# HG changeset patch
# User Timo Sirainen <timo.sirainen@dovecot.fi>
# Date 1525356364 -10800
# Node ID 34315e5fd52ee4e5f7a932e14c0da968fd29cc76
# Parent  f10330f73af60c2cb3f379c0b0f1f4f5c0a530e5
cassandra: Use fallback_consistency on more types of errors

This could allow for example read_consistency=local-quorum with
read_fallback_consistency=quorum, so most of the time the reads are
from local datacenter, but in case it has problems you can switch to
other datacenters.

diff -r f10330f73af6 -r 34315e5fd52e src/lib-sql/driver-cassandra.c
--- a/src/lib-sql/driver-cassandra.c	Thu May 03 16:58:21 2018 +0300
+++ b/src/lib-sql/driver-cassandra.c	Thu May 03 17:06:04 2018 +0300
@@ -911,11 +911,25 @@
 static bool query_error_want_fallback(CassError error)
 {
 	switch (error) {
+	case CASS_ERROR_LIB_WRITE_ERROR:
+	case CASS_ERROR_LIB_REQUEST_TIMED_OUT:
+		/* Communication problems on client side. Maybe it will work
+		   with fallback consistency? */
+		return TRUE;
 	case CASS_ERROR_LIB_NO_HOSTS_AVAILABLE:
 		/* The client library couldn't connect to enough Cassandra
 		   nodes. The error message text is the same as for
 		   CASS_ERROR_SERVER_UNAVAILABLE. */
 		return TRUE;
+	case CASS_ERROR_SERVER_SERVER_ERROR:
+	case CASS_ERROR_SERVER_OVERLOADED:
+	case CASS_ERROR_SERVER_IS_BOOTSTRAPPING:
+	case CASS_ERROR_SERVER_READ_TIMEOUT:
+	case CASS_ERROR_SERVER_READ_FAILURE:
+	case CASS_ERROR_SERVER_WRITE_FAILURE:
+		/* Servers are having trouble. Maybe with fallback consistency
+		   we can reach non-troubled servers? */
+		return TRUE;
 	case CASS_ERROR_SERVER_UNAVAILABLE:
 		/* Cassandra server knows that there aren't enough nodes
 		   available. "All hosts in current policy attempted and were