Added default connect_timeout in cluster config

api/envoy/config/cluster/v3/cluster.proto

@@ -709,6 +709,7 @@ message Cluster {
   EdsClusterConfig eds_cluster_config = 3;
 
   // The timeout for new network connections to hosts in the cluster.
+  // If not set, a default value of 5s will be used.
   google.protobuf.Duration connect_timeout = 4 [(validate.rules).duration = {gt {}}];
 
   // Soft limit on size of the cluster’s connections read and write buffers. If

docs/root/faq/configuration/timeouts.rst

@@ -104,8 +104,8 @@ TCP
 ---
 
 * The cluster :ref:`connect_timeout <envoy_v3_api_field_config.cluster.v3.Cluster.connect_timeout>` specifies the amount
-  of time Envoy will wait for an upstream TCP connection to be established. This timeout has no
-  default, but is required in the configuration.
+  of time Envoy will wait for an upstream TCP connection to be established. If this value is not set,
+  a default value of 5 seconds will be used.
 
   .. attention::
 

docs/root/version_history/current.rst

@@ -20,6 +20,7 @@ Minor Behavior Changes
   requests to S3, ES or Glacier, which used the literal string ``UNSIGNED-PAYLOAD``. Buffering can
   be now be disabled in favor of using unsigned payloads with compatible services via the new
   `use_unsigned_payload` filter option (default false).
+* cluster: added default value of 5 seconds for :ref:`connect_timeout <envoy_v3_api_field_config.cluster.v3.Cluster.connect_timeout>`.
 * http: disable the integration between :ref:`ExtensionWithMatcher <envoy_v3_api_msg_extensions.common.matching.v3.ExtensionWithMatcher>`
   and HTTP filters by default to reflects its experimental status. This feature can be enabled by seting
   ``envoy.reloadable_features.experimental_matching_api`` to true.

source/common/upstream/upstream_impl.cc

@@ -741,7 +741,7 @@ ClusterInfoImpl::ClusterInfoImpl(
           runtime_.snapshot().getInteger(Http::MaxResponseHeadersCountOverrideKey,
                                          Http::DEFAULT_MAX_HEADERS_COUNT))),
       connect_timeout_(
-          std::chrono::milliseconds(PROTOBUF_GET_MS_REQUIRED(config, connect_timeout))),
+          std::chrono::milliseconds(PROTOBUF_GET_MS_OR_DEFAULT(config, connect_timeout, 5000))),
       per_upstream_preconnect_ratio_(PROTOBUF_GET_WRAPPED_OR_DEFAULT(
           config.preconnect_policy(), per_upstream_preconnect_ratio, 1.0)),
       peekahead_ratio_(PROTOBUF_GET_WRAPPED_OR_DEFAULT(config.preconnect_policy(),

test/common/upstream/upstream_impl_test.cc

@@ -2612,6 +2612,20 @@ TEST_F(ClusterInfoImplTest, TestTrackRemainingResourcesGauges) {
   EXPECT_EQ(4U, high_remaining_retries.value());
 }
 
+TEST_F(ClusterInfoImplTest, DefaultConnectTimeout) {
+  const std::string yaml = R"EOF(
+  name: cluster1
+  type: STRICT_DNS
+  lb_policy: ROUND_ROBIN
+)EOF";
+
+  auto cluster = makeCluster(yaml);
+  envoy::config::cluster::v3::Cluster cluster_config = parseClusterFromV3Yaml(yaml);
+
+  EXPECT_FALSE(cluster_config.has_connect_timeout());
+  EXPECT_EQ(std::chrono::seconds(5), cluster->info()->connectTimeout());
+}
+
 TEST_F(ClusterInfoImplTest, Timeouts) {
   const std::string yaml = R"EOF(
     name: name