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db_include/postmaster/syslogger.h

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+/*-------------------------------------------------------------------------
+ *
+ * syslogger.h
+ *	  Exports from postmaster/syslogger.c.
+ *
+ * Copyright (c) 2004-2021, PostgreSQL Global Development Group
+ *
+ * src/include/postmaster/syslogger.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef _SYSLOGGER_H
+#define _SYSLOGGER_H
+
+#include <limits.h>				/* for PIPE_BUF */
+
+
+/*
+ * Primitive protocol structure for writing to syslogger pipe(s).  The idea
+ * here is to divide long messages into chunks that are not more than
+ * PIPE_BUF bytes long, which according to POSIX spec must be written into
+ * the pipe atomically.  The pipe reader then uses the protocol headers to
+ * reassemble the parts of a message into a single string.  The reader can
+ * also cope with non-protocol data coming down the pipe, though we cannot
+ * guarantee long strings won't get split apart.
+ *
+ * We use non-nul bytes in is_last to make the protocol a tiny bit
+ * more robust against finding a false double nul byte prologue. But
+ * we still might find it in the len and/or pid bytes unless we're careful.
+ */
+
+#ifdef PIPE_BUF
+/* Are there any systems with PIPE_BUF > 64K?  Unlikely, but ... */
+#if PIPE_BUF > 65536
+#define PIPE_CHUNK_SIZE  65536
+#else
+#define PIPE_CHUNK_SIZE  ((int) PIPE_BUF)
+#endif
+#else							/* not defined */
+/* POSIX says the value of PIPE_BUF must be at least 512, so use that */
+#define PIPE_CHUNK_SIZE  512
+#endif
+
+typedef struct
+{
+	char		nuls[2];		/* always \0\0 */
+	uint16		len;			/* size of this chunk (counts data only) */
+	int32		pid;			/* writer's pid */
+	char		is_last;		/* last chunk of message? 't' or 'f' ('T' or
+								 * 'F' for CSV case) */
+	char		data[FLEXIBLE_ARRAY_MEMBER];	/* data payload starts here */
+} PipeProtoHeader;
+
+typedef union
+{
+	PipeProtoHeader proto;
+	char		filler[PIPE_CHUNK_SIZE];
+} PipeProtoChunk;
+
+#define PIPE_HEADER_SIZE  offsetof(PipeProtoHeader, data)
+#define PIPE_MAX_PAYLOAD  ((int) (PIPE_CHUNK_SIZE - PIPE_HEADER_SIZE))
+
+
+/* GUC options */
+extern bool Logging_collector;
+extern int	Log_RotationAge;
+extern int	Log_RotationSize;
+extern PGDLLIMPORT char *Log_directory;
+extern PGDLLIMPORT char *Log_filename;
+extern bool Log_truncate_on_rotation;
+extern int	Log_file_mode;
+
+#ifndef WIN32
+extern int	syslogPipe[2];
+#else
+extern HANDLE syslogPipe[2];
+#endif
+
+
+extern int	SysLogger_Start(void);
+
+extern void write_syslogger_file(const char *buffer, int count, int dest);
+
+#ifdef EXEC_BACKEND
+extern void SysLoggerMain(int argc, char *argv[]) pg_attribute_noreturn();
+#endif
+
+extern bool CheckLogrotateSignal(void);
+extern void RemoveLogrotateSignalFiles(void);
+
+/*
+ * Name of files saving meta-data information about the log
+ * files currently in use by the syslogger
+ */
+#define LOG_METAINFO_DATAFILE  "current_logfiles"
+#define LOG_METAINFO_DATAFILE_TMP  LOG_METAINFO_DATAFILE ".tmp"
+
+#endif							/* _SYSLOGGER_H */