting: %d\n"),
ControlFile->max_worker_processes);
+ printf(_("max_wal_senders setting: %d\n"),
+ ControlFile->max_wal_senders);
printf(_("max_prepared_xacts setting: %d\n"),
ControlFile->max_prepared_xacts);
printf(_("max_locks_per_xact setting: %d\n"),
diff --git a/src/bin/pg_resetwal/pg_resetwal.c b/src/bin/pg_resetwal/pg_resetwal.c
index 562c27904f0..2af87132166 100644
--- a/src/bin/pg_resetwal/pg_resetwal.c
+++ b/src/bin/pg_resetwal/pg_resetwal.c
@@ -728,6 +728,7 @@ GuessControlValues(void)
ControlFile.wal_log_hints = false;
ControlFile.track_commit_timestamp = false;
ControlFile.MaxConnections = 100;
+ ControlFile.max_wal_senders = 10;
ControlFile.max_worker_processes = 8;
ControlFile.max_prepared_xacts = 0;
ControlFile.max_locks_per_xact = 64;
@@ -955,6 +956,7 @@ RewriteControlFile(void)
ControlFile.wal_log_hints = false;
ControlFile.track_commit_timestamp = false;
ControlFile.MaxConnections = 100;
+ ControlFile.max_wal_senders = 10;
ControlFile.max_worker_processes = 8;
ControlFile.max_prepared_xacts = 0;
ControlFile.max_locks_per_xact = 64;
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index 3c860372515..42d1065d1e0 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -31,7 +31,7 @@
/*
* Each page of XLOG file has a header like this:
*/
-#define XLOG_PAGE_MAGIC 0xD098 /* can be used as WAL version indicator */
+#define XLOG_PAGE_MAGIC 0xD099 /* can be used as WAL version indicator */
typedef struct XLogPageHeaderData
{
@@ -226,6 +226,7 @@ typedef struct xl_parameter_change
{
int MaxConnections;
int max_worker_processes;
+ int max_wal_senders;
int max_prepared_xacts;
int max_locks_per_xact;
int wal_level;
diff --git a/src/include/catalog/pg_control.h b/src/include/catalog/pg_control.h
index a4aa83bae8f..a3910a5f997 100644
--- a/src/include/catalog/pg_control.h
+++ b/src/include/catalog/pg_control.h
@@ -21,7 +21,7 @@
/* Version identifier for this pg_control format */
-#define PG_CONTROL_VERSION 1100
+#define PG_CONTROL_VERSION 1200
/* Nonce key length, see below */
#define MOCK_AUTH_NONCE_LEN 32
@@ -177,6 +177,7 @@ typedef struct ControlFileData
bool wal_log_hints;
int MaxConnections;
int max_worker_processes;
+ int max_wal_senders;
int max_prepared_xacts;
int max_locks_per_xact;
bool track_commit_timestamp;
diff --git a/src/include/storage/proc.h b/src/include/storage/proc.h
index d203acbb30b..1cee7db89df 100644
--- a/src/include/storage/proc.h
+++ b/src/include/storage/proc.h
@@ -255,6 +255,8 @@ typedef struct PROC_HDR
PGPROC *autovacFreeProcs;
/* Head of list of bgworker free PGPROC structures */
PGPROC *bgworkerFreeProcs;
+ /* Head of list of walsender free PGPROC structures */
+ PGPROC *walsenderFreeProcs;
/* First pgproc waiting for group XID clear */
pg_atomic_uint32 procArrayGroupFirst;
/* First pgproc waiting for group transaction status update */