integration

Writing new tests

The Envoy integration test framework is designed to make it simple to test downstream-Envoy-upstream communication. In the common case, one

• Sends a request from downstream through Envoy
• Verifies the request is received upstream, and possibly inspects elements of the headers or body
• Sends a response from upstream through Envoy
• Verifies the request is received downstream, again possibly inspecting headers and body

For the simplest variant of this, one could do the following.

// start Envoy, set up the fake upstreams.
initialize();

// Create a client aimed at Envoy’s default HTTP port.
codec_client_ = makeHttpConnection(makeClientConnection((lookupPort("http"))));

// Create some request headers.
Http::TestHeaderMapImpl request_headers{{":method", "GET"},
                                        {":path", "/test/long/url"},
                                        {":scheme", "http"},
                                        {":authority", "host"}};

// Send the request headers from the client, wait until they are received upstream. When they
// are received, send the default response headers from upstream and wait until they are
// received at by client
sendRequestAndWaitForResponse(request_headers, 0, default_response_headers_, 0);

// Verify the proxied request was received upstream, as expected.
EXPECT_TRUE(upstream_request_->complete());
EXPECT_EQ(0U, upstream_request_->bodyLength());
// Verify the proxied response was received downstream, as expected.
EXPECT_TRUE(response_->complete());
EXPECT_STREQ("200", response_->headers().Status()->value().c_str());
EXPECT_EQ(0U, response_->body().size());

Once you have the basic end-to-end test, it is fairly straight forward to modify it to test more interesting corner cases. There are existing tests which send requests with bodies, have downstream or upstream disconnect or time out, send multiple simultaneous requests on the same connection, etc. Given that many of the disconnect/timeout cases are covered, a common case for testing is covering a newly added configuration option.

Most of Envoy's tests have been migrated from using json flatfiles to using a basic configuration defined as basic_config in config/utility.cc. This configuration may be modified before the call to initialize(). The ConfigHelper has utilities for common alterations such as:

// Set the default protocol to HTTP2
setDownstreamProtocol(Http::CodecClient::Type::HTTP2);

or

// Add a buffering filter on the request path
config_helper_.addFilter(ConfigHelper::DEFAULT_BUFFER_FILTER);

For other edits which are less likely reusable, one can add config modifiers. Config modifiers allow arbitrary modification of Envoy’s configuration just before Envoy is brought up. One can add a config modifier to alter the bootstrap proto, one which affects the first HttpConnectionManager object in the config, or mix and match. Config modifiers are operated on in the order they are added, so one could, for example, modify the default HttpConnectionManager, duplicate the listening config, and then change the first HttpConnectionManager to be different from the second.

An example of modifying the bootstrap proto to overwrite runtime defaults:

TestEnvironment::writeStringToFileForTest("runtime/ratelimit.tcp_filter_enabled", "100");
config_helper_.addConfigModifier([&](envoy::config::bootstrap::v2::Bootstrap& bootstrap) -> void {
  bootstrap.mutable_runtime()->set_symlink_root(TestEnvironment::temporaryPath("runtime");
});

An example of modifying HttpConnectionManager to change Envoy’s HTTP/1.1 processing:

config_helper_.addConfigModifier([&](envoy::config::filter::network::http_connection_manager::v2::HttpConnectionManager& hcm) -> void {
  envoy::api::v2::core::Http1ProtocolOptions options;
  options.mutable_allow_absolute_url()->set_value(true);
  hcm.mutable_http_protocol_options()->CopyFrom(options);
};);

An example of modifying HttpConnectionManager to add an additional upstream cluster:

   config_helper_.addConfigModifier([](envoy::config::bootstrap::v2::Bootstrap& bootstrap) {
      bootstrap.mutable_rate_limit_service()->set_cluster_name("ratelimit");
      auto* ratelimit_cluster = bootstrap.mutable_static_resources()->add_clusters();
      ratelimit_cluster->MergeFrom(bootstrap.static_resources().clusters()[0]);
      ratelimit_cluster->set_name("ratelimit");
      ratelimit_cluster->mutable_http2_protocol_options();
    });

In addition to the existing test framework, which allows for carefully timed interaction and ordering of events between downstream, Envoy, and Upstream, there is now an “autonomous” framework which simplifies the common case where the timing is not essential (or bidirectional streaming is desired). When AutonomousUpstream is used, by setting autonomous_upstream_ = true before initialize(), upstream will by default create AutonomousHttpConnections for each incoming connection and AutonomousStreams for each incoming stream. By default, the streams will respond to each complete request with “200 OK” and 10 bytes of payload, but this behavior can be altered by setting various request headers, as documented in autonomous_upstream.h

Extending the test framework

The Envoy integration test framework is most definitely a work in progress. When encountering features which do not exist (actions for the autonomous backend, testing new sections of configuration) please use your best judgement if the changes will be needed by one specific test file, or will be likely reused in other integration tests. If it's likely be reused, please add the appropriate functions to existing utilities or add new test utilities. If it's likely a one-off change, it can be scoped to the existing test file.

Debugging integration tests

The Envoy integration test framework is generally designed to fast-fail when things go wrong, with an explanatory message such as "Timed out waiting for new connection." but it's not always clear what the underlying cause is. Because there are many Envoy components under test, often the best tool for debugging is to try to get a run of the test with --test_arg="-l debug", or --test_arg="-l trace" ideally with a clean run (if it's a code change which caused test breakage) or a comparable test (if it's a new test failing). Looking at the conn_manager_impl.cc logs, router.cc logs, and fake_upstream.cc logs, can often give you a feel for what unexpected event is occurring. If that doesn't help, following the GDB instructions to run the test in a debugger or sprinkling cerrs around are both often helpful.

Deflaking tests

The instructions below assume the developer is running tests natively with bazel rather than in docker. For developers using docker the best workaround today is to replace //test/... on the relevant ci/do_ci.shwith the command lines referenced below and remember to back those changes out before sending the fix upstream!

Reproducing test flakes

The first step of fixing test flakes is reproducing the test flake. In general if you have written a test which flakes, you can start by running

bazel test [test_name] --runs_per_test=1000

Which runs the full test many times. If this works, great! If not, it's worth trying to stress your system more by running more tests in parallel, by setting --jobs and --local_resources.

Once you've managed to reproduce a failure it may be beneficial to limit your test run to the specific failing test(s) with --gtest_filter. This may cause the test to flake less often (i.e. if two tests are interfering with each other, scoping to your specific test name may harm rather than help reproducibility.) but if it works it lets you iterate faster.

Another helpful tip for debugging is turn turn up Envoy trace logs with --test_arg="-l trace". Again if the test failure is due to a race, this may make it harder to reproduce, and it may also hide any custom logging you add, but it's a handy thing to know of to follow the general flow.

The full command might look something like

bazel test //test/integration:http2_upstream_integration_test \
--test_arg=--gtest_filter="IpVersions/Http2UpstreamIntegrationTest.RouterRequestAndResponseWithBodyNoBuffer/IPv6" \
--jobs 60 --local_resources 100000000000,100000000000,10000000 --runs_per_test=1000 --test_arg="-l trace"

Debugging test flakes

Once you've managed to reproduce your test flake, you get to figure out what's going on. If your failure mode isn't documented below, ideally some combination of cerr << logging and trace logs will help you sort out what is going on (and please add to this document as you figure it out!)

Unexpected disconnects

As commented in HttpIntegrationTest::cleanupUpstreamAndDownstream(), the tear-down sequence between upstream, Envoy, and client is somewhat sensitive to ordering. If a given unit test does not use the provided member variables, for example opens multiple client or upstream connections, the test author should be aware of test best practices for clean-up which boil down to "Clean up upstream first".

Upstream connections run in their own threads, so if the client disconnects with open streams, there's a race where Envoy detects the disconnect, and kills the corresponding upstream stream, which is indistinguishable from an unexpected disconnect and triggers test failure. Because the client is run from the main thread, if upstream is closed first, the client will not detect the inverse close, so no test failure will occur.

Unparented upstream connections

The most common failure mode here is if the test adds additional fake upstreams for *DS connections (ADS, EDS etc) which are not properly shut down (for a very sensitive test framework)

The failure mode here is that during test teardown one closes the DS connection and then shuts down Envoy. Unfortunately as Envoy is running in its own thread, it will try to re-establish the *DS connection, sometimes creating a connection which is then "unparented". The solution here is to explicitly allow Envoy reconnects before closing the connection, using

my_ds_upstream_->set_allow_unexpected_disconnects(true);