From de5908c122d1ce9ec1aa754a0a7b7b729122d0b8 Mon Sep 17 00:00:00 2001
From: Ian Barwick <ian@2ndquadrant.com>
Date: Fri, 1 Apr 2016 11:07:17 +0900
Subject: [PATCH] Make witness server node update an atomic operation

If the connection to the primary is lost, roll back to the previously
known state.

TRUNCATE is of course not MVCC-friendly, but that shouldn't matter here
as only one process should ever be looking at this table.
---
 dbutils.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/dbutils.c b/dbutils.c
index 9bc8792d..755982a0 100644
--- a/dbutils.c
+++ b/dbutils.c
@@ -1125,6 +1125,8 @@ copy_configuration(PGconn *masterconn, PGconn *witnessconn, char *cluster_name)
 	PGresult   *res;
 	int			i;
 
+	begin_transaction(witnessconn);
+
 	sqlquery_snprintf(sqlquery, "TRUNCATE TABLE %s.repl_nodes", get_repmgr_schema_quoted(witnessconn));
 
 	log_verbose(LOG_DEBUG, "copy_configuration():\n%s\n", sqlquery);
@@ -1149,6 +1151,8 @@ copy_configuration(PGconn *masterconn, PGconn *witnessconn, char *cluster_name)
 		log_err("Unable to retrieve node records from master:\n%s\n",
 				PQerrorMessage(masterconn));
 		PQclear(res);
+		rollback_transaction(witnessconn);
+
 		return false;
 	}
 
@@ -1186,11 +1190,15 @@ copy_configuration(PGconn *masterconn, PGconn *witnessconn, char *cluster_name)
 
 			log_err("Unable to copy node record to witness database\n%s\n",
 					PQerrorMessage(witnessconn));
+			rollback_transaction(witnessconn);
+
 			return false;
 		}
 	}
 	PQclear(res);
 
+	commit_transaction(witnessconn);
+
 	return true;
 }