Allow extensions to add new backup targets.

Commit 3500ccc allowed for base backup
targets, meaning that we could do something with the backup other than
send it to the client, but all of those targets had to be baked in to
the core code. This commit makes it possible for extensions to define
additional backup targets.

Patch by me, reviewed by Abhijit Menon-Sen.

Discussion: http://postgr.es/m/CA+TgmoaqvdT-u3nt+_kkZ7bgDAyqDB0i-+XOMmr5JN2Rd37hxw@mail.gmail.com

Author: robertmhaas

src/backend/replication/Makefile

@@ -24,6 +24,7 @@ OBJS = \
 	basebackup_progress.o \
 	basebackup_server.o \
 	basebackup_sink.o \
+	basebackup_target.o \
 	basebackup_throttle.o \
 	repl_gram.o \
 	slot.o \

src/backend/replication/Makefile.orig

@@ -0,0 +1,49 @@
+#-------------------------------------------------------------------------
+#
+# Makefile--
+#    Makefile for src/backend/replication
+#
+# IDENTIFICATION
+#    src/backend/replication/Makefile
+#
+#-------------------------------------------------------------------------
+
+subdir = src/backend/replication
+top_builddir = ../../..
+include $(top_builddir)/src/Makefile.global
+
+override CPPFLAGS := -I. -I$(srcdir) $(CPPFLAGS)
+
+OBJS = \
+	backup_manifest.o \
+	basebackup.o \
+	basebackup_copy.o \
+	basebackup_gzip.o \
+	basebackup_lz4.o \
+	basebackup_zstd.o \
+	basebackup_progress.o \
+	basebackup_server.o \
+	basebackup_sink.o \
+	basebackup_throttle.o \
+	repl_gram.o \
+	slot.o \
+	slotfuncs.o \
+	syncrep.o \
+	syncrep_gram.o \
+	walreceiver.o \
+	walreceiverfuncs.o \
+	walsender.o
+
+SUBDIRS = logical
+
+include $(top_srcdir)/src/backend/common.mk
+
+# repl_scanner is compiled as part of repl_gram
+repl_gram.o: repl_scanner.c
+
+# syncrep_scanner is compiled as part of syncrep_gram
+syncrep_gram.o: syncrep_scanner.c
+
+# repl_gram.c, repl_scanner.c, syncrep_gram.c and syncrep_scanner.c
+# are in the distribution tarball, so they are not cleaned here.
+# (Our parent Makefile takes care of them during maintainer-clean.)

src/backend/replication/basebackup.c

@@ -28,6 +28,7 @@
 #include "postmaster/syslogger.h"
 #include "replication/basebackup.h"
 #include "replication/basebackup_sink.h"
+#include "replication/basebackup_target.h"
 #include "replication/backup_manifest.h"
 #include "replication/walsender.h"
 #include "replication/walsender_private.h"
@@ -53,13 +54,6 @@
  */
 #define SINK_BUFFER_LENGTH			Max(32768, BLCKSZ)
 
-typedef enum
-{
-	BACKUP_TARGET_BLACKHOLE,
-	BACKUP_TARGET_CLIENT,
-	BACKUP_TARGET_SERVER
-} backup_target_type;
-
 typedef enum
 {
 	BACKUP_COMPRESSION_NONE,
@@ -77,8 +71,9 @@ typedef struct
 	bool		includewal;
 	uint32		maxrate;
 	bool		sendtblspcmapfile;
-	backup_target_type target;
-	char	   *target_detail;
+	bool		send_to_client;
+	bool		use_copytblspc;
+	BaseBackupTargetHandle *target_handle;
 	backup_manifest_option manifest;
 	basebackup_compression_type	compression;
 	int			compression_level;
@@ -715,12 +710,12 @@ parse_basebackup_options(List *options, basebackup_options *opt)
 	bool		o_manifest_checksums = false;
 	bool		o_target = false;
 	bool		o_target_detail = false;
-	char	   *target_str = "compat";	/* placate compiler */
+	char	   *target_str = NULL;
+	char	   *target_detail_str = NULL;
 	bool		o_compression = false;
 	bool		o_compression_level = false;
 
 	MemSet(opt, 0, sizeof(*opt));
-	opt->target = BACKUP_TARGET_CLIENT;
 	opt->manifest = MANIFEST_OPTION_NO;
 	opt->manifest_checksum_type = CHECKSUM_TYPE_CRC32C;
 	opt->compression = BACKUP_COMPRESSION_NONE;
@@ -864,22 +859,11 @@ parse_basebackup_options(List *options, basebackup_options *opt)
 		}
 		else if (strcmp(defel->defname, "target") == 0)
 		{
-			target_str = defGetString(defel);
-
 			if (o_target)
 				ereport(ERROR,
 						(errcode(ERRCODE_SYNTAX_ERROR),
 						 errmsg("duplicate option \"%s\"", defel->defname)));
-			if (strcmp(target_str, "blackhole") == 0)
-				opt->target = BACKUP_TARGET_BLACKHOLE;
-			else if (strcmp(target_str, "client") == 0)
-				opt->target = BACKUP_TARGET_CLIENT;
-			else if (strcmp(target_str, "server") == 0)
-				opt->target = BACKUP_TARGET_SERVER;
-			else
-				ereport(ERROR,
-						(errcode(ERRCODE_SYNTAX_ERROR),
-						 errmsg("unrecognized target: \"%s\"", target_str)));
+			target_str = defGetString(defel);
 			o_target = true;
 		}
 		else if (strcmp(defel->defname, "target_detail") == 0)
@@ -890,7 +874,7 @@ parse_basebackup_options(List *options, basebackup_options *opt)
 				ereport(ERROR,
 						(errcode(ERRCODE_SYNTAX_ERROR),
 						 errmsg("duplicate option \"%s\"", defel->defname)));
-			opt->target_detail = optval;
+			target_detail_str = optval;
 			o_target_detail = true;
 		}
 		else if (strcmp(defel->defname, "compression") == 0)
@@ -942,22 +926,28 @@ parse_basebackup_options(List *options, basebackup_options *opt)
 					 errmsg("manifest checksums require a backup manifest")));
 		opt->manifest_checksum_type = CHECKSUM_TYPE_NONE;
 	}
-	if (opt->target == BACKUP_TARGET_SERVER)
+
+	if (target_str == NULL)
 	{
-		if (opt->target_detail == NULL)
+		if (target_detail_str != NULL)
 			ereport(ERROR,
 					(errcode(ERRCODE_SYNTAX_ERROR),
-					 errmsg("target '%s' requires a target detail",
-							target_str)));
+					 errmsg("target detail cannot be used without target")));
+		opt->use_copytblspc = true;
+		opt->send_to_client = true;
 	}
-	else
+	else if (strcmp(target_str, "client") == 0)
 	{
-		if (opt->target_detail != NULL)
+		if (target_detail_str != NULL)
 			ereport(ERROR,
 					(errcode(ERRCODE_SYNTAX_ERROR),
 					 errmsg("target '%s' does not accept a target detail",
 							target_str)));
+		opt->send_to_client = true;
 	}
+	else
+		opt->target_handle =
+			BaseBackupGetTargetHandle(target_str, target_detail_str);
 
 	if (o_compression_level && !o_compression)
 		ereport(ERROR,
@@ -993,32 +983,14 @@ SendBaseBackup(BaseBackupCmd *cmd)
 	}
 
 	/*
-	 * If the TARGET option was specified, then we can use the new copy-stream
-	 * protocol. If the target is specifically 'client' then set up to stream
-	 * the backup to the client; otherwise, it's being sent someplace else and
-	 * should not be sent to the client.
-	 */
-	if (opt.target == BACKUP_TARGET_CLIENT)
-		sink = bbsink_copystream_new(true);
-	else
-		sink = bbsink_copystream_new(false);
-
-	/*
-	 * If a non-default backup target is in use, arrange to send the data
-	 * wherever it needs to go.
+	 * If the target is specifically 'client' then set up to stream the backup
+	 * to the client; otherwise, it's being sent someplace else and should not
+	 * be sent to the client. BaseBackupGetSink has the job of setting up a
+	 * sink to send the backup data wherever it needs to go.
 	 */
-	switch (opt.target)
-	{
-		case BACKUP_TARGET_BLACKHOLE:
-			/* Nothing to do, just discard data. */
-			break;
-		case BACKUP_TARGET_CLIENT:
-			/* Nothing to do, handling above is sufficient. */
-			break;
-		case BACKUP_TARGET_SERVER:
-			sink = bbsink_server_new(sink, opt.target_detail);
-			break;
-	}
+	sink = bbsink_copystream_new(opt.send_to_client);
+	if (opt.target_handle != NULL)
+		sink = BaseBackupGetSink(opt.target_handle, sink);
 
 	/* Set up network throttling, if client requested it */
 	if (opt.maxrate > 0)