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Commit217919d

Browse files
author
Amit Kapila
committed
Raise a WARNING for max_slot_wal_keep_size in pg_createsubscriber.
During the pg_createsubscriber execution, it is possible that the requiredWAL is removed from the primary/publisher node due to'max_slot_wal_keep_size'.This patch raises a WARNING during the '--dry-run' mode if the'max_slot_wal_keep_size' is set to a non-default value on theprimary/publisher node.Author: Shubham Khanna <khannashubham1197@gmail.com>Reviewed-by: Peter Smith <smithpb2250@gmail.com>Reviewed-by: Hayato Kuroda <kuroda.hayato@fujitsu.com>Reviewed-by: Vignesh C <vignesh21@gmail.com>Discussion:https://postgr.es/m/CAHv8Rj+deqsQXOMa7Tck8CBQUbsua=+4AuMVQ2=MPM0f-ZHbjA@mail.gmail.com
1 parent53d3daa commit217919d

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2 files changed

+26
-1
lines changed

2 files changed

+26
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lines changed

‎doc/src/sgml/ref/pg_createsubscriber.sgml

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Original file line numberDiff line numberDiff line change
@@ -377,6 +377,13 @@ PostgreSQL documentation
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server. If the target server has a standby, replication will break and a
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fresh standby should be created.
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</para>
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<para>
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Replication failures can occur if required WAL files are missing. To prevent
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this, the source server must set
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<xref linkend="guc-max-slot-wal-keep-size"/> to <literal>-1</literal> to
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ensure that required WAL files are not prematurely removed.
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</para>
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</refsect2>
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<refsect2>

‎src/bin/pg_basebackup/pg_createsubscriber.c

Lines changed: 19 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -849,6 +849,7 @@ check_publisher(const struct LogicalRepInfo *dbinfo)
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intmax_walsenders;
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intcur_walsenders;
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intmax_prepared_transactions;
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char*max_slot_wal_keep_size;
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pg_log_info("checking settings on publisher");
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@@ -872,6 +873,7 @@ check_publisher(const struct LogicalRepInfo *dbinfo)
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* - wal_level = logical
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* - max_replication_slots >= current + number of dbs to be converted
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* - max_wal_senders >= current + number of dbs to be converted
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* - max_slot_wal_keep_size = -1 (to prevent deletion of required WAL files)
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* -----------------------------------------------------------------------
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*/
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res=PQexec(conn,
@@ -880,7 +882,8 @@ check_publisher(const struct LogicalRepInfo *dbinfo)
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" (SELECT count(*) FROM pg_catalog.pg_replication_slots),"
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" pg_catalog.current_setting('max_wal_senders'),"
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" (SELECT count(*) FROM pg_catalog.pg_stat_activity WHERE backend_type = 'walsender'),"
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" pg_catalog.current_setting('max_prepared_transactions')");
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" pg_catalog.current_setting('max_prepared_transactions'),"
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" pg_catalog.current_setting('max_slot_wal_keep_size')");
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if (PQresultStatus(res)!=PGRES_TUPLES_OK)
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{
@@ -895,6 +898,7 @@ check_publisher(const struct LogicalRepInfo *dbinfo)
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max_walsenders=atoi(PQgetvalue(res,0,3));
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cur_walsenders=atoi(PQgetvalue(res,0,4));
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max_prepared_transactions=atoi(PQgetvalue(res,0,5));
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max_slot_wal_keep_size=pg_strdup(PQgetvalue(res,0,6));
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PQclear(res);
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@@ -905,6 +909,8 @@ check_publisher(const struct LogicalRepInfo *dbinfo)
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pg_log_debug("publisher: current wal senders: %d",cur_walsenders);
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pg_log_debug("publisher: max_prepared_transactions: %d",
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max_prepared_transactions);
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pg_log_debug("publisher: max_slot_wal_keep_size: %s",
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max_slot_wal_keep_size);
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disconnect_database(conn, false);
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@@ -939,6 +945,18 @@ check_publisher(const struct LogicalRepInfo *dbinfo)
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"Prepared transactions will be replicated at COMMIT PREPARED.");
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}
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/*
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* Validate 'max_slot_wal_keep_size'. If this parameter is set to a
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* non-default value, it may cause replication failures due to required
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* WAL files being prematurely removed.
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*/
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if (dry_run&& (strcmp(max_slot_wal_keep_size,"-1")!=0))
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{
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pg_log_warning("required WAL could be removed from the publisher");
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pg_log_warning_hint("Set the configuration parameter \"%s\" to -1 to ensure that required WAL files are not prematurely removed.",
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"max_slot_wal_keep_size");
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}
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pg_free(wal_level);
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if (failed)

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