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102 lines
3.5 KiB
C
102 lines
3.5 KiB
C
/*--------------------------------------------------------------------
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* bgworker.h
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* POSTGRES pluggable background workers interface
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*
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* A background worker is a process able to run arbitrary, user-supplied code,
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* including normal transactions.
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*
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* Any external module loaded via shared_preload_libraries can register a
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* worker. Then, at the appropriate time, the worker process is forked from
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* the postmaster and runs the user-supplied "main" function. This code may
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* connect to a database and run transactions. Once started, it stays active
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* until shutdown or crash. The process should sleep during periods of
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* inactivity.
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*
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* If the fork() call fails in the postmaster, it will try again later. Note
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* that the failure can only be transient (fork failure due to high load,
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* memory pressure, too many processes, etc); more permanent problems, like
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* failure to connect to a database, are detected later in the worker and dealt
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* with just by having the worker exit normally. Postmaster will launch a new
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* worker again later.
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*
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* Note that there might be more than one worker in a database concurrently,
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* and the same module may request more than one worker running the same (or
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* different) code.
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*
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*
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* Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* IDENTIFICATION
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* src/include/postmaster/bgworker.h
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*--------------------------------------------------------------------
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*/
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#ifndef BGWORKER_H
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#define BGWORKER_H
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/*---------------------------------------------------------------------
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* External module API.
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*---------------------------------------------------------------------
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*/
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/*
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* Pass this flag to have your worker be able to connect to shared memory.
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*/
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#define BGWORKER_SHMEM_ACCESS 0x0001
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/*
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* This flag means the bgworker requires a database connection. The connection
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* is not established automatically; the worker must establish it later.
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* It requires that BGWORKER_SHMEM_ACCESS was passed too.
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*/
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#define BGWORKER_BACKEND_DATABASE_CONNECTION 0x0002
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typedef void (*bgworker_main_type) (Datum main_arg);
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/*
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* Points in time at which a bgworker can request to be started
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*/
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typedef enum
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{
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BgWorkerStart_PostmasterStart,
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BgWorkerStart_ConsistentState,
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BgWorkerStart_RecoveryFinished
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} BgWorkerStartTime;
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#define BGW_DEFAULT_RESTART_INTERVAL 60
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#define BGW_NEVER_RESTART -1
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#define BGW_MAXLEN 64
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typedef struct BackgroundWorker
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{
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char bgw_name[BGW_MAXLEN];
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int bgw_flags;
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BgWorkerStartTime bgw_start_time;
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int bgw_restart_time; /* in seconds, or BGW_NEVER_RESTART */
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bgworker_main_type bgw_main;
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Datum bgw_main_arg;
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} BackgroundWorker;
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/* Register a new bgworker */
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extern void RegisterBackgroundWorker(BackgroundWorker *worker);
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/* This is valid in a running worker */
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extern PGDLLIMPORT BackgroundWorker *MyBgworkerEntry;
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/*
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* Connect to the specified database, as the specified user. Only a worker
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* that passed BGWORKER_BACKEND_DATABASE_CONNECTION during registration may
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* call this.
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*
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* If username is NULL, bootstrapping superuser is used.
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* If dbname is NULL, connection is made to no specific database;
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* only shared catalogs can be accessed.
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*/
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extern void BackgroundWorkerInitializeConnection(char *dbname, char *username);
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/* Block/unblock signals in a background worker process */
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extern void BackgroundWorkerBlockSignals(void);
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extern void BackgroundWorkerUnblockSignals(void);
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#endif /* BGWORKER_H */
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