xds: Include max concurrent request limit in the error status for concurre… (grpc#11845)

Include max concurrent request limit in the error status for concurrent connections limit exceeded

Author: kannanjgithub

xds/src/main/java/io/grpc/xds/ClusterImplLoadBalancer.java

@@ -59,6 +59,7 @@
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Objects;
 import java.util.concurrent.atomic.AtomicLong;
@@ -406,7 +407,8 @@ public PickResult pickSubchannel(PickSubchannelArgs args) {
                 dropStats.recordDroppedRequest();
               }
               return PickResult.withDrop(Status.UNAVAILABLE.withDescription(
-                  "Cluster max concurrent requests limit exceeded"));
+                  String.format(Locale.US, "Cluster max concurrent requests limit of %d exceeded",
+                      maxConcurrentRequests)));
             }
           }
           final AtomicReference<ClusterLocality> clusterLocality =

xds/src/test/java/io/grpc/xds/ClusterImplLoadBalancerTest.java

@@ -636,7 +636,7 @@ private void subtest_maxConcurrentRequests_appliedByLbConfig(boolean enableCircu
       assertThat(result.getStatus().isOk()).isFalse();
       assertThat(result.getStatus().getCode()).isEqualTo(Code.UNAVAILABLE);
       assertThat(result.getStatus().getDescription())
-          .isEqualTo("Cluster max concurrent requests limit exceeded");
+          .isEqualTo("Cluster max concurrent requests limit of 100 exceeded");
       assertThat(clusterStats.totalDroppedRequests()).isEqualTo(1L);
     } else {
       assertThat(result.getStatus().isOk()).isTrue();
@@ -667,7 +667,7 @@ private void subtest_maxConcurrentRequests_appliedByLbConfig(boolean enableCircu
       assertThat(result.getStatus().isOk()).isFalse();
       assertThat(result.getStatus().getCode()).isEqualTo(Code.UNAVAILABLE);
       assertThat(result.getStatus().getDescription())
-          .isEqualTo("Cluster max concurrent requests limit exceeded");
+          .isEqualTo("Cluster max concurrent requests limit of 101 exceeded");
       assertThat(clusterStats.totalDroppedRequests()).isEqualTo(1L);
     } else {
       assertThat(result.getStatus().isOk()).isTrue();
@@ -731,7 +731,7 @@ private void subtest_maxConcurrentRequests_appliedWithDefaultValue(
       assertThat(result.getStatus().isOk()).isFalse();
       assertThat(result.getStatus().getCode()).isEqualTo(Code.UNAVAILABLE);
       assertThat(result.getStatus().getDescription())
-          .isEqualTo("Cluster max concurrent requests limit exceeded");
+          .isEqualTo("Cluster max concurrent requests limit of 1024 exceeded");
       assertThat(clusterStats.totalDroppedRequests()).isEqualTo(1L);
     } else {
       assertThat(result.getStatus().isOk()).isTrue();