One awkward omission in the new built-in standby mode, mainly used for
streaming replication, is that there is no easy way to delete old
archived files like you do with the %r parameter to restore_command.
This was discussed at
http://archives.postgresql.org/pgsql-hackers/2010-02/msg01003.php, among
other things.
Per discussion, attached patch adds a new restartpoint_command option to
recovery.conf. That's an external shell command just like
recovery_end_command that's executed at every restartpoint. You can use
the %r parameter to pass the filename of the oldest WAL file that needs
to be retained.
While developing this I noticed that %r in recovery_end_command is not
working correctly:
LOG: redo done at 0/14000C10
LOG: last completed transaction was at log time 2000-01-01
02:21:08.816445+02
cp: cannot stat
`/home/hlinnaka/pgsql.cvshead/walarchive/000000010000000000000014': No
such file or directory
cp: cannot stat
`/home/hlinnaka/pgsql.cvshead/walarchive/00000002.history': No such file
or directory
LOG: selected new timeline ID: 2
cp: cannot stat
`/home/hlinnaka/pgsql.cvshead/walarchive/00000001.history': No such file
or directory
LOG: archive recovery complete
LOG: checkpoint starting: end-of-recovery immediate wait
LOG: checkpoint complete: wrote 0 buffers (0.0%); 0 transaction log
file(s) added, 0 removed, 0 recycled; write=0.000 s, sync=0.000 s,
total=0.003 s
LOG: executing recovery_end_command "echo recovery_end_command %r"
recovery_end_command 000000000000000000000000
LOG: database system is ready to accept connections
LOG: autovacuum launcher started
Note how %r is always expanded to 000000000000000000000000. That's
because %r is expanded only when InRedo is true, which makes sense for
restore_command where that piece of code was copy-pasted from, but it's
never true anymore when recovery_end_command is run. The attached patch
fixes that too.
Barring objections, I will commit this later today.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
diff --git a/doc/src/sgml/recovery-config.sgml b/doc/src/sgml/recovery-config.sgml
index 6404768..7b7a8bd 100644
--- a/doc/src/sgml/recovery-config.sgml
+++ b/doc/src/sgml/recovery-config.sgml
@@ -59,14 +59,15 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"' # Windows
</listitem>
</varlistentry>
- <varlistentry id="recovery-end-command" xreflabel="recovery_end_command">
- <term><varname>recovery_end_command</varname> (<type>string</type>)</term>
+ <varlistentry id="restartpoint-command" xreflabel="restartpoint_command">
+ <term><varname>restartpoint_command</varname> (<type>string</type>)</term>
<listitem>
<para>
- This parameter specifies a shell command that will be executed once only
- at the end of recovery. This parameter is optional. The purpose of the
- <varname>recovery_end_command</> is to provide a mechanism for cleanup
- following replication or recovery.
+ This parameter specifies a shell command that will be executed at
+ every restartpoint. This parameter is optional. The purpose of the
+ <varname>restartpoint_command</> is to provide a mechanism for cleaning
+ up old archived WAL files that are no longer needed by the standby
+ server.
Any <literal>%r</> is replaced by the name of the file
containing the last valid restart point. That is the earliest file that
must be kept to allow a restore to be restartable, so this information
@@ -79,6 +80,24 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"' # Windows
</para>
<para>
If the command returns a non-zero exit status then a WARNING log
+ message will be written.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="recovery-end-command" xreflabel="recovery_end_command">
+ <term><varname>recovery_end_command</varname> (<type>string</type>)</term>
+ <listitem>
+ <para>
+ This parameter specifies a shell command that will be executed once only
+ at the end of recovery. This parameter is optional. The purpose of the
+ <varname>recovery_end_command</> is to provide a mechanism for cleanup
+ following replication or recovery.
+ Any <literal>%r</> is replaced by the name of the file containing the
+ last valid restart point, like in <xref linkend="restartpoint-command">.
+ </para>
+ <para>
+ If the command returns a non-zero exit status then a WARNING log
message will be written and the database will proceed to start up
anyway. An exception is that if the command was terminated by a
signal, the database will not proceed with startup.
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 995794a..519526e 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -171,6 +171,7 @@ static bool restoredFromArchive = false;
/* options taken from recovery.conf for archive recovery */
static char *recoveryRestoreCommand = NULL;
static char *recoveryEndCommand = NULL;
+static char *restartPointCommand = NULL;
static bool recoveryTarget = false;
static bool recoveryTargetExact = false;
static bool recoveryTargetInclusive = true;
@@ -370,6 +371,11 @@ typedef struct XLogCtlData
int XLogCacheBlck; /* highest allocated xlog buffer index */
TimeLineID ThisTimeLineID;
TimeLineID RecoveryTargetTLI;
+ /*
+ * restartPointCommand is read from recovery.conf but needs to be in
+ * shared memory so that the bgwriter process can access it.
+ */
+ char restartPointCommand[MAXPGPATH];
/*
* SharedRecoveryInProgress indicates if we're still in crash or archive
@@ -520,7 +526,8 @@ static bool XLogPageRead(XLogRecPtr *RecPtr, int emode, bool fetching_ckpt,
static void XLogFileClose(void);
static bool RestoreArchivedFile(char *path, const char *xlogfname,
const char *recovername, off_t expectedSize);
-static void ExecuteRecoveryEndCommand(void);
+static void ExecuteRecoveryCommand(char *command, char *commandName,
+ bool failOnerror);
static void PreallocXlogFiles(XLogRecPtr endptr);
static void RemoveOldXlogFiles(uint32 log, uint32 seg, XLogRecPtr endptr);
static void ValidateXLOGDirectoryStructure(void);
@@ -2990,12 +2997,19 @@ not_available:
}
/*
- * Attempt to execute the recovery_end_command.
+ * Attempt to execute an external recovery command.
+ *
+ * 'command' is the shell command to be executed, 'commandName' is a human-
+ * readable name describing the command emitted in the logs. If 'failonSignal'
+ * is true and the command is killed by a signal, a FATAL error is thrown.
+ * Otherwise a WARNING is emitted.
+ *
+ * This is currently used for restore_end_command and restartpoint_command.
*/
static void
-ExecuteRecoveryEndCommand(void)
+ExecuteRecoveryCommand(char *command, char *commandName, bool failOnSignal)
{
- char xlogRecoveryEndCmd[MAXPGPATH];
+ char xlogRecoveryCmd[MAXPGPATH];
char lastRestartPointFname[MAXPGPATH];
char *dp;
char *endp;
@@ -3005,7 +3019,7 @@ ExecuteRecoveryEndCommand(void)
uint32 restartLog;
uint32 restartSeg;
- Assert(recoveryEndCommand);
+ Assert(command && commandName);
/*
* Calculate the archive file cutoff point for use during log shipping
@@ -3023,25 +3037,22 @@ ExecuteRecoveryEndCommand(void)
* flags to signify the point when we can begin deleting WAL files from
* the archive.
*/
- if (InRedo)
- {
- XLByteToSeg(ControlFile->checkPointCopy.redo,
- restartLog, restartSeg);
- XLogFileName(lastRestartPointFname,
- ControlFile->checkPointCopy.ThisTimeLineID,
- restartLog, restartSeg);
- }
- else
- XLogFileName(lastRestartPointFname, 0, 0, 0);
+ LWLockAcquire(ControlFileLock, LW_SHARED);
+ XLByteToSeg(ControlFile->checkPointCopy.redo,
+ restartLog, restartSeg);
+ XLogFileName(lastRestartPointFname,
+ ControlFile->checkPointCopy.ThisTimeLineID,
+ restartLog, restartSeg);
+ LWLockRelease(ControlFileLock);
/*
* construct the command to be executed
*/
- dp = xlogRecoveryEndCmd;
- endp = xlogRecoveryEndCmd + MAXPGPATH - 1;
+ dp = xlogRecoveryCmd;
+ endp = xlogRecoveryCmd + MAXPGPATH - 1;
*endp = '\0';
- for (sp = recoveryEndCommand; *sp; sp++)
+ for (sp = command; *sp; sp++)
{
if (*sp == '%')
{
@@ -3075,13 +3086,12 @@ ExecuteRecoveryEndCommand(void)
*dp = '\0';
ereport(DEBUG3,
- (errmsg_internal("executing recovery end command \"%s\"",
- xlogRecoveryEndCmd)));
+ (errmsg_internal("executing %s \"%s\"", commandName, command)));
/*
* execute the constructed command
*/
- rc = system(xlogRecoveryEndCmd);
+ rc = system(xlogRecoveryCmd);
if (rc != 0)
{
/*
@@ -3091,9 +3101,13 @@ ExecuteRecoveryEndCommand(void)
*/
signaled = WIFSIGNALED(rc) || WEXITSTATUS(rc) > 125;
- ereport(signaled ? FATAL : WARNING,
- (errmsg("recovery_end_command \"%s\": return code %d",
- xlogRecoveryEndCmd, rc)));
+ /*
+ * translator: First %s represents a recovery.conf parameter name like
+ * "recovery_end_command", and the 2nd is the value of that parameter.
+ */
+ ereport((signaled && failOnSignal) ? FATAL : WARNING,
+ (errmsg("%s \"%s\": return code %d", commandName,
+ command, rc)));
}
}
@@ -4936,6 +4950,13 @@ readRecoveryCommandFile(void)
(errmsg("recovery_end_command = '%s'",
recoveryEndCommand)));
}
+ else if (strcmp(tok1, "restartpoint_command") == 0)
+ {
+ restartPointCommand = pstrdup(tok2);
+ ereport(DEBUG2,
+ (errmsg("restartpoint_command = '%s'",
+ restartPointCommand)));
+ }
else if (strcmp(tok1, "recovery_target_timeline") == 0)
{
rtliGiven = true;
@@ -5505,8 +5526,14 @@ StartupXLOG(void)
recoveryTargetTLI,
ControlFile->checkPointCopy.ThisTimeLineID)));
- /* Save the selected recovery target timeline ID in shared memory */
+ /*
+ * Save the selected recovery target timeline ID and restartpoint_command
+ * in shared memory so that other processes can see them
+ */
XLogCtl->RecoveryTargetTLI = recoveryTargetTLI;
+ strncpy(XLogCtl->restartPointCommand,
+ restartPointCommand ? restartPointCommand : "",
+ sizeof(XLogCtl->restartPointCommand));
if (read_backup_label(&checkPointLoc))
{
@@ -6129,7 +6156,9 @@ StartupXLOG(void)
* And finally, execute the recovery_end_command, if any.
*/
if (recoveryEndCommand)
- ExecuteRecoveryEndCommand();
+ ExecuteRecoveryCommand(recoveryEndCommand,
+ "recovery_end_command",
+ true);
}
/*
@@ -7318,6 +7347,15 @@ CreateRestartPoint(int flags)
timestamptz_to_str(GetLatestXLogTime()))));
LWLockRelease(CheckpointLock);
+
+ /*
+ * Finally, execute restartpoint_command, if any.
+ */
+ if (XLogCtl->restartPointCommand[0])
+ ExecuteRecoveryCommand(XLogCtl->restartPointCommand,
+ "restartpoint_command",
+ false);
+
return true;
}
--
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