Remove am_syslogger global variable

Use the new MyBackendType instead.  More similar changes for other "am
something" variables are possible.  This one was just particularly
simple.
Reviewed-by: Julien Rouhaud <rjuju123@gmail.com>
Reviewed-by: Kuntal Ghosh <kuntalghosh.2007@gmail.com>
Reviewed-by: Alvaro Herrera <alvherre@2ndquadrant.com>
Discussion: https://www.postgresql.org/message-id/flat/c65e5196-4f04-4ead-9353-6088c19615a3@2ndquadrant.com

src/backend/postmaster/syslogger.c

@@ -74,11 +74,6 @@ char	   *Log_filename = NULL;
 bool		Log_truncate_on_rotation = false;
 int			Log_file_mode = S_IRUSR | S_IWUSR;
 
-/*
- * Globally visible state (used by elog.c)
- */
-bool		am_syslogger = false;
-
 extern bool redirection_done;
 
 /*
@@ -177,8 +172,6 @@ SysLoggerMain(int argc, char *argv[])
 	syslogger_parseArgs(argc, argv);
 #endif							/* EXEC_BACKEND */
 
-	am_syslogger = true;
-
 	MyBackendType = B_LOGGER;
 	init_ps_display(NULL);
 
@@ -1078,7 +1071,7 @@ flush_pipe_input(char *logbuffer, int *bytes_in_logbuffer)
 /*
  * Write text to the currently open logfile
  *
- * This is exported so that elog.c can call it when am_syslogger is true.
+ * This is exported so that elog.c can call it when MyBackendType is B_LOGGER.
  * This allows the syslogger process to record elog messages of its own,
  * even though its stderr does not point at the syslog pipe.
  */

src/backend/utils/error/elog.c

@@ -2923,7 +2923,7 @@ write_csvlog(ErrorData *edata)
 	appendStringInfoChar(&buf, '\n');
 
 	/* If in the syslogger process, try to write messages direct to file */
-	if (am_syslogger)
+	if (MyBackendType == B_LOGGER)
 		write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
 	else
 		write_pipe_chunks(buf.data, buf.len, LOG_DESTINATION_CSVLOG);
@@ -3117,7 +3117,7 @@ send_message_to_server_log(ErrorData *edata)
 		 * catching stderr output, and we are not ourselves the syslogger.
 		 * Otherwise, just do a vanilla write to stderr.
 		 */
-		if (redirection_done && !am_syslogger)
+		if (redirection_done && MyBackendType != B_LOGGER)
 			write_pipe_chunks(buf.data, buf.len, LOG_DESTINATION_STDERR);
 #ifdef WIN32
 
@@ -3136,13 +3136,13 @@ send_message_to_server_log(ErrorData *edata)
 	}
 
 	/* If in the syslogger process, try to write messages direct to file */
-	if (am_syslogger)
+	if (MyBackendType == B_LOGGER)
 		write_syslogger_file(buf.data, buf.len, LOG_DESTINATION_STDERR);
 
 	/* Write to CSV log if enabled */
 	if (Log_destination & LOG_DESTINATION_CSVLOG)
 	{
-		if (redirection_done || am_syslogger)
+		if (redirection_done || MyBackendType == B_LOGGER)
 		{
 			/*
 			 * send CSV data if it's safe to do so (syslogger doesn't need the

src/include/postmaster/syslogger.h

@@ -70,8 +70,6 @@ extern PGDLLIMPORT char *Log_filename;
 extern bool Log_truncate_on_rotation;
 extern int	Log_file_mode;
 
-extern bool am_syslogger;
-
 #ifndef WIN32
 extern int	syslogPipe[2];
 #else