The error occurs when name resolution completes after the channel is
shut down. What ManagedChannelImpl doing right now is violating the
TransportManager interface, because TransportManager.getTransport()
should never return null.
- Channel builders decide the default port based on whether TLS is used.
- Channel builders populate the default port via an Attributes object
passed to NameResolver.Factory#newNameResolver
Although it is unlikely the awaits return false, it would be useful
information to know about the failure if they did.
This should provide more clues in case the test flakes again (#1146)
- NameResolverRegistry contains all the official NameResolvers. Users
can also add custom NameResolvers to it. It looks up NameResolver by
try-and-fail. It is the default NameResolver.Factory for builders.
DnsNameResolver.
- Pass target as Strings instead of URIs from the channel builder to
ManagedChannelImpl. A target string is not necessarily a valid URI, in
which case ManagedChannelImpl will add "dns:///" to the beginning of
the target and use it as URI.
- DnsNameResolver will require scheme "dns" to be present. It no longer
allows scheme-absent URIs.
Otherwise, when DelayedStream is created it ends up calling
clientTransportProvider a second time. However, we already have a
transportFuture available, we should just use it instead.
transportFailsOnStart was still flaky. By looking at history, it became
obvious that transportFailsOnStart was created to test two cases we no
longer support: the transport throwing an exception during start and the
transport calling listener.transportShutdown during start. The part of
the test checking throwing an exception was removed earlier.
The scheduling on another thread led to a race where sometimes the
future wasn't completed by the time isDone() was checked in
ClientCallImpl causing the usage of DelayedStream, which really messed
up what the test was trying to do.
- Add NameResolver and LoadBalancer interfaces.
- ManagedChannelImpl now uses NameResolver and LoadBalancer for
transport selection, which may return transports to multiple
addresses.
- Transports are still owned by ManagedChannelImpl, which implements
TransportManager interface that is provided to LoadBalancer, so that
LoadBalancer doesn't worry about Transport lifecycles.
- Channel builders can be created by forTarget() that accepts the fully
qualified target name, which is an URI. (TODO) it's not tested.
- The old address-based construction pattern is supported by using
AbstractManagedChannelImplBuilder.DirectAddressNameResolver.
- (TODO) DnsNameResolver and SimpleLoadBalancer are currently
incomplete. They merely work for the single-address scenario.
- ListenableFutures of transports, instead of actual transports, are
passed through multiple layers to ClientCallImpl, so that name
resolution and load-balancing, which may delay the creation of
transports, won't block the creation of ClientCall. This also
simplifies reconnect logic.
- Moved Transport management for a single address to a separate class
TransportSet. Later, ManagedChannelImpl will own multiple
TransportSets instead of one.
- ClientCallImpl will buffer requests in DelayedStream until transport
is ready.
This test occasionally flakes due to the way the deadline timer cancels the stream. Stream cancellation immediately closes the outbound status, disallowing the sending of further messages. The true cancellation is done sometime later in the transport thread in Netty. So there is a race between closing the outbound status and performing the actual cancellation where sent messages will fail with the wrong status.
ServerCall already had "headers must be sent before any messages, which
must be sent before closing," but the implementation did not enforce it
and our async server handler didn't obey.
The benefit of forcing sending headers first is that it removes the only
implicit call in our API and interceptors dealing just with metadata
don't need to override sendMessage. The implicit behavior was bug-prone
since it wasn't obvious you were forgetting that headers may not be
sent.
It is typically used for receiving, but is on the sending object. It
would be a pain for users to coordinate, and the implementation is
already thread-safe because we always thought it would be thread-safe.
So make it part of the documentation.
We want to allow overriding authority in the ManagedChannelBuilder for
testing. In doing that, we basically require that all Channels support
authority. In reality, this simplifies things and is already being done
by the C implementation, as their unix domain socket support uses
"localhost" just like our in-process transport now does.
We can debate some whether "localhost" is really the most appropriate
authority for the in-process transport, but that should probably happen
later since "localhost" is "good enough" for now.
Although the functionality is currently available by passing a
manually-created InetAddress, that requires that the user do I/O before
calling our API and does not work with naming in the future.
There is no need to use ServerMethodDefinition in codegen. The create()
method itself could be helpful to a dynamic HandlerRegistry
implementation, so we won't remove it.
This provides an API for applications to use gRPC without using
ExperimentalApis. It also allows swapping out a transport implementation
in the future.
Eric Anderson
Xudong Ma
Kun Zhang
Carl Mastrangelo
nmittler
Éamonn McManus