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Not to send any request at GrpcSubscriptionImpl destructor #4178

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Not to send any request at GrpcSubscriptionImpl destructor #4178

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8 changes: 8 additions & 0 deletions source/common/config/grpc_mux_impl.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,14 @@ GrpcMuxImpl::~GrpcMuxImpl() {
}
}

void GrpcMuxImpl::noMoreRequestSending() {
for (const auto& api_state : api_state_) {
for (auto watch : api_state.second.watches_) {
watch->send_update_ = false;
}
}
}

void GrpcMuxImpl::start() { establishNewStream(); }

void GrpcMuxImpl::setRetryTimer() {
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8 changes: 6 additions & 2 deletions source/common/config/grpc_mux_impl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,9 @@ class GrpcMuxImpl : public GrpcMux,
MonotonicTimeSource& time_source = ProdMonotonicTimeSource::instance_);
~GrpcMuxImpl();

// Not to send any request, the object is about to be deleted.
void noMoreRequestSending();

void start() override;
GrpcMuxWatchPtr subscribe(const std::string& type_url, const std::vector<std::string>& resources,
GrpcMuxCallbacks& callbacks) override;
Expand Down Expand Up @@ -57,14 +60,14 @@ class GrpcMuxImpl : public GrpcMux,
GrpcMuxWatchImpl(const std::vector<std::string>& resources, GrpcMuxCallbacks& callbacks,
const std::string& type_url, GrpcMuxImpl& parent)
: resources_(resources), callbacks_(callbacks), type_url_(type_url), parent_(parent),
inserted_(true) {
inserted_(true), send_update_(true) {
entry_ = parent.api_state_[type_url].watches_.emplace(
parent.api_state_[type_url].watches_.begin(), this);
}
~GrpcMuxWatchImpl() override {
if (inserted_) {
parent_.api_state_[type_url_].watches_.erase(entry_);
if (!resources_.empty()) {
if (send_update_ && !resources_.empty()) {
parent_.sendDiscoveryRequest(type_url_);
}
}
Expand All @@ -75,6 +78,7 @@ class GrpcMuxImpl : public GrpcMux,
GrpcMuxImpl& parent_;
std::list<GrpcMuxWatchImpl*>::iterator entry_;
bool inserted_;
bool send_update_;
};

// Per muxed API state.
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1 change: 1 addition & 0 deletions source/common/config/grpc_subscription_impl.h
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Expand Up @@ -19,6 +19,7 @@ class GrpcSubscriptionImpl : public Config::Subscription<ResourceType> {
const Protobuf::MethodDescriptor& service_method, SubscriptionStats stats)
: grpc_mux_(node, std::move(async_client), dispatcher, service_method, random),
grpc_mux_subscription_(grpc_mux_, stats) {}
~GrpcSubscriptionImpl() { grpc_mux_.noMoreRequestSending(); }
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This doesn't seem correct; grpc_mux_ might be an ADS connection. When I delete an individual subscriber, e.g. EDS, I shouldn't permanently disable the muxer. It seems like what we had before is the right thing, the gRPC subscription should relinquish its watch by deleting it, and then via RAII it cleans up its state in the gRPC mux. But, from the issue, there is some bug still. Can you deep dive?

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GrpcSubscriptionImpl owns grpc_mux_. Look at line 39 of this file.
At its destructor, grpc_mux_ is about to be deleted. It is OK to mark all its watchers; not to send request when a watcher is removed.

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Oh, right, was confusing this with GrpcMuxSubscriptionImpl. It's still not right IMHO, since you're reaching in and dealing with internals in a way that breaks abstractions. The correct solution should clean up via RAII of watchers.

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@htuch htuch Aug 17, 2018 •
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I had a look at the code a bit more. I think even with your change, there is a race to worry about. The completion thread should still be live when the client is deleted, as that lives in TLS (are you seeing https://github.com/envoyproxy/envoy/blob/master/source/common/grpc/google_async_client_impl.cc#L19 invoked?). The async client should have reset the stream on its way out. I wonder if we have an issue in https://github.com/envoyproxy/envoy/blob/master/source/common/grpc/google_async_client_impl.cc#L363?

Can you provide a full trace level log and backtrace with line numbers? Thanks.

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I added a trace log to the issue: #4167

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(I'm following up with @qiwzhang on IM offline, it looks like SDS still has an active gRPC subscription after TLS shutdown has begun, this is dangerous and we need to figure out a way to avoid that)


// Config::Subscription
void start(const std::vector<std::string>& resources,
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2 changes: 0 additions & 2 deletions test/common/config/grpc_subscription_test_harness.h
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Expand Up @@ -43,8 +43,6 @@ class GrpcSubscriptionTestHarness : public SubscriptionTestHarness {
dispatcher_, random_, *method_descriptor_, stats_));
}

~GrpcSubscriptionTestHarness() { EXPECT_CALL(async_stream_, sendMessage(_, false)); }

void expectSendMessage(const std::vector<std::string>& cluster_names,
const std::string& version) override {
expectSendMessage(cluster_names, version, Grpc::Status::GrpcStatus::Ok, "");
Expand Down