There are currently three boolean flags, and there will be one more
soon. Put them all in the top-level class instead of passing them as
arguments on lower levels.
Raise visibility of AutoConfiguredLoadBalancerFactory as internal
tests need to access it from a different package.
Rename HealthCheckingLoadBalancerFactory.LoadBalancerImpl to
*.HealthCheckingLoadBalancer so that its toString() output is more
informative.
This is needed for internal issue b/119247688.
A particular test that runs GRPC Android build in a non-Android
environment failed because RoundRobinLoadBalancerProvider was deleted
by ProGuard but the service-loader META-INF file still referred to it,
causing a loading failure.
This could be fixed by adding RoundRobinLoadBalancerProvider to the
hard-coded list, which is recognized by ProGuard then it will keep the
class.
However, we don't expect anyone to use RoundRobinLoadBalancerProvider
on Android, including the class on Android would increase code size,
which Android apps are sensitive to. Hence we move
RoundRobinLoadBalancerProvider to a different package (util), which is
built as a separate artifact internally which Android users usually
don't depend on. (Note that in open-source util is in the same artifact as core,
which is unfortunately).
Remove unused variables and prefer ArrayDeque to LinkedList. The swap to
Queue from Deque was just to make it more obvious what the usage was,
since the original swap to Deque was to avoid the same LinkedList lint
violation (3d51756d).
Introduce ChannelLogger, which is a utility provided to LoadBalancer implementations (potentially NameResolvers too) for recording events to channel trace. This is immediately required by client-side health checking (#4932, https://github.com/grpc/proposal/blob/master/A17-client-side-health-checking.md) to record an error about disabling health checking. It is also useful for any LoadBalancer implementations to record important information.
ChannelLogger implementation is backed by the internal ChannelTracer/Channelz. Because Channelz limits the number of retained events, and events are lost once the process ends, I have expanded it to also log Java logger. This would provide a "last resort" in cases where there are too many events or off-line investigation is needed. All logs are prefixed with logId so that they can be easily associated with the involved Channel/Subchannel.
To prevent log spamming, the logs are all at FINE level or below so that they are not visible by default. They are logged to ChannelLogger's logger, so that user can have precise control.
There are also more verbose information that may not fit in ChannelTracer, but can be useful for debugging. It's desirable that these logs are associated with logId, but they currently manually include the logId, which is cumbersome and may result in inconsistency. For this use case, I added the DEBUG level for ChannelLogger, which formats the log in the same way as other levels, while not recorded to Channelz.
I have converted most logging and channel tracer recording in the Channel implementation and LoadBalancers.
The ManagedChannelImpl change prevents any LB initialization failure
from producing a useless exception like:
java.lang.NullPointerException
at io.grpc.internal.ManagedChannelImpl.shutdownNameResolverAndLoadBalancer(ManagedChannelImpl.java:321)
at io.grpc.internal.ManagedChannelImpl.panic(ManagedChannelImpl.java:738)
at io.grpc.internal.ManagedChannelImpl$1.uncaughtException(ManagedChannelImpl.java:144)
Instead, now it will have the expected panic behavior of an INTERNAL
Status with a proper cause.
Since the NPE in AutoConfiguredLoadBalancerFactory wouldn't mean much to
users, it now has a more explicit message.
Following the [spec](https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md) on duplicate header names:
**Custom-Metadata** header order is not guaranteed to be preserved except for values with duplicate header names. Duplicate header names may have their values joined with "," as the delimiter and be considered semantically equivalent. Implementations must split Binary-Headers on "," before decoding the Base64-encoded values.
Because otherwise the user logic around Subchannel creation will
likely to race with handleSubchannelState().
Will log a warning if LoadBalancer.Helper.createSubChannel() is called
outside of the SynchronizationContext.
Adds SynchronizationContext.throwIfNotInThisSynchronizationContext()
to facilitate this warning. It can also be used by LoadBalancer
implementations to make it a requirement.
LoadBalancerProvider is the interface that extends LoadBalancer.Factory. LoadBalancerRegistry is the one that loads the providers through service loader, and allows users to access providers through their names.
pick_first and round_robin balancer factories, which are experimental public API are now deprecated. Their providers are internal, as they are accessible by policy name.
AutoConfiguredLoadBalancerFactory is modified to access implementations purely by their names, thus hard-coded class names are no longer needed, and it can support arbitrary policy selected by service config.
The trailing dot denotes the hostname to be absolute. It is fine to
leave, but removing it makes the authority match the more common form
and hopefully reduces confusion.
This happens to works around SNI failures caused when using gRPC-LB,
since SNI prohibits the trailing dot. However, that is not the reason
for this change as we have to support users directly providing a
hostname with the trailing dot anyway (and doing so is not hard).
See #4912
Swapping MetadataApplier to an abstract class is not ABI-safe for
callers. So I revert back to the previous interface definition and
introduce a CallCredentials2.MetadataApplier which is an abstract class.
Once everyone is on CallCredentials2 then we can swap it to an abstract
class again.
Fixes#5002
Provides a `SynchronizationContext` for scheduling tasks, with and without delay, from LoadBalancer implementations. This absorbs and extends the internal utility `ChannelExecutor`. It supersedes `Helper.runSerialized()`, which is now deprecated.
# Motivation
I see multiple cases that schedule tasks with a delay while requiring the task to run in the "Channel Executor". There have been repeated work to wrap scheduled tasks and handle races between cancellation and task run (see the diff in `GrpclbState.java` for example). The LoadBalancer implementation (e.g., GrpclbLoadBalancer) also has to acquire the `ScheduledExecutorService` from somewhere and release it upon shutdown.
The upcoming HealthCheckLoadBalancer (#4932), which would use back-off policy to retry health-checking streams, would have to do all the things above. At this point I think we need to provide something that combines `runSerialized()` with a scheduled executor with the same synchronization guarantees.
# Design details
`SynchronizationContext` is a similar to `ScheduledExecutorService` but tailored for use in `LoadBalancer` and potentially other cases outside of `LoadBalancer`. It offers task queuing and serialization and delayed scheduling. It guarantees non-reentrancy and happens-before among tasks. It owns no thread, but run tasks on caller's or caller-provided threads.
All channel-level state mutations and callback methods on `LoadBalancer` are done in a SynchronizationContext, which was previously referred to as "Channel Executor".
`SynchronizationContext.schedule()` returns a `ScheduledHandle` for status checking and cancellation. `ScheduedFuture` from `SchedulingExecutorService.schedule()` is too broad for our use cases (e.g., the blocking `get()` should never be used).
`SynchronizationContext.schedule()` requires a `ScheduledExecutorService`, which is now available through `Helper.getScheduledExecutorService()`. LoadBalancers don't need to worry about where to get `SchedulingExecutorService` any more.
# Alternatives
Alternatively, we could keep `Helper.runSerialized()` and add something like `Helper.runSerialiezdWithDelay()`, but having them on their own interface allows clean fake implementation by `FakeClock` for test, and allows other components (potentially `InternalSubchannel` for reconnection backoff) to use it too.
Instead of asking caller of `schedule()` to provide the `ScheduledExecutorService`, we considered having SynchronizationContext take a `ScheduledExecutorService` at construction. It would be inconvenient for LoadBalancer implementations that don't use `schedule()`, as they would be forced to provide a fake `ScheduledExecutorService` (which is cumbersome).
Instead of making `SynchronizationContext` a (semi-)concrete class, we considered making it an pure abstract class. However, we found it nontrivial to implement `execute()` correctly with the non-reentrancy guarantee.
This reverts commit ef8a84421d.
Firebase is not yet ready to migrate to the new API. Will try again once we made the release and migrated them to CallCredentials2.
This will allow enabling Error Prone on JDK 10+ (after
updating the net.ltgt.errorprone plugin), and is also a
prerequisite to that plugin update.
Also remove net.ltgt.apt plugin, as Gradle has native
support for annotationProcessor.
This change is mainly to fix a test, but it also is an implementation of the proposal here: https://github.com/grpc/proposal/pull/79
In short:
* Do not do SRV or TXT lookups when the target name is `localhost`. This can be overriden by a system property
* Do not do SRV or TXT lookups when the target name is an IPv6 or IPv4 address. This _cannot_ be overriden. The constructed domains for these queries would themselves not be valid. (e.g. _grpclb._tcp.192.168.0.1)
* Speeds up initial connection when communicating over local host, since it is extremely uncommon that such a connection would need gRPCLB or SRV records
I expect to remove the system property after a release if no one asks about it.
This is a rename of the pre-existing Netty builder method, so aliases
were added to the Netty builders.
Fixes#4050. This API was a minor rename to the pre-existing Netty API,
so has already undergone API review and thus is not ExperimentalApi.
There is a known issue that causes DNS lookup issue when network
siwtchover on android. This issue is tracked separately in #4962.
This change simply disables DNS cache to avoid the issue on Android.
Those overrides are kept for backward compatibility and convenience
for callers. Documentation already says implementations should not
override them. Making them final reduces confusion around which
override should be verified in tests and be overridden in forwarding
classes, thus prevents bugs caused by such confusion.
Returns a Channel that allows a LoadBalancer to make auxiliary RPCs on already-established application connections. We need this to implement client-side health-checking (#4932)
See comments on the API for its semantics.
Notable changes:
- Transports are modified to use InUseStateAggregator so that they can exclude RPCs made on Subchannel.asChannel() when reporting in-use state for idle mode.
- OobChannel shares the same Executor as Subchannel.asChannel(). Because the latter is not a ManagedChannel and doesn't have life-cycle, thus can't determine when to return the Executor to a pool, the Executor is now returned only when ManagedChannelImpl is terminated.
This change does 3 main things (in 3 commits):
1. Refactor the resolution runnable to be testable
2. Add Finer level logging to aid in debugging
3. Check that there are addresses before passing them to ManagedChannelImpl.
Kun Zhang
zpencer
ZHANG Dapeng
Jihun Cho
Eric Anderson
Rodrigo Queiro
Yang Song
Carl Mastrangelo
Thomas Broyer