This resolves#5523
While bumping `com.android.tools.build:gradle:3.1.2` to `3.3.0`, some other plugins/artifacts/maven repo/buildscripts have to be updated:
- gradle (wrapper) need to upgrade to 4.10.x
- protobuf gradle plugin need to bump a version compatible with gradle version.
- need add `google()` and `jcenter()` repos for android (otherwise `com.android.tools.build:aapt2:3.3.0x` and `trove4j` will not be found resp.)
- need to accept license for Android "build-tools;28.0.3" in kokoro env.
The `ThreadlessExecutor` currently used for blocking calls uses `LinkedBlockingQueue` which is relatively heavy both in terms of allocations and synchronization overhead (e.g. when compared to `ConcurrentLinkedQueue`). It accounts for ~10% of allocations and ~5% of allocated bytes per-call in the `TransportBenchmark` when using in-process transport with [stats and tracing disabled](https://github.com/grpc/grpc-java/issues/5510).
Changing to use a `ConcurrentLinkedQueue` results in a ~5% speedup of that benchmark.
Before:
```
Benchmark (direct) (transport) Mode Cnt Score Error Units
TransportBenchmark.unaryCall1024 true INPROCESS avgt 60 1877.339 ± 46.309 ns/op
TransportBenchmark.unaryCall1024 false INPROCESS avgt 60 12680.525 ± 208.684 ns/op
```
After:
```
Benchmark (direct) (transport) Mode Cnt Score Error Units
TransportBenchmark.unaryCall1024 true INPROCESS avgt 60 1779.188 ± 36.769 ns/op
TransportBenchmark.unaryCall1024 false INPROCESS avgt 60 12532.470 ± 238.271 ns/op
```
* grpclb: use a stopwatch to manage elapased time for LB backoff
* reformatt lines
* create a new Stopwatch for each single newly created HC stream
* use existing stopwatch supplier provided by FakeClock in tests
Using Long.MAX_VALUE as the delay for Netty's NioEventLoop#schedule can
cause (long) deadlines for scheduled tasks to wrap into negative values,
which is unspecified behavior. Recent versions of netty are guarding
against overflows, but not all versions of grpc-java are using a recent
enough netty.
When connections are gracefully closed, Netty's Http2ConnectionHandler
sets up a timeout task forcing resources to be freed after a grace
period. When their deadlines wrap into negative values, a race was
observed in production systems (with grpc-java <= 1.12.1) causing Netty
to never properly release buffers associated with active streams in the
connection being (gracefully) closed.
The problem: GrpclbState tracks Subchannels' states as a mutable
attribute in Subchannel.getAttributes(). However, GrpclbState only
update this attribute for the Subchannels its managing. For those
cached in SubchannelPool, their state attributes are stale. When they
are given back to GrpclbState, IDLE state is assumed. As a result, if
a Subchannel is READY when it's reclaimed from the pool, it will not
be picked.
To fix that, this change expands SubchannelPool interface to handle
Subchannel state updates, which GrpclbState will call. SubchannelPool
saves the latest state and delivers it when it's returned to
GrpclbState by scheduling a call to handleSubchannelState() in the
SynchronizationContext, so that GrpclbState will take the latest state
as if it was just reported from the Channel.
Make the "logged" method be consistent, and refer to the public logging class name and method. This makes the log statements return the same class name used to set the log level.
Before:
```
190306 13:29:39.290:D 1 [io.grpc.internal.ChannelTracer.logOnly] [Channel<1>: (localhost:10000)] Channel for 'localhost:10000' created
190306 13:29:39.414:D 1 [io.grpc.internal.ChannelTracer.logOnly] [Channel<1>: (localhost:10000)] Exiting idle mode
190306 13:29:39.622:D 17 [io.grpc.internal.ChannelTracer.logOnly] [Channel<1>: (localhost:10000)] Resolved address: [[[/127.0.0.1:10000]/{}]], config={}
190306 13:29:39.623:D 17 [io.grpc.internal.ChannelTracer.logOnly] [Channel<1>: (localhost:10000)] Address resolved: [[[/127.0.0.1:10000]/{}]]
190306 13:29:39.624:D 17 [io.grpc.internal.ChannelTracer.logOnly] [Subchannel<3>] Subchannel for [[[/127.0.0.1:10000]/{}]] created
```
After:
```
190306 13:49:15.654:D 1 [io.grpc.ChannelLogger.log] [Channel<1>: (localhost:10000)] Channel for 'localhost:10000' created
190306 13:49:15.772:D 1 [io.grpc.ChannelLogger.log] [Channel<1>: (localhost:10000)] Exiting idle mode
190306 13:49:15.995:D 18 [io.grpc.ChannelLogger.log] [Channel<1>: (localhost:10000)] Resolved address: [[[/127.0.0.1:10000]/{}]], config={}
190306 13:49:15.995:D 18 [io.grpc.ChannelLogger.log] [Channel<1>: (localhost:10000)] Address resolved: [[[/127.0.0.1:10000]/{}]]
190306 13:49:15.997:D 18 [io.grpc.ChannelLogger.log] [Subchannel<3>] Subchannel for [[[/127.0.0.1:10000]/{}]] created
190306 13:49:15.999:D 18 [io.grpc.ChannelLogger.log] [Channel<1>: (localhost:10000)] Child Subchannel created
```
The PICK_FIRST mode puts all backend addresses in a single Subchannel. There are a few points where it's different from the default ROUND_ROBIN mode:
1. PICK_FIRST doesn't eagerly connect to backends like ROUND_ROBIN does. Instead, it requests for connections when the Subchannel is picked.
2. PICK_FIRST adds tokens to the headers via a different code path (`TokenAttachingTracerFactory`) than ROUND_ROBIN
3. For simple implementation, when the mode is changed by service config when the LoadBalancer is working, we will shut down `GrpclbState` and starts a new one with the new mode. All connections will be closed during the transition. We don't expect this to happen in practice given the specific use case of PICK_FIRST.
ZHANG Dapeng
Carl Mastrangelo
Nick Hill
Kun Zhang
Chengyuan Zhang
apolcyn
Tim van der Lippe
Fabio Kung
Derek Perez
Jiangtao Li
Eric Anderson
Dan Torrey
Jihun Cho
Brendan Linn