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Add hooks for session start and session end, take two
These hooks can be used in loadable modules. A simple test module is included. The first attempt was done with cd8ce3a but we lacked handling for NO_INSTALLCHECK in the MSVC scripts (problem solved afterwards by 431f159) so the buildfarm got angry. This also fixes a couple of issues noticed upon review compared to the first attempt, so the code has slightly changed, resulting in a more simple test module. Author: Fabrízio de Royes Mello, Yugo Nagata Reviewed-by: Andrew Dunstan, Michael Paquier, Aleksandr Parfenov Discussion: https://postgr.es/m/20170720204733.40f2b7eb.nagata@sraoss.co.jp Discussion: https://postgr.es/m/20190823042602.GB5275@paquier.xyz
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‎src/backend/tcop/postgres.c

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@@ -171,6 +171,9 @@ static ProcSignalReason RecoveryConflictReason;
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static MemoryContext row_description_context = NULL;
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static StringInfoData row_description_buf;
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/* Hook for plugins to get control at start of session */
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session_start_hook_type session_start_hook = NULL;
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/* ----------------------------------------------------------------
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* decls for routines only used in this file
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* ----------------------------------------------------------------
@@ -3968,6 +3971,9 @@ PostgresMain(int argc, char *argv[],
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if (!IsUnderPostmaster)
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PgStartTime = GetCurrentTimestamp();
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if (session_start_hook)
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(*session_start_hook) ();
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/*
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* POSTGRES main processing loop begins here
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*

‎src/backend/utils/init/postinit.c

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@@ -78,6 +78,8 @@ static bool ThereIsAtLeastOneRole(void);
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static void process_startup_options(Port *port, bool am_superuser);
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static void process_settings(Oid databaseid, Oid roleid);
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/* Hook for plugins to get control at end of session */
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session_end_hook_type session_end_hook = NULL;
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/*** InitPostgres support ***/
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@@ -1195,6 +1197,10 @@ ShutdownPostgres(int code, Datum arg)
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* them explicitly.
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*/
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LockReleaseAll(USER_LOCKMETHOD, true);
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/* Hook at session end */
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if (session_end_hook)
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(*session_end_hook) ();
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}
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‎src/include/tcop/tcopprot.h

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@@ -30,6 +30,13 @@ extern PGDLLIMPORT const char *debug_query_string;
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extern int max_stack_depth;
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extern int PostAuthDelay;
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/* Hook for plugins to get control at start and end of session */
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typedef void (*session_start_hook_type) (void);
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typedef void (*session_end_hook_type) (void);
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extern PGDLLIMPORT session_start_hook_type session_start_hook;
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extern PGDLLIMPORT session_end_hook_type session_end_hook;
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/* GUC-configurable parameters */
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typedef enum

‎src/test/modules/Makefile

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@@ -21,6 +21,7 @@ SUBDIRS = \
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test_predtest \
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test_rbtree \
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test_rls_hooks \
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test_session_hooks \
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test_shm_mq \
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unsafe_tests \
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worker_spi

‎src/test/modules/test_session_hooks/.gitignore

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# Generated subdirectories
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/log/
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/results/
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/tmp_check/

‎src/test/modules/test_session_hooks/Makefile

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# src/test/modules/test_session_hooks/Makefile
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MODULE_big = test_session_hooks
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OBJS = test_session_hooks.o $(WIN32RES)
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PGFILEDESC = "test_session_hooks - tests for start and end session hooks"
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REGRESS = test_session_hooks
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REGRESS_OPTS = --temp-config=$(top_srcdir)/src/test/modules/test_session_hooks/session_hooks.conf
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# Disabled because these tests require extra configuration with
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# "shared_preload_libraries=test_session_hooks", which typical
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# installcheck users do not have (e.g. buildfarm clients).
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NO_INSTALLCHECK = 1
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ifdef USE_PGXS
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PG_CONFIG = pg_config
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PGXS := $(shell $(PG_CONFIG) --pgxs)
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include $(PGXS)
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else
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subdir = src/test/modules/test_session_hooks
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top_builddir = ../../../..
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include $(top_builddir)/src/Makefile.global
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include $(top_srcdir)/contrib/contrib-global.mk
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endif

‎src/test/modules/test_session_hooks/README

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test_session_hooks
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==================
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test_session_hooks is an example of how to use session start and end
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hooks.
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This module will insert into a pre-existing table called "session_hook_log"
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a log activity which happens at session start and end. It is possible
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to control which user information is logged when using the configuration
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parameter "test_session_hooks.username". If set, the hooks will log only
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information of the session user matching the parameter value.

‎src/test/modules/test_session_hooks/expected/test_session_hooks.out

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--
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-- Tests for start and end session hooks
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--
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-- Only activity from role regress_sess_hook_usr2 is logged.
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CREATE ROLE regress_sess_hook_usr1 SUPERUSER LOGIN;
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CREATE ROLE regress_sess_hook_usr2 SUPERUSER LOGIN;
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\set prevdb :DBNAME
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\set prevusr :USER
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CREATE TABLE session_hook_log(id SERIAL, dbname TEXT, username TEXT, hook_at TEXT);
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SELECT * FROM session_hook_log ORDER BY id;
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id | dbname | username | hook_at
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----+--------+----------+---------
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(0 rows)
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\c :prevdb regress_sess_hook_usr1
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SELECT * FROM session_hook_log ORDER BY id;
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id | dbname | username | hook_at
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----+--------+----------+---------
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(0 rows)
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\c :prevdb regress_sess_hook_usr2
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SELECT * FROM session_hook_log ORDER BY id;
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id | dbname | username | hook_at
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----+--------------------+------------------------+---------
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1 | contrib_regression | regress_sess_hook_usr2 | START
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(1 row)
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\c :prevdb :prevusr
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SELECT * FROM session_hook_log ORDER BY id;
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id | dbname | username | hook_at
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----+--------------------+------------------------+---------
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1 | contrib_regression | regress_sess_hook_usr2 | START
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2 | contrib_regression | regress_sess_hook_usr2 | END
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(2 rows)
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DROP ROLE regress_sess_hook_usr1;
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DROP ROLE regress_sess_hook_usr2;

‎src/test/modules/test_session_hooks/session_hooks.conf

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shared_preload_libraries = 'test_session_hooks'
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test_session_hooks.username = regress_sess_hook_usr2

‎src/test/modules/test_session_hooks/sql/test_session_hooks.sql

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--
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-- Tests for start and end session hooks
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--
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-- Only activity from role regress_sess_hook_usr2 is logged.
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CREATE ROLE regress_sess_hook_usr1 SUPERUSER LOGIN;
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CREATE ROLE regress_sess_hook_usr2 SUPERUSER LOGIN;
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\set prevdb :DBNAME
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\set prevusr :USER
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CREATE TABLE session_hook_log(id SERIAL, dbname TEXT, username TEXT, hook_at TEXT);
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SELECT * FROM session_hook_log ORDER BY id;
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\c :prevdb regress_sess_hook_usr1
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SELECT * FROM session_hook_log ORDER BY id;
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\c :prevdb regress_sess_hook_usr2
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SELECT * FROM session_hook_log ORDER BY id;
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\c :prevdb :prevusr
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SELECT * FROM session_hook_log ORDER BY id;
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DROP ROLE regress_sess_hook_usr1;
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DROP ROLE regress_sess_hook_usr2;

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