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postgresql/src/include/replication/walsender.h

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Introduce Streaming Replication. This includes two new kinds of postmaster processes, walsenders and walreceiver. Walreceiver is responsible for connecting to the primary server and streaming WAL to disk, while walsender runs in the primary server and streams WAL from disk to the client. Documentation still needs work, but the basics are there. We will probably pull the replication section to a new chapter later on, as well as the sections describing file-based replication. But let's do that as a separate patch, so that it's easier to see what has been added/changed. This patch also adds a new section to the chapter about FE/BE protocol, documenting the protocol used by walsender/walreceivxer. Bump catalog version because of two new functions, pg_last_xlog_receive_location() and pg_last_xlog_replay_location(), for monitoring the progress of replication. Fujii Masao, with additional hacking by me
2010-01-15 10:19:10 +01:00
/*-------------------------------------------------------------------------
*
* walsender.h
* Exports from replication/walsender.c.
*
Update copyright for 2022 Backpatch-through: 10
2022-01-08 01:04:57 +01:00
* Portions Copyright (c) 2010-2022, PostgreSQL Global Development Group
Introduce Streaming Replication. This includes two new kinds of postmaster processes, walsenders and walreceiver. Walreceiver is responsible for connecting to the primary server and streaming WAL to disk, while walsender runs in the primary server and streams WAL from disk to the client. Documentation still needs work, but the basics are there. We will probably pull the replication section to a new chapter later on, as well as the sections describing file-based replication. But let's do that as a separate patch, so that it's easier to see what has been added/changed. This patch also adds a new section to the chapter about FE/BE protocol, documenting the protocol used by walsender/walreceivxer. Bump catalog version because of two new functions, pg_last_xlog_receive_location() and pg_last_xlog_replay_location(), for monitoring the progress of replication. Fujii Masao, with additional hacking by me
2010-01-15 10:19:10 +01:00
*
Remove cvs keywords from all files.
2010-09-20 22:08:53 +02:00
* src/include/replication/walsender.h
Introduce Streaming Replication. This includes two new kinds of postmaster processes, walsenders and walreceiver. Walreceiver is responsible for connecting to the primary server and streaming WAL to disk, while walsender runs in the primary server and streams WAL from disk to the client. Documentation still needs work, but the basics are there. We will probably pull the replication section to a new chapter later on, as well as the sections describing file-based replication. But let's do that as a separate patch, so that it's easier to see what has been added/changed. This patch also adds a new section to the chapter about FE/BE protocol, documenting the protocol used by walsender/walreceivxer. Bump catalog version because of two new functions, pg_last_xlog_receive_location() and pg_last_xlog_replay_location(), for monitoring the progress of replication. Fujii Masao, with additional hacking by me
2010-01-15 10:19:10 +01:00
*
*-------------------------------------------------------------------------
*/
#ifndef _WALSENDER_H
#define _WALSENDER_H
Split walsender.h in public/private headers This dramatically cuts short the number of headers the public one brings into whatever includes it.
2011-09-12 20:24:29 +02:00
#include <signal.h>
Efficient transaction-controlled synchronous replication. If a standby is broadcasting reply messages and we have named one or more standbys in synchronous_standby_names then allow users who set synchronous_replication to wait for commit, which then provides strict data integrity guarantees. Design avoids sending and receiving transaction state information so minimises bookkeeping overheads. We synchronize with the highest priority standby that is connected and ready to synchronize. Other standbys can be defined to takeover in case of standby failure. This version has very strict behaviour; more relaxed options may be added at a later date. Simon Riggs and Fujii Masao, with reviews by Yeb Havinga, Jaime Casanova, Heikki Linnakangas and Robert Haas, plus the assistance of many other design reviewers.
2011-03-06 23:49:16 +01:00
Logical replication support for initial data copy Add functionality for a new subscription to copy the initial data in the tables and then sync with the ongoing apply process. For the copying, add a new internal COPY option to have the COPY source data provided by a callback function. The initial data copy works on the subscriber by receiving COPY data from the publisher and then providing it locally into a COPY that writes to the destination table. A WAL receiver can now execute full SQL commands. This is used here to obtain information about tables and publications. Several new options were added to CREATE and ALTER SUBSCRIPTION to control whether and when initial table syncing happens. Change pg_dump option --no-create-subscription-slots to --no-subscription-connect and use the new CREATE SUBSCRIPTION ... NOCONNECT option for that. Author: Petr Jelinek <petr.jelinek@2ndquadrant.com> Tested-by: Erik Rijkers <er@xs4all.nl>
2017-03-23 13:36:36 +01:00
/*
* What to do with a snapshot in create replication slot command.
*/
typedef enum
{
CRS_EXPORT_SNAPSHOT,
CRS_NOEXPORT_SNAPSHOT,
CRS_USE_SNAPSHOT
} CRSSnapshotAction;
Introduce Streaming Replication. This includes two new kinds of postmaster processes, walsenders and walreceiver. Walreceiver is responsible for connecting to the primary server and streaming WAL to disk, while walsender runs in the primary server and streams WAL from disk to the client. Documentation still needs work, but the basics are there. We will probably pull the replication section to a new chapter later on, as well as the sections describing file-based replication. But let's do that as a separate patch, so that it's easier to see what has been added/changed. This patch also adds a new section to the chapter about FE/BE protocol, documenting the protocol used by walsender/walreceivxer. Bump catalog version because of two new functions, pg_last_xlog_receive_location() and pg_last_xlog_replay_location(), for monitoring the progress of replication. Fujii Masao, with additional hacking by me
2010-01-15 10:19:10 +01:00
/* global state */
Apply PGDLLIMPORT markings broadly. Up until now, we've had a policy of only marking certain variables in the PostgreSQL header files with PGDLLIMPORT, but now we've decided to mark them all. This means that extensions running on Windows should no longer operate at a disadvantage as compared to extensions running on Linux: if the variable is present in a header file, it should be accessible. Discussion: http://postgr.es/m/CA+TgmoYanc1_FSfimhgiWSqVyP5KKmh5NP2BWNwDhO8Pg2vGYQ@mail.gmail.com
2022-04-08 14:16:38 +02:00
extern PGDLLIMPORT bool am_walsender;
extern PGDLLIMPORT bool am_cascading_walsender;
extern PGDLLIMPORT bool am_db_walsender;
extern PGDLLIMPORT bool wake_wal_senders;
Introduce Streaming Replication. This includes two new kinds of postmaster processes, walsenders and walreceiver. Walreceiver is responsible for connecting to the primary server and streaming WAL to disk, while walsender runs in the primary server and streams WAL from disk to the client. Documentation still needs work, but the basics are there. We will probably pull the replication section to a new chapter later on, as well as the sections describing file-based replication. But let's do that as a separate patch, so that it's easier to see what has been added/changed. This patch also adds a new section to the chapter about FE/BE protocol, documenting the protocol used by walsender/walreceivxer. Bump catalog version because of two new functions, pg_last_xlog_receive_location() and pg_last_xlog_replay_location(), for monitoring the progress of replication. Fujii Masao, with additional hacking by me
2010-01-15 10:19:10 +01:00
/* user-settable parameters */
Apply PGDLLIMPORT markings broadly. Up until now, we've had a policy of only marking certain variables in the PostgreSQL header files with PGDLLIMPORT, but now we've decided to mark them all. This means that extensions running on Windows should no longer operate at a disadvantage as compared to extensions running on Linux: if the variable is present in a header file, it should be accessible. Discussion: http://postgr.es/m/CA+TgmoYanc1_FSfimhgiWSqVyP5KKmh5NP2BWNwDhO8Pg2vGYQ@mail.gmail.com
2022-04-08 14:16:38 +02:00
extern PGDLLIMPORT int max_wal_senders;
extern PGDLLIMPORT int wal_sender_timeout;
extern PGDLLIMPORT bool log_replication_commands;
Introduce Streaming Replication. This includes two new kinds of postmaster processes, walsenders and walreceiver. Walreceiver is responsible for connecting to the primary server and streaming WAL to disk, while walsender runs in the primary server and streams WAL from disk to the client. Documentation still needs work, but the basics are there. We will probably pull the replication section to a new chapter later on, as well as the sections describing file-based replication. But let's do that as a separate patch, so that it's easier to see what has been added/changed. This patch also adds a new section to the chapter about FE/BE protocol, documenting the protocol used by walsender/walreceivxer. Bump catalog version because of two new functions, pg_last_xlog_receive_location() and pg_last_xlog_replay_location(), for monitoring the progress of replication. Fujii Masao, with additional hacking by me
2010-01-15 10:19:10 +01:00
Use the regular main processing loop also in walsenders. The regular backend's main loop handles signal handling and error recovery better than the current WAL sender command loop does. For example, if the client hangs and a SIGTERM is received before starting streaming, the walsender will now terminate immediately, rather than hang until the connection times out.
2012-10-05 16:13:07 +02:00
extern void InitWalSender(void);
Logical replication support for initial data copy Add functionality for a new subscription to copy the initial data in the tables and then sync with the ongoing apply process. For the copying, add a new internal COPY option to have the COPY source data provided by a callback function. The initial data copy works on the subscriber by receiving COPY data from the publisher and then providing it locally into a COPY that writes to the destination table. A WAL receiver can now execute full SQL commands. This is used here to obtain information about tables and publications. Several new options were added to CREATE and ALTER SUBSCRIPTION to control whether and when initial table syncing happens. Change pg_dump option --no-create-subscription-slots to --no-subscription-connect and use the new CREATE SUBSCRIPTION ... NOCONNECT option for that. Author: Petr Jelinek <petr.jelinek@2ndquadrant.com> Tested-by: Erik Rijkers <er@xs4all.nl>
2017-03-23 13:36:36 +01:00
extern bool exec_replication_command(const char *query_string);
Use the regular main processing loop also in walsenders. The regular backend's main loop handles signal handling and error recovery better than the current WAL sender command loop does. For example, if the client hangs and a SIGTERM is received before starting streaming, the walsender will now terminate immediately, rather than hang until the connection times out.
2012-10-05 16:13:07 +02:00
extern void WalSndErrorCleanup(void);
Generate backup manifests for base backups, and validate them. A manifest is a JSON document which includes (1) the file name, size, last modification time, and an optional checksum for each file backed up, (2) timelines and LSNs for whatever WAL will need to be replayed to make the backup consistent, and (3) a checksum for the manifest itself. By default, we use CRC-32C when checksumming data files, because we are trying to detect corruption and user error, not foil an adversary. However, pg_basebackup and the server-side BASE_BACKUP command now have options to select a different algorithm, so users wanting a cryptographic hash function can select SHA-224, SHA-256, SHA-384, or SHA-512. Users not wanting file checksums at all can disable them, or disable generating of the backup manifest altogether. Using a cryptographic hash function in place of CRC-32C consumes significantly more CPU cycles, which may slow down backups in some cases. A new tool called pg_validatebackup can validate a backup against the manifest. If no checksums are present, it can still check that the right files exist and that they have the expected sizes. If checksums are present, it can also verify that each file has the expected checksum. Additionally, it calls pg_waldump to verify that the expected WAL files are present and parseable. Only plain format backups can be validated directly, but tar format backups can be validated after extracting them. Robert Haas, with help, ideas, review, and testing from David Steele, Stephen Frost, Andrew Dunstan, Rushabh Lathia, Suraj Kharage, Tushar Ahuja, Rajkumar Raghuwanshi, Mark Dilger, Davinder Singh, Jeevan Chalke, Amit Kapila, Andres Freund, and Noah Misch. Discussion: http://postgr.es/m/CA+TgmoZV8dw1H2bzZ9xkKwdrk8+XYa+DC9H=F7heO2zna5T6qg@mail.gmail.com
2020-04-03 20:59:47 +02:00
extern void WalSndResourceCleanup(bool isCommit);
Introduce Streaming Replication. This includes two new kinds of postmaster processes, walsenders and walreceiver. Walreceiver is responsible for connecting to the primary server and streaming WAL to disk, while walsender runs in the primary server and streams WAL from disk to the client. Documentation still needs work, but the basics are there. We will probably pull the replication section to a new chapter later on, as well as the sections describing file-based replication. But let's do that as a separate patch, so that it's easier to see what has been added/changed. This patch also adds a new section to the chapter about FE/BE protocol, documenting the protocol used by walsender/walreceivxer. Bump catalog version because of two new functions, pg_last_xlog_receive_location() and pg_last_xlog_replay_location(), for monitoring the progress of replication. Fujii Masao, with additional hacking by me
2010-01-15 10:19:10 +01:00
extern void WalSndSignals(void);
extern Size WalSndShmemSize(void);
extern void WalSndShmemInit(void);
Introduce latches. A latch is a boolean variable, with the capability to wait until it is set. Latches can be used to reliably wait until a signal arrives, which is hard otherwise because signals don't interrupt select() on some platforms, and even when they do, there's race conditions. On Unix, latches use the so called self-pipe trick under the covers to implement the sleep until the latch is set, without race conditions. On Windows, Windows events are used. Use the new latch abstraction to sleep in walsender, so that as soon as a transaction finishes, walsender is woken up to immediately send the WAL to the standby. This reduces the latency between master and standby, which is good. Preliminary work by Fujii Masao. The latch implementation is by me, with helpful comments from many people.
2010-09-11 17:48:04 +02:00
extern void WalSndWakeup(void);
Prevent possibility of panics during shutdown checkpoint. When the checkpointer writes the shutdown checkpoint, it checks afterwards whether any WAL has been written since it started and throws a PANIC if so. At that point, only walsenders are still active, so one might think this could not happen, but walsenders can also generate WAL, for instance in BASE_BACKUP and logical decoding related commands (e.g. via hint bits). So they can trigger this panic if such a command is run while the shutdown checkpoint is being written. To fix this, divide the walsender shutdown into two phases. First, checkpointer, itself triggered by postmaster, sends a PROCSIG_WALSND_INIT_STOPPING signal to all walsenders. If the backend is idle or runs an SQL query this causes the backend to shutdown, if logical replication is in progress all existing WAL records are processed followed by a shutdown. Otherwise this causes the walsender to switch to the "stopping" state. In this state, the walsender will reject any further replication commands. The checkpointer begins the shutdown checkpoint once all walsenders are confirmed as stopping. When the shutdown checkpoint finishes, the postmaster sends us SIGUSR2. This instructs walsender to send any outstanding WAL, including the shutdown checkpoint record, wait for it to be replicated to the standby, and then exit. Author: Andres Freund, based on an earlier patch by Michael Paquier Reported-By: Fujii Masao, Andres Freund Reviewed-By: Michael Paquier Discussion: https://postgr.es/m/20170602002912.tqlwn4gymzlxpvs2@alap3.anarazel.de Backpatch: 9.4, where logical decoding was introduced
2017-06-06 03:53:41 +02:00
extern void WalSndInitStopping(void);
extern void WalSndWaitStopping(void);
extern void HandleWalSndInitStopping(void);
Cascading replication feature for streaming log-based replication. Standby servers can now have WALSender processes, which can work with either WALReceiver or archive_commands to pass data. Fully updated docs, including new conceptual terms of sending server, upstream and downstream servers. WALSenders terminated when promote to master. Fujii Masao, review, rework and doc rewrite by Simon Riggs
2011-07-19 04:40:03 +02:00
extern void WalSndRqstFileReload(void);
Introduce Streaming Replication. This includes two new kinds of postmaster processes, walsenders and walreceiver. Walreceiver is responsible for connecting to the primary server and streaming WAL to disk, while walsender runs in the primary server and streams WAL from disk to the client. Documentation still needs work, but the basics are there. We will probably pull the replication section to a new chapter later on, as well as the sections describing file-based replication. But let's do that as a separate patch, so that it's easier to see what has been added/changed. This patch also adds a new section to the chapter about FE/BE protocol, documenting the protocol used by walsender/walreceivxer. Bump catalog version because of two new functions, pg_last_xlog_receive_location() and pg_last_xlog_replay_location(), for monitoring the progress of replication. Fujii Masao, with additional hacking by me
2010-01-15 10:19:10 +01:00
Make walsender more responsive. Per testing by Andres Freund, this improves replication performance and reduces replication latency and latency jitter. I was a bit concerned about moving more work into XLogInsert, but testing seems to show that it's not a problem in practice. Along the way, improve comments for WaitLatchOrSocket. Andres Freund. Review and stylistic cleanup by me.
2012-07-02 15:36:34 +02:00
/*
* Remember that we want to wakeup walsenders later
*
* This is separated from doing the actual wakeup because the writeout is done
* while holding contended locks.
*/
#define WalSndWakeupRequest() \
do { wake_wal_senders = true; } while (0)
/*
* wakeup walsenders if there is work to be done
*/
#define WalSndWakeupProcessRequests() \
do \
{ \
if (wake_wal_senders) \
{ \
wake_wal_senders = false; \
if (max_wal_senders > 0) \
WalSndWakeup(); \
} \
} while (0)
Introduce Streaming Replication. This includes two new kinds of postmaster processes, walsenders and walreceiver. Walreceiver is responsible for connecting to the primary server and streaming WAL to disk, while walsender runs in the primary server and streams WAL from disk to the client. Documentation still needs work, but the basics are there. We will probably pull the replication section to a new chapter later on, as well as the sections describing file-based replication. But let's do that as a separate patch, so that it's easier to see what has been added/changed. This patch also adds a new section to the chapter about FE/BE protocol, documenting the protocol used by walsender/walreceivxer. Bump catalog version because of two new functions, pg_last_xlog_receive_location() and pg_last_xlog_replay_location(), for monitoring the progress of replication. Fujii Masao, with additional hacking by me
2010-01-15 10:19:10 +01:00
#endif /* _WALSENDER_H */