/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.tinkerpop.gremlin.server.op.traversal;
import com.codahale.metrics.Timer;
import com.github.benmanes.caffeine.cache.Cache;
import com.github.benmanes.caffeine.cache.Caffeine;
import io.netty.channel.ChannelHandlerContext;
import org.apache.commons.lang.time.StopWatch;
import org.apache.tinkerpop.gremlin.driver.MessageSerializer;
import org.apache.tinkerpop.gremlin.driver.Tokens;
import org.apache.tinkerpop.gremlin.driver.message.RequestMessage;
import org.apache.tinkerpop.gremlin.driver.message.ResponseMessage;
import org.apache.tinkerpop.gremlin.driver.message.ResponseStatusCode;
import org.apache.tinkerpop.gremlin.jsr223.JavaTranslator;
import org.apache.tinkerpop.gremlin.process.traversal.Bytecode;
import org.apache.tinkerpop.gremlin.process.traversal.Traversal;
import org.apache.tinkerpop.gremlin.process.traversal.TraversalSideEffects;
import org.apache.tinkerpop.gremlin.process.traversal.TraversalSource;
import org.apache.tinkerpop.gremlin.process.traversal.util.BytecodeHelper;
import org.apache.tinkerpop.gremlin.server.Context;
import org.apache.tinkerpop.gremlin.server.GraphManager;
import org.apache.tinkerpop.gremlin.server.GremlinServer;
import org.apache.tinkerpop.gremlin.server.OpProcessor;
import org.apache.tinkerpop.gremlin.server.Settings;
import org.apache.tinkerpop.gremlin.server.handler.Frame;
import org.apache.tinkerpop.gremlin.server.handler.StateKey;
import org.apache.tinkerpop.gremlin.server.op.AbstractOpProcessor;
import org.apache.tinkerpop.gremlin.server.op.OpProcessorException;
import org.apache.tinkerpop.gremlin.server.util.MetricManager;
import org.apache.tinkerpop.gremlin.server.util.SideEffectIterator;
import org.apache.tinkerpop.gremlin.server.util.TraverserIterator;
import org.apache.tinkerpop.gremlin.structure.Graph;
import org.apache.tinkerpop.gremlin.structure.io.graphson.GraphSONMapper;
import org.apache.tinkerpop.gremlin.structure.io.graphson.GraphSONVersion;
import org.apache.tinkerpop.gremlin.util.function.ThrowingConsumer;
import org.apache.tinkerpop.shaded.jackson.databind.ObjectMapper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import javax.script.SimpleBindings;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.UUID;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import static com.codahale.metrics.MetricRegistry.name;
/**
* Simple {@link OpProcessor} implementation that iterates remotely submitted serialized {@link Traversal} objects.
*
* @author Stephen Mallette (http://stephen.genoprime.com)
*/
public class TraversalOpProcessor extends AbstractOpProcessor {
private static final Logger logger = LoggerFactory.getLogger(TraversalOpProcessor.class);
private static final ObjectMapper mapper = GraphSONMapper.build().version(GraphSONVersion.V2_0).create().createMapper();
public static final String OP_PROCESSOR_NAME = "traversal";
public static final Timer traversalOpTimer = MetricManager.INSTANCE.getTimer(name(GremlinServer.class, "op", "traversal"));
public static final Settings.ProcessorSettings DEFAULT_SETTINGS = new Settings.ProcessorSettings();
/**
* Configuration setting for how long a cached side-effect will be available before it is evicted from the cache.
*/
public static final String CONFIG_CACHE_EXPIRATION_TIME = "cacheExpirationTime";
/**
* Default timeout for a cached side-effect is ten minutes.
*/
public static final long DEFAULT_CACHE_EXPIRATION_TIME = 600000;
/**
* Configuration setting for the maximum number of entries the cache will have.
*/
public static final String CONFIG_CACHE_MAX_SIZE = "cacheMaxSize";
/**
* Default size of the max size of the cache.
*/
public static final long DEFAULT_CACHE_MAX_SIZE = 1000;
static {
DEFAULT_SETTINGS.className = TraversalOpProcessor.class.getCanonicalName();
DEFAULT_SETTINGS.config = new HashMap<String, Object>() {{
put(CONFIG_CACHE_EXPIRATION_TIME, DEFAULT_CACHE_EXPIRATION_TIME);
put(CONFIG_CACHE_MAX_SIZE, DEFAULT_CACHE_MAX_SIZE);
}};
}
protected static Cache<UUID, TraversalSideEffects> cache = null;
public TraversalOpProcessor() {
super(false);
}
@Override
public String getName() {
return OP_PROCESSOR_NAME;
}
@Override
public void close() throws Exception {
// do nothing = no resources to release
}
@Override
public void init(final Settings settings) {
final Settings.ProcessorSettings processorSettings = settings.processors.stream()
.filter(p -> p.className.equals(TraversalOpProcessor.class.getCanonicalName()))
.findAny().orElse(TraversalOpProcessor.DEFAULT_SETTINGS);
final long maxSize = Long.parseLong(processorSettings.config.get(TraversalOpProcessor.CONFIG_CACHE_MAX_SIZE).toString());
final long expirationTime = Long.parseLong(processorSettings.config.get(TraversalOpProcessor.CONFIG_CACHE_EXPIRATION_TIME).toString());
cache = Caffeine.newBuilder()
.expireAfterWrite(expirationTime, TimeUnit.MILLISECONDS)
.maximumSize(maxSize)
.build();
logger.info("Initialized cache for {} with size {} and expiration time of {} ms",
TraversalOpProcessor.class.getSimpleName(), maxSize, expirationTime);
}
@Override
public ThrowingConsumer<Context> select(final Context ctx) throws OpProcessorException {
final RequestMessage message = ctx.getRequestMessage();
logger.debug("Selecting processor for RequestMessage {}", message);
final ThrowingConsumer<Context> op;
switch (message.getOp()) {
case Tokens.OPS_BYTECODE:
validateTraversalSourceAlias(ctx, message, validateTraversalRequest(message));
op = this::iterateBytecodeTraversal;
break;
case Tokens.OPS_GATHER:
final Optional<String> sideEffectForGather = message.optionalArgs(Tokens.ARGS_SIDE_EFFECT);
if (!sideEffectForGather.isPresent()) {
final String msg = String.format("A message with an [%s] op code requires a [%s] argument.", Tokens.OPS_GATHER, Tokens.ARGS_SIDE_EFFECT);
throw new OpProcessorException(msg, ResponseMessage.build(message).code(ResponseStatusCode.REQUEST_ERROR_INVALID_REQUEST_ARGUMENTS).statusMessage(msg).create());
}
final Optional<String> sideEffectKey = message.optionalArgs(Tokens.ARGS_SIDE_EFFECT_KEY);
if (!sideEffectKey.isPresent()) {
final String msg = String.format("A message with an [%s] op code requires a [%s] argument.", Tokens.OPS_GATHER, Tokens.ARGS_SIDE_EFFECT_KEY);
throw new OpProcessorException(msg, ResponseMessage.build(message).code(ResponseStatusCode.REQUEST_ERROR_INVALID_REQUEST_ARGUMENTS).statusMessage(msg).create());
}
validateTraversalSourceAlias(ctx, message, validatedAliases(message).get());
op = this::gatherSideEffect;
break;
case Tokens.OPS_KEYS:
final Optional<String> sideEffectForKeys = message.optionalArgs(Tokens.ARGS_SIDE_EFFECT);
if (!sideEffectForKeys.isPresent()) {
final String msg = String.format("A message with an [%s] op code requires a [%s] argument.", Tokens.OPS_GATHER, Tokens.ARGS_SIDE_EFFECT);
throw new OpProcessorException(msg, ResponseMessage.build(message).code(ResponseStatusCode.REQUEST_ERROR_INVALID_REQUEST_ARGUMENTS).statusMessage(msg).create());
}
op = context -> {
final RequestMessage msg = context.getRequestMessage();
final Optional<UUID> sideEffect = msg.optionalArgs(Tokens.ARGS_SIDE_EFFECT);
final TraversalSideEffects sideEffects = cache.getIfPresent(sideEffect.get());
if (null == sideEffects)
logger.warn("Request for side-effect keys on {} returned no side-effects in the cache", sideEffect.get());
handleIterator(context, null == sideEffects ? Collections.emptyIterator() : sideEffects.keys().iterator());
};
break;
case Tokens.OPS_CLOSE:
final Optional<String> sideEffectForClose = message.optionalArgs(Tokens.ARGS_SIDE_EFFECT);
if (!sideEffectForClose.isPresent()) {
final String msg = String.format("A message with an [%s] op code requires a [%s] argument.", Tokens.OPS_CLOSE, Tokens.ARGS_SIDE_EFFECT);
throw new OpProcessorException(msg, ResponseMessage.build(message).code(ResponseStatusCode.REQUEST_ERROR_INVALID_REQUEST_ARGUMENTS).statusMessage(msg).create());
}
op = context -> {
final RequestMessage msg = context.getRequestMessage();
logger.debug("Close request {} for in thread {}", msg.getRequestId(), Thread.currentThread().getName());
final Optional<UUID> sideEffect = msg.optionalArgs(Tokens.ARGS_SIDE_EFFECT);
cache.invalidate(sideEffect.get());
final String successMessage = String.format("Successfully cleared side effect cache for [%s].", Tokens.ARGS_SIDE_EFFECT);
ctx.getChannelHandlerContext().writeAndFlush(ResponseMessage.build(message).code(ResponseStatusCode.NO_CONTENT).statusMessage(successMessage).create());
};
break;
case Tokens.OPS_INVALID:
final String msgInvalid = String.format("Message could not be parsed. Check the format of the request. [%s]", message);
throw new OpProcessorException(msgInvalid, ResponseMessage.build(message).code(ResponseStatusCode.REQUEST_ERROR_MALFORMED_REQUEST).statusMessage(msgInvalid).create());
default:
final String msgDefault = String.format("Message with op code [%s] is not recognized.", message.getOp());
throw new OpProcessorException(msgDefault, ResponseMessage.build(message).code(ResponseStatusCode.REQUEST_ERROR_MALFORMED_REQUEST).statusMessage(msgDefault).create());
}
return op;
}
private static void validateTraversalSourceAlias(final Context ctx, final RequestMessage message, final Map<String, String> aliases) throws OpProcessorException {
final String traversalSourceBindingForAlias = aliases.values().iterator().next();
if (!ctx.getGraphManager().getTraversalSourceNames().contains(traversalSourceBindingForAlias)) {
final String msg = String.format("The traversal source [%s] for alias [%s] is not configured on the server.", traversalSourceBindingForAlias, Tokens.VAL_TRAVERSAL_SOURCE_ALIAS);
throw new OpProcessorException(msg, ResponseMessage.build(message).code(ResponseStatusCode.REQUEST_ERROR_INVALID_REQUEST_ARGUMENTS).statusMessage(msg).create());
}
}
private static Map<String, String> validateTraversalRequest(final RequestMessage message) throws OpProcessorException {
if (!message.optionalArgs(Tokens.ARGS_GREMLIN).isPresent()) {
final String msg = String.format("A message with [%s] op code requires a [%s] argument.", Tokens.OPS_BYTECODE, Tokens.ARGS_GREMLIN);
throw new OpProcessorException(msg, ResponseMessage.build(message).code(ResponseStatusCode.REQUEST_ERROR_INVALID_REQUEST_ARGUMENTS).statusMessage(msg).create());
}
return validatedAliases(message).get();
}
private static Optional<Map<String, String>> validatedAliases(final RequestMessage message) throws OpProcessorException {
final Optional<Map<String, String>> aliases = message.optionalArgs(Tokens.ARGS_ALIASES);
if (!aliases.isPresent()) {
final String msg = String.format("A message with [%s] op code requires a [%s] argument.", Tokens.OPS_BYTECODE, Tokens.ARGS_ALIASES);
throw new OpProcessorException(msg, ResponseMessage.build(message).code(ResponseStatusCode.REQUEST_ERROR_INVALID_REQUEST_ARGUMENTS).statusMessage(msg).create());
}
if (aliases.get().size() != 1 || !aliases.get().containsKey(Tokens.VAL_TRAVERSAL_SOURCE_ALIAS)) {
final String msg = String.format("A message with [%s] op code requires the [%s] argument to be a Map containing one alias assignment named '%s'.",
Tokens.OPS_BYTECODE, Tokens.ARGS_ALIASES, Tokens.VAL_TRAVERSAL_SOURCE_ALIAS);
throw new OpProcessorException(msg, ResponseMessage.build(message).code(ResponseStatusCode.REQUEST_ERROR_INVALID_REQUEST_ARGUMENTS).statusMessage(msg).create());
}
return aliases;
}
private void gatherSideEffect(final Context context) throws OpProcessorException {
final RequestMessage msg = context.getRequestMessage();
logger.debug("Side-effect request {} for in thread {}", msg.getRequestId(), Thread.currentThread().getName());
// earlier validation in selection of this op method should free us to cast this without worry
final Optional<UUID> sideEffect = msg.optionalArgs(Tokens.ARGS_SIDE_EFFECT);
final Optional<String> sideEffectKey = msg.optionalArgs(Tokens.ARGS_SIDE_EFFECT_KEY);
final Map<String, String> aliases = (Map<String, String>) msg.optionalArgs(Tokens.ARGS_ALIASES).get();
final GraphManager graphManager = context.getGraphManager();
final String traversalSourceName = aliases.entrySet().iterator().next().getValue();
final TraversalSource g = graphManager.getTraversalSource(traversalSourceName);
final Timer.Context timerContext = traversalOpTimer.time();
try {
final ChannelHandlerContext ctx = context.getChannelHandlerContext();
final Graph graph = g.getGraph();
context.getGremlinExecutor().getExecutorService().submit(() -> {
try {
beforeProcessing(graph, context);
try {
final TraversalSideEffects sideEffects = cache.getIfPresent(sideEffect.get());
if (null == sideEffects) {
final String errorMessage = String.format("Could not find side-effects for %s.", sideEffect.get());
logger.warn(errorMessage);
ctx.writeAndFlush(ResponseMessage.build(msg).code(ResponseStatusCode.SERVER_ERROR).statusMessage(errorMessage).create());
onError(graph, context);
return;
}
if (!sideEffects.exists(sideEffectKey.get())) {
final String errorMessage = String.format("Could not find side-effect key for %s in %s.", sideEffectKey.get(), sideEffect.get());
logger.warn(errorMessage);
ctx.writeAndFlush(ResponseMessage.build(msg).code(ResponseStatusCode.SERVER_ERROR).statusMessage(errorMessage).create());
onError(graph, context);
return;
}
handleIterator(context, new SideEffectIterator(sideEffects.get(sideEffectKey.get()), sideEffectKey.get()));
} catch (TimeoutException ex) {
final String errorMessage = String.format("Response iteration exceeded the configured threshold for request [%s] - %s", msg.getRequestId(), ex.getMessage());
logger.warn(errorMessage);
ctx.writeAndFlush(ResponseMessage.build(msg).code(ResponseStatusCode.SERVER_ERROR_TIMEOUT)
.statusMessage(errorMessage)
.statusAttributeException(ex).create());
onError(graph, context);
return;
} catch (Exception ex) {
logger.warn(String.format("Exception processing a side-effect on iteration for request [%s].", msg.getRequestId()), ex);
ctx.writeAndFlush(ResponseMessage.build(msg).code(ResponseStatusCode.SERVER_ERROR)
.statusMessage(ex.getMessage())
.statusAttributeException(ex).create());
onError(graph, context);
return;
}
onSideEffectSuccess(graph, context);
} catch (Exception ex) {
logger.warn(String.format("Exception processing a side-effect on request [%s].", msg.getRequestId()), ex);
ctx.writeAndFlush(ResponseMessage.build(msg).code(ResponseStatusCode.SERVER_ERROR)
.statusMessage(ex.getMessage())
.statusAttributeException(ex).create());
onError(graph, context);
} finally {
timerContext.stop();
}
});
} catch (Exception ex) {
timerContext.stop();
throw new OpProcessorException("Could not iterate the side-effect instance",
ResponseMessage.build(msg).code(ResponseStatusCode.SERVER_ERROR)
.statusMessage(ex.getMessage())
.statusAttributeException(ex).create());
}
}
private void iterateBytecodeTraversal(final Context context) throws Exception {
final RequestMessage msg = context.getRequestMessage();
logger.debug("Traversal request {} for in thread {}", msg.getRequestId(), Thread.currentThread().getName());
// right now the TraversalOpProcessor can take a direct GraphSON representation of Bytecode or directly take
// deserialized Bytecode object.
final Object bytecodeObj = msg.getArgs().get(Tokens.ARGS_GREMLIN);
final Bytecode bytecode = bytecodeObj instanceof Bytecode ? (Bytecode) bytecodeObj :
mapper.readValue(bytecodeObj.toString(), Bytecode.class);
// earlier validation in selection of this op method should free us to cast this without worry
final Map<String, String> aliases = (Map<String, String>) msg.optionalArgs(Tokens.ARGS_ALIASES).get();
final GraphManager graphManager = context.getGraphManager();
final String traversalSourceName = aliases.entrySet().iterator().next().getValue();
final TraversalSource g = graphManager.getTraversalSource(traversalSourceName);
final Traversal.Admin<?, ?> traversal;
try {
final Optional<String> lambdaLanguage = BytecodeHelper.getLambdaLanguage(bytecode);
if (!lambdaLanguage.isPresent())
traversal = JavaTranslator.of(g).translate(bytecode);
else {
final SimpleBindings b = new SimpleBindings();
b.put(Tokens.VAL_TRAVERSAL_SOURCE_ALIAS, g);
traversal = context.getGremlinExecutor().eval(bytecode, b, lambdaLanguage.get());
}
} catch (Exception ex) {
logger.error("Could not deserialize the Traversal instance", context);
throw new OpProcessorException("Could not deserialize the Traversal instance",
ResponseMessage.build(msg).code(ResponseStatusCode.SERVER_ERROR_SERIALIZATION)
.statusMessage(ex.getMessage())
.statusAttributeException(ex).create());
}
final Timer.Context timerContext = traversalOpTimer.time();
try {
final ChannelHandlerContext ctx = context.getChannelHandlerContext();
final Graph graph = g.getGraph();
context.getGremlinExecutor().getExecutorService().submit(() -> {
try {
beforeProcessing(graph, context);
try {
// compile the traversal - without it getEndStep() has nothing in it
traversal.applyStrategies();
handleIterator(context, new TraverserIterator(traversal), graph);
} catch (TimeoutException ex) {
final String errorMessage = String.format("Response iteration exceeded the configured threshold for request [%s] - %s", msg.getRequestId(), ex.getMessage());
logger.warn(errorMessage);
ctx.writeAndFlush(ResponseMessage.build(msg).code(ResponseStatusCode.SERVER_ERROR_TIMEOUT)
.statusMessage(errorMessage)
.statusAttributeException(ex).create());
onError(graph, context);
return;
} catch (Exception ex) {
logger.warn(String.format("Exception processing a Traversal on iteration for request [%s].", msg.getRequestId()), ex);
ctx.writeAndFlush(ResponseMessage.build(msg).code(ResponseStatusCode.SERVER_ERROR)
.statusMessage(ex.getMessage())
.statusAttributeException(ex).create());
onError(graph, context);
return;
}
} catch (Exception ex) {
logger.warn(String.format("Exception processing a Traversal on request [%s].", msg.getRequestId()), ex);
ctx.writeAndFlush(ResponseMessage.build(msg).code(ResponseStatusCode.SERVER_ERROR)
.statusMessage(ex.getMessage())
.statusAttributeException(ex).create());
onError(graph, context);
} finally {
timerContext.stop();
}
});
} catch (Exception ex) {
timerContext.stop();
throw new OpProcessorException("Could not iterate the Traversal instance",
ResponseMessage.build(msg).code(ResponseStatusCode.SERVER_ERROR)
.statusMessage(ex.getMessage())
.statusAttributeException(ex).create());
}
}
@Override
protected void iterateComplete(final ChannelHandlerContext ctx, final RequestMessage msg, final Iterator itty) {
if (itty instanceof TraverserIterator) {
final Traversal.Admin traversal = ((TraverserIterator) itty).getTraversal();
if (!traversal.getSideEffects().isEmpty()) {
cache.put(msg.getRequestId(), traversal.getSideEffects());
}
}
}
protected void beforeProcessing(final Graph graph, final Context ctx) {
if (graph.features().graph().supportsTransactions() && graph.tx().isOpen()) graph.tx().rollback();
}
protected void onError(final Graph graph, final Context ctx) {
if (graph.features().graph().supportsTransactions() && graph.tx().isOpen()) graph.tx().rollback();
}
protected void onTraversalSuccess(final Graph graph, final Context ctx) {
if (graph.features().graph().supportsTransactions() && graph.tx().isOpen()) graph.tx().commit();
}
protected void onSideEffectSuccess(final Graph graph, final Context ctx) {
// there was no "writing" here, just side-effect retrieval, so if a transaction was opened then
// just close with rollback
if (graph.features().graph().supportsTransactions() && graph.tx().isOpen()) graph.tx().rollback();
}
@Override
protected Map<String, Object> generateMetaData(final ChannelHandlerContext ctx, final RequestMessage msg,
final ResponseStatusCode code, final Iterator itty) {
Map<String, Object> metaData = Collections.emptyMap();
if (itty instanceof SideEffectIterator) {
final SideEffectIterator traversalIterator = (SideEffectIterator) itty;
final String key = traversalIterator.getSideEffectKey();
if (key != null) {
metaData = new HashMap<>();
metaData.put(Tokens.ARGS_SIDE_EFFECT_KEY, key);
metaData.put(Tokens.ARGS_AGGREGATE_TO, traversalIterator.getSideEffectAggregator());
}
}
return metaData;
}
protected void handleIterator(final Context context, final Iterator itty, final Graph graph) throws TimeoutException, InterruptedException {
final ChannelHandlerContext ctx = context.getChannelHandlerContext();
final RequestMessage msg = context.getRequestMessage();
final Settings settings = context.getSettings();
final MessageSerializer serializer = ctx.channel().attr(StateKey.SERIALIZER).get();
final boolean useBinary = ctx.channel().attr(StateKey.USE_BINARY).get();
boolean warnOnce = false;
// we have an empty iterator - happens on stuff like: g.V().iterate()
if (!itty.hasNext()) {
// as there is nothing left to iterate if we are transaction managed then we should execute a
// commit here before we send back a NO_CONTENT which implies success
onTraversalSuccess(graph, context);
ctx.writeAndFlush(ResponseMessage.build(msg)
.code(ResponseStatusCode.NO_CONTENT)
.create());
return;
}
// timer for the total serialization time
final StopWatch stopWatch = new StopWatch();
stopWatch.start();
// the batch size can be overridden by the request
final int resultIterationBatchSize = (Integer) msg.optionalArgs(Tokens.ARGS_BATCH_SIZE)
.orElse(settings.resultIterationBatchSize);
List<Object> aggregate = new ArrayList<>(resultIterationBatchSize);
// use an external control to manage the loop as opposed to just checking hasNext() in the while. this
// prevent situations where auto transactions create a new transaction after calls to commit() withing
// the loop on calls to hasNext().
boolean hasMore = itty.hasNext();
while (hasMore) {
if (Thread.interrupted()) throw new InterruptedException();
// check if an implementation needs to force flush the aggregated results before the iteration batch
// size is reached.
final boolean forceFlush = isForceFlushed(ctx, msg, itty);
// have to check the aggregate size because it is possible that the channel is not writeable (below)
// so iterating next() if the message is not written and flushed would bump the aggregate size beyond
// the expected resultIterationBatchSize. Total serialization time for the response remains in
// effect so if the client is "slow" it may simply timeout.
//
// there is a need to check hasNext() on the iterator because if the channel is not writeable the
// previous pass through the while loop will have next()'d the iterator and if it is "done" then a
// NoSuchElementException will raise its head. also need a check to ensure that this iteration doesn't
// require a forced flush which can be forced by sub-classes.
//
// this could be placed inside the isWriteable() portion of the if-then below but it seems better to
// allow iteration to continue into a batch if that is possible rather than just doing nothing at all
// while waiting for the client to catch up
if (aggregate.size() < resultIterationBatchSize && itty.hasNext() && !forceFlush) aggregate.add(itty.next());
// send back a page of results if batch size is met or if it's the end of the results being iterated.
// also check writeability of the channel to prevent OOME for slow clients.
if (ctx.channel().isWritable()) {
if (forceFlush || aggregate.size() == resultIterationBatchSize || !itty.hasNext()) {
final ResponseStatusCode code = itty.hasNext() ? ResponseStatusCode.PARTIAL_CONTENT : ResponseStatusCode.SUCCESS;
// serialize here because in sessionless requests the serialization must occur in the same
// thread as the eval. as eval occurs in the GremlinExecutor there's no way to get back to the
// thread that processed the eval of the script so, we have to push serialization down into that
Frame frame = null;
try {
frame = makeFrame(ctx, msg, serializer, useBinary, aggregate, code, generateMetaData(ctx, msg, code, itty));
} catch (Exception ex) {
// a frame may use a Bytebuf which is a countable release - if it does not get written
// downstream it needs to be released here
if (frame != null) frame.tryRelease();
// exception is handled in makeFrame() - serialization error gets written back to driver
// at that point
onError(graph, context);
break;
}
try {
// only need to reset the aggregation list if there's more stuff to write
if (itty.hasNext())
aggregate = new ArrayList<>(resultIterationBatchSize);
else {
// iteration and serialization are both complete which means this finished successfully. note that
// errors internal to script eval or timeout will rollback given GremlinServer's global configurations.
// local errors will get rolledback below because the exceptions aren't thrown in those cases to be
// caught by the GremlinExecutor for global rollback logic. this only needs to be committed if
// there are no more items to iterate and serialization is complete
onTraversalSuccess(graph, context);
// exit the result iteration loop as there are no more results left. using this external control
// because of the above commit. some graphs may open a new transaction on the call to
// hasNext()
hasMore = false;
}
} catch (Exception ex) {
// a frame may use a Bytebuf which is a countable release - if it does not get written
// downstream it needs to be released here
if (frame != null) frame.tryRelease();
throw ex;
}
if (!itty.hasNext()) iterateComplete(ctx, msg, itty);
// the flush is called after the commit has potentially occurred. in this way, if a commit was
// required then it will be 100% complete before the client receives it. the "frame" at this point
// should have completely detached objects from the transaction (i.e. serialization has occurred)
// so a new one should not be opened on the flush down the netty pipeline
ctx.writeAndFlush(frame);
}
} else {
// don't keep triggering this warning over and over again for the same request
if (!warnOnce) {
logger.warn("Pausing response writing as writeBufferHighWaterMark exceeded on {} - writing will continue once client has caught up", msg);
warnOnce = true;
}
// since the client is lagging we can hold here for a period of time for the client to catch up.
// this isn't blocking the IO thread - just a worker.
TimeUnit.MILLISECONDS.sleep(10);
}
stopWatch.split();
if (settings.serializedResponseTimeout > 0 && stopWatch.getSplitTime() > settings.serializedResponseTimeout) {
final String timeoutMsg = String.format("Serialization of the entire response exceeded the 'serializeResponseTimeout' setting %s",
warnOnce ? "[Gremlin Server paused writes to client as messages were not being consumed quickly enough]" : "");
throw new TimeoutException(timeoutMsg.trim());
}
stopWatch.unsplit();
}
stopWatch.stop();
}
}