From: Craig Ringer <craig@2ndquadrant.com>
Date: Mon, 15 Dec 2014 10:42:39 +0000 (+0800)
Subject: bdr: Prevent slot creation on output plugin if bdr ext missing
X-Git-Tag: bdr-plugin/0.8.0~26
X-Git-Url: http://git.postgresql.org/gitweb/static/gitweb.js?a=commitdiff_plain;h=2f0160f5f7d463ff52a9a50f30db2655895d1677;p=2ndquadrant_bdr.git

bdr: Prevent slot creation on output plugin if bdr ext missing

We shouldn't allow slot creation if the BDR extension is not installed
in a database.
---

diff --git a/bdr_output.c b/bdr_output.c
index 57cdea0709..a9dc5051ab 100644
--- a/bdr_output.c
+++ b/bdr_output.c
@@ -219,12 +219,13 @@ bdr_req_param(const char *param)
 }
 
 /*
- * Check bdr.bdr_nodes entry in local DB and if status != r,
- * raise an error.
+ * Check bdr.bdr_nodes entry in local DB and if status != r
+ * and we're trying to begin logical replay, raise an error.
  *
- * If this function returns it's safe to begin replay.
+ * Also prevents slot creation if the BDR extension isn't installed in the
+ * local node.
  *
- * Must be called inside transaction.
+ * If this function returns it's safe to begin replay.
  */
 static void
 bdr_ensure_node_ready()
@@ -348,7 +349,7 @@ pg_decode_startup(LogicalDecodingContext * ctx, OutputPluginOptions *opt, bool i
 	ListCell   *option;
 	BdrOutputData *data;
 	Oid schema_oid;
-	bool tx_started = true;
+	bool tx_started = false;
 
 	bdr_worker_type = BDR_WORKER_WALSENDER;
 
@@ -462,6 +463,41 @@ pg_decode_startup(LogicalDecodingContext * ctx, OutputPluginOptions *opt, bool i
 		}
 	}
 
+	/*
+	 * Ensure that the BDR extension is installed on this database.
+	 *
+	 * We must prevent slot creation before the BDR extension is created,
+	 * otherwise the event trigger for DDL replication will record the
+	 * extension's creation in bdr.bdr_queued_commands and the slot position
+	 * will be before then, causing CREATE EXTENSION to be replayed. Since
+	 * the other end already has the BDR extension (obviously) this will
+	 * cause replay to fail.
+	 *
+	 * TODO: Should really test for the extension its self, but this is faster
+	 * and easier...
+	 */
+	if (!IsTransactionState())
+	{
+		tx_started = true;
+		StartTransactionCommand();
+	}
+
+#ifdef BUILDING_BDR
+	/*
+	 * If running BDR, we expect the remote end (us) to have the BDR extension
+	 * installed before we permit slot creation. This prevents replication of
+	 * the CREATE EXTENSION bdr; command its self.
+	 */
+	if (get_namespace_oid("bdr", true) == InvalidOid)
+	{
+		ereport(ERROR,
+			    (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("bdr extension does not exist on " BDR_LOCALID_FORMAT,
+						BDR_LOCALID_FORMAT_ARGS),
+				 errdetail("Cannot create a BDR slot without the BDR extension installed")));
+	}
+#endif
+
 	/* no options are passed in during initialization, so don't complain there */
 	if (!is_init)
 	{
@@ -547,12 +583,6 @@ pg_decode_startup(LogicalDecodingContext * ctx, OutputPluginOptions *opt, bool i
 		if (data->client_pg_version / 100 != PG_VERSION_NUM / 100)
 			data->allow_sendrecv_protocol = false;
 
-		if (!IsTransactionState())
-		{
-			tx_started = false;
-			StartTransactionCommand();
-		}
-
 		bdr_maintain_schema();
 
 		data->bdr_schema_oid = get_namespace_oid("bdr", true);
@@ -585,13 +615,14 @@ pg_decode_startup(LogicalDecodingContext * ctx, OutputPluginOptions *opt, bool i
 
 		/*
 		 * Make sure it's safe to begin playing changes to the remote end.
-		 * This'll ERROR out if we're not ready.
+		 * This'll ERROR out if we're not ready. Note that this does NOT
+		 * prevent slot creation, only START_REPLICATION from the slot.
 		 */
 		bdr_ensure_node_ready();
-
-		if (!tx_started)
-			CommitTransactionCommand();
 	}
+
+	if (tx_started)
+		CommitTransactionCommand();
 }
 
 /*
diff --git a/expected/init.out b/expected/init.out
index ab7045bd5d..4dd05289da 100644
--- a/expected/init.out
+++ b/expected/init.out
@@ -9,7 +9,7 @@ CREATE USER super SUPERUSER;
 GRANT ALL ON SCHEMA public TO nonsuper;
 \c regression
 GRANT ALL ON SCHEMA public TO nonsuper;
-SELECT pg_sleep(5);
+SELECT pg_sleep(10);
  pg_sleep 
 ----------
  
diff --git a/sql/init.sql b/sql/init.sql
index a614cb93cc..1027119873 100644
--- a/sql/init.sql
+++ b/sql/init.sql
@@ -12,7 +12,7 @@ GRANT ALL ON SCHEMA public TO nonsuper;
 \c regression
 GRANT ALL ON SCHEMA public TO nonsuper;
 
-SELECT pg_sleep(5);
+SELECT pg_sleep(10);
 
 -- emulate the pg_xlog_wait_remote_apply on vanilla postgres
 DO $DO$BEGIN