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6912acc04f
Adds write_lag, flush_lag and replay_lag cols to pg_stat_replication. Implements a lag tracker module that reports the lag times based upon measurements of the time taken for recent WAL to be written, flushed and replayed and for the sender to hear about it. These times represent the commit lag that was (or would have been) introduced by each synchronous commit level, if the remote server was configured as a synchronous standby. For an asynchronous standby, the replay_lag column approximates the delay before recent transactions became visible to queries. If the standby server has entirely caught up with the sending server and there is no more WAL activity, the most recently measured lag times will continue to be displayed for a short time and then show NULL. Physical replication lag tracking is automatic. Logical replication tracking is possible but is the responsibility of the logical decoding plugin. Tracking is a private module operating within each walsender individually, with values reported to shared memory. Module not used outside of walsender. Design and code is good enough now to commit - kudos to the author. In many ways a difficult topic, with important and subtle behaviour so this shoudl be expected to generate discussion and multiple open items: Test now! Author: Thomas Munro, following designs by Fujii Masao and Simon Riggs Review: Simon Riggs, Ian Barwick and Craig Ringer
113 lines
3.1 KiB
C
113 lines
3.1 KiB
C
/*-------------------------------------------------------------------------
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* logical.h
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* PostgreSQL logical decoding coordination
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*
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* Copyright (c) 2012-2017, PostgreSQL Global Development Group
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef LOGICAL_H
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#define LOGICAL_H
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#include "replication/slot.h"
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#include "access/xlog.h"
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#include "access/xlogreader.h"
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#include "replication/output_plugin.h"
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struct LogicalDecodingContext;
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typedef void (*LogicalOutputPluginWriterWrite) (
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struct LogicalDecodingContext *lr,
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XLogRecPtr Ptr,
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TransactionId xid,
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bool last_write
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);
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typedef LogicalOutputPluginWriterWrite LogicalOutputPluginWriterPrepareWrite;
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typedef struct LogicalDecodingContext
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{
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/* memory context this is all allocated in */
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MemoryContext context;
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/* The associated replication slot */
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ReplicationSlot *slot;
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/* infrastructure pieces for decoding */
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XLogReaderState *reader;
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struct ReorderBuffer *reorder;
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struct SnapBuild *snapshot_builder;
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OutputPluginCallbacks callbacks;
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OutputPluginOptions options;
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/*
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* User specified options
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*/
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List *output_plugin_options;
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/*
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* User-Provided callback for writing/streaming out data.
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*/
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LogicalOutputPluginWriterPrepareWrite prepare_write;
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LogicalOutputPluginWriterWrite write;
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/*
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* Output buffer.
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*/
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StringInfo out;
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/*
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* Private data pointer of the output plugin.
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*/
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void *output_plugin_private;
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/*
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* Private data pointer for the data writer.
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*/
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void *output_writer_private;
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/*
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* State for writing output.
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*/
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bool accept_writes;
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bool prepared_write;
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XLogRecPtr write_location;
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TransactionId write_xid;
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} LogicalDecodingContext;
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extern void CheckLogicalDecodingRequirements(void);
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extern LogicalDecodingContext *CreateInitDecodingContext(char *plugin,
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List *output_plugin_options,
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XLogPageReadCB read_page,
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LogicalOutputPluginWriterPrepareWrite prepare_write,
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LogicalOutputPluginWriterWrite do_write);
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extern LogicalDecodingContext *CreateDecodingContext(
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XLogRecPtr start_lsn,
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List *output_plugin_options,
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XLogPageReadCB read_page,
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LogicalOutputPluginWriterPrepareWrite prepare_write,
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LogicalOutputPluginWriterWrite do_write);
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extern void DecodingContextFindStartpoint(LogicalDecodingContext *ctx);
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extern bool DecodingContextReady(LogicalDecodingContext *ctx);
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extern void FreeDecodingContext(LogicalDecodingContext *ctx);
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extern LogicalDecodingContext *CreateCopyDecodingContext(
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List *output_plugin_options,
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LogicalOutputPluginWriterPrepareWrite prepare_write,
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LogicalOutputPluginWriterWrite do_write);
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extern List *DecodingContextGetTableList(LogicalDecodingContext *ctx);
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extern void LogicalIncreaseXminForSlot(XLogRecPtr lsn, TransactionId xmin);
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extern void LogicalIncreaseRestartDecodingForSlot(XLogRecPtr current_lsn,
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XLogRecPtr restart_lsn);
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extern void LogicalConfirmReceivedLocation(XLogRecPtr lsn);
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extern void LagTrackerWrite(XLogRecPtr lsn, TimestampTz local_flush_time);
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extern bool filter_by_origin_cb_wrapper(LogicalDecodingContext *ctx, RepOriginId origin_id);
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#endif
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