1 files changed, 65 insertions, 17 deletions

diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 43969ebbd1b..bff9b478f66 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -99,6 +99,8 @@ static int ldapServiceLookup(const char *purl, PQconninfoOption *options,
 
 /* This is part of the protocol so just define it */
 #define ERRCODE_INVALID_PASSWORD "28P01"
+/* This too */
+#define ERRCODE_CANNOT_CONNECT_NOW "57P03"
 
 /*
  * fall back options if they are not specified by arguments or defined
@@ -376,10 +378,15 @@ PQconnectdbParams(const char **keywords,
 
 }
 
+/*
+ *		PQpingParams
+ *
+ * check server status, accepting parameters identical to PQconnectdbParams
+ */
 PGPing
 PQpingParams(const char **keywords,
-				  const char **values,
-				  int expand_dbname)
+			 const char **values,
+			 int expand_dbname)
 {
 	PGconn	   *conn = PQconnectStartParams(keywords, values, expand_dbname);
 	PGPing		ret;
@@ -423,6 +430,11 @@ PQconnectdb(const char *conninfo)
 	return conn;
 }
 
+/*
+ *		PQping
+ *
+ * check server status, accepting parameters identical to PQconnectdb
+ */
 PGPing
 PQping(const char *conninfo)
 {
@@ -1261,6 +1273,7 @@ connectDBStart(PGconn *conn)
 			appendPQExpBuffer(&conn->errorMessage,
 							  libpq_gettext("invalid port number: \"%s\"\n"),
 							  conn->pgport);
+			conn->options_valid = false;
 			goto connect_errReturn;
 		}
 	}
@@ -1309,6 +1322,7 @@ connectDBStart(PGconn *conn)
 							  portstr, gai_strerror(ret));
 		if (addrs)
 			pg_freeaddrinfo_all(hint.ai_family, addrs);
+		conn->options_valid = false;
 		goto connect_errReturn;
 	}
 
@@ -2555,27 +2569,61 @@ error_return:
 
 /*
  * internal_ping
- *	Determine if a server is running and if we can connect to it.
+ *		Determine if a server is running and if we can connect to it.
+ *
+ * The argument is a connection that's been started, but not completed.
  */
 PGPing
 internal_ping(PGconn *conn)
 {
-	if (conn && conn->status != CONNECTION_BAD)
-	{
+	/* Say "no attempt" if we never got to PQconnectPoll */
+	if (!conn || !conn->options_valid)
+		return PQPING_NO_ATTEMPT;
+
+	/* Attempt to complete the connection */
+	if (conn->status != CONNECTION_BAD)
 		(void) connectDBComplete(conn);
 
-		/*
-		 *	If the connection needs a password, we can consider the
-		 *	server as accepting connections.
-		 */
-	    if (conn && (conn->status != CONNECTION_BAD ||
-		    PQconnectionNeedsPassword(conn)))
-			return PQACCESS;
-		else
-			return PQREJECT;
-	}
-	else
-		return PQNORESPONSE;
+	/* Definitely OK if we succeeded */
+	if (conn->status != CONNECTION_BAD)
+		return PQPING_OK;
+
+	/*
+	 * Here is the interesting part of "ping": determine the cause of the
+	 * failure in sufficient detail to decide what to return.  We do not want
+	 * to report that the server is not up just because we didn't have a valid
+	 * password, for example.
+	 *
+	 * If we failed to get any ERROR response from the postmaster, report
+	 * PQPING_NO_RESPONSE.  This result could be somewhat misleading for a
+	 * pre-7.4 server, since it won't send back a SQLSTATE, but those are long
+	 * out of support.  Another corner case where the server could return a
+	 * failure without a SQLSTATE is fork failure, but NO_RESPONSE isn't
+	 * totally unreasonable for that anyway.  We expect that every other
+	 * failure case in a modern server will produce a report with a SQLSTATE.
+	 *
+	 * NOTE: whenever we get around to making libpq generate SQLSTATEs for
+	 * client-side errors, we should either not store those into
+	 * last_sqlstate, or add an extra flag so we can tell client-side errors
+	 * apart from server-side ones.
+	 */
+	if (strlen(conn->last_sqlstate) != 5)
+		return PQPING_NO_RESPONSE;
+
+	/*
+	 * Report PQPING_REJECT if server says it's not accepting connections.
+	 * (We distinguish this case mainly for the convenience of pg_ctl.)
+	 */
+	if (strcmp(conn->last_sqlstate, ERRCODE_CANNOT_CONNECT_NOW) == 0)
+		return PQPING_REJECT;
+
+	/*
+	 * Any other SQLSTATE can be taken to indicate that the server is up.
+	 * Presumably it didn't like our username, password, or database name; or
+	 * perhaps it had some transient failure, but that should not be taken as
+	 * meaning "it's down".
+	 */
+	return PQPING_OK;
 }