Remove code duplication to get a node's current timeline

Michael Paquier · Michael Paquier · commit e2bbf6940321 · 2016-01-15T14:09:31.000+09:00
The same code was duplicated between restore and backup. At the same
time this commit introduces routines to fetch the control data file.
diff --git a/backup.c b/backup.c
@@ -17,7 +17,6 @@
 #include <dirent.h>
 #include <time.h>
 
-#include "catalog/pg_control.h"
 #include "libpq/pqsignal.h"
 #include "pgut/pgut-port.h"
 
@@ -54,7 +53,6 @@ static void create_file_list(parray *files,
 							 const char *subdir,
 							 const char *prefix,
 							 bool is_append);
-static TimeLineID get_current_timeline(void);
 
 /*
  * Take a backup of database and return the list of files backed up.
@@ -1047,27 +1045,3 @@ create_file_list(parray *files,
 		fclose(fp);
 	}
 }
-
-/*
- * Scan control file of given cluster at obtain the current timeline
- * since last checkpoint that occurred on it.
- */
-static TimeLineID
-get_current_timeline(void)
-{
-	char	   *buffer;
-	size_t		size;
-	ControlFileData control_file;
-
-	/* First fetch file... */
-	buffer = slurpFile(pgdata, "global/pg_control", &size);
-
-	/* .. Then interpret it */
-    if (size != PG_CONTROL_SIZE)
-		elog(ERROR_CORRUPTED, "unexpected control file size %d, expected %d",
-			 (int) size, PG_CONTROL_SIZE);
-	memcpy(&control_file, buffer, sizeof(ControlFileData));
-
-	/* Finally return the timeline wanted */
-	return control_file.checkPointCopy.ThisTimeLineID;
-}
diff --git a/pg_arman.h b/pg_arman.h
@@ -289,6 +289,7 @@ extern bool copy_file(const char *from_root, const char *to_root,
 					  pgFile *file);
 
 /* in util.c */
+extern TimeLineID get_current_timeline(void);
 extern void time2iso(char *buf, size_t len, time_t time);
 extern const char *status2str(BackupStatus status);
 extern void remove_trailing_space(char *buf, int comment_mark);
diff --git a/restore.c b/restore.c
@@ -29,7 +29,6 @@ static parray * readTimeLineHistory(TimeLineID targetTLI);
 static bool satisfy_timeline(const parray *timelines, const pgBackup *backup);
 static bool satisfy_recovery_target(const pgBackup *backup,
 									const pgRecoveryTarget *rt);
-static TimeLineID get_current_timeline(void);
 static TimeLineID get_fullbackup_timeline(parray *backups,
 										  const pgRecoveryTarget *rt);
 static void print_backup_lsn(const pgBackup *backup);
@@ -624,62 +623,6 @@ satisfy_timeline(const parray *timelines, const pgBackup *backup)
 	return false;
 }
 
-/* get TLI of the current database */
-static TimeLineID
-get_current_timeline(void)
-{
-	ControlFileData ControlFile;
-	int			fd;
-	char		ControlFilePath[MAXPGPATH];
-	pg_crc32	crc;
-	TimeLineID	ret;
-
-	snprintf(ControlFilePath, MAXPGPATH, "%s/global/pg_control", pgdata);
-
-	if ((fd = open(ControlFilePath, O_RDONLY | PG_BINARY, 0)) == -1)
-	{
-		elog(WARNING, "cannot open pg_controldata file \"%s\": %s",
-			ControlFilePath, strerror(errno));
-		return 0;
-	}
-
-	if (read(fd, &ControlFile, sizeof(ControlFileData)) != sizeof(ControlFileData))
-	{
-		elog(WARNING, "cannot read pg_controldata file \"%s\": %s",
-			ControlFilePath, strerror(errno));
-		return 0;
-	}
-	close(fd);
-
-	/* Check the CRC. */
-	INIT_CRC32C(crc);
-	COMP_CRC32C(crc,
-		   	(char *) &ControlFile,
-		   	offsetof(ControlFileData, crc));
-	FIN_CRC32C(crc);
-
-	if (!EQ_CRC32C(crc, ControlFile.crc))
-	{
-		elog(WARNING, "Calculated CRC checksum does not match value stored in file.\n"
-			"Either the file is corrupt, or it has a different layout than this program\n"
-			"is expecting.  The results below are untrustworthy.\n");
-		return 0;
-	}
-
-	if (ControlFile.pg_control_version % 65536 == 0 && ControlFile.pg_control_version / 65536 != 0)
-	{
-		elog(WARNING, "possible byte ordering mismatch\n"
-			"The byte ordering used to store the pg_control file might not match the one\n"
-			"used by this program.  In that case the results below would be incorrect, and\n"
-			"the PostgreSQL installation would be incompatible with this data directory.\n");
-		return 0;
-	}
-
-	ret = ControlFile.checkPointCopy.ThisTimeLineID;
-
-	return ret;
-}
-
 /* get TLI of the latest full backup */
 static TimeLineID
 get_fullbackup_timeline(parray *backups, const pgRecoveryTarget *rt)
diff --git a/util.c b/util.c
@@ -11,6 +11,66 @@
 
 #include <time.h>
 
+#include "catalog/pg_control.h"
+
+static void
+checkControlFile(ControlFileData *ControlFile)
+{
+	pg_crc32c   crc;
+
+	/* Calculate CRC */
+	INIT_CRC32C(crc);
+	COMP_CRC32C(crc, (char *) ControlFile, offsetof(ControlFileData, crc));
+	FIN_CRC32C(crc);
+
+	/* Then compare it */
+    if (!EQ_CRC32C(crc, ControlFile->crc))
+		elog(ERROR_CORRUPTED, "Calculated CRC checksum does not match value stored in file.\n"
+			 "Either the file is corrupt, or it has a different layout than this program\n"
+			 "is expecting. The results below are untrustworthy.\n");
+
+	if (ControlFile->pg_control_version % 65536 == 0 && ControlFile->pg_control_version / 65536 != 0)
+		elog(ERROR_CORRUPTED, "possible byte ordering mismatch\n"
+			 "The byte ordering used to store the pg_control file might not match the one\n"
+			 "used by this program. In that case the results below would be incorrect, and\n"
+			 "the PostgreSQL installation would be incompatible with this data directory.\n");
+}
+
+/*
+ * Verify control file contents in the buffer src, and copy it to *ControlFile.
+ */
+static void
+digestControlFile(ControlFileData *ControlFile, char *src, size_t size)
+{
+	if (size != PG_CONTROL_SIZE)
+		elog(ERROR_PG_INCOMPATIBLE, "unexpected control file size %d, expected %d\n",
+			 (int) size, PG_CONTROL_SIZE);
+
+	memcpy(ControlFile, src, sizeof(ControlFileData));
+
+	/* Additional checks on control file */
+	checkControlFile(ControlFile);
+}
+
+/*
+ * Utility shared by backup and restore to fetch the current timeline
+ * used by a node.
+ */
+TimeLineID
+get_current_timeline(void)
+{
+	ControlFileData ControlFile;
+	char       *buffer;
+	size_t      size;
+
+	/* First fetch file... */
+	buffer = slurpFile(pgdata, "global/pg_control", &size);
+	digestControlFile(&ControlFile, buffer, size);
+	pg_free(buffer);
+
+	return ControlFile.checkPointCopy.ThisTimeLineID;
+}
+
 /*
  * Convert time_t value to ISO-8601 format string
  */
