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Perform apply of large transactions by parallel workers.

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Currently, for large transactions, the publisher sends the data in
multiple streams (changes divided into chunks depending upon
logical_decoding_work_mem), and then on the subscriber-side, the apply
worker writes the changes into temporary files and once it receives the
commit, it reads from those files and applies the entire transaction. To
improve the performance of such transactions, we can instead allow them to
be applied via parallel workers.

In this approach, we assign a new parallel apply worker (if available) as
soon as the xact's first stream is received and the leader apply worker
will send changes to this new worker via shared memory. The parallel apply
worker will directly apply the change instead of writing it to temporary
files. However, if the leader apply worker times out while attempting to
send a message to the parallel apply worker, it will switch to
"partial serialize" mode -  in this mode, the leader serializes all
remaining changes to a file and notifies the parallel apply workers to
read and apply them at the end of the transaction. We use a non-blocking
way to send the messages from the leader apply worker to the parallel
apply to avoid deadlocks. We keep this parallel apply assigned till the
transaction commit is received and also wait for the worker to finish at
commit. This preserves commit ordering and avoid writing to and reading
from files in most cases. We still need to spill if there is no worker
available.

This patch also extends the SUBSCRIPTION 'streaming' parameter so that the
user can control whether to apply the streaming transaction in a parallel
apply worker or spill the change to disk. The user can set the streaming
parameter to 'on/off', or 'parallel'. The parameter value 'parallel' means
the streaming will be applied via a parallel apply worker, if available.
The parameter value 'on' means the streaming transaction will be spilled
to disk. The default value is 'off' (same as current behaviour).

In addition, the patch extends the logical replication STREAM_ABORT
message so that abort_lsn and abort_time can also be sent which can be
used to update the replication origin in parallel apply worker when the
streaming transaction is aborted. Because this message extension is needed
to support parallel streaming, parallel streaming is not supported for
publications on servers < PG16.

Author: Hou Zhijie, Wang wei, Amit Kapila with design inputs from Sawada Masahiko
Reviewed-by: Sawada Masahiko, Peter Smith, Dilip Kumar, Shi yu, Kuroda Hayato, Shveta Mallik
Discussion: https://postgr.es/m/CAA4eK1+wyN6zpaHUkCLorEWNx75MG0xhMwcFhvjqm2KURZEAGw@mail.gmail.com
This commit is contained in:
Amit Kapila
2023-01-09 07:00:39 +05:30
parent 5687e7810f
commit 216a784829
58 changed files with 4497 additions and 745 deletions
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28
src/include/replication/logicalproto.h
View File

@@ -32,12 +32,17 @@
*
* LOGICALREP_PROTO_TWOPHASE_VERSION_NUM is the minimum protocol version with
* support for two-phase commit decoding (at prepare time). Introduced in PG15.
*
* LOGICALREP_PROTO_STREAM_PARALLEL_VERSION_NUM is the minimum protocol version
* where we support applying large streaming transactions in parallel.
* Introduced in PG16.
*/
#define LOGICALREP_PROTO_MIN_VERSION_NUM 1
#define LOGICALREP_PROTO_VERSION_NUM 1
#define LOGICALREP_PROTO_STREAM_VERSION_NUM 2
#define LOGICALREP_PROTO_TWOPHASE_VERSION_NUM 3
#define LOGICALREP_PROTO_MAX_VERSION_NUM LOGICALREP_PROTO_TWOPHASE_VERSION_NUM
#define LOGICALREP_PROTO_STREAM_PARALLEL_VERSION_NUM 4
#define LOGICALREP_PROTO_MAX_VERSION_NUM LOGICALREP_PROTO_STREAM_PARALLEL_VERSION_NUM
/*
* Logical message types
@@ -175,6 +180,17 @@ typedef struct LogicalRepRollbackPreparedTxnData
char gid[GIDSIZE];
} LogicalRepRollbackPreparedTxnData;
/*
* Transaction protocol information for stream abort.
*/
typedef struct LogicalRepStreamAbortData
{
TransactionId xid;
TransactionId subxid;
XLogRecPtr abort_lsn;
TimestampTz abort_time;
} LogicalRepStreamAbortData;
extern void logicalrep_write_begin(StringInfo out, ReorderBufferTXN *txn);
extern void logicalrep_read_begin(StringInfo in,
LogicalRepBeginData *begin_data);
@@ -246,9 +262,13 @@ extern void logicalrep_write_stream_commit(StringInfo out, ReorderBufferTXN *txn
extern TransactionId logicalrep_read_stream_commit(StringInfo in,
LogicalRepCommitData *commit_data);
extern void logicalrep_write_stream_abort(StringInfo out, TransactionId xid,
TransactionId subxid);
extern void logicalrep_read_stream_abort(StringInfo in, TransactionId *xid,
TransactionId *subxid);
TransactionId subxid,
XLogRecPtr abort_lsn,
TimestampTz abort_time,
bool write_abort_info);
extern void logicalrep_read_stream_abort(StringInfo in,
LogicalRepStreamAbortData *abort_data,
bool read_abort_info);
extern char *logicalrep_message_type(LogicalRepMsgType action);
#endif /* LOGICAL_PROTO_H */