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Add support for prepared transactions to built-in logical replication.

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To add support for streaming transactions at prepare time into the
built-in logical replication, we need to do the following things:

* Modify the output plugin (pgoutput) to implement the new two-phase API
callbacks, by leveraging the extended replication protocol.

* Modify the replication apply worker, to properly handle two-phase
transactions by replaying them on prepare.

* Add a new SUBSCRIPTION option "two_phase" to allow users to enable
two-phase transactions. We enable the two_phase once the initial data sync
is over.

We however must explicitly disable replication of two-phase transactions
during replication slot creation, even if the plugin supports it. We
don't need to replicate the changes accumulated during this phase,
and moreover, we don't have a replication connection open so we don't know
where to send the data anyway.

The streaming option is not allowed with this new two_phase option. This
can be done as a separate patch.

We don't allow to toggle two_phase option of a subscription because it can
lead to an inconsistent replica. For the same reason, we don't allow to
refresh the publication once the two_phase is enabled for a subscription
unless copy_data option is false.

Author: Peter Smith, Ajin Cherian and Amit Kapila based on previous work by Nikhil Sontakke and Stas Kelvich
Reviewed-by: Amit Kapila, Sawada Masahiko, Vignesh C, Dilip Kumar, Takamichi Osumi, Greg Nancarrow
Tested-By: Haiying Tang
Discussion: https://postgr.es/m/02DA5F5E-CECE-4D9C-8B4B-418077E2C010@postgrespro.ru
Discussion: https://postgr.es/m/CAA4eK1+opiV4aFTmWWUF9h_32=HfPOW9vZASHarT0UA5oBrtGw@mail.gmail.com
This commit is contained in:
Amit Kapila
2021-07-14 07:33:50 +05:30
parent 6c9c283166
commit a8fd13cab0
43 changed files with 2382 additions and 191 deletions
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201
src/backend/replication/pgoutput/pgoutput.c
View File

@@ -51,6 +51,16 @@ static void pgoutput_message(LogicalDecodingContext *ctx,
Size sz, const char *message);
static bool pgoutput_origin_filter(LogicalDecodingContext *ctx,
RepOriginId origin_id);
static void pgoutput_begin_prepare_txn(LogicalDecodingContext *ctx,
ReorderBufferTXN *txn);
static void pgoutput_prepare_txn(LogicalDecodingContext *ctx,
ReorderBufferTXN *txn, XLogRecPtr prepare_lsn);
static void pgoutput_commit_prepared_txn(LogicalDecodingContext *ctx,
ReorderBufferTXN *txn, XLogRecPtr commit_lsn);
static void pgoutput_rollback_prepared_txn(LogicalDecodingContext *ctx,
ReorderBufferTXN *txn,
XLogRecPtr prepare_end_lsn,
TimestampTz prepare_time);
static void pgoutput_stream_start(struct LogicalDecodingContext *ctx,
ReorderBufferTXN *txn);
static void pgoutput_stream_stop(struct LogicalDecodingContext *ctx,
@@ -70,6 +80,9 @@ static void publication_invalidation_cb(Datum arg, int cacheid,
uint32 hashvalue);
static void send_relation_and_attrs(Relation relation, TransactionId xid,
LogicalDecodingContext *ctx);
static void send_repl_origin(LogicalDecodingContext *ctx,
RepOriginId origin_id, XLogRecPtr origin_lsn,
bool send_origin);
/*
* Entry in the map used to remember which relation schemas we sent.
@@ -145,6 +158,11 @@ _PG_output_plugin_init(OutputPluginCallbacks *cb)
cb->truncate_cb = pgoutput_truncate;
cb->message_cb = pgoutput_message;
cb->commit_cb = pgoutput_commit_txn;
cb->begin_prepare_cb = pgoutput_begin_prepare_txn;
cb->prepare_cb = pgoutput_prepare_txn;
cb->commit_prepared_cb = pgoutput_commit_prepared_txn;
cb->rollback_prepared_cb = pgoutput_rollback_prepared_txn;
cb->filter_by_origin_cb = pgoutput_origin_filter;
cb->shutdown_cb = pgoutput_shutdown;
@@ -156,6 +174,8 @@ _PG_output_plugin_init(OutputPluginCallbacks *cb)
cb->stream_change_cb = pgoutput_change;
cb->stream_message_cb = pgoutput_message;
cb->stream_truncate_cb = pgoutput_truncate;
/* transaction streaming - two-phase commit */
cb->stream_prepare_cb = NULL;
}
static void
@@ -167,10 +187,12 @@ parse_output_parameters(List *options, PGOutputData *data)
bool binary_option_given = false;
bool messages_option_given = false;
bool streaming_given = false;
bool two_phase_option_given = false;
data->binary = false;
data->streaming = false;
data->messages = false;
data->two_phase = false;
foreach(lc, options)
{
@@ -246,8 +268,29 @@ parse_output_parameters(List *options, PGOutputData *data)
data->streaming = defGetBoolean(defel);
}
else if (strcmp(defel->defname, "two_phase") == 0)
{
if (two_phase_option_given)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("conflicting or redundant options")));
two_phase_option_given = true;
data->two_phase = defGetBoolean(defel);
}
else
elog(ERROR, "unrecognized pgoutput option: %s", defel->defname);
/*
* Do additional checking for the disallowed combination of two_phase
* and streaming. While streaming and two_phase can theoretically be
* supported, it needs more analysis to allow them together.
*/
if (data->two_phase && data->streaming)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("%s and %s are mutually exclusive options",
"two_phase", "streaming")));
}
}
@@ -319,6 +362,27 @@ pgoutput_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
/* Also remember we're currently not streaming any transaction. */
in_streaming = false;
/*
* Here, we just check whether the two-phase option is passed by
* plugin and decide whether to enable it at later point of time. It
* remains enabled if the previous start-up has done so. But we only
* allow the option to be passed in with sufficient version of the
* protocol, and when the output plugin supports it.
*/
if (!data->two_phase)
ctx->twophase_opt_given = false;
else if (data->protocol_version < LOGICALREP_PROTO_TWOPHASE_VERSION_NUM)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("requested proto_version=%d does not support two-phase commit, need %d or higher",
data->protocol_version, LOGICALREP_PROTO_TWOPHASE_VERSION_NUM)));
else if (!ctx->twophase)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("two-phase commit requested, but not supported by output plugin")));
else
ctx->twophase_opt_given = true;
/* Init publication state. */
data->publications = NIL;
publications_valid = false;
@@ -331,8 +395,12 @@ pgoutput_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
}
else
{
/* Disable the streaming during the slot initialization mode. */
/*
* Disable the streaming and prepared transactions during the slot
* initialization mode.
*/
ctx->streaming = false;
ctx->twophase = false;
}
}
@@ -347,29 +415,8 @@ pgoutput_begin_txn(LogicalDecodingContext *ctx, ReorderBufferTXN *txn)
OutputPluginPrepareWrite(ctx, !send_replication_origin);
logicalrep_write_begin(ctx->out, txn);
if (send_replication_origin)
{
char *origin;
/*----------
* XXX: which behaviour do we want here?
*
* Alternatives:
* - don't send origin message if origin name not found
* (that's what we do now)
* - throw error - that will break replication, not good
* - send some special "unknown" origin
*----------
*/
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);
}
}
send_repl_origin(ctx, txn->origin_id, txn->origin_lsn,
send_replication_origin);
OutputPluginWrite(ctx, true);
}
@@ -388,6 +435,68 @@ pgoutput_commit_txn(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
OutputPluginWrite(ctx, true);
}
/*
* BEGIN PREPARE callback
*/
static void
pgoutput_begin_prepare_txn(LogicalDecodingContext *ctx, ReorderBufferTXN *txn)
{
bool send_replication_origin = txn->origin_id != InvalidRepOriginId;
OutputPluginPrepareWrite(ctx, !send_replication_origin);
logicalrep_write_begin_prepare(ctx->out, txn);
send_repl_origin(ctx, txn->origin_id, txn->origin_lsn,
send_replication_origin);
OutputPluginWrite(ctx, true);
}
/*
* PREPARE callback
*/
static void
pgoutput_prepare_txn(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
XLogRecPtr prepare_lsn)
{
OutputPluginUpdateProgress(ctx);
OutputPluginPrepareWrite(ctx, true);
logicalrep_write_prepare(ctx->out, txn, prepare_lsn);
OutputPluginWrite(ctx, true);
}
/*
* COMMIT PREPARED callback
*/
static void
pgoutput_commit_prepared_txn(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
XLogRecPtr commit_lsn)
{
OutputPluginUpdateProgress(ctx);
OutputPluginPrepareWrite(ctx, true);
logicalrep_write_commit_prepared(ctx->out, txn, commit_lsn);
OutputPluginWrite(ctx, true);
}
/*
* ROLLBACK PREPARED callback
*/
static void
pgoutput_rollback_prepared_txn(LogicalDecodingContext *ctx,
ReorderBufferTXN *txn,
XLogRecPtr prepare_end_lsn,
TimestampTz prepare_time)
{
OutputPluginUpdateProgress(ctx);
OutputPluginPrepareWrite(ctx, true);
logicalrep_write_rollback_prepared(ctx->out, txn, prepare_end_lsn,
prepare_time);
OutputPluginWrite(ctx, true);
}
/*
* Write the current schema of the relation and its ancestor (if any) if not
* done yet.
@@ -839,18 +948,8 @@ pgoutput_stream_start(struct LogicalDecodingContext *ctx,
OutputPluginPrepareWrite(ctx, !send_replication_origin);
logicalrep_write_stream_start(ctx->out, txn->xid, !rbtxn_is_streamed(txn));
if (send_replication_origin)
{
char *origin;
if (replorigin_by_oid(txn->origin_id, true, &origin))
{
/* Message boundary */
OutputPluginWrite(ctx, false);
OutputPluginPrepareWrite(ctx, true);
logicalrep_write_origin(ctx->out, origin, InvalidXLogRecPtr);
}
}
send_repl_origin(ctx, txn->origin_id, InvalidXLogRecPtr,
send_replication_origin);
OutputPluginWrite(ctx, true);
@@ -1270,3 +1369,33 @@ rel_sync_cache_publication_cb(Datum arg, int cacheid, uint32 hashvalue)
entry->pubactions.pubtruncate = false;
}
}
/* Send Replication origin */
static void
send_repl_origin(LogicalDecodingContext *ctx, RepOriginId origin_id,
XLogRecPtr origin_lsn, bool send_origin)
{
if (send_origin)
{
char *origin;
/*----------
* XXX: which behaviour do we want here?
*
* Alternatives:
* - don't send origin message if origin name not found
* (that's what we do now)
* - throw error - that will break replication, not good
* - send some special "unknown" origin
*----------
*/
if (replorigin_by_oid(origin_id, true, &origin))
{
/* Message boundary */
OutputPluginWrite(ctx, false);
OutputPluginPrepareWrite(ctx, true);
logicalrep_write_origin(ctx->out, origin, origin_lsn);
}
}
}