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Remove the unnecessary PrepareWrite in pgoutput. 

This issue exists from the inception of this code (PG-10) but got exposed
by the recent commit ce0fdbfe97 where we are using origins in tablesync
workers. The problem was that we were sometimes sending the prepare_write
('w') message but then the actual message was not being sent and on the
subscriber side, we always expect a message after prepare_write message
which led to this bug.

I refrained from backpatching this because there is no way in the core
code to hit this prior to commit ce0fdbfe97 and we haven't received any
complaints so far.

Reported-by: Erik Rijkers
Author: Amit Kapila and Vignesh C
Tested-by: Erik Rijkers
Discussion: https://postgr.es/m/1295168140.139428.1613133237154@webmailclassic.xs4all.nl
This commit is contained in:
Amit Kapila 2021-02-16 07:26:50 +05:30
parent 8001cb77ee
commit f672df5fdd
2 changed files with 80 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
src/backend/replication/pgoutput/pgoutput.c
View File

@ -342,10 +342,6 @@ pgoutput_begin_txn(LogicalDecodingContext *ctx, ReorderBufferTXN *txn)
{
char *origin;
/* Message boundary */
OutputPluginWrite(ctx, false);
OutputPluginPrepareWrite(ctx, true);
/*----------
* XXX: which behaviour do we want here?
*
@ -357,7 +353,13 @@ pgoutput_begin_txn(LogicalDecodingContext *ctx, ReorderBufferTXN *txn)
*----------
*/
if (replorigin_by_oid(txn->origin_id, true, &origin))
{
/* Message boundary */
OutputPluginWrite(ctx, false);
OutputPluginPrepareWrite(ctx, true);
logicalrep_write_origin(ctx->out, origin, txn->origin_lsn);
}
}
OutputPluginWrite(ctx, true);
@ -780,12 +782,13 @@ pgoutput_stream_start(struct LogicalDecodingContext *ctx,
{
char *origin;
/* Message boundary */
OutputPluginWrite(ctx, false);
OutputPluginPrepareWrite(ctx, true);
if (replorigin_by_oid(txn->origin_id, true, &origin))
{
/* Message boundary */
OutputPluginWrite(ctx, false);
OutputPluginPrepareWrite(ctx, true);
logicalrep_write_origin(ctx->out, origin, InvalidXLogRecPtr);
}
}
OutputPluginWrite(ctx, true);

69
src/test/subscription/t/100_bugs.pl
View File

@ -153,3 +153,72 @@ is($node_twoways->safe_psql('d2', "SELECT count(f) FROM t"),
$rows * 2, "2x$rows rows in t");
is($node_twoways->safe_psql('d2', "SELECT count(f) FROM t2"),
$rows * 2, "2x$rows rows in t2");
# Verify table data is synced with cascaded replication setup. This is mainly
# to test whether the data written by tablesync worker gets replicated.
my $node_pub = get_new_node('testpublisher1');
$node_pub->init(allows_streaming => 'logical');
$node_pub->start;
my $node_pub_sub = get_new_node('testpublisher_subscriber');
$node_pub_sub->init(allows_streaming => 'logical');
$node_pub_sub->start;
my $node_sub = get_new_node('testsubscriber1');
$node_sub->init(allows_streaming => 'logical');
$node_sub->start;
# Create the tables in all nodes.
$node_pub->safe_psql('postgres', "CREATE TABLE tab1 (a int)");
$node_pub_sub->safe_psql('postgres', "CREATE TABLE tab1 (a int)");
$node_sub->safe_psql('postgres', "CREATE TABLE tab1 (a int)");
# Create a cascaded replication setup like:
# N1 - Create publication testpub1.
# N2 - Create publication testpub2 and also include subscriber which subscribes
# to testpub1.
# N3 - Create subscription testsub2 subscribes to testpub2.
#
# Note that subscription on N3 needs to be created before subscription on N2 to
# test whether the data written by tablesync worker of N2 gets replicated.
$node_pub->safe_psql('postgres',
"CREATE PUBLICATION testpub1 FOR TABLE tab1");
$node_pub_sub->safe_psql('postgres',
"CREATE PUBLICATION testpub2 FOR TABLE tab1");
my $publisher1_connstr = $node_pub->connstr . ' dbname=postgres';
my $publisher2_connstr = $node_pub_sub->connstr . ' dbname=postgres';
$node_sub->safe_psql('postgres',
"CREATE SUBSCRIPTION testsub2 CONNECTION '$publisher2_connstr' PUBLICATION testpub2"
);
$node_pub_sub->safe_psql('postgres',
"CREATE SUBSCRIPTION testsub1 CONNECTION '$publisher1_connstr' PUBLICATION testpub1"
);
$node_pub->safe_psql('postgres',
"INSERT INTO tab1 values(generate_series(1,10))");
# Verify that the data is cascaded from testpub1 to testsub1 and further from
# testpub2 (which had testsub1) to testsub2.
$node_pub->wait_for_catchup('testsub1');
$node_pub_sub->wait_for_catchup('testsub2');
# Drop subscriptions as we don't need them anymore
$node_pub_sub->safe_psql('postgres', "DROP SUBSCRIPTION testsub1");
$node_sub->safe_psql('postgres', "DROP SUBSCRIPTION testsub2");
# Drop publications as we don't need them anymore
$node_pub->safe_psql('postgres', "DROP PUBLICATION testpub1");
$node_pub_sub->safe_psql('postgres', "DROP PUBLICATION testpub2");
# Clean up the tables on both publisher and subscriber as we don't need them
$node_pub->safe_psql('postgres', "DROP TABLE tab1");
$node_pub_sub->safe_psql('postgres', "DROP TABLE tab1");
$node_sub->safe_psql('postgres', "DROP TABLE tab1");
$node_pub->stop('fast');
$node_pub_sub->stop('fast');
$node_sub->stop('fast');