Hello,
I'll add this to CF2017-09.
At Mon, 06 Mar 2017 18:20:06 +0900 (Tokyo Standard Time), Kyotaro HORIGUCHI
<[email protected]> wrote in
<[email protected]>
> Thank you for the comment.
>
> At Fri, 3 Mar 2017 14:47:20 -0500, Peter Eisentraut
> <[email protected]> wrote in
> <[email protected]>
> > 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.
- Following to min/max_wal_size, the variable was renamed to
"max_slot_wal_keep_size_mb" and used as ConvertToXSegs(x)"
- Stopped warning when checkpoint doesn't flush segments required
by slots even if max_slot_wal_keep_size have worked.
- Avoided subraction that may be negative.
regards,
*** a/src/backend/access/transam/xlog.c
--- b/src/backend/access/transam/xlog.c
***************
*** 105,110 **** int wal_level = WAL_LEVEL_MINIMAL;
--- 105,111 ----
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_mb = 0;
#ifdef WAL_DEBUG
bool XLOG_DEBUG = false;
***************
*** 9353,9361 **** KeepLogSeg(XLogRecPtr recptr, XLogSegNo *logSegNo)
--- 9354,9385 ----
if (max_replication_slots > 0 && keep != InvalidXLogRecPtr)
{
XLogSegNo slotSegNo;
+ int slotlimitsegs = ConvertToXSegs(max_slot_wal_keep_size_mb);
XLByteToSeg(keep, slotSegNo);
+ /*
+ * ignore slots if too many wal segments are kept.
+ * max_slot_wal_keep_size is just accumulated on wal_keep_segments.
+ */
+ if (max_slot_wal_keep_size_mb > 0 && slotSegNo + slotlimitsegs < segno)
+ {
+ segno = segno - slotlimitsegs; /* must be positive */
+
+ /*
+ * warn only if the checkpoint flushes the required segment.
+ * we assume here that *logSegNo is calculated keep location.
+ */
+ if (slotSegNo < *logSegNo)
+ ereport(WARNING,
+ (errmsg ("restart LSN of replication slots is ignored by checkpoint"),
+ errdetail("Some replication slots have lost required WAL segnents to continue by up to %ld segments.",
+ (segno < *logSegNo ? segno : *logSegNo) - slotSegNo)));
+
+ /* emergency vent */
+ slotSegNo = segno;
+ }
+
if (slotSegNo <= 0)
segno = 1;
else if (slotSegNo < segno)
*** a/src/backend/utils/misc/guc.c
--- b/src/backend/utils/misc/guc.c
***************
*** 2366,2371 **** static struct config_int ConfigureNamesInt[] =
--- 2366,2382 ----
},
{
+ {"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_MB
+ },
+ &max_slot_wal_keep_size_mb,
+ 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,
*** a/src/backend/utils/misc/postgresql.conf.sample
--- b/src/backend/utils/misc/postgresql.conf.sample
***************
*** 235,240 ****
--- 235,241 ----
#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
*** a/src/include/access/xlog.h
--- b/src/include/access/xlog.h
***************
*** 97,102 **** extern bool reachedConsistency;
--- 97,103 ----
extern int min_wal_size_mb;
extern int max_wal_size_mb;
extern int wal_keep_segments;
+ extern int max_slot_wal_keep_size_mb;
extern int XLOGbuffers;
extern int XLogArchiveTimeout;
extern int wal_retrieve_retry_interval;
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