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etcd3 java client and utilities
/*
* Copyright 2017, 2018 IBM Corp. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy
* of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*/
package com.ibm.etcd.client;
import static java.util.concurrent.TimeUnit.MILLISECONDS;
import java.lang.reflect.Proxy;
import java.net.ConnectException;
import java.net.NoRouteToHostException;
import java.util.ArrayDeque;
import java.util.Queue;
import java.util.concurrent.CancellationException;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executor;
import java.util.concurrent.Future;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.function.Supplier;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.google.common.base.Preconditions;
import com.google.common.base.Predicate;
import com.google.common.base.Predicates;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
import com.google.common.util.concurrent.ListeningScheduledExecutorService;
import com.google.common.util.concurrent.MoreExecutors;
import io.grpc.CallCredentials;
import io.grpc.CallOptions;
import io.grpc.Deadline;
import io.grpc.ManagedChannel;
import io.grpc.MethodDescriptor;
import io.grpc.Status;
import io.grpc.Status.Code;
import io.grpc.stub.ClientCallStreamObserver;
import io.grpc.stub.ClientCalls;
import io.grpc.stub.ClientResponseObserver;
import io.grpc.stub.StreamObserver;
/**
* grpc client support - non-etcd specific
*
*/
public class GrpcClient {
private static final Logger logger = LoggerFactory.getLogger(GrpcClient.class);
private final long defaultTimeoutMs;
//TODO maybe combine these into an auth provider intface
private final Supplier refreshCreds;
private final Predicate reauthRequired;
private final ManagedChannel channel;
protected final ListeningScheduledExecutorService ses;
// modified only by reauthenticate() method
private CallOptions callOptions = CallOptions.DEFAULT; // volatile tbd - lazy probably ok
//TODO whether some/all of the channel construction is moved in here
public GrpcClient(ManagedChannel channel,
Predicate reauthRequired,
Supplier credsSupplier,
ScheduledExecutorService executor,
long defaultTimeoutMs) {
Preconditions.checkArgument((reauthRequired == null) == (credsSupplier == null),
"must supply both or neither reauth and creds");
this.channel = channel;
this.refreshCreds = credsSupplier;
this.reauthRequired = reauthRequired;
this.ses = MoreExecutors.listeningDecorator(executor);
this.defaultTimeoutMs = defaultTimeoutMs;
}
public ScheduledExecutorService getExecutor() {
return ses;
}
public void authenticateNow() {
if(refreshCreds != null) reauthenticate(getCallOptions());
}
protected CallOptions getCallOptions() {
return callOptions;
}
static final RetryDecision IDEMP = (t,r) -> {
Status status = Status.fromThrowable(t);
Code code = status != null ? status.getCode() : null;
return code == Code.UNAVAILABLE
|| (code == Code.UNKNOWN
&& status.getDescription() != null
&& status.getDescription().startsWith("Channel closed"));
//TODO and maybe some DEADLINE_EXCEEDED cases (but not for overall deadline)
};
static final RetryDecision NON_IDEMP = (t,r)
-> codeFromThrowable(t) == Code.UNAVAILABLE && isConnectException(t);
@SuppressWarnings("unchecked")
public static final RetryDecision retryDecision(boolean idempotent) {
return (RetryDecision) (idempotent ? IDEMP : NON_IDEMP);
}
public ListenableFuture call(MethodDescriptor method,
ReqT request, boolean idempotent) {
return call(method, null, request, retryDecision(idempotent), 0, false, null, 0L);
}
//TODO probably move this
public static interface RetryDecision {
boolean retry(Throwable t, ReqT request);
}
public ListenableFuture call(MethodDescriptor method,
Condition precondition, ReqT request, RetryDecision retry,
boolean backoff, Deadline deadline, long timeoutMs) {
return call(method, precondition, request, retry, 0,
backoff, null, timeoutMs);
}
// deadline is for entire request (including retry pauses),
// timeout is per-attempt and 0 means not specified
private ListenableFuture call(MethodDescriptor method,
Condition precondition, ReqT request, RetryDecision retry,
int attempt, boolean backoff, Deadline deadline, long timeoutMs) {
if(precondition != null && !precondition.satisfied()) {
return Futures.immediateFailedFuture(new CancellationException("precondition false"));
}
//TODO(maybe) in delay case (attempt > 1), if "session" is inactive,
// skip attempt (and dont increment attempt #)
final CallOptions baseCallOpts = getCallOptions();
CallOptions callOpts = deadline != null ? baseCallOpts.withDeadline(deadline) : baseCallOpts;
return Futures.catchingAsync(fuCall(method, request, callOpts, timeoutMs), Exception.class, t -> {
boolean reauth;
if((!backoff && attempt > 0) || (!(reauth = reauthIfRequired(t, baseCallOpts))
&& !retry.retry(t, request))) return Futures.immediateFailedFuture(t);
if(attempt == 0 || reauth) return call(method, precondition, request, retry,
reauth ? attempt : 1, backoff, deadline, timeoutMs);
long delay = 500L * (1L << Math.min(attempt-2, 4)); //TODO review backoff pattern
return Futures.dereference(ses.schedule(() -> call(method, precondition, request,
retry, attempt+1, backoff, deadline, timeoutMs), delay, MILLISECONDS));
});
}
//TODO(maybe) for retriable RPCs consider fail-fast first timeout and longer retry timeout
protected ListenableFuture fuCall(MethodDescriptor method, ReqT request,
CallOptions callOptions, long timeoutMs) {
if(timeoutMs <= 0L) timeoutMs = defaultTimeoutMs;
if(timeoutMs > 0L) {
Deadline deadline = callOptions.getDeadline();
Deadline timeoutDeadline = Deadline.after(timeoutMs, MILLISECONDS);
if(deadline == null || timeoutDeadline.isBefore(deadline)) {
callOptions = callOptions.withDeadline(timeoutDeadline);
}
}
return ClientCalls.futureUnaryCall(channel.newCall(method, callOptions), request);
}
protected boolean retryStream(Throwable error, CallOptions callOpts) {
return reauthIfRequired(error, callOpts) ||
(Status.fromThrowable(error).getCode() != Code.INVALID_ARGUMENT
&& !causedByJavaError(error));
}
protected static boolean causedByJavaError(Throwable t) {
return causedBy(t, Error.class);
}
protected boolean reauthIfRequired(Throwable error, CallOptions callOpts) {
if(reauthRequired == null || !reauthRequired.apply(error)) return false;
reauthenticate(callOpts);
return true;
}
public static boolean isConnectException(Throwable t) {
return causedBy(t, ConnectException.class) || causedBy(t, NoRouteToHostException.class);
}
public static Code codeFromThrowable(Throwable t) {
Status status = Status.fromThrowable(t);
return status != null ? status.getCode() : null;
}
private void reauthenticate(CallOptions failedOpts) {
// assert name != null && password != null;
if(getCallOptions() != failedOpts) return; // obj identity comparison intentional
synchronized(this) {
CallOptions callOpts = getCallOptions();
if(callOpts != failedOpts) return;
callOptions = callOpts.withCallCredentials(refreshCreds.get());
}
}
public StreamObserver callStream(MethodDescriptor method,
ResilientResponseObserver respStream) {
return callStream(method, respStream, null);
}
public StreamObserver callStream(MethodDescriptor method,
ResilientResponseObserver respStream, Executor responseExecutor) {
// must explicitly auth in stream case to ensure unauthenticated version isn't used
if(refreshCreds != null && getCallOptions() == CallOptions.DEFAULT) authenticateNow();
return new ResilientBiDiStream<>(method, respStream, responseExecutor).start();
}
public static interface ResilientResponseObserver extends StreamObserver {
/**
* Called once initially, and once after each {@link #onReplaced(StreamObserver)},
* to indicate the corresponding (sub) stream is successfully established
*/
public void onEstablished();
/**
* Indicates the underlying stream failed and will be re-established. There is
* no guarantee that any requests sent to the current request stream have
* been delivered, the provided stream should be used in its place to send
* all subsequent requests, including re-submissions if necessary. Any subsequent
* {@link #onEstablished()} or {@link #onNext(Object)} calls received will
* be responses from this new stream, it's guaranteed that there will
* be no more from the prior stream.
*
* @param newStreamRequestObserver
*/
public void onReplaced(StreamObserver newStreamRequestObserver);
}
class ResilientBiDiStream {
private final MethodDescriptor method;
private final ResilientResponseObserver respStream;
private final Executor responseExecutor;
// accessed only from response thread and retry task scheduled
// from the onError message (prior to stream being reestablished)
private CallOptions sentCallOptions;
private int errCounter = 0;
// provided to user, buffers and wraps real req stream when active.
// field accessed only from response thread
private RequestSubStream userReqStream;
// finished reflects *user* closing stream via terminal method (not incoming stream closure)
// error == null indicates complete versus failed when finished == true
// modified only by response thread
private boolean finished;
private Throwable error;
/**
*
* @param method
* @param respStream
* @param responseExecutor must be serialized
*/
public ResilientBiDiStream(MethodDescriptor method,
ResilientResponseObserver respStream,
Executor responseExecutor) {
this.method = method;
this.respStream = respStream;
this.responseExecutor = serialized(responseExecutor != null
? responseExecutor : ses, 0);
}
// must only be called once - enforcement logic omitted since private
StreamObserver start() {
RequestSubStream firstStream = new RequestSubStream();
userReqStream = firstStream;
refreshBackingStream();
return firstStream;
}
class RequestSubStream implements StreamObserver {
// lifecycle: null -> real stream -> EMPTY_STREAM
private volatile StreamObserver grpcReqStream; // only modified by response thread
// grpcReqStream non-null => preConnectBuffer null
private Queue preConnectBuffer;
// called by user thread
@Override
public void onNext(ReqT value) {
if(finished) return; // illegal usage
StreamObserver rs = grpcReqStream;
if(rs == null) synchronized(this) {
rs = grpcReqStream;
if(rs == null) {
if(preConnectBuffer == null) {
preConnectBuffer = new ArrayDeque<>(8); // bounded TBD
}
preConnectBuffer.add(value);
return;
}
}
rs.onNext(value); // (***)
}
// called by user thread
@Override
public void onError(Throwable t) {
onFinish(t);
}
// called by user thread
@Override
public void onCompleted() {
onFinish(null);
}
// called from response thread
boolean established(StreamObserver stream) {
StreamObserver curStream = grpcReqStream;
if(curStream == null) synchronized(this) {
Queue pcb = preConnectBuffer;
if(pcb != null) {
ReqT req;
while((req = pcb.poll()) != null) stream.onNext(req);
preConnectBuffer = null;
}
if(finished) grpcReqStream = emptyStream();
else {
grpcReqStream = stream;
return true;
}
}
else if(stream == curStream) return false;
// here either finished or it's an unexpected new stream
Throwable err = error;
if(err == null) stream.onCompleted();
else stream.onError(err);
return false;
}
boolean isEstablished() {
return grpcReqStream != null;
}
// called from grpc response thread
void discard(Throwable err) {
StreamObserver curStream = grpcReqStream, empty = emptyStream();
if(curStream == empty) return;
if(curStream == null) synchronized(this) {
grpcReqStream = empty;
preConnectBuffer = null;
}
//TODO this *could* overlap with an in-progress
// onNext (***) above, but unlikely
// ideas:
// - sync both on the stream itself - not ideal
// - defer until user call is made on the new stream
else close(err);
}
// called from grpc response thread
void close(Throwable err) {
StreamObserver curStream = grpcReqStream, empty = emptyStream();
if(curStream == null || curStream == empty) return;
grpcReqStream = empty;
//assert preConnectBuffer == null;
if(err == null) curStream.onCompleted();
else curStream.onError(err);
}
}
// called by user thread
private void onFinish(Throwable err) {
if(finished) return; // shouldn't be called more than once anyhow
responseExecutor.execute(() -> {
if(finished) return;
// don't treat this as final if authentication
// is enabled and the error reflects that reauth
// is required - instead just cancel the "current"
// stream which will cause the top-level stream
// to be refreshed after a reauth is done
if(err == null || reauthRequired == null
|| !reauthRequired.apply(err)) {
error = err;
finished = true;
}
userReqStream.close(err);
});
}
/*
* We assume the caller (grpc) abides by StreamObserver contract
*/
private final StreamObserver respWrapper = new ClientResponseObserver() {
@Override public void beforeStart(ClientCallStreamObserver rs) {
rs.setOnReadyHandler(() -> {
// called from grpc response thread
if(rs.isReady()) {
errCounter = 0;
boolean notify = userReqStream.established(rs);
if(notify) respStream.onEstablished();
}
});
}
// called from grpc response thread
@Override public void onNext(RespT value) {
respStream.onNext(value);
}
// called from grpc response thread
@Override public void onError(Throwable t) {
boolean finalError = finished || !retryStream(t, sentCallOptions);
if(!finalError) {
String msg = "retryable onError on underlying stream of method "
+method.getFullMethodName();
if(logger.isDebugEnabled()) logger.info(msg, t);
else logger.info(msg+": "+t.getClass().getName()+": "+t.getMessage());
RequestSubStream userStreamBefore = userReqStream;
if(userStreamBefore.isEstablished()) {
userReqStream = new RequestSubStream();
userStreamBefore.discard(null);
// must call onReplaced prior to refreshing the stream, otherwise
// the response observer may be called with responses from the
// new stream prior to onReplaced returning
respStream.onReplaced(userReqStream);
}
// else no need to replace user stream
int errCount = errCounter++;
if(errCount == 0) refreshBackingStream();
else {
long delay = 500L * (1L << Math.min(errCount-2, 4));
ses.schedule(ResilientBiDiStream.this::refreshBackingStream,
delay, TimeUnit.MILLISECONDS);
}
} else {
sentCallOptions = null;
userReqStream.discard(t);
respStream.onError(t);
}
}
// called from grpc response thread
@Override public void onCompleted() {
//TODO(maybe) reestablish stream in this case if !finished?
sentCallOptions = null;
userReqStream.discard(null);
respStream.onCompleted();
}
};
// called only from:
// - start() method
// - grpc response thread
// - scheduled retry (no active stream)
private void refreshBackingStream() {
if(finished) return;
CallOptions callOpts = getCallOptions();
sentCallOptions = callOpts;
callOpts = callOpts.withExecutor(responseExecutor);
ClientCalls.asyncBidiStreamingCall(channel
.newCall(method, callOpts), respWrapper);
}
}
// ------- utilities
public static T waitFor(Future fut) {
return waitFor(fut, -1L);
}
public static T waitFor(Future fut, long timeoutMillis) {
try {
return timeoutMillis < 0L ? fut.get() : fut.get(timeoutMillis, MILLISECONDS);
} catch(InterruptedException|CancellationException e) {
fut.cancel(true);
throw Status.CANCELLED.withCause(e).asRuntimeException();
} catch(ExecutionException ee) {
throw Status.fromThrowable(ee.getCause()).asRuntimeException();
} catch(TimeoutException te) {
fut.cancel(true);
throw Status.DEADLINE_EXCEEDED.withCause(te)
.withDescription("local timeout of "+timeoutMillis+"ms exceeded")
.asRuntimeException();
} catch(RuntimeException rte) {
fut.cancel(true);
throw Status.fromThrowable(rte).asRuntimeException();
}
}
@SuppressWarnings("rawtypes")
private static final StreamObserver EMPTY_STREAM = new StreamObserver() {
@Override public void onCompleted() {}
@Override public void onError(Throwable t) {}
@Override public void onNext(Object value) {}
};
@SuppressWarnings("unchecked")
protected static StreamObserver emptyStream() {
return (StreamObserver) EMPTY_STREAM;
}
protected static Predicate constantPredicate(boolean val) {
return val ? Predicates.alwaysTrue() : Predicates.alwaysFalse();
}
protected static boolean contains(String str, String subStr) {
return str != null && str.contains(subStr);
}
public static boolean causedBy(Throwable t, Class exClass) {
return t != null && (exClass.isAssignableFrom(t.getClass())
|| causedBy(t.getCause(), exClass));
}
@SuppressWarnings("unchecked")
public static I sentinel(Class intface) {
return (I) Proxy.newProxyInstance(intface.getClassLoader(),
new Class[] {intface}, (p,m,a) -> {
if("toString".equals(m.getName())) return "SENTINEL";
if("hashCode".equals(m.getName())) return System.identityHashCode(p);
if("equals".equals(m.getName())) return a[0] == p;
throw new IllegalStateException("attempt to invoke sentinel");
});
}
public static Executor serialized(Executor parent, int bufferSize) {
return parent instanceof SerializingExecutor
|| parent instanceof io.grpc.internal.SerializingExecutor
|| parent == MoreExecutors.directExecutor()
? parent : new SerializingExecutor(parent, bufferSize);
}
}