On Tue, Oct 25, 2016 at 10:35 PM, Michael Paquier
<michael.paqu...@gmail.com> wrote:
> On Mon, Oct 17, 2016 at 4:00 PM, Masahiko Sawada <sawada.m...@gmail.com>
> wrote:
>> Attached latest patch.
>> Please review it.
>
> Okay, so let's move on with this patch...
Thank you for reviewing this patch.
> + <para>
> + The keyword <literal>ANY</> is omissible, but note that there is
> + not compatibility between <productname>PostgreSQL</> version 10 and
> + 9.6 or before. For example, <literal>1 (s1, s2)</> is the same as
> the
> + configuration with <literal>FIRST</> and <replaceable
> class="parameter">
> + num_sync</replaceable> equal to 1 in <productname>PostgreSQL</> 9.6
> + or before. On the other hand, It's the same as the configuration
> with
> + <literal>ANY</> and <replaceable
> class="parameter">num_sync</> equal to
> + 1 in <productname>PostgreSQL</> 10 or later.
> + </para>
> This paragraph could be reworded:
> If FIRST or ANY are not specified, this parameter behaves as ANY. Note
> that this grammar is incompatible with PostgreSQL 9.6, where no
> keyword specified is equivalent as if FIRST was specified.
> In short, there is no real need to specify num_sync as this behavior
> does not have changed, as well as it is not necessary to mention
> pre-9.6 versions as the multi-sync grammar has been added in 9.6.
Fixed.
> - Specifying more than one standby name can allow very high
> availability.
> Why removing this sentence?
>
> + The keyword <literal>ANY</>, coupeld with an interger number N,
> s/coupeld/coupled/ and s/interger/integer/, for a double hit in one
> line, still...
>
> + The keyword <literal>ANY</>, coupeld with an interger number N,
> + chooses N standbys in a set of standbys with the same, lowest,
> + priority and makes transaction commit when WAL records are received
> + those N standbys.
> This could be reworded more simply, for example: The keyword ANY,
> coupled with an integer number N, makes transaction commits wait until
> WAL records are received from N connected standbys among those defined
> in the list of synchronous_standby_names.
>
> + <literal>s2</> and <literal>s3</> wil be considered as synchronous
> standby
> s/wil/will/
>
> + when standby is considered as a condidate of quorum commit.</entry>
> s/condidate/candidate/
>
> [... stopping here ...] Please be more careful with the documentation
> and comment grammar. There are other things in the patch..
I fix some typo as much as I found.
> A bunch of comments at the top of syncrep.c need to be updated.
>
> +extern List *SyncRepGetSyncStandbysPriority(bool *am_sync);
> +extern List *SyncRepGetSyncStandbysQuorum(bool *am_sync);
> Those two should be static routines in syncrep.c, let's keep the whole
> logic about quorum and higher-priority definition only there and not
> bother the callers of them about that.
Fixed.
> + if (SyncRepConfig->sync_method == SYNC_REP_PRIORITY)
> + return SyncRepGetSyncStandbysPriority(am_sync);
> + else /* SYNC_REP_QUORUM */
> + return SyncRepGetSyncStandbysQuorum(am_sync);
> Both routines share the same logic to detect if a WAL sender can be
> selected as a candidate for sync evaluation or not, still per the
> selection they do I agree that it is better to keep them as separate.
>
> + /* In quroum method, all sync standby priorities are always 1 */
> + if (found && SyncRepConfig->sync_method == SYNC_REP_QUORUM)
> + priority = 1;
> Honestly I don't understand why you are enforcing that. Priority can
> be important for users willing to switch from ANY to FIRST to have a
> look immediately at what are the standbys that would become sync or
> potential.
I thought that since all standbys appearing in s_s_names list are
treated equally in quorum method, these standbys should have same
priority.
If these standby have different sync_priority, it looks like that
master server replicates to standby server based on priority.
> else if (list_member_int(sync_standbys, i))
> - values[7] = CStringGetTextDatum("sync");
> + values[7] = SyncRepConfig->sync_method == SYNC_REP_PRIORITY ?
> + CStringGetTextDatum("sync") :
> CStringGetTextDatum("quorum");
> The comment at the top of this code block needs to be refreshed.
Fixed.
> The representation given to the user in pg_stat_replication is not
> enough IMO. For example, imagine a cluster with 4 standbys:
> =# select application_name, sync_priority, sync_state from
> pg_stat_replication ;
> application_name | sync_priority | sync_state
> ------------------+---------------+------------
> node_5433 | 0 | async
> node_5434 | 0 | async
> node_5435 | 0 | async
> node_5436 | 0 | async
> (4 rows)
>
> If FIRST N is used, is it easy for the user to understand what are the
> nodes in sync:
> =# alter system set synchronous_standby_names = 'FIRST 2 (node_5433,
> node_5434, node_5435)';
> ALTER SYSTEM
> =# select pg_reload_conf();
> pg_reload_conf
> ----------------
> t
> (1 row)
> =# select application_name, sync_priority, sync_state from
> pg_stat_replication ;
> application_name | sync_priority | sync_state
> ------------------+---------------+------------
> node_5433 | 1 | sync
> node_5434 | 2 | sync
> node_5435 | 3 | potential
> node_5436 | 0 | async
> (4 rows)
>
> In this case it is easy to understand that two nodes are required to be in
> sync.
>
> When using ANY similarly for three nodes, here is what
> pg_stat_replication tells:
> =# select application_name, sync_priority, sync_state from
> pg_stat_replication ;
> application_name | sync_priority | sync_state
> ------------------+---------------+------------
> node_5433 | 1 | quorum
> node_5434 | 1 | quorum
> node_5435 | 1 | quorum
> node_5436 | 0 | async
> (4 rows)
>
> It is not possible to guess from how many standbys this needs to wait
> for. One idea would be to mark the sync_state not as "quorum", but
> "quorum-N", or just add a new column to indicate how many in the set
> need to give a commit confirmation.
As Simon suggested before, we could support another feature that
allows the client to control the quorum number.
Considering adding that feature, I thought it's better to have and
control that information as a GUC parameter.
Thought?
Attached latest v5 patch.
Please review it.
Regards,
--
Masahiko Sawada
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index adab2f8..8078cda 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -3028,42 +3028,76 @@ include_dir 'conf.d'
transactions waiting for commit will be allowed to proceed after
these standby servers confirm receipt of their data.
The synchronous standbys will be those whose names appear
- earlier in this list, and
+ in this list, and
that are both currently connected and streaming data in real-time
(as shown by a state of <literal>streaming</literal> in the
<link linkend="monitoring-stats-views-table">
- <literal>pg_stat_replication</></link> view).
- Other standby servers appearing later in this list represent potential
- synchronous standbys. If any of the current synchronous
- standbys disconnects for whatever reason,
- it will be replaced immediately with the next-highest-priority standby.
- Specifying more than one standby name can allow very high availability.
+ <literal>pg_stat_replication</></link> view). If the keyword
+ <literal>FIRST</> is specified, other standby servers appearing
+ later in this list represent potential synchronous standbys.
+ If any of the current synchronous standbys disconnects for
+ whatever reason, it will be replaced immediately with the
+ next-highest-priority standby. Specifying more than one standby
+ name can allow very high availability.
</para>
<para>
This parameter specifies a list of standby servers using
either of the following syntaxes:
<synopsis>
-<replaceable class="parameter">num_sync</replaceable> ( <replaceable class="parameter">standby_name</replaceable> [, ...] )
+[ANY] <replaceable class="parameter">num_sync</replaceable> ( <replaceable class="parameter">standby_name</replaceable> [, ...] )
+FIRST <replaceable class="parameter">num_sync</replaceable> ( <replaceable class="parameter">standby_name</replaceable> [, ...] )
<replaceable class="parameter">standby_name</replaceable> [, ...]
</synopsis>
where <replaceable class="parameter">num_sync</replaceable> is
the number of synchronous standbys that transactions need to
wait for replies from,
and <replaceable class="parameter">standby_name</replaceable>
- is the name of a standby server. For example, a setting of
- <literal>3 (s1, s2, s3, s4)</> makes transaction commits wait
- until their WAL records are received by three higher-priority standbys
- chosen from standby servers <literal>s1</>, <literal>s2</>,
- <literal>s3</> and <literal>s4</>.
+ is the name of a standby server.
+ <literal>FIRST</> and <literal>ANY</> specify the method of
+ that how master server controls the standby servers.
</para>
<para>
- The second syntax was used before <productname>PostgreSQL</>
+ The keyword <literal>FIRST</>, coupled with an integer
+ number N higher-priority standbys and makes transaction commit
+ when their WAL records are received.
+ For example, a setting of <literal>FIRST 3 (s1, s2, s3, s4)</>
+ makes transaction commits wait until their WAL records are received
+ by three higher-priority standbys chosen from standby servers
+ <literal>s1</>, <literal>s2</>, <literal>s3</> and <literal>s4</>.
+ </para>
+ <para>
+ The keyword <literal>ANY</>, coupled with an integer number N,
+ makes transaction commits wait until WAL records are received
+ from N connected standbys among those defined in the list of
+ <varname>synchronous_standby_names</>. For example, a setting
+ of <literal>ANY 3 (s1, s2, s3, s4)</> makes transaction commits
+ wait until receiving receipts from at least any three standbys
+ of four listed servers <literal>s1</>, <literal>s2</>, <literal>s3</>,
+ <literal>s4</>.
+ </para>
+ <para>
+ <literal>FIRST</> and <literal>ANY</> are case-insensitive word
+ and the standby name having these words are must be double-quoted.
+ </para>
+ <para>
+ The third syntax was used before <productname>PostgreSQL</>
version 9.6 and is still supported. It's the same as the first syntax
- with <replaceable class="parameter">num_sync</replaceable> equal to 1.
- For example, <literal>1 (s1, s2)</> and
- <literal>s1, s2</> have the same meaning: either <literal>s1</>
- or <literal>s2</> is chosen as a synchronous standby.
- </para>
+ with <literal>FIRST</> and <replaceable class="parameter">num_sync</replaceable>
+ equal to 1. For example, <literal>FIRST 1 (s1, s2)</> and <literal>s1, s2</>
+ have the same meaning: either <literal>s1</> or <literal>s2</> is
+ chosen as a synchronous standby.
+ </para>
+ <note>
+ <para>
+ If <literal>FIRST</> or <literal>ANY</> are not specified, this parameter
+ behaves as <literal>ANY</>. Note that this grammar is incompatible with
+ <productname>PostgresSQL</> 9.6, where no keyword specified is equivalent
+ as if <literal>FIRST</> was specified. In short, there is no real need to
+ specify <replaceable class="parameter">num_sync</replaceable> as this
+ behavior does not have changed, as well as it is not necessary to mention
+ pre-9.6 versions are the multi-sync grammar has been added in 9.6.
+ </para>
+ </note>
<para>
The name of a standby server for this purpose is the
<varname>application_name</> setting of the standby, as set in the
diff --git a/doc/src/sgml/high-availability.sgml b/doc/src/sgml/high-availability.sgml
index 5bedaf2..7a0a22a 100644
--- a/doc/src/sgml/high-availability.sgml
+++ b/doc/src/sgml/high-availability.sgml
@@ -1150,7 +1150,7 @@ primary_slot_name = 'node_a_slot'
An example of <varname>synchronous_standby_names</> for multiple
synchronous standbys is:
<programlisting>
-synchronous_standby_names = '2 (s1, s2, s3)'
+synchronous_standby_names = 'FIRST 2 (s1, s2, s3)'
</programlisting>
In this example, if four standby servers <literal>s1</>, <literal>s2</>,
<literal>s3</> and <literal>s4</> are running, the two standbys
@@ -1161,6 +1161,18 @@ synchronous_standby_names = '2 (s1, s2, s3)'
<literal>s2</> fails. <literal>s4</> is an asynchronous standby since
its name is not in the list.
</para>
+ <para>
+ Another example of <varname>synchronous_standby_names</> for multiple
+ synchronous standby is:
+<programlisting>
+ synchronous_standby_names = 'ANY 2 (s1, s2, s3)'
+</programlisting>
+ In this example, if four standby servers <literal>s1</>, <literal>s2</>,
+ <literal>s3</> and <literal>s4</> are running, the three standbys <literal>s1</>,
+ <literal>s2</> and <literal>s3</> will be considered as synchronous standby
+ candidates. The master server will wait for at least 2 replies from them.
+ <literal>s4</> is an asynchronous standby since its name is not in the list.
+ </para>
</sect3>
<sect3 id="synchronous-replication-performance">
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3de489e..b44dadb 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -1389,7 +1389,10 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
<row>
<entry><structfield>sync_state</></entry>
<entry><type>text</></entry>
- <entry>Synchronous state of this standby server</entry>
+ <entry>Synchronous state of this standby server. <literal>quorum-N</>
+ , where N is the number of synchronous standbys that transactions
+ need to wait for replies from, when standby is considered as a
+ candidate of quorum commit.</entry>
</row>
</tbody>
</tgroup>
diff --git a/src/backend/replication/Makefile b/src/backend/replication/Makefile
index c99717e..da8bcf0 100644
--- a/src/backend/replication/Makefile
+++ b/src/backend/replication/Makefile
@@ -26,7 +26,7 @@ repl_gram.o: repl_scanner.c
# syncrep_scanner is complied as part of syncrep_gram
syncrep_gram.o: syncrep_scanner.c
-syncrep_scanner.c: FLEXFLAGS = -CF -p
+syncrep_scanner.c: FLEXFLAGS = -CF -p -i
syncrep_scanner.c: FLEX_NO_BACKUP=yes
# repl_gram.c, repl_scanner.c, syncrep_gram.c and syncrep_scanner.c
diff --git a/src/backend/replication/syncrep.c b/src/backend/replication/syncrep.c
index ac29f56..74093cd 100644
--- a/src/backend/replication/syncrep.c
+++ b/src/backend/replication/syncrep.c
@@ -31,16 +31,19 @@
*
* In 9.5 or before only a single standby could be considered as
* synchronous. In 9.6 we support multiple synchronous standbys.
- * The number of synchronous standbys that transactions must wait for
- * replies from is specified in synchronous_standby_names.
- * This parameter also specifies a list of standby names,
- * which determines the priority of each standby for being chosen as
- * a synchronous standby. The standbys whose names appear earlier
- * in the list are given higher priority and will be considered as
- * synchronous. Other standby servers appearing later in this list
- * represent potential synchronous standbys. If any of the current
- * synchronous standbys disconnects for whatever reason, it will be
- * replaced immediately with the next-highest-priority standby.
+ * In 10.0 we support two synchronization methods, priority and
+ * quorum. The number of synchronous standbys that transactions
+ * must wait for replies from and synchronization method are specified
+ * in synchronous_standby_names. This parameter also specifies a list
+ * of standby names, which determines the priority of each standby for
+ * being chosen as a synchronous standby. In priority method, the standbys
+ * whose names appear earlier in the list are given higher priority
+ * and will be considered as synchronous. Other standby servers appearing
+ * later in this list represent potential synchronous standbys. If any of
+ * the current synchronous standbys disconnects for whatever reason,
+ * it will be replaced immediately with the next-highest-priority standby.
+ * In quorum method, the all standbys appearing in the list are
+ * considered as a candidate for quorum commit.
*
* Before the standbys chosen from synchronous_standby_names can
* become the synchronous standbys they must have caught up with
@@ -73,24 +76,27 @@
/* User-settable parameters for sync rep */
char *SyncRepStandbyNames;
+SyncRepConfigData *SyncRepConfig = NULL;
#define SyncStandbysDefined() \
(SyncRepStandbyNames != NULL && SyncRepStandbyNames[0] != '\0')
static bool announce_next_takeover = true;
-static SyncRepConfigData *SyncRepConfig = NULL;
static int SyncRepWaitMode = SYNC_REP_NO_WAIT;
static void SyncRepQueueInsert(int mode);
static void SyncRepCancelWait(void);
static int SyncRepWakeQueue(bool all, int mode);
-static bool SyncRepGetOldestSyncRecPtr(XLogRecPtr *writePtr,
- XLogRecPtr *flushPtr,
- XLogRecPtr *applyPtr,
- bool *am_sync);
+static bool SyncRepGetSyncRecPtr(XLogRecPtr *writePtr,
+ XLogRecPtr *flushPtr,
+ XLogRecPtr *applyPtr,
+ bool *am_sync);
static int SyncRepGetStandbyPriority(void);
+static List *SyncRepGetSyncStandbysPriority(bool *am_sync);
+static List *SyncRepGetSyncStandbysQuorum(bool *am_sync);
+static int cmp_lsn(const void *a, const void *b);
#ifdef USE_ASSERT_CHECKING
static bool SyncRepQueueIsOrderedByLSN(int mode);
@@ -386,7 +392,7 @@ SyncRepReleaseWaiters(void)
XLogRecPtr writePtr;
XLogRecPtr flushPtr;
XLogRecPtr applyPtr;
- bool got_oldest;
+ bool got_recptr;
bool am_sync;
int numwrite = 0;
int numflush = 0;
@@ -413,11 +419,10 @@ SyncRepReleaseWaiters(void)
LWLockAcquire(SyncRepLock, LW_EXCLUSIVE);
/*
- * Check whether we are a sync standby or not, and calculate the oldest
- * positions among all sync standbys.
+ * Check whether we are a sync standby or not, and calculate the synced
+ * positions among all sync standbys using method.
*/
- got_oldest = SyncRepGetOldestSyncRecPtr(&writePtr, &flushPtr,
- &applyPtr, &am_sync);
+ got_recptr = SyncRepGetSyncRecPtr(&writePtr, &flushPtr, &applyPtr, &am_sync);
/*
* If we are managing a sync standby, though we weren't prior to this,
@@ -435,7 +440,7 @@ SyncRepReleaseWaiters(void)
* If the number of sync standbys is less than requested or we aren't
* managing a sync standby then just leave.
*/
- if (!got_oldest || !am_sync)
+ if (!got_recptr || !am_sync)
{
LWLockRelease(SyncRepLock);
announce_next_takeover = !am_sync;
@@ -471,17 +476,45 @@ SyncRepReleaseWaiters(void)
}
/*
- * Calculate the oldest Write, Flush and Apply positions among sync standbys.
+ * Return the list of sync standbys using according to synchronous method,
+ * or NIL if no sync standby is connected. The caller must hold SyncRepLock.
+ *
+ * On return, *am_sync is set to true if this walsender is connecting to
+ * sync standby. Otherwise it's set to false.
+ */
+List *
+SyncRepGetSyncStandbys(bool *am_sync)
+{
+ /* Set default result */
+ if (am_sync != NULL)
+ *am_sync = false;
+
+ /* Quick exit if sync replication is not requested */
+ if (SyncRepConfig == NULL)
+ return NIL;
+
+ if (SyncRepConfig->sync_method == SYNC_REP_PRIORITY)
+ return SyncRepGetSyncStandbysPriority(am_sync);
+ else /* SYNC_REP_QUORUM */
+ return SyncRepGetSyncStandbysQuorum(am_sync);
+}
+
+/*
+ * Calculate the Write, Flush and Apply positions among sync standbys.
*
* Return false if the number of sync standbys is less than
* synchronous_standby_names specifies. Otherwise return true and
- * store the oldest positions into *writePtr, *flushPtr and *applyPtr.
+ * store the positions into *writePtr, *flushPtr and *applyPtr.
+ *
+ * In priority method, we need the oldest these positions among sync
+ * standbys. In quorum method, we need the newest these positions
+ * specified by SyncRepConfig->num_sync.
*
* On return, *am_sync is set to true if this walsender is connecting to
* sync standby. Otherwise it's set to false.
*/
static bool
-SyncRepGetOldestSyncRecPtr(XLogRecPtr *writePtr, XLogRecPtr *flushPtr,
+SyncRepGetSyncRecPtr(XLogRecPtr *writePtr, XLogRecPtr *flushPtr,
XLogRecPtr *applyPtr, bool *am_sync)
{
List *sync_standbys;
@@ -507,29 +540,74 @@ SyncRepGetOldestSyncRecPtr(XLogRecPtr *writePtr, XLogRecPtr *flushPtr,
return false;
}
- /*
- * Scan through all sync standbys and calculate the oldest Write, Flush
- * and Apply positions.
- */
- foreach(cell, sync_standbys)
+ if (SyncRepConfig->sync_method == SYNC_REP_PRIORITY)
{
- WalSnd *walsnd = &WalSndCtl->walsnds[lfirst_int(cell)];
- XLogRecPtr write;
- XLogRecPtr flush;
- XLogRecPtr apply;
-
- SpinLockAcquire(&walsnd->mutex);
- write = walsnd->write;
- flush = walsnd->flush;
- apply = walsnd->apply;
- SpinLockRelease(&walsnd->mutex);
-
- if (XLogRecPtrIsInvalid(*writePtr) || *writePtr > write)
- *writePtr = write;
- if (XLogRecPtrIsInvalid(*flushPtr) || *flushPtr > flush)
- *flushPtr = flush;
- if (XLogRecPtrIsInvalid(*applyPtr) || *applyPtr > apply)
- *applyPtr = apply;
+ /*
+ * Scan through all sync standbys and calculate the oldest
+ * Write, Flush and Apply positions.
+ */
+ foreach (cell, sync_standbys)
+ {
+ WalSnd *walsnd = &WalSndCtl->walsnds[lfirst_int(cell)];
+ XLogRecPtr write;
+ XLogRecPtr flush;
+ XLogRecPtr apply;
+
+ SpinLockAcquire(&walsnd->mutex);
+ write = walsnd->write;
+ flush = walsnd->flush;
+ apply = walsnd->apply;
+ SpinLockRelease(&walsnd->mutex);
+
+ if (XLogRecPtrIsInvalid(*writePtr) || *writePtr > write)
+ *writePtr = write;
+ if (XLogRecPtrIsInvalid(*flushPtr) || *flushPtr > flush)
+ *flushPtr = flush;
+ if (XLogRecPtrIsInvalid(*applyPtr) || *applyPtr > apply)
+ *applyPtr = apply;
+ }
+ }
+ else /* SYNC_REP_QUORUM */
+ {
+ XLogRecPtr *write_array;
+ XLogRecPtr *flush_array;
+ XLogRecPtr *apply_array;
+ int len;
+ int i = 0;
+
+ len = list_length(sync_standbys);
+ write_array = (XLogRecPtr *) palloc(sizeof(XLogRecPtr) * len);
+ flush_array = (XLogRecPtr *) palloc(sizeof(XLogRecPtr) * len);
+ apply_array = (XLogRecPtr *) palloc(sizeof(XLogRecPtr) * len);
+
+ foreach (cell, sync_standbys)
+ {
+ WalSnd *walsnd = &WalSndCtl->walsnds[lfirst_int(cell)];
+
+ SpinLockAcquire(&walsnd->mutex);
+ write_array[i] = walsnd->write;
+ flush_array[i]= walsnd->flush;
+ apply_array[i] = walsnd->flush;
+ SpinLockRelease(&walsnd->mutex);
+
+ i++;
+ }
+
+ qsort(write_array, len, sizeof(XLogRecPtr), cmp_lsn);
+ qsort(flush_array, len, sizeof(XLogRecPtr), cmp_lsn);
+ qsort(apply_array, len, sizeof(XLogRecPtr), cmp_lsn);
+
+ /*
+ * Get N-th newest Write, Flush, Apply positions
+ * specified by SyncRepConfig->num_sync.
+ */
+ *writePtr = write_array[SyncRepConfig->num_sync - 1];
+ *flushPtr = flush_array[SyncRepConfig->num_sync - 1];
+ *applyPtr = apply_array[SyncRepConfig->num_sync - 1];
+
+ pfree(write_array);
+ pfree(flush_array);
+ pfree(apply_array);
}
list_free(sync_standbys);
@@ -537,17 +615,66 @@ SyncRepGetOldestSyncRecPtr(XLogRecPtr *writePtr, XLogRecPtr *flushPtr,
}
/*
- * Return the list of sync standbys, or NIL if no sync standby is connected.
+ * Return the list of sync standbys using quorum method, or
+ * NIL if no sync standby is connected. In quorum method, all standby
+ * priorities are same, that is 1. So this function returns the list of
+ * standbys except for the standbys which are not active, or connected
+ * as async.
*
- * If there are multiple standbys with the same priority,
+ * On return, *am_sync is set to true if this walsender is connecting to
+ * sync standby. Otherwise it's set to false.
+ */
+static List *
+SyncRepGetSyncStandbysQuorum(bool *am_sync)
+{
+ List *result = NIL;
+ int i;
+
+ Assert(SyncRepConfig->sync_method == SYNC_REP_QUORUM);
+
+ for (i = 0; i < max_wal_senders; i++)
+ {
+ volatile WalSnd *walsnd = &WalSndCtl->walsnds[i];
+
+ /* Must be active */
+ if (walsnd->pid == 0)
+ continue;
+
+ /* Must be streaming */
+ if (walsnd->state != WALSNDSTATE_STREAMING)
+ continue;
+
+ /* Must be synchronous */
+ if (walsnd->sync_standby_priority == 0)
+ continue;
+
+ /* Must have a valid flush position */
+ if (XLogRecPtrIsInvalid(walsnd->flush))
+ continue;
+
+ /*
+ * Consider this standby as candidate of sync and append
+ * it to the result.
+ */
+ result = lappend_int(result, i);
+ if (am_sync != NULL && walsnd == MyWalSnd)
+ *am_sync = true;
+ }
+
+ return result;
+}
+
+/*
+ * Return the list of sync standbys using priority method, or
+ * NIL if no sync standby is connected. In priority method,
+ * if there are multiple standbys with the same priority,
* the first one found is selected preferentially.
- * The caller must hold SyncRepLock.
*
* On return, *am_sync is set to true if this walsender is connecting to
* sync standby. Otherwise it's set to false.
*/
-List *
-SyncRepGetSyncStandbys(bool *am_sync)
+static List *
+SyncRepGetSyncStandbysPriority(bool *am_sync)
{
List *result = NIL;
List *pending = NIL;
@@ -560,13 +687,7 @@ SyncRepGetSyncStandbys(bool *am_sync)
volatile WalSnd *walsnd; /* Use volatile pointer to prevent code
* rearrangement */
- /* Set default result */
- if (am_sync != NULL)
- *am_sync = false;
-
- /* Quick exit if sync replication is not requested */
- if (SyncRepConfig == NULL)
- return NIL;
+ Assert(SyncRepConfig->sync_method == SYNC_REP_PRIORITY);
lowest_priority = SyncRepConfig->nmembers;
next_highest_priority = lowest_priority + 1;
@@ -749,6 +870,10 @@ SyncRepGetStandbyPriority(void)
standby_name += strlen(standby_name) + 1;
}
+ /* In quorum method, all sync standby priorities are always 1 */
+ if (found && SyncRepConfig->sync_method == SYNC_REP_QUORUM)
+ priority = 1;
+
return (found ? priority : 0);
}
@@ -892,6 +1017,23 @@ SyncRepQueueIsOrderedByLSN(int mode)
#endif
/*
+ * Compare lsn in order to sort array in descending order.
+ */
+static int
+cmp_lsn(const void *a, const void *b)
+{
+ XLogRecPtr lsn1 = *((const XLogRecPtr *) a);
+ XLogRecPtr lsn2 = *((const XLogRecPtr *) b);
+
+ if (lsn1 > lsn2)
+ return -1;
+ else if (lsn1 == lsn2)
+ return 0;
+ else
+ return 1;
+}
+
+/*
* ===========================================================
* Synchronous Replication functions executed by any process
* ===========================================================
diff --git a/src/backend/replication/syncrep_gram.y b/src/backend/replication/syncrep_gram.y
index 35c2776..e10be8b 100644
--- a/src/backend/replication/syncrep_gram.y
+++ b/src/backend/replication/syncrep_gram.y
@@ -21,7 +21,7 @@ SyncRepConfigData *syncrep_parse_result;
char *syncrep_parse_error_msg;
static SyncRepConfigData *create_syncrep_config(const char *num_sync,
- List *members);
+ List *members, int sync_method);
/*
* Bison doesn't allocate anything that needs to live across parser calls,
@@ -46,7 +46,7 @@ static SyncRepConfigData *create_syncrep_config(const char *num_sync,
SyncRepConfigData *config;
}
-%token <str> NAME NUM JUNK
+%token <str> NAME NUM JUNK ANY FIRST
%type <config> result standby_config
%type <list> standby_list
@@ -60,8 +60,10 @@ result:
;
standby_config:
- standby_list { $$ = create_syncrep_config("1", $1); }
- | NUM '(' standby_list ')' { $$ = create_syncrep_config($1, $3); }
+ standby_list { $$ = create_syncrep_config("1", $1, SYNC_REP_PRIORITY); }
+ | NUM '(' standby_list ')' { $$ = create_syncrep_config($1, $3, SYNC_REP_QUORUM); }
+ | ANY NUM '(' standby_list ')' { $$ = create_syncrep_config($2, $4, SYNC_REP_QUORUM); }
+ | FIRST NUM '(' standby_list ')' { $$ = create_syncrep_config($2, $4, SYNC_REP_PRIORITY); }
;
standby_list:
@@ -77,7 +79,7 @@ standby_name:
static SyncRepConfigData *
-create_syncrep_config(const char *num_sync, List *members)
+create_syncrep_config(const char *num_sync, List *members, int sync_method)
{
SyncRepConfigData *config;
int size;
@@ -98,6 +100,7 @@ create_syncrep_config(const char *num_sync, List *members)
config->config_size = size;
config->num_sync = atoi(num_sync);
+ config->sync_method = sync_method;
config->nmembers = list_length(members);
ptr = config->member_names;
foreach(lc, members)
diff --git a/src/backend/replication/syncrep_scanner.l b/src/backend/replication/syncrep_scanner.l
index d20662e..403fd7d 100644
--- a/src/backend/replication/syncrep_scanner.l
+++ b/src/backend/replication/syncrep_scanner.l
@@ -54,6 +54,8 @@ digit [0-9]
ident_start [A-Za-z\200-\377_]
ident_cont [A-Za-z\200-\377_0-9\$]
identifier {ident_start}{ident_cont}*
+any_ident any
+first_ident first
dquote \"
xdstart {dquote}
@@ -64,6 +66,14 @@ xdinside [^"]+
%%
{space}+ { /* ignore */ }
+{any_ident} {
+ yylval.str = pstrdup(yytext);
+ return ANY;
+ }
+{first_ident} {
+ yylval.str = pstrdup(yytext);
+ return FIRST;
+ }
{xdstart} {
initStringInfo(&xdbuf);
BEGIN(xd);
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index bc5e508..ecfbd78 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -2860,12 +2860,14 @@ pg_stat_get_wal_senders(PG_FUNCTION_ARGS)
/*
* More easily understood version of standby state. This is purely
- * informational, not different from priority.
+ * informational. In quorum method, we add the number to indicate
+ * how many in the set need to give a commit confirmation.
*/
if (priority == 0)
values[7] = CStringGetTextDatum("async");
else if (list_member_int(sync_standbys, i))
- values[7] = CStringGetTextDatum("sync");
+ values[7] = SyncRepConfig->sync_method == SYNC_REP_PRIORITY ?
+ CStringGetTextDatum("sync") : CStringGetTextDatum("quorum");
else
values[7] = CStringGetTextDatum("potential");
}
diff --git a/src/include/replication/syncrep.h b/src/include/replication/syncrep.h
index e4e0e27..8dd74a3 100644
--- a/src/include/replication/syncrep.h
+++ b/src/include/replication/syncrep.h
@@ -32,6 +32,10 @@
#define SYNC_REP_WAITING 1
#define SYNC_REP_WAIT_COMPLETE 2
+/* sync_method of SyncRepConfigData */
+#define SYNC_REP_PRIORITY 0
+#define SYNC_REP_QUORUM 1
+
/*
* Struct for the configuration of synchronous replication.
*
@@ -45,10 +49,13 @@ typedef struct SyncRepConfigData
int num_sync; /* number of sync standbys that we need to
* wait for */
int nmembers; /* number of members in the following list */
+ int sync_method; /* synchronization method */
/* member_names contains nmembers consecutive nul-terminated C strings */
char member_names[FLEXIBLE_ARRAY_MEMBER];
} SyncRepConfigData;
+extern SyncRepConfigData *SyncRepConfig;
+
/* communication variables for parsing synchronous_standby_names GUC */
extern SyncRepConfigData *syncrep_parse_result;
extern char *syncrep_parse_error_msg;
diff --git a/src/test/recovery/t/007_sync_rep.pl b/src/test/recovery/t/007_sync_rep.pl
index 0c87226..c6af72f 100644
--- a/src/test/recovery/t/007_sync_rep.pl
+++ b/src/test/recovery/t/007_sync_rep.pl
@@ -3,7 +3,7 @@ use strict;
use warnings;
use PostgresNode;
use TestLib;
-use Test::More tests => 8;
+use Test::More tests => 10;
# Query checking sync_priority and sync_state of each standby
my $check_sql =
@@ -107,7 +107,7 @@ test_sync_state(
$node_master, qq(standby2|2|sync
standby3|3|sync),
'2 synchronous standbys',
- '2(standby1,standby2,standby3)');
+ 'First 2(standby1,standby2,standby3)');
# Start standby1
$node_standby_1->start;
@@ -138,7 +138,7 @@ standby2|4|sync
standby3|3|sync
standby4|1|sync),
'num_sync exceeds the num of potential sync standbys',
- '6(standby4,standby0,standby3,standby2)');
+ 'First 6(standby4,standby0,standby3,standby2)');
# The setting that * comes before another standby name is acceptable
# but does not make sense in most cases. Check that sync_state is
@@ -150,7 +150,7 @@ standby2|2|sync
standby3|2|potential
standby4|2|potential),
'asterisk comes before another standby name',
- '2(standby1,*,standby2)');
+ 'First 2(standby1,*,standby2)');
# Check that the setting of '2(*)' chooses standby2 and standby3 that are stored
# earlier in WalSnd array as sync standbys.
@@ -160,7 +160,7 @@ standby2|1|sync
standby3|1|sync
standby4|1|potential),
'multiple standbys having the same priority are chosen as sync',
- '2(*)');
+ 'First 2(*)');
# Stop Standby3 which is considered in 'sync' state.
$node_standby_3->stop;
@@ -172,3 +172,25 @@ test_sync_state(
standby2|1|sync
standby4|1|potential),
'potential standby found earlier in array is promoted to sync');
+
+# Check that the state of standbys listed as a voter are having
+# same priority when synchronous_standby_names uses quorum method.
+test_sync_state(
+$node_master, qq(standby1|1|quorum
+standby2|1|quorum
+standby4|0|async),
+'2 quorum and 1 async',
+'Any 2(standby1, standby2)');
+
+# Start Standby3 which will be considered in 'quorum' state.
+$node_standby_3->start;
+
+# Check that set setting of 'Any 2(*)' chooses all standbys as
+# voter.
+test_sync_state(
+$node_master, qq(standby1|1|quorum
+standby2|1|quorum
+standby3|1|quorum
+standby4|1|quorum),
+'all standbys are considered as candidates for quorum commit',
+'Any 2(*)');
--
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