1/*--------------------------------------------------------------------
3 * POSTGRES pluggable background workers interface
5 * A background worker is a process able to run arbitrary, user-supplied code,
6 * including normal transactions.
8 * Any external module loaded via shared_preload_libraries can register a
9 * worker. Workers can also be registered dynamically at runtime. In either
10 * case, the worker process is forked from the postmaster and runs the
11 * user-supplied "main" function. This code may connect to a database and
12 * run transactions. Workers can remain active indefinitely, but will be
13 * terminated if a shutdown or crash occurs.
15 * If the fork() call fails in the postmaster, it will try again later. Note
16 * that the failure can only be transient (fork failure due to high load,
17 * memory pressure, too many processes, etc); more permanent problems, like
18 * failure to connect to a database, are detected later in the worker and dealt
19 * with just by having the worker exit normally. A worker which exits with
20 * a return code of 0 will never be restarted and will be removed from worker
21 * list. A worker which exits with a return code of 1 will be restarted after
22 * the configured restart interval (unless that interval is BGW_NEVER_RESTART).
23 * The TerminateBackgroundWorker() function can be used to terminate a
24 * dynamically registered background worker; the worker will be sent a SIGTERM
25 * and will not be restarted after it exits. Whenever the postmaster knows
26 * that a worker will not be restarted, it unregisters the worker, freeing up
27 * that worker's slot for use by a new worker.
29 * Note that there might be more than one worker in a database concurrently,
30 * and the same module may request more than one worker running the same (or
34 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
35 * Portions Copyright (c) 1994, Regents of the University of California
38 * src/include/postmaster/bgworker.h
39 *--------------------------------------------------------------------
44/*---------------------------------------------------------------------
45 * External module API.
46 *---------------------------------------------------------------------
50 * Pass this flag to have your worker be able to connect to shared memory.
51 * This flag is required.
53 #define BGWORKER_SHMEM_ACCESS 0x0001
56 * This flag means the bgworker requires a database connection. The connection
57 * is not established automatically; the worker must establish it later.
58 * It requires that BGWORKER_SHMEM_ACCESS was passed too.
60 #define BGWORKER_BACKEND_DATABASE_CONNECTION 0x0002
63 * This class is used internally for parallel queries, to keep track of the
64 * number of active parallel workers and make sure we never launch more than
65 * max_parallel_workers parallel workers at the same time. Third party
66 * background workers should not use this class.
68 #define BGWORKER_CLASS_PARALLEL 0x0010
69/* add additional bgworker classes here */
75 * Points in time at which a bgworker can request to be started
84 #define BGW_DEFAULT_RESTART_INTERVAL 60
85 #define BGW_NEVER_RESTART -1
87 #define BGW_EXTRALEN 128
114/* Register a new bgworker during shared_preload_libraries */
117/* Register a new bgworker from a regular backend */
121/* Query the status of a bgworker */
129/* Terminate a bgworker */
132/* This is valid in a running worker */
136 * Connect to the specified database, as the specified user. Only a worker
137 * that passed BGWORKER_BACKEND_DATABASE_CONNECTION during registration may
140 * If username is NULL, bootstrapping superuser is used.
141 * If dbname is NULL, connection is made to no specific database;
142 * only shared catalogs can be accessed.
146/* Just like the above, but specifying database and user by OID. */
150 * Flags to BackgroundWorkerInitializeConnection et al
153 * Allow bypassing datallowconn restrictions and login check when connecting
156 #define BGWORKER_BYPASS_ALLOWCONN 0x0001
157 #define BGWORKER_BYPASS_ROLELOGINCHECK 0x0002
160/* Block/unblock signals in a background worker process */
164#endif /* BGWORKER_H */
void RegisterBackgroundWorker(BackgroundWorker *worker)
BgwHandleStatus WaitForBackgroundWorkerStartup(BackgroundWorkerHandle *handle, pid_t *pidp)
BgwHandleStatus WaitForBackgroundWorkerShutdown(BackgroundWorkerHandle *)
void BackgroundWorkerInitializeConnection(const char *dbname, const char *username, uint32 flags)
void TerminateBackgroundWorker(BackgroundWorkerHandle *handle)
void BackgroundWorkerUnblockSignals(void)
void BackgroundWorkerInitializeConnectionByOid(Oid dboid, Oid useroid, uint32 flags)
@ BgWorkerStart_RecoveryFinished
@ BgWorkerStart_ConsistentState
@ BgWorkerStart_PostmasterStart
void BackgroundWorkerBlockSignals(void)
struct BackgroundWorker BackgroundWorker
BgwHandleStatus GetBackgroundWorkerPid(BackgroundWorkerHandle *handle, pid_t *pidp)
PGDLLIMPORT BackgroundWorker * MyBgworkerEntry
void(* bgworker_main_type)(Datum main_arg)
const char * GetBackgroundWorkerTypeByPid(pid_t pid)
bool RegisterDynamicBackgroundWorker(BackgroundWorker *worker, BackgroundWorkerHandle **handle)
char bgw_function_name[BGW_MAXLEN]
char bgw_name[BGW_MAXLEN]
char bgw_type[BGW_MAXLEN]
BgWorkerStartTime bgw_start_time
char bgw_extra[BGW_EXTRALEN]
char bgw_library_name[MAXPGPATH]