Thank you for the comment.
At Fri, 3 Mar 2017 14:47:20 -0500, Peter Eisentraut
<peter.eisentr...@2ndquadrant.com> wrote in
<ac510b45-7805-7ccc-734c-1b38a6645...@2ndquadrant.com>
> On 3/1/17 19:54, Kyotaro HORIGUCHI wrote:
> >> Please measure it in size, not in number of segments.
> > It was difficult to dicide which is reaaonable but I named it
> > after wal_keep_segments because it has the similar effect.
> >
> > In bytes(or LSN)
> > max_wal_size
> > min_wal_size
> > wal_write_flush_after
> >
> > In segments
> > wal_keep_segments
>
> We have been moving away from measuring in segments. For example,
> checkpoint_segments was replaced by max_wal_size.
>
> Also, with the proposed patch that allows changing the segment size more
> easily, this will become more important. (I wonder if that will require
> wal_keep_segments to change somehow.)
Agreed. It is 'max_slot_wal_keep_size' in the new version.
wal_keep_segments might should be removed someday.
regards,
--
Kyotaro Horiguchi
NTT Open Source Software Center
>From a646db76ac71ba1bff1105d55b8042fb451022bf Mon Sep 17 00:00:00 2001
From: Kyotaro Horiguchi <horiguchi.kyot...@lab.ntt.co.jp>
Date: Tue, 28 Feb 2017 11:39:48 +0900
Subject: [PATCH] Add WAL releaf vent for replication slots
Adds a capability to limit the number of segments kept by replication
slots by a GUC variable.
---
src/backend/access/transam/xlog.c | 12 ++++++++++++
src/backend/utils/misc/guc.c | 11 +++++++++++
src/backend/utils/misc/postgresql.conf.sample | 1 +
src/include/access/xlog.h | 1 +
4 files changed, 25 insertions(+)
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 8973583..cb23fbc 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -104,6 +104,7 @@ int wal_level = WAL_LEVEL_MINIMAL;
int CommitDelay = 0; /* precommit delay in microseconds */
int CommitSiblings = 5; /* # concurrent xacts needed to sleep */
int wal_retrieve_retry_interval = 5000;
+int max_slot_wal_keep_size = 0;
#ifdef WAL_DEBUG
bool XLOG_DEBUG = false;
@@ -9267,6 +9268,17 @@ KeepLogSeg(XLogRecPtr recptr, XLogSegNo *logSegNo)
XLByteToSeg(keep, slotSegNo);
+ /* emergency vent */
+ if (max_slot_wal_keep_size > 0 &&
+ segno - slotSegNo > max_slot_wal_keep_size)
+ {
+ ereport(WARNING,
+ (errmsg ("restart LSN of replication slots is ignored by checkpoint"),
+ errdetail("Some replication slots lose required WAL segnents to continue.")));
+ /* slotSegNo cannot be negative here */
+ slotSegNo = segno - max_slot_wal_keep_size;
+ }
+
if (slotSegNo <= 0)
segno = 1;
else if (slotSegNo < segno)
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 0707f66..20fe29a 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -2335,6 +2335,17 @@ static struct config_int ConfigureNamesInt[] =
},
{
+ {"max_slot_wal_keep_size", PGC_SIGHUP, REPLICATION_SENDING,
+ gettext_noop("Sets the maximum size of extra WALs kept by replication slots."),
+ NULL,
+ GUC_UNIT_XSEGS
+ },
+ &max_slot_wal_keep_size,
+ 0, 0, INT_MAX,
+ NULL, NULL, NULL
+ },
+
+ {
{"wal_sender_timeout", PGC_SIGHUP, REPLICATION_SENDING,
gettext_noop("Sets the maximum time to wait for WAL replication."),
NULL,
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 157d775..93e2f13 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -233,6 +233,7 @@
#max_wal_senders = 10 # max number of walsender processes
# (change requires restart)
#wal_keep_segments = 0 # in logfile segments, 16MB each; 0 disables
+#max_slot_wal_keep_size = 0 # measured in bytes; 0 disables
#wal_sender_timeout = 60s # in milliseconds; 0 disables
#max_replication_slots = 10 # max number of replication slots
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index 9f036c7..93ee819 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -97,6 +97,7 @@ extern bool reachedConsistency;
extern int min_wal_size;
extern int max_wal_size;
extern int wal_keep_segments;
+extern int max_slot_wal_keep_size;
extern int XLOGbuffers;
extern int XLogArchiveTimeout;
extern int wal_retrieve_retry_interval;
--
2.9.2
--
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