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README.online-recovery
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README.online-recovery
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/*
* $Header$
*
* pgpool: a language independent connection pool server for PostgreSQL
* written by Tatsuo Ishii
*
* Copyright (c) 2003-2010 PgPool Global Development Group
*
* Permission to use, copy, modify, and distribute this software and
* its documentation for any purpose and without fee is hereby
* granted, provided that the above copyright notice appear in all
* copies and that both that copyright notice and this permission
* notice appear in supporting documentation, and that the name of the
* author not be used in advertising or publicity pertaining to
* distribution of the software without specific, written prior
* permission. The author makes no representations about the
* suitability of this software for any purpose. It is provided "as
* is" without express or implied warranty.
*
*/
How does online reconvery work?
pcp_recovery_node calls pcp_recovery_node() API
pcp_recovery_node(int node_id) does:
pcp_recovery_node sends "O" to pcp_child process requesting online
recovery
pcp_child calls start_recovery() and waits for its completion
start_recovery() sets Req_info->kind to NODE_RECOVERY_REQUEST
start_recovery calls execute_checkpoint() execute CHEKPOINT
command
start_recovery calls exec_recovery
exec_recovery executes SELECT pgpool_recovery()
execute 1st stage command
/* start 2nd stage */
sets InRecovery to 1
wait_connection_closed() to wait for all frontend exits
calls execute_checkpoint() execute CHEKPOINT
calls exec_recovery to execute 2nd stage script
calls exec_remote_start to start postmaster
calls check_postmaster_started to wait for postmaster starts
up
set pcp_wakeup request to 0
calls send_failback_request()
waits for failback completion every 1 second until
pcp_wakeup_request becomes non 0.
set pcp_wakeup request to 0
start_recovery calls finish_recovery()
finish_recovery sets InRecovery to 0
sends SIGUSR2 signal to parent
Upon receiving SIGUSR2 pgpool parent calls
kill_all_children() which sends SIGUSR2 to all pgpool
children
child pgpool processes wake up from pause()