http: per-stream idle timeout. #3841

htuch · 2018-07-11T17:29:00Z

Risk level: Medium. A very conservative 5 minute default idle timeout has been set, which should not affect most deployments with default timeout already kicking in for connection idle or upstream idle. This will however affect things like hanging POSTs.
Testing: Integration and unit tests added for various timeout scenarios.

Signed-off-by: Harvey Tuch htuch@google.com

Fixes envoyproxy#1778. Risk level: Low (opt in). Testing: Integration and unit tests added for various timeout scenarios. Signed-off-by: Harvey Tuch <htuch@google.com>

alyssawilk

YAY! I'm so excited to have idle timeouts already. Thanks for tackling this!

alyssawilk · 2018-07-11T17:57:15Z

api/envoy/api/v2/route/route.proto

@@ -437,6 +439,22 @@ message RouteAction {
    google.protobuf.Duration per_try_timeout = 3 [(gogoproto.stdduration) = true];
  }

+  // Specifies the idle timeout for the route. If not specified, there is no
+  // stream level timeout. This is distinct to :ref:`timeout


Do we think this is the right default? Given the lack of request timeouts I'd say having an overall timeout would be good, even if it's really high like the default response timeout.

I'm OK with setting something here like 30s. I think we should make it > default response timeout (15s), to reduce the chance of flakes in timeout due to idle vs. due to total response timeout. Does this work?

Yeah I think a default here is fine as long as it's greater than the default of 15s. However, I don't think that's the whole story. For people that have increased the timeout above 15s (or disabled it), this could cause problems. So, I think we either have to not have a default here, or actually have the logic to make the default if not set at least as long as the configured request timeout. Thoughts?

There's also the per-connection idle timeout and per-retry timetouts to consider as well. I think if we want this to be unsurprising to existing users we will have to make it a max function of all the relevant timeouts. Might be easier to leave it to default off.

TBH that's my feeling also. I would leave it without default.

I'm less worried about the trickle attack DoS vector (Envoy has plenty of those yet) and more about folks losing their connection without the FIN being transmitted. This is a real thing that happens frequently on internet facing traffic and will cause connection (so fd and memory) leakage without the buffer filter present. It's true that either having a default request timeout would address my concern as well, I was just hoping to fix the resource leakage sooner rather than later.
If you really think this should be off by default and the default timeout should be in the should-be-moved request timeout I'll cede the issue.

I agree this is a big problem, and I'm kicking myself for ending up where we are, but what's done is done. The issue mainly is that Lyft solves this problem w/ the buffer filter at the edge as we discussed offline. Totally agree we need a built-in timeout, but I'm also concerned that setting a default here is going to break people. I think we should have some big warning in the docs somewhere about this (where?) and I guess we could do a timeout here but IMO the default needs to be really high if we set one. E.g., like 5 minutes or something. Or we need to do some complex logic to infer the timeout somehow from the other timeouts people set.

I think a default idle-timeout of 5 minutes (or longer) should be fine. I also agree that having a POST overall timeout is useful, but I think that one is impossible to have a reasonable default value for.

OK, 5 minutes default, going once, twice, ...

Works for me! As said I'm also fine landing and then changing the default in a separate PR (even a after a long window) if you want to have the risky change minimal.

alyssawilk · 2018-07-11T17:59:53Z

api/envoy/api/v2/route/route.proto

+  // <envoy_api_field_route.RouteAction.idle_timeout>` instead bounds the amount
+  // of time the request's stream may be idle.
+  //
+  // After header decoding, and assuming that this is not a WebSocket upgrade,


Wait, why are we not doing this for websocket upgrade? I totally want forward-progress timeouts.
Did you mean assuming it's not an old-style tcp proxy upgrade?

Yes, this is only for the TCP proxy upgrade scenario, will clarify.

alyssawilk · 2018-07-11T18:01:31Z

api/envoy/api/v2/route/route.proto

+  // time an encode/decode event for headers or data is processed for the
+  // stream, the timer will be reset. If the timeout fires, the stream is
+  // terminated with a 408 Request Timeout error code if no upstream response
+  // header has been received, otherwise a stream reset occurs.


At some point when we have priorities properly implemented we may need to take into account stream starvation here (if HighPriStream3 is consuming all outgoing bandwidth but LowPriStream5 is otherwise ready to write it shouldn't time out). Thankfully not something we have to worry about now.

Brainstorming other failure modes, if we have connections with very many streams, we might hit problems where the progress is super bunchy and causes artificial timeouts. I think basically when there's space in the write buffer, every stream is informed and can do a full read and write, and then won't be called upon again until all those writes drain. I don't know if there are enough users with backed up connections and many streams that it's worth calling out, but it's food for thought.

I think it's probably going to confuse more than help to call this out, even though I agree, at extreme queueing scenarios this can happen.

alyssawilk · 2018-07-11T18:19:24Z

source/common/http/conn_manager_impl.cc

@@ -396,6 +396,25 @@ ConnectionManagerImpl::ActiveStream::~ActiveStream() {
  ASSERT(state_.filter_call_state_ == 0);
 }

+void ConnectionManagerImpl::ActiveStream::resetIdleTimer() {
+  if (idle_timer_ != nullptr) {
+    idle_timer_->enableTimer(idle_timeout_ms_);


Have you tried a loadtest run with this on? I believe internally we ended up needing to latch "time of last data" and when the alarm fired resetting the alarm if necessary because the adds/removes were expensive enough we couldn't afford to thrash. I don't know if Envoy has a more efficient alarm management under the hood so I'm unsure if we'll have the same problem here.

Realistically if we leave it opt in or high timeouts, you're going to be the one who tracks down any perf problem so I'm fine with you landing first and seeing if it's a problem :-P

I discussed this with @mattklein123 earlier; we agreed that libevent timers are probably fine for now, and we should leave this as a TODO for later optimization. Will actually put a TODO there.

I've thought about this (because I added idle-timeout to tcp proxy, with the same perf concern). I think we could probably make this fast enough if we add a tunable to timers for inaccuracy-percent or something. Then keep track of the current time it will expire, look at the new time, and if it has moved by less than X%, don't reschedule the timer.

But I decided not to bother until rescheduling timers showed up hot in a profile that I cared about.

It's possible/likely that on super high throughput streaming case this timer reset behavior is going to show up on perf traces, but TBH I don't know how much and yeah I think it's probably fine for now. I would probably go for the simple approach first and we can make better later if needed?

SGTM. As said Harvey ends up doing most of our perf tuning so if it shows up I'm sure he'll just deal with it later :-)

alyssawilk · 2018-07-11T18:23:14Z

source/common/http/conn_manager_impl.cc

+  if (response_headers_ != nullptr) {
+    // TODO(htuch): We could send trailers here with an x-envoy timeout header
+    // or gRPC status code.
+    maybeEndEncode(true);


Isn't this the clean shutdown route? I'd expect resetStream().
I think if we do things this way the connection may be reused for a subsequent HTTP/1.1 request.

Yeah we need to reset here (optimally w/ a relevant h2 reset code if one exists, not sure). I think this will end up resetting the stream, but I think it will also do some stat/log accounting to call the response complete which we don't want, so I think you will need to go deeper than this function and possibly call doEndStream() directly or something else.

alyssawilk · 2018-07-11T18:28:58Z

source/common/http/conn_manager_impl.cc

@@ -882,6 +914,8 @@ void ConnectionManagerImpl::ActiveStream::encode100ContinueHeaders(

 void ConnectionManagerImpl::ActiveStream::encodeHeaders(ActiveStreamEncoderFilter* filter,


resetIdleTimer on encode100ContinueHeaders?

alyssawilk · 2018-07-11T18:31:05Z

test/integration/http_integration.cc

+        auto* route_config = hcm.mutable_route_config();
+        auto* virtual_host = route_config->mutable_virtual_hosts(0);
+        auto* route = virtual_host->mutable_routes(0)->mutable_route();
+        route->mutable_idle_timeout()->set_seconds(1);


You may want shorter idle timeouts but a scaleTimeoutForTsan/Asan function. Your call.

alyssawilk · 2018-07-11T18:36:37Z

test/integration/http_integration.h

@@ -159,6 +159,11 @@ class HttpIntegrationTest : public BaseIntegrationTest {
  void testDrainClose();
  void testRetry();
  void testRetryHittingBufferLimit();
+  IntegrationStreamDecoderPtr setupPerStreamIdleTimeoutTest();


Did I miss it or are there test of timeouts on the request path?
I don't think you need to do every stage as it's less interesting than the "have headers been sent" response path but it'd be good to have one.

+1, testing the reset case is important.

The reset case is being tested, I can add a test for request headers + data sent, then timeout, which is missing. In general, with these tests, its not really implied whether you are timing out on the request or the response path, since the timeout could be due to either party not doing its thang.

alyssawilk · 2018-07-11T18:39:34Z

test/integration/http_integration.cc

+        auto* virtual_host = route_config->mutable_virtual_hosts(0);
+        auto* route = virtual_host->mutable_routes(0)->mutable_route();
+        route->mutable_idle_timeout()->set_seconds(1);
+      });


Let's define this once and call it from both places, a la setAllowHttp10WithDefaultHost
Alternately I don't think it'd be a bad one to add into the config utils.

alyssawilk · 2018-07-11T18:41:37Z

test/integration/http2_integration_test.cc

@@ -85,6 +85,20 @@ TEST_P(Http2IntegrationTest, TwoRequests) { testTwoRequests(); }

 TEST_P(Http2IntegrationTest, Retry) { testRetry(); }

+TEST_P(Http2IntegrationTest, PerStreamIdleTimeoutBeforeUpstreamHeaders) {


Optional but I'd like to move away from the "add each test to 3 files" paradigm towards using HttpProtocolIntegrationTest

If we're going to leave the timeouts 1s I'd encourage moving these to their own file,
defining typedef HttpProtocolIntegrationTest IdleTimeoutsTest and just running all 4 without all the extra TEST_Ps.

Feel free to leave it here for consistency and I'll go split things out at some later point.

mattklein123 · 2018-07-11T20:49:56Z

api/envoy/api/v2/route/route.proto

@@ -437,6 +439,22 @@ message RouteAction {
    google.protobuf.Duration per_try_timeout = 3 [(gogoproto.stdduration) = true];
  }

+  // Specifies the idle timeout for the route. If not specified, there is no
+  // stream level timeout. This is distinct to :ref:`timeout


Yeah I think a default here is fine as long as it's greater than the default of 15s. However, I don't think that's the whole story. For people that have increased the timeout above 15s (or disabled it), this could cause problems. So, I think we either have to not have a default here, or actually have the logic to make the default if not set at least as long as the configured request timeout. Thoughts?

mattklein123 · 2018-07-11T20:53:47Z

api/envoy/api/v2/route/route.proto

+  // stream, the timer will be reset. If the timeout fires, the stream is
+  // terminated with a 408 Request Timeout error code if no upstream response
+  // header has been received, otherwise a stream reset occurs.
+  google.protobuf.Duration idle_timeout = 24


Are we concerned that people are going to want different idle timeouts for decode than for encode? I could see this happening w/ asymmetric streaming APIs. I agree that resetting the idle timeout in both cases means that a single value can be used, I'm just concerned that we might end up adding different timeouts later. Do we think this can happen or can we say it will never be needed? If we think it can happen should we future proof the API somehow to make this not awkward? Would rather not have to go through a deprecation cycle to deal with that.

I seem to recall we had this discussion for the TCP proxy idle timeouts (@ggreenway). What we have there is the bidi idle timeout (as in this PR), and then unidirectional idle timeouts (not implemented yet). I think ultimately you want both bidi and unidirectional as separate configurable options, since being able to only set the timeout in each directions has different semantics to bidi. E.g. if I configure 10s for encode and 10s for decode, I still don't have the same behavior as a 10s symmetrical timeout.

Yes, that sounds correct.

mattklein123 · 2018-07-11T20:55:02Z

source/common/http/conn_manager_impl.cc

@@ -396,6 +396,25 @@ ConnectionManagerImpl::ActiveStream::~ActiveStream() {
  ASSERT(state_.filter_call_state_ == 0);
 }

+void ConnectionManagerImpl::ActiveStream::resetIdleTimer() {
+  if (idle_timer_ != nullptr) {
+    idle_timer_->enableTimer(idle_timeout_ms_);


It's possible/likely that on super high throughput streaming case this timer reset behavior is going to show up on perf traces, but TBH I don't know how much and yeah I think it's probably fine for now. I would probably go for the simple approach first and we can make better later if needed?

mattklein123 · 2018-07-11T20:56:38Z

source/common/http/conn_manager_impl.cc

+  if (response_headers_ != nullptr) {
+    // TODO(htuch): We could send trailers here with an x-envoy timeout header
+    // or gRPC status code.
+    maybeEndEncode(true);


Yeah we need to reset here (optimally w/ a relevant h2 reset code if one exists, not sure). I think this will end up resetting the stream, but I think it will also do some stat/log accounting to call the response complete which we don't want, so I think you will need to go deeper than this function and possibly call doEndStream() directly or something else.

mattklein123 · 2018-07-11T21:02:13Z

test/integration/http_integration.h

@@ -159,6 +159,11 @@ class HttpIntegrationTest : public BaseIntegrationTest {
  void testDrainClose();
  void testRetry();
  void testRetryHittingBufferLimit();
+  IntegrationStreamDecoderPtr setupPerStreamIdleTimeoutTest();


+1, testing the reset case is important.

Signed-off-by: Harvey Tuch <htuch@google.com>

alyssawilk

Sweet! Only a few more comments on my end - if you get Matt's approval Friday (and verify tests are happy with 1k runs) don't wait to merge on my account. :-)

alyssawilk · 2018-07-12T20:09:55Z

api/envoy/api/v2/route/route.proto

-  // Specifies the idle timeout for the route. If not specified, there is no
-  // stream level timeout. This is distinct to :ref:`timeout
+  // Specifies the idle timeout for the route. If not specified, this defaults
+  // to 5 minutes. The default value was select so as not to interfere with any


Yay!

Let's update the PR description and risk and such accordingly :-)

alyssawilk · 2018-07-12T20:12:16Z

api/envoy/api/v2/route/route.proto

-  // stream, the timer will be reset. If the timeout fires, the stream is
-  // terminated with a 408 Request Timeout error code if no upstream response
-  // header has been received, otherwise a stream reset occurs.
+  // After header decoding, the idle timeout will apply on downstream and


I know the existing hcm timeout applies when there are no streams. Do we have an open window where we've started reading headers for stream but have not completed reading headers for a stream where we will still leak stale connections?

Because we can't do a route-specific timeout until we have complete headers I don't believe you could fix any timeout-gap in this PR, but if it'd still exist it'd be good to file a tracking issue.

Agree; I think a global stream idle timeout makes sense to fix this. I've filed #3853 and will do a followup PR once this one merges to introduce that.

alyssawilk · 2018-07-12T20:18:19Z

test/integration/idle_timeout_integration_test.cc

+TEST_P(IdleTimeoutIntegrationTest, PerStreamIdleTimeoutAfterData) {
+  auto response = setupPerStreamIdleTimeoutTest();
+
+  Sleep();


Mind giving this a flake check with
--jobs 60 --local_resources 100000000000,100000000000,10000000 --runs_per_test=1000
? I'd expect it to be flaky or slow, but I may just be biased against sleep tests :-P

Yep, passes with:

INFO: Elapsed time: 282.940s, Critical Path: 19.66s INFO: 1001 processes: 1001 linux-sandbox. INFO: Build completed successfully, 1002 total actions //test/integration:idle_timeout_integration_test PASSED in 19.5s Stats over 1000 runs: max = 19.5s, min = 14.7s, avg = 16.4s, dev = 0.9s

alyssawilk · 2018-07-12T20:26:07Z

test/integration/idle_timeout_integration_test.cc

+                        HttpProtocolIntegrationTest::protocolTestParamsToString);
+
+// Per-stream idle timeout when waiting for initial upstream headers.
+TEST_P(IdleTimeoutIntegrationTest, PerStreamIdleTimeoutBeforeUpstreamHeaders) {


Can you audit these tests for flakes?

I think a bunch of them are subject to the failure mode I've been fixing where Envoy will reset both upstream and downstream because [timeout] and then there's a race in cleanUpstreamAndDownstream because if the FIN arrives when we post the close() it registers as an unexpected disconnect.
(Alternately I'd be happy to say we shouldn't detect unexpected disconnect in cleanup and fix it once and for all there, but I think @mattklein123's preference is to have things which are closed explicitly handled.)
I believe fake_upstream_connection_->waitForDisconnect(); right after the code client closing will fix any of these.

Will fix by adding fake_upstreams_->set_allow_unexpected_disconnects(true); to setup.

alyssawilk · 2018-07-12T20:31:48Z

test/integration/idle_timeout_integration_test.cc

+                        testing::ValuesIn(HttpProtocolIntegrationTest::getProtocolTestParams()),
+                        HttpProtocolIntegrationTest::protocolTestParamsToString);
+
+// Per-stream idle timeout when waiting for initial upstream headers.


Can we update these descriptions? I'd say if we're sending a request-with-body we're not really waiting on upstream headers, it's more timing out waiting for downstream body.

Signed-off-by: Harvey Tuch <htuch@google.com>

mattklein123

LGTM, few small questions/comments. Thank for getting this done!

mattklein123 · 2018-07-13T21:06:38Z

api/envoy/api/v2/route/route.proto

+  // to the introduction of this feature, while introducing robustness to TCP
+  // connections that terminate without FIN.
+  //
+  // The idle timeout is distinct to :ref:`timeout


Perhaps also compare to connection idle timeout. Better, would it make sense to make a small timeout section in the HTTP arch overview or general config guide about timeouts, describe them all, and then link back to that section from all of these config options? It's only going to get more confusing as we add more configurable timeouts. Thoughts?

Agreed. I'll take this as an action item for my followup when I introduce the global HCM idle timeout if that's OK.

mattklein123 · 2018-07-13T21:07:17Z

docs/root/intro/version_history.rst

@@ -11,6 +11,8 @@ Version history
 * health check: added support for :ref:`custom health check <envoy_api_field_core.HealthCheck.custom_health_check>`.
 * health check: added support for :ref:`specifying jitter as a percentage <envoy_api_field_core.HealthCheck.interval_jitter_percent>`.
 * health_check: added support for :ref:`health check event logging <arch_overview_health_check_logging>`.
+* http: added support for a :ref:`per-stream idle timeout
+  <envoy_api_field_route.RouteAction.idle_timeout>`.


Perhaps say what the default is with a small warning about comparing to existing configured timeouts?

mattklein123 · 2018-07-13T21:08:15Z

api/envoy/api/v2/route/route.proto

@@ -437,6 +439,27 @@ message RouteAction {
    google.protobuf.Duration per_try_timeout = 3 [(gogoproto.stdduration) = true];
  }

+  // Specifies the idle timeout for the route. If not specified, this defaults


How does one fully disable it if they want? Do we tell them to set a really big value? Or should we support 0 to mean no timeout? Thoughts?

mattklein123 · 2018-07-13T21:09:19Z

source/common/http/async_client_impl.h

@@ -195,6 +195,7 @@ class AsyncStreamImpl : public AsyncClient::Stream,
        return std::chrono::milliseconds(0);
      }
    }
+    absl::optional<std::chrono::milliseconds> idleTimeout() const override { return absl::nullopt; }


Random orthogonal thought that might eventually want to plumb this through for real so that we could have idle timeouts for local origin requests/streams. No action now.

Signed-off-by: Harvey Tuch <htuch@google.com>

This is a followup to envoyproxy#3841, where we introduce HCM-wide stream idle timeouts. This has two effects: 1. We can now timeout immediately after stream creation, potentially before receiving request headers and routing. 2. A default timeout can be configured across all routes. This is overridable on a per-route basis. The default and overriding semantics are explained in the docs. Also added as a bonus some docs about how timeouts interact more generally in Envoy. Fixes envoyproxy#3853. Risk Level: Low. While there is some change to the per-route vs. HCM wide semantics for stream idle timeouts, it's not anticipated this feature is in common use yet (it's only a couple of days since landing), and the caveats in envoyproxy#3841 with the new 5 minute default timeout should already apply. Testing: Unit/integration tests added. Signed-off-by: Harvey Tuch <htuch@google.com>

This is a followup to #3841, where we introduce HCM-wide stream idle timeouts. This has two effects: 1. We can now timeout immediately after stream creation, potentially before receiving request headers and routing. 2. A default timeout can be configured across all routes. This is overridable on a per-route basis. The default and overriding semantics are explained in the docs. Also added as a bonus some docs about how timeouts interact more generally in Envoy. Fixes #3853. Risk Level: Low. While there is some change to the per-route vs. HCM wide semantics for stream idle timeouts, it's not anticipated this feature is in common use yet (it's only a couple of days since landing), and the caveats in #3841 with the new 5 minute default timeout should already apply. Testing: Unit/integration tests added. Signed-off-by: Harvey Tuch <htuch@google.com>

http: per-stream idle timeout.

b1e2322

Fixes envoyproxy#1778. Risk level: Low (opt in). Testing: Integration and unit tests added for various timeout scenarios. Signed-off-by: Harvey Tuch <htuch@google.com>

htuch assigned mattklein123 and alyssawilk Jul 11, 2018

htuch requested review from mattklein123 and alyssawilk July 11, 2018 17:29

alyssawilk reviewed Jul 11, 2018

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mattklein123 reviewed Jul 11, 2018

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htuch added 2 commits July 12, 2018 13:08

Merge remote-tracking branch 'upstream/master' into idle-timeout

65c47ad

Reviewer feedback.

5024440

Signed-off-by: Harvey Tuch <htuch@google.com>

alyssawilk reviewed Jul 12, 2018

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htuch added 2 commits July 12, 2018 18:13

More review feedback.

820202c

Signed-off-by: Harvey Tuch <htuch@google.com>

Merge remote-tracking branch 'upstream/master' into idle-timeout

bc7f524

htuch mentioned this pull request Jul 13, 2018

Timeouts for streams hanging prior to route determination #3853

Closed

mattklein123 reviewed Jul 13, 2018

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htuch added 2 commits July 15, 2018 16:16

Merge remote-tracking branch 'upstream/master' into idle-timeout

add1860

More review feedback.

4d2b4df

Signed-off-by: Harvey Tuch <htuch@google.com>

mattklein123 approved these changes Jul 16, 2018

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htuch merged commit 45fe83e into envoyproxy:master Jul 16, 2018

htuch mentioned this pull request Jul 17, 2018

http: global connection manager per-stream idle timeouts. #3879

Merged

dankirkpatrick mentioned this pull request Feb 20, 2019

503 upstream connect error or disconnect/reset before headers istio/istio#9906

Closed

		@@ -882,6 +914,8 @@ void ConnectionManagerImpl::ActiveStream::encode100ContinueHeaders(

		void ConnectionManagerImpl::ActiveStream::encodeHeaders(ActiveStreamEncoderFilter* filter,

		@@ -85,6 +85,20 @@ TEST_P(Http2IntegrationTest, TwoRequests) { testTwoRequests(); }

		TEST_P(Http2IntegrationTest, Retry) { testRetry(); }

		TEST_P(Http2IntegrationTest, PerStreamIdleTimeoutBeforeUpstreamHeaders) {

http: per-stream idle timeout. #3841

http: per-stream idle timeout. #3841

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