Thanks for suggestions.

Patch updated.


Mon, 22 Dec 2014 12:07:06 +0900 от Michael Paquier <michael.paqu...@gmail.com>:
>On Tue, Nov 4, 2014 at 6:25 AM, Alexey Vasiliev < leopard...@inbox.ru > wrote:
>> Added new patch.
>Seems useful to me to be able to tune this interval of time.
>
>I would simply reword the documentation as follows:
>If <varname>restore_command</> returns nonzero exit status code, retry
>command after the interval of time specified by this parameter.
>Default value is <literal>5s</>.
>
>Also, I think that it would be a good idea to error out if this
>parameter has a value of let's say, less than 1s instead of doing a
>check for a positive value in the waiting latch. On top of that, the
>default value of restore_command_retry_interval should be 5000 and not
>0 to simplify the code.
>-- 
>Michael
>
>
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-- 
Alexey Vasiliev
diff --git a/doc/src/sgml/recovery-config.sgml b/doc/src/sgml/recovery-config.sgml
index ef78bc0..53ccf13 100644
--- a/doc/src/sgml/recovery-config.sgml
+++ b/doc/src/sgml/recovery-config.sgml
@@ -145,6 +145,29 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"'  # Windows
       </listitem>
      </varlistentry>
 
+     <varlistentry id="restore-command-retry-interval" xreflabel="restore_command_retry_interval">
+      <term><varname>restore_command_retry_interval</varname> (<type>integer</type>)
+      <indexterm>
+        <primary><varname>restore_command_retry_interval</> recovery parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        If <varname>restore_command</> returns nonzero exit status code, retry
+        command after the interval of time specified by this parameter.
+        Default value is <literal>5s</>.
+       </para>
+       <para>
+        This is useful, if I using for restore of wal logs some
+        external storage (like AWS S3) and no matter what the slave database
+        will lag behind the master. The problem, what for each request to
+        AWS S3 need to pay, what is why for N nodes, which try to get next
+        wal log each 5 seconds will be bigger price, than for example each
+        30 seconds.
+       </para>
+      </listitem>
+     </varlistentry>
+
     </variablelist>
 
   </sect1>
diff --git a/src/backend/access/transam/recovery.conf.sample b/src/backend/access/transam/recovery.conf.sample
index b777400..7ed6f3b 100644
--- a/src/backend/access/transam/recovery.conf.sample
+++ b/src/backend/access/transam/recovery.conf.sample
@@ -58,6 +58,11 @@
 #
 #recovery_end_command = ''
 #
+# specifies an optional timeout after nonzero code of restore_command.
+# This can be useful to increase/decrease number of a restore_command calls.
+#
+#restore_command_retry_interval = 5s
+#
 #---------------------------------------------------------------------------
 # RECOVERY TARGET PARAMETERS
 #---------------------------------------------------------------------------
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index e5dddd4..02c55a8 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -235,6 +235,7 @@ static TimestampTz recoveryTargetTime;
 static char *recoveryTargetName;
 static int	recovery_min_apply_delay = 0;
 static TimestampTz recoveryDelayUntilTime;
+static int 	restore_command_retry_interval = 5000L;
 
 /* options taken from recovery.conf for XLOG streaming */
 static bool StandbyModeRequested = false;
@@ -4881,6 +4882,28 @@ readRecoveryCommandFile(void)
 					(errmsg_internal("trigger_file = '%s'",
 									 TriggerFile)));
 		}
+		else if (strcmp(item->name, "restore_command_retry_interval") == 0)
+		{
+			const char *hintmsg;
+
+			if (!parse_int(item->value, &restore_command_retry_interval, GUC_UNIT_MS,
+						   &hintmsg))
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("parameter \"%s\" requires a temporal value",
+								"restore_command_retry_interval"),
+						 hintmsg ? errhint("%s", _(hintmsg)) : 0));
+			ereport(DEBUG2,
+					(errmsg_internal("restore_command_retry_interval = '%s'", item->value)));
+
+			if (restore_command_retry_interval <= 0)
+			{
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("\"%s\" must be bigger zero",
+					"restore_command_retry_interval")));
+			}
+		}
 		else if (strcmp(item->name, "recovery_min_apply_delay") == 0)
 		{
 			const char *hintmsg;
@@ -10658,13 +10681,14 @@ WaitForWALToBecomeAvailable(XLogRecPtr RecPtr, bool randAccess,
 					}
 
 					/*
-					 * Wait for more WAL to arrive. Time out after 5 seconds,
+					 * Wait for more WAL to arrive. Time out after
+					 * restore_command_retry_interval (5 seconds by default),
 					 * like when polling the archive, to react to a trigger
 					 * file promptly.
 					 */
 					WaitLatch(&XLogCtl->recoveryWakeupLatch,
 							  WL_LATCH_SET | WL_TIMEOUT,
-							  5000L);
+							  restore_command_retry_interval);
 					ResetLatch(&XLogCtl->recoveryWakeupLatch);
 					break;
 				}
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