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e652273e07
Formerly, Unix builds of pg_dump/pg_restore would trap SIGINT and similar signals and set a flag that was tested in various data-transfer loops. This was prone to errors of omission (cf commit 3c8aa6654); and even if the client-side response was prompt, we did nothing that would cause long-running SQL commands (e.g. CREATE INDEX) to terminate early. Also, the master process would effectively do nothing at all upon receipt of SIGINT; the only reason it seemed to work was that in typical scenarios the signal would also be delivered to the child processes. We should support termination when a signal is delivered only to the master process, though. Windows builds had no console interrupt handler, so they would just fall over immediately at control-C, again leaving long-running SQL commands to finish unmolested. To fix, remove the flag-checking approach altogether. Instead, allow the Unix signal handler to send a cancel request directly and then exit(1). In the master process, also have it forward the signal to the children. On Windows, add a console interrupt handler that behaves approximately the same. The main difference is that a single execution of the Windows handler can send all the cancel requests since all the info is available in one process, whereas on Unix each process sends a cancel only for its own database connection. In passing, fix an old problem that DisconnectDatabase tends to send a cancel request before exiting a parallel worker, even if nothing went wrong. This is at least a waste of cycles, and could lead to unexpected log messages, or maybe even data loss if it happened in pg_restore (though in the current code the problem seems to affect only pg_dump). The cause was that after a COPY step, pg_dump was leaving libpq in PGASYNC_BUSY state, causing PQtransactionStatus() to report PQTRANS_ACTIVE. That's normally harmless because the next PQexec() will silently clear the PGASYNC_BUSY state; but in a parallel worker we might exit without any additional SQL commands after a COPY step. So add an extra PQgetResult() call after a COPY to allow libpq to return to PGASYNC_IDLE state. This is a bug fix, IMO, so back-patch to 9.3 where parallel dump/restore were introduced. Thanks to Kyotaro Horiguchi for Windows testing and code suggestions. Original-Patch: <7005.1464657274@sss.pgh.pa.us> Discussion: <20160602.174941.256342236.horiguchi.kyotaro@lab.ntt.co.jp>
88 lines
2.2 KiB
C
88 lines
2.2 KiB
C
/*-------------------------------------------------------------------------
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*
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* parallel.h
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*
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* Parallel support header file for the pg_dump archiver
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*
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* Portions Copyright (c) 1996-2016, 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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* The author is not responsible for loss or damages that may
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* result from its use.
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*
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* IDENTIFICATION
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* src/bin/pg_dump/parallel.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef PG_DUMP_PARALLEL_H
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#define PG_DUMP_PARALLEL_H
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#include "pg_backup_archiver.h"
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typedef enum
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{
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WRKR_TERMINATED = 0,
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WRKR_IDLE,
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WRKR_WORKING,
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WRKR_FINISHED
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} T_WorkerStatus;
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/* Arguments needed for a worker process */
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typedef struct ParallelArgs
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{
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ArchiveHandle *AH;
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TocEntry *te;
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} ParallelArgs;
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/* State for each parallel activity slot */
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typedef struct ParallelSlot
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{
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ParallelArgs *args;
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T_WorkerStatus workerStatus;
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int status;
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int pipeRead; /* master's end of the pipes */
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int pipeWrite;
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int pipeRevRead; /* child's end of the pipes */
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int pipeRevWrite;
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#ifdef WIN32
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uintptr_t hThread;
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unsigned int threadId;
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#else
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pid_t pid;
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#endif
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} ParallelSlot;
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#define NO_SLOT (-1)
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typedef struct ParallelState
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{
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int numWorkers;
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ParallelSlot *parallelSlot;
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} ParallelState;
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#ifdef WIN32
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extern bool parallel_init_done;
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extern DWORD mainThreadId;
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#endif
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extern void init_parallel_dump_utils(void);
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extern int GetIdleWorker(ParallelState *pstate);
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extern bool IsEveryWorkerIdle(ParallelState *pstate);
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extern void ListenToWorkers(ArchiveHandle *AH, ParallelState *pstate, bool do_wait);
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extern int ReapWorkerStatus(ParallelState *pstate, int *status);
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extern void EnsureIdleWorker(ArchiveHandle *AH, ParallelState *pstate);
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extern void EnsureWorkersFinished(ArchiveHandle *AH, ParallelState *pstate);
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extern ParallelState *ParallelBackupStart(ArchiveHandle *AH);
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extern void DispatchJobForTocEntry(ArchiveHandle *AH,
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ParallelState *pstate,
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TocEntry *te, T_Action act);
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extern void ParallelBackupEnd(ArchiveHandle *AH, ParallelState *pstate);
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extern void set_archive_cancel_info(ArchiveHandle *AH, PGconn *conn);
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#endif /* PG_DUMP_PARALLEL_H */
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