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Diffstat (limited to 'src/include/postmaster/bgworker.h')
| -rw-r--r-- | src/include/postmaster/bgworker.h | 161 |
1 files changed, 161 insertions, 0 deletions
diff --git a/src/include/postmaster/bgworker.h b/src/include/postmaster/bgworker.h new file mode 100644 index 0000000..4c6ebaa --- /dev/null +++ b/src/include/postmaster/bgworker.h @@ -0,0 +1,161 @@ +/*-------------------------------------------------------------------- + * bgworker.h + * POSTGRES pluggable background workers interface + * + * A background worker is a process able to run arbitrary, user-supplied code, + * including normal transactions. + * + * Any external module loaded via shared_preload_libraries can register a + * worker. Workers can also be registered dynamically at runtime. In either + * case, the worker process is forked from the postmaster and runs the + * user-supplied "main" function. This code may connect to a database and + * run transactions. Workers can remain active indefinitely, but will be + * terminated if a shutdown or crash occurs. + * + * If the fork() call fails in the postmaster, it will try again later. Note + * that the failure can only be transient (fork failure due to high load, + * memory pressure, too many processes, etc); more permanent problems, like + * failure to connect to a database, are detected later in the worker and dealt + * with just by having the worker exit normally. A worker which exits with + * a return code of 0 will never be restarted and will be removed from worker + * list. A worker which exits with a return code of 1 will be restarted after + * the configured restart interval (unless that interval is BGW_NEVER_RESTART). + * The TerminateBackgroundWorker() function can be used to terminate a + * dynamically registered background worker; the worker will be sent a SIGTERM + * and will not be restarted after it exits. Whenever the postmaster knows + * that a worker will not be restarted, it unregisters the worker, freeing up + * that worker's slot for use by a new worker. + * + * Note that there might be more than one worker in a database concurrently, + * and the same module may request more than one worker running the same (or + * different) code. + * + * + * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group + * Portions Copyright (c) 1994, Regents of the University of California + * + * IDENTIFICATION + * src/include/postmaster/bgworker.h + *-------------------------------------------------------------------- + */ +#ifndef BGWORKER_H +#define BGWORKER_H + +/*--------------------------------------------------------------------- + * External module API. + *--------------------------------------------------------------------- + */ + +/* + * Pass this flag to have your worker be able to connect to shared memory. + */ +#define BGWORKER_SHMEM_ACCESS 0x0001 + +/* + * This flag means the bgworker requires a database connection. The connection + * is not established automatically; the worker must establish it later. + * It requires that BGWORKER_SHMEM_ACCESS was passed too. + */ +#define BGWORKER_BACKEND_DATABASE_CONNECTION 0x0002 + +/* + * This class is used internally for parallel queries, to keep track of the + * number of active parallel workers and make sure we never launch more than + * max_parallel_workers parallel workers at the same time. Third party + * background workers should not use this class. + */ +#define BGWORKER_CLASS_PARALLEL 0x0010 +/* add additional bgworker classes here */ + + +typedef void (*bgworker_main_type) (Datum main_arg); + +/* + * Points in time at which a bgworker can request to be started + */ +typedef enum +{ + BgWorkerStart_PostmasterStart, + BgWorkerStart_ConsistentState, + BgWorkerStart_RecoveryFinished +} BgWorkerStartTime; + +#define BGW_DEFAULT_RESTART_INTERVAL 60 +#define BGW_NEVER_RESTART -1 +#define BGW_MAXLEN 96 +#define BGW_EXTRALEN 128 + +typedef struct BackgroundWorker +{ + char bgw_name[BGW_MAXLEN]; + char bgw_type[BGW_MAXLEN]; + int bgw_flags; + BgWorkerStartTime bgw_start_time; + int bgw_restart_time; /* in seconds, or BGW_NEVER_RESTART */ + char bgw_library_name[BGW_MAXLEN]; + char bgw_function_name[BGW_MAXLEN]; + Datum bgw_main_arg; + char bgw_extra[BGW_EXTRALEN]; + pid_t bgw_notify_pid; /* SIGUSR1 this backend on start/stop */ +} BackgroundWorker; + +typedef enum BgwHandleStatus +{ + BGWH_STARTED, /* worker is running */ + BGWH_NOT_YET_STARTED, /* worker hasn't been started yet */ + BGWH_STOPPED, /* worker has exited */ + BGWH_POSTMASTER_DIED /* postmaster died; worker status unclear */ +} BgwHandleStatus; + +struct BackgroundWorkerHandle; +typedef struct BackgroundWorkerHandle BackgroundWorkerHandle; + +/* Register a new bgworker during shared_preload_libraries */ +extern void RegisterBackgroundWorker(BackgroundWorker *worker); + +/* Register a new bgworker from a regular backend */ +extern bool RegisterDynamicBackgroundWorker(BackgroundWorker *worker, + BackgroundWorkerHandle **handle); + +/* Query the status of a bgworker */ +extern BgwHandleStatus GetBackgroundWorkerPid(BackgroundWorkerHandle *handle, + pid_t *pidp); +extern BgwHandleStatus WaitForBackgroundWorkerStartup(BackgroundWorkerHandle *handle, pid_t *pid); +extern BgwHandleStatus + WaitForBackgroundWorkerShutdown(BackgroundWorkerHandle *); +extern const char *GetBackgroundWorkerTypeByPid(pid_t pid); + +/* Terminate a bgworker */ +extern void TerminateBackgroundWorker(BackgroundWorkerHandle *handle); + +/* This is valid in a running worker */ +extern PGDLLIMPORT BackgroundWorker *MyBgworkerEntry; + +/* + * Connect to the specified database, as the specified user. Only a worker + * that passed BGWORKER_BACKEND_DATABASE_CONNECTION during registration may + * call this. + * + * If username is NULL, bootstrapping superuser is used. + * If dbname is NULL, connection is made to no specific database; + * only shared catalogs can be accessed. + */ +extern void BackgroundWorkerInitializeConnection(const char *dbname, const char *username, uint32 flags); + +/* Just like the above, but specifying database and user by OID. */ +extern void BackgroundWorkerInitializeConnectionByOid(Oid dboid, Oid useroid, uint32 flags); + +/* + * Flags to BackgroundWorkerInitializeConnection et al + * + * + * Allow bypassing datallowconn restrictions when connecting to database + */ +#define BGWORKER_BYPASS_ALLOWCONN 1 + + +/* Block/unblock signals in a background worker process */ +extern void BackgroundWorkerBlockSignals(void); +extern void BackgroundWorkerUnblockSignals(void); + +#endif /* BGWORKER_H */ |