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2d77d83540
The previous protocol expected a set of matching characters to check if a message sent was the last one or not, that changed depending on the destination wanted: - 't' and 'f' tracked the last message of a log sent to stderr. - 'T' and 'F' tracked the last message of a log sent to csvlog. This could be extended with more characters when introducing new destinations, but using a bitmask is much more elegant. This commit changes the protocol so as a bitmask is used in the header of a log chunk message sent to the syslogger, with the following options available for now: - log_destination as stderr. - log_destination as csvlog. - if a message is the last chunk of a message. Sehrope found this issue in a patch set to introduce JSON as an option for log_destination, but his patch made the size of the protocol header larger. This commit keeps the same size as the original, and adapts the protocol as wanted. Thanks also to Andrew Dunstan and Greg Stark for the discussion. Author: Michael Paquier, Sehrope Sarkuni Discussion: https://postgr.es/m/CAH7T-aqswBM6JWe4pDehi1uOiufqe06DJWaU5=X7dDLyqUExHg@mail.gmail.com
103 lines
3.0 KiB
C
103 lines
3.0 KiB
C
/*-------------------------------------------------------------------------
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*
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* syslogger.h
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* Exports from postmaster/syslogger.c.
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*
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* Copyright (c) 2004-2021, PostgreSQL Global Development Group
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*
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* src/include/postmaster/syslogger.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef _SYSLOGGER_H
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#define _SYSLOGGER_H
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#include <limits.h> /* for PIPE_BUF */
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/*
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* Primitive protocol structure for writing to syslogger pipe(s). The idea
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* here is to divide long messages into chunks that are not more than
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* PIPE_BUF bytes long, which according to POSIX spec must be written into
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* the pipe atomically. The pipe reader then uses the protocol headers to
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* reassemble the parts of a message into a single string. The reader can
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* also cope with non-protocol data coming down the pipe, though we cannot
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* guarantee long strings won't get split apart.
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*
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* We use non-nul bytes in is_last to make the protocol a tiny bit
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* more robust against finding a false double nul byte prologue. But
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* we still might find it in the len and/or pid bytes unless we're careful.
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*/
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#ifdef PIPE_BUF
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/* Are there any systems with PIPE_BUF > 64K? Unlikely, but ... */
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#if PIPE_BUF > 65536
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#define PIPE_CHUNK_SIZE 65536
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#else
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#define PIPE_CHUNK_SIZE ((int) PIPE_BUF)
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#endif
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#else /* not defined */
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/* POSIX says the value of PIPE_BUF must be at least 512, so use that */
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#define PIPE_CHUNK_SIZE 512
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#endif
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typedef struct
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{
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char nuls[2]; /* always \0\0 */
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uint16 len; /* size of this chunk (counts data only) */
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int32 pid; /* writer's pid */
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bits8 flags; /* bitmask of PIPE_PROTO_* */
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char data[FLEXIBLE_ARRAY_MEMBER]; /* data payload starts here */
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} PipeProtoHeader;
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typedef union
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{
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PipeProtoHeader proto;
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char filler[PIPE_CHUNK_SIZE];
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} PipeProtoChunk;
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#define PIPE_HEADER_SIZE offsetof(PipeProtoHeader, data)
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#define PIPE_MAX_PAYLOAD ((int) (PIPE_CHUNK_SIZE - PIPE_HEADER_SIZE))
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/* flag bits for PipeProtoHeader->flags */
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#define PIPE_PROTO_IS_LAST 0x01 /* last chunk of message? */
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/* log destinations */
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#define PIPE_PROTO_DEST_STDERR 0x10
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#define PIPE_PROTO_DEST_CSVLOG 0x20
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/* GUC options */
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extern bool Logging_collector;
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extern int Log_RotationAge;
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extern int Log_RotationSize;
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extern PGDLLIMPORT char *Log_directory;
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extern PGDLLIMPORT char *Log_filename;
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extern bool Log_truncate_on_rotation;
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extern int Log_file_mode;
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#ifndef WIN32
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extern int syslogPipe[2];
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#else
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extern HANDLE syslogPipe[2];
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#endif
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extern int SysLogger_Start(void);
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extern void write_syslogger_file(const char *buffer, int count, int dest);
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#ifdef EXEC_BACKEND
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extern void SysLoggerMain(int argc, char *argv[]) pg_attribute_noreturn();
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#endif
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extern bool CheckLogrotateSignal(void);
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extern void RemoveLogrotateSignalFiles(void);
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/*
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* Name of files saving meta-data information about the log
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* files currently in use by the syslogger
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*/
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#define LOG_METAINFO_DATAFILE "current_logfiles"
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#define LOG_METAINFO_DATAFILE_TMP LOG_METAINFO_DATAFILE ".tmp"
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#endif /* _SYSLOGGER_H */
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