LoadBalancers shouldn't be called after shutdown(), but RingHashLb could
have enqueued work to the SynchronizationContext that executed after
shutdown(). This commit fixes problems discovered when auditing all LBs
usage of the syncContext for that type of problem.
Similarly, PickFirstLb could have requested a new connection after
shutdown(). We want to avoid that sort of thing too.
RingHashLb's test changed from CONNECTING to TRANSIENT_FAILURE to get
the latest picker. Because two subchannels have failed it will be in
TRANSIENT_FAILURE. Previously the test was using an older picker with
out-of-date subchannelView, and the verifyConnection() was too imprecise
to notice it was creating the wrong subchannel.
As discovered in b/430347751, where ClusterImplLb was seeing a new
subchannel being called after the child LB was shutdown (the shutdown
itself had been caused by RingHashConfig not implementing equals() and
was fixed by a8de9f07ab, which caused ClusterResolverLb to replace its
state):
```
java.lang.NullPointerException
at io.grpc.xds.ClusterImplLoadBalancer$ClusterImplLbHelper.createClusterLocalityFromAttributes(ClusterImplLoadBalancer.java:322)
at io.grpc.xds.ClusterImplLoadBalancer$ClusterImplLbHelper.createSubchannel(ClusterImplLoadBalancer.java:236)
at io.grpc.util.ForwardingLoadBalancerHelper.createSubchannel(ForwardingLoadBalancerHelper.java:47)
at io.grpc.util.ForwardingLoadBalancerHelper.createSubchannel(ForwardingLoadBalancerHelper.java:47)
at io.grpc.internal.PickFirstLeafLoadBalancer.createNewSubchannel(PickFirstLeafLoadBalancer.java:527)
at io.grpc.internal.PickFirstLeafLoadBalancer.requestConnection(PickFirstLeafLoadBalancer.java:459)
at io.grpc.internal.PickFirstLeafLoadBalancer.acceptResolvedAddresses(PickFirstLeafLoadBalancer.java:174)
at io.grpc.xds.LazyLoadBalancer$LazyDelegate.activate(LazyLoadBalancer.java:64)
at io.grpc.xds.LazyLoadBalancer$LazyDelegate.requestConnection(LazyLoadBalancer.java:97)
at io.grpc.util.ForwardingLoadBalancer.requestConnection(ForwardingLoadBalancer.java:61)
at io.grpc.xds.RingHashLoadBalancer$RingHashPicker.lambda$pickSubchannel$0(RingHashLoadBalancer.java:440)
at io.grpc.SynchronizationContext.drain(SynchronizationContext.java:96)
at io.grpc.SynchronizationContext.execute(SynchronizationContext.java:128)
at io.grpc.xds.client.XdsClientImpl$ResourceSubscriber.onData(XdsClientImpl.java:817)
```
The plugin now outputs to "generated/sources". The IDE configuration
explicitly adding the folders to the source sets hasn't been needed for
some years.
Bazel had the dependency added because of #5046, where Guava was
depending on it as compile-only and Bazel build have "unknown enum
constant" warnings. Guava now has a compile dependency on j2objc, so
this workaround is no longer needed. There are currently no version skew
issues in Gradle, which was the only usage.
The GSON upgrade slightly changed an error string, so the test was
updated to be less of a change detector.
Some OpenTelemetry dependencies are alpha versions, so needed an
adjustment in build.gradle to accept the versions. Similarly, Undertow
includes Final in its version numbers which needs to be accepted.
Add gRPC OpenTelemetry example. The example uses Prometheus exporter to export metrics and can be verified locally.
It also provides an example using LoggingMetricExporter to export and log the metrics using java.util.logging.
According to the docs, I can use bazel to build examples, but
retry-example is not supported in bazel config. So If you'll try to
build this example with bazel, you'll get an error:
```
examples git:(master) ✗ bazel build :retrying-hello-world-server :retrying-hello-world-client
ERROR: Skipping ':retrying-hello-world-client': no such target '//:retrying-hello-world-client': target 'retrying-hello-world-client' not declared in package '' defined by /Users/rostik404/projects/grpc-java/examples/BUILD.bazel
ERROR: no such target '//:retrying-hello-world-client': target 'retrying-hello-world-client' not declared in package '' defined by /Users/rostik404/projects/grpc-java/examples/BUILD.bazel
INFO: Elapsed time: 0.331s
INFO: 0 processes.
ERROR: Build did NOT complete successfully
```
The gradle wrapper was removed from example-oauth because we don't want
to maintain the wrapper copy in each example (at least right now it
doesn't make sense for it to be the only other example to have the
gradle wrapper).
Or rather, server response is ambiguous and this usage is not generally
what we mean when we say it. The example shows how to get an error for
any failed RPC, not just those coming from a failing server.
The existing comment caused confusion at
https://stackoverflow.com/a/78104828
Eric Anderson