modified caching test

added logic to test that cached response is specific to request payload.
Removed trailing '\0' from query parameter

src/core/lib/channel/http_client_filter.c

@@ -332,10 +332,8 @@ static grpc_error *hc_mutate_op(grpc_exec_ctx *exec_ctx,
          */
         char *t = (char *)GRPC_SLICE_START_PTR(path_with_query_slice);
         /* safe to use strlen since base64_encode will always add '\0' */
-        size_t path_length = strlen(t) + 1;
-        *(t + path_length) = '\0';
         path_with_query_slice =
-            grpc_slice_sub(path_with_query_slice, 0, path_length);
+            grpc_slice_sub(path_with_query_slice, 0, strlen(t));
 
         /* substitute previous path with the new path+query */
         grpc_mdelem mdelem_path_and_query = grpc_mdelem_from_slices(

test/cpp/interop/interop_client.cc

@@ -918,6 +918,26 @@ bool InteropClient::DoCacheableUnary() {
   // second response is a cached copy of the first response
   GPR_ASSERT(response2.payload().body() == response1.payload().body());
 
+  // Request 3
+  // Modify the request body so it will not get a cache hit
+  ts = gpr_now(GPR_CLOCK_PRECISE);
+  timestamp = std::to_string((long long unsigned)ts.tv_nsec);
+  SimpleRequest request1;
+  request1.mutable_payload()->set_body(timestamp.c_str(), timestamp.size());
+  ClientContext context3;
+  SimpleResponse response3;
+  context3.set_cacheable(true);
+  context3.AddMetadata("x-user-ip", "1.2.3.4");
+  Status s3 =
+      serviceStub_.Get()->CacheableUnaryCall(&context3, request1, &response3);
+  if (!AssertStatusOk(s3)) {
+    return false;
+  }
+  gpr_log(GPR_DEBUG, "response 3 payload: %s",
+          response3.payload().body().c_str());
+
+  // Check that the response is different from the previous response.
+  GPR_ASSERT(response3.payload().body() != response1.payload().body());
   return true;
 }