Define PG_REPLSLOT_DIR for path pg_replslot/ in data folder

This commit replaces most of the hardcoded values of "pg_replslot" by a
new PG_REPLSLOT_DIR #define.  This makes the style more consistent with
the existing PG_STAT_TMP_DIR, for example.  More places will follow a
similar change.

Author: Bertrand Drouvot
Reviewed-by: Ashutosh Bapat, Yugo Nagata, Michael Paquier
Discussion: https://postgr.es/m/ZryVvjqS9SnV1GPP@ip-10-97-1-34.eu-west-3.compute.internal

src/backend/backup/basebackup.c

@@ -36,6 +36,7 @@
 #include "port.h"
 #include "postmaster/syslogger.h"
 #include "postmaster/walsummarizer.h"
+#include "replication/slot.h"
 #include "replication/walsender.h"
 #include "replication/walsender_private.h"
 #include "storage/bufpage.h"
@@ -161,7 +162,7 @@ static const char *const excludeDirContents[] =
 	 * even if the intention is to restore to another primary. See backup.sgml
 	 * for a more detailed description.
 	 */
-	"pg_replslot",
+	PG_REPLSLOT_DIR,
 
 	/* Contents removed on startup, see dsm_cleanup_for_mmap(). */
 	PG_DYNSHMEM_DIR,

src/backend/replication/logical/reorderbuffer.c

@@ -4595,9 +4595,9 @@ ReorderBufferCleanupSerializedTXNs(const char *slotname)
 	DIR		   *spill_dir;
 	struct dirent *spill_de;
 	struct stat statbuf;
-	char		path[MAXPGPATH * 2 + 12];
+	char		path[MAXPGPATH * 2 + sizeof(PG_REPLSLOT_DIR)];
 
-	sprintf(path, "pg_replslot/%s", slotname);
+	sprintf(path, "%s/%s", PG_REPLSLOT_DIR, slotname);
 
 	/* we're only handling directories here, skip if it's not ours */
 	if (lstat(path, &statbuf) == 0 && !S_ISDIR(statbuf.st_mode))
@@ -4610,14 +4610,14 @@ ReorderBufferCleanupSerializedTXNs(const char *slotname)
 		if (strncmp(spill_de->d_name, "xid", 3) == 0)
 		{
 			snprintf(path, sizeof(path),
-					 "pg_replslot/%s/%s", slotname,
+					 "%s/%s/%s", PG_REPLSLOT_DIR, slotname,
 					 spill_de->d_name);
 
 			if (unlink(path) != 0)
 				ereport(ERROR,
 						(errcode_for_file_access(),
-						 errmsg("could not remove file \"%s\" during removal of pg_replslot/%s/xid*: %m",
-								path, slotname)));
+						 errmsg("could not remove file \"%s\" during removal of %s/%s/xid*: %m",
+								path, PG_REPLSLOT_DIR, slotname)));
 		}
 	}
 	FreeDir(spill_dir);
@@ -4636,7 +4636,8 @@ ReorderBufferSerializedPath(char *path, ReplicationSlot *slot, TransactionId xid
 
 	XLogSegNoOffsetToRecPtr(segno, 0, wal_segment_size, recptr);
 
-	snprintf(path, MAXPGPATH, "pg_replslot/%s/xid-%u-lsn-%X-%X.spill",
+	snprintf(path, MAXPGPATH, "%s/%s/xid-%u-lsn-%X-%X.spill",
+			 PG_REPLSLOT_DIR,
 			 NameStr(MyReplicationSlot->data.name),
 			 xid, LSN_FORMAT_ARGS(recptr));
 }
@@ -4651,8 +4652,8 @@ StartupReorderBuffer(void)
 	DIR		   *logical_dir;
 	struct dirent *logical_de;
 
-	logical_dir = AllocateDir("pg_replslot");
-	while ((logical_de = ReadDir(logical_dir, "pg_replslot")) != NULL)
+	logical_dir = AllocateDir(PG_REPLSLOT_DIR);
+	while ((logical_de = ReadDir(logical_dir, PG_REPLSLOT_DIR)) != NULL)
 	{
 		if (strcmp(logical_de->d_name, ".") == 0 ||
 			strcmp(logical_de->d_name, "..") == 0)

src/backend/replication/slot.c

@@ -20,11 +20,11 @@
  * on standbys (to support cascading setups).  The requirement that slots be
  * usable on standbys precludes storing them in the system catalogs.
  *
- * Each replication slot gets its own directory inside the $PGDATA/pg_replslot
- * directory. Inside that directory the state file will contain the slot's
- * own data. Additional data can be stored alongside that file if required.
- * While the server is running, the state data is also cached in memory for
- * efficiency.
+ * Each replication slot gets its own directory inside the directory
+ * $PGDATA / PG_REPLSLOT_DIR.  Inside that directory the state file will
+ * contain the slot's own data.  Additional data can be stored alongside that
+ * file if required.  While the server is running, the state data is also
+ * cached in memory for efficiency.
  *
  * ReplicationSlotAllocationLock must be taken in exclusive mode to allocate
  * or free a slot. ReplicationSlotControlLock must be taken in shared mode
@@ -916,8 +916,8 @@ ReplicationSlotDropPtr(ReplicationSlot *slot)
 	LWLockAcquire(ReplicationSlotAllocationLock, LW_EXCLUSIVE);
 
 	/* Generate pathnames. */
-	sprintf(path, "pg_replslot/%s", NameStr(slot->data.name));
-	sprintf(tmppath, "pg_replslot/%s.tmp", NameStr(slot->data.name));
+	sprintf(path, "%s/%s", PG_REPLSLOT_DIR, NameStr(slot->data.name));
+	sprintf(tmppath, "%s/%s.tmp", PG_REPLSLOT_DIR, NameStr(slot->data.name));
 
 	/*
 	 * Rename the slot directory on disk, so that we'll no longer recognize
@@ -938,7 +938,7 @@ ReplicationSlotDropPtr(ReplicationSlot *slot)
 		 */
 		START_CRIT_SECTION();
 		fsync_fname(tmppath, true);
-		fsync_fname("pg_replslot", true);
+		fsync_fname(PG_REPLSLOT_DIR, true);
 		END_CRIT_SECTION();
 	}
 	else
@@ -1016,7 +1016,7 @@ ReplicationSlotSave(void)
 
 	Assert(MyReplicationSlot != NULL);
 
-	sprintf(path, "pg_replslot/%s", NameStr(MyReplicationSlot->data.name));
+	sprintf(path, "%s/%s", PG_REPLSLOT_DIR, NameStr(MyReplicationSlot->data.name));
 	SaveSlotToPath(MyReplicationSlot, path, ERROR);
 }
 
@@ -1881,7 +1881,7 @@ CheckPointReplicationSlots(bool is_shutdown)
 			continue;
 
 		/* save the slot to disk, locking is handled in SaveSlotToPath() */
-		sprintf(path, "pg_replslot/%s", NameStr(s->data.name));
+		sprintf(path, "%s/%s", PG_REPLSLOT_DIR, NameStr(s->data.name));
 
 		/*
 		 * Slot's data is not flushed each time the confirmed_flush LSN is
@@ -1922,17 +1922,17 @@ StartupReplicationSlots(void)
 	elog(DEBUG1, "starting up replication slots");
 
 	/* restore all slots by iterating over all on-disk entries */
-	replication_dir = AllocateDir("pg_replslot");
-	while ((replication_de = ReadDir(replication_dir, "pg_replslot")) != NULL)
+	replication_dir = AllocateDir(PG_REPLSLOT_DIR);
+	while ((replication_de = ReadDir(replication_dir, PG_REPLSLOT_DIR)) != NULL)
 	{
-		char		path[MAXPGPATH + 12];
+		char		path[MAXPGPATH + sizeof(PG_REPLSLOT_DIR)];
 		PGFileType	de_type;
 
 		if (strcmp(replication_de->d_name, ".") == 0 ||
 			strcmp(replication_de->d_name, "..") == 0)
 			continue;
 
-		snprintf(path, sizeof(path), "pg_replslot/%s", replication_de->d_name);
+		snprintf(path, sizeof(path), "%s/%s", PG_REPLSLOT_DIR, replication_de->d_name);
 		de_type = get_dirent_type(path, replication_de, false, DEBUG1);
 
 		/* we're only creating directories here, skip if it's not our's */
@@ -1949,7 +1949,7 @@ StartupReplicationSlots(void)
 								path)));
 				continue;
 			}
-			fsync_fname("pg_replslot", true);
+			fsync_fname(PG_REPLSLOT_DIR, true);
 			continue;
 		}
 
@@ -1987,8 +1987,8 @@ CreateSlotOnDisk(ReplicationSlot *slot)
 	 * takes out the lock, if we'd take the lock here, we'd deadlock.
 	 */
 
-	sprintf(path, "pg_replslot/%s", NameStr(slot->data.name));
-	sprintf(tmppath, "pg_replslot/%s.tmp", NameStr(slot->data.name));
+	sprintf(path, "%s/%s", PG_REPLSLOT_DIR, NameStr(slot->data.name));
+	sprintf(tmppath, "%s/%s.tmp", PG_REPLSLOT_DIR, NameStr(slot->data.name));
 
 	/*
 	 * It's just barely possible that some previous effort to create or drop a
@@ -2027,7 +2027,7 @@ CreateSlotOnDisk(ReplicationSlot *slot)
 	START_CRIT_SECTION();
 
 	fsync_fname(path, true);
-	fsync_fname("pg_replslot", true);
+	fsync_fname(PG_REPLSLOT_DIR, true);
 
 	END_CRIT_SECTION();
 }
@@ -2170,7 +2170,7 @@ SaveSlotToPath(ReplicationSlot *slot, const char *dir, int elevel)
 
 	fsync_fname(path, false);
 	fsync_fname(dir, true);
-	fsync_fname("pg_replslot", true);
+	fsync_fname(PG_REPLSLOT_DIR, true);
 
 	END_CRIT_SECTION();
 
@@ -2195,8 +2195,8 @@ RestoreSlotFromDisk(const char *name)
 {
 	ReplicationSlotOnDisk cp;
 	int			i;
-	char		slotdir[MAXPGPATH + 12];
-	char		path[MAXPGPATH + 22];
+	char		slotdir[MAXPGPATH + sizeof(PG_REPLSLOT_DIR)];
+	char		path[MAXPGPATH + sizeof(PG_REPLSLOT_DIR) + 10];
 	int			fd;
 	bool		restored = false;
 	int			readBytes;
@@ -2205,7 +2205,7 @@ RestoreSlotFromDisk(const char *name)
 	/* no need to lock here, no concurrent access allowed yet */
 
 	/* delete temp file if it exists */
-	sprintf(slotdir, "pg_replslot/%s", name);
+	sprintf(slotdir, "%s/%s", PG_REPLSLOT_DIR, name);
 	sprintf(path, "%s/state.tmp", slotdir);
 	if (unlink(path) < 0 && errno != ENOENT)
 		ereport(PANIC,
@@ -2332,7 +2332,7 @@ RestoreSlotFromDisk(const char *name)
 					(errmsg("could not remove directory \"%s\"",
 							slotdir)));
 		}
-		fsync_fname("pg_replslot", true);
+		fsync_fname(PG_REPLSLOT_DIR, true);
 		return;
 	}
 

src/backend/utils/adt/genfile.c

@@ -708,7 +708,7 @@ pg_ls_logicalmapdir(PG_FUNCTION_ARGS)
 }
 
 /*
- * Function to return the list of files in the pg_replslot/<replication_slot>
+ * Function to return the list of files in the PG_REPLSLOT_DIR/<slot_name>
  * directory.
  */
 Datum
@@ -728,6 +728,7 @@ pg_ls_replslotdir(PG_FUNCTION_ARGS)
 				 errmsg("replication slot \"%s\" does not exist",
 						slotname)));
 
-	snprintf(path, sizeof(path), "pg_replslot/%s", slotname);
+	snprintf(path, sizeof(path), "%s/%s", PG_REPLSLOT_DIR, slotname);
+
 	return pg_ls_dir_files(fcinfo, path, false);
 }

src/bin/pg_rewind/filemap.c

@@ -97,7 +97,7 @@ static const char *const excludeDirContents[] =
 	 * even if the intention is to restore to another primary. See backup.sgml
 	 * for a more detailed description.
 	 */
-	"pg_replslot",
+	"pg_replslot",				/* defined as PG_REPLSLOT_DIR */
 
 	/* Contents removed on startup, see dsm_cleanup_for_mmap(). */
 	"pg_dynshmem",				/* defined as PG_DYNSHMEM_DIR */

src/include/replication/slot.h

@@ -17,6 +17,9 @@
 #include "storage/spin.h"
 #include "replication/walreceiver.h"
 
+/* directory to store replication slot data in */
+#define PG_REPLSLOT_DIR     "pg_replslot"
+
 /*
  * Behaviour of replication slots, upon release or crash.
  *