From 109f056e257aba70dddc8d466767ed0a1db371e2 Mon Sep 17 00:00:00 2001 From: Kyotaro Horiguchi Date: Tue, 28 Feb 2017 11:39:48 +0900 Subject: [PATCH 1/2] 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 | 39 +++++++++++++++++++++++++++ src/backend/utils/misc/guc.c | 11 ++++++++ src/backend/utils/misc/postgresql.conf.sample | 1 + src/include/access/xlog.h | 1 + 4 files changed, 52 insertions(+) diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index dd028a1..cfdae39 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -105,6 +105,7 @@ 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_mb = 0; #ifdef WAL_DEBUG bool XLOG_DEBUG = false; @@ -9432,9 +9433,47 @@ KeepLogSeg(XLogRecPtr recptr, XLogSegNo *logSegNo) if (max_replication_slots > 0 && keep != InvalidXLogRecPtr) { XLogSegNo slotSegNo; + int slotlimitsegs; + uint64 recptroff; + uint64 slotlimitbytes; + uint64 slotlimitfragment; + + recptroff = XLogSegmentOffset(recptr, wal_segment_size); + slotlimitbytes = 1024 * 1024 * max_slot_wal_keep_size_mb; + slotlimitfragment = XLogSegmentOffset(slotlimitbytes, + wal_segment_size); + + /* calculate segments to keep by max_slot_wal_keep_size_mb */ + slotlimitsegs = ConvertToXSegs(max_slot_wal_keep_size_mb, + wal_segment_size); + /* honor the fragment */ + if (recptroff < slotlimitfragment) + slotlimitsegs++; XLByteToSeg(keep, slotSegNo, wal_segment_size); + /* + * 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) diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c index 65372d7..511023a 100644 --- a/src/backend/utils/misc/guc.c +++ b/src/backend/utils/misc/guc.c @@ -2368,6 +2368,17 @@ 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_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, diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample index 368b280..e76c73a 100644 --- a/src/backend/utils/misc/postgresql.conf.sample +++ b/src/backend/utils/misc/postgresql.conf.sample @@ -234,6 +234,7 @@ #max_wal_senders = 10 # max number of walsender processes # (change requires restart) #wal_keep_segments = 0 # in logfile segments; 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 0f2b8bd..f0c0255 100644 --- a/src/include/access/xlog.h +++ b/src/include/access/xlog.h @@ -98,6 +98,7 @@ extern int wal_segment_size; 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; -- 2.9.2