[ 
https://issues.apache.org/jira/browse/TINKERPOP-2245?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17317378#comment-17317378
 ] 

ASF GitHub Bot commented on TINKERPOP-2245:
-------------------------------------------

spmallette commented on a change in pull request #1414:
URL: https://github.com/apache/tinkerpop/pull/1414#discussion_r609943250



##########
File path: 
gremlin-server/src/main/java/org/apache/tinkerpop/gremlin/server/handler/AbstractRexster.java
##########
@@ -0,0 +1,758 @@
+/*
+ * 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.handler;
+
+import groovy.lang.GroovyRuntimeException;
+import io.netty.channel.Channel;
+import io.netty.channel.ChannelHandlerContext;
+import org.apache.commons.lang3.exception.ExceptionUtils;
+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.driver.ser.MessageTextSerializer;
+import 
org.apache.tinkerpop.gremlin.groovy.jsr223.TimedInterruptTimeoutException;
+import org.apache.tinkerpop.gremlin.jsr223.GremlinScriptEngine;
+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.TraversalSource;
+import 
org.apache.tinkerpop.gremlin.process.traversal.strategy.verification.VerificationException;
+import org.apache.tinkerpop.gremlin.process.traversal.util.BytecodeHelper;
+import 
org.apache.tinkerpop.gremlin.process.traversal.util.TraversalInterruptedException;
+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.Settings;
+import org.apache.tinkerpop.gremlin.server.auth.AuthenticatedUser;
+import org.apache.tinkerpop.gremlin.server.util.ExceptionHelper;
+import org.apache.tinkerpop.gremlin.server.util.TraverserIterator;
+import org.apache.tinkerpop.gremlin.structure.Graph;
+import org.apache.tinkerpop.gremlin.structure.Transaction;
+import org.apache.tinkerpop.gremlin.structure.util.TemporaryException;
+import org.apache.tinkerpop.gremlin.util.iterator.IteratorUtils;
+import org.codehaus.groovy.control.MultipleCompilationErrorsException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.script.Bindings;
+import javax.script.ScriptException;
+import javax.script.SimpleBindings;
+import java.io.InterruptedIOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.Future;
+import java.util.concurrent.FutureTask;
+import java.util.concurrent.ScheduledFuture;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.stream.Stream;
+
+/**
+ * A base implementation of {@link Rexster} which offers some common 
functionality that matches typical Gremlin Server
+ * request response expectations for script, bytecode and graph operations. 
The class is designed to be extended but
+ * take care in understanding the way that different methods are called as 
they do depend on one another a bit. It
+ * maybe best to examine the source code to determine how best to use this 
class or to extend from the higher order
+ * classes of {@link SingleRexster} or {@link MultiRexster}.
+ */
+public abstract class AbstractRexster implements Rexster, AutoCloseable {
+    private static final Logger logger = 
LoggerFactory.getLogger(AbstractRexster.class);
+    private static final Logger auditLogger = 
LoggerFactory.getLogger(GremlinServer.AUDIT_LOGGER_NAME);
+
+    private final boolean sessionIdOnRequest;
+    private final Channel initialChannel;
+    private final boolean transactionManaged;
+    private final String sessionId;
+    private final AtomicReference<ScheduledFuture<?>> sessionCancelFuture = 
new AtomicReference<>();
+    private final AtomicReference<Future<?>> sessionFuture = new 
AtomicReference<>();
+    private long actualTimeoutLengthWhenClosed = 0;
+    private Thread sessionThread;
+    protected final boolean maintainStateAfterException;
+    protected final AtomicReference<CloseReason> closeReason = new 
AtomicReference<>();
+    protected final GraphManager graphManager;
+    protected final ConcurrentMap<String, Rexster> sessions;
+    protected final Set<String> aliasesUsedByRexster = new HashSet<>();
+
+    protected enum CloseReason { UNDETERMINED, CHANNEL_CLOSED, 
SESSION_TIMEOUT, REQUEST_TIMEOUT, NORMAL }
+
+    AbstractRexster(final Context gremlinContext, final String sessionId,
+                    final boolean transactionManaged,
+                    final ConcurrentMap<String, Rexster> sessions) {
+        // this only applies to sessions
+        this.maintainStateAfterException = (boolean) 
gremlinContext.getRequestMessage().
+                
optionalArgs(Tokens.ARGS_MAINTAIN_STATE_AFTER_EXCEPTION).orElse(false);
+        this.sessionIdOnRequest = 
gremlinContext.getRequestMessage().optionalArgs(Tokens.ARGS_SESSION).isPresent();
+        this.transactionManaged = transactionManaged;
+        this.sessionId = sessionId;
+        this.initialChannel = 
gremlinContext.getChannelHandlerContext().channel();
+
+        // close Rexster if the channel closes to cleanup and close 
transactions
+        this.initialChannel.closeFuture().addListener(f -> {
+            if (closeReason.compareAndSet(null, CloseReason.CHANNEL_CLOSED)) {
+                // cancel session worker or it will keep waiting for items to 
appear in the session queue
+                cancel(true);
+                close();
+            }
+        });
+        this.sessions = sessions;
+        this.graphManager = gremlinContext.getGraphManager();
+    }
+
+    protected synchronized void cancel(final boolean mayInterruptIfRunning) {
+        final FutureTask<?> sf = (FutureTask) sessionFuture.get();
+        if (sf != null && !sf.isDone()) {
+            sf.cancel(mayInterruptIfRunning);
+        }
+    }
+
+    public boolean isTransactionManaged() {
+        return transactionManaged;
+    }
+
+    public String getSessionId() {
+        return sessionId;
+    }
+
+    public boolean isBoundTo(final Channel channel) {
+        return channel == initialChannel;
+    }
+
+    public long getActualTimeoutLengthWhenClosed() {
+        return actualTimeoutLengthWhenClosed;
+    }
+
+    public Optional<CloseReason> getCloseReason() {
+        return Optional.ofNullable(closeReason.get());
+    }
+
+    public GremlinScriptEngine getScriptEngine(final Context context, final 
String language) {
+        return 
context.getGremlinExecutor().getScriptEngineManager().getEngineByName(language);
+    }
+
+    public void setSessionThread(final Thread runner) {
+        this.sessionThread = runner;
+    }
+
+    @Override
+    public void setSessionCancelFuture(final ScheduledFuture<?> f) {
+        if (!sessionCancelFuture.compareAndSet(null, f))
+            throw new IllegalStateException("Session cancellation future is 
already set");
+    }
+
+    @Override
+    public void setSessionFuture(final Future<?> f) {
+        if (!sessionFuture.compareAndSet(null, f))
+            throw new IllegalStateException("Session future is already set");
+    }
+
+    @Override
+    public synchronized void triggerTimeout(final long timeout, final boolean 
causedBySession) {
+        // triggering timeout triggers the stop of the Rexster Runnable which 
will end in close()
+        // for final cleanup
+        final Future<?> f = sessionFuture.get();
+        if (f != null && !f.isDone()) {
+            if (closeReason.compareAndSet(null, causedBySession ? 
CloseReason.SESSION_TIMEOUT : CloseReason.REQUEST_TIMEOUT)) {
+                actualTimeoutLengthWhenClosed = timeout;
+
+                // if caused by a session timeout for a session OR if it is a 
request timeout for a sessionless
+                // request then we can just straight cancel() the Rexster 
instance
+                if (causedBySession || !sessionIdOnRequest)
+                    cancel(true);
+                else
+                    sessionThread.interrupt();
+            }
+        }
+    }
+
+    protected void process(final Context gremlinContext) throws 
RexsterException {
+        final RequestMessage msg = gremlinContext.getRequestMessage();
+        final Map<String, Object> args = msg.getArgs();
+        final Object gremlinToExecute = args.get(Tokens.ARGS_GREMLIN);
+
+        // for strict transactions track the aliases used so that we can 
commit them and only them on close()
+        if (gremlinContext.getSettings().strictTransactionManagement)
+            msg.optionalArgs(Tokens.ARGS_ALIASES).ifPresent(m -> 
aliasesUsedByRexster.addAll(((Map<String,String>) m).values()));
+
+        try {
+            // itty is optional as Bytecode could be a "graph operation" 
rather than a Traversal. graph operations
+            // don't need to be iterated and handle their own lifecycle
+            final Optional<Iterator<?>> itty = gremlinToExecute instanceof 
Bytecode ?
+                    fromBytecode(gremlinContext, (Bytecode) gremlinToExecute) :
+                    Optional.of(fromScript(gremlinContext, (String) 
gremlinToExecute));
+
+            processAuditLog(gremlinContext.getSettings(), 
gremlinContext.getChannelHandlerContext(), gremlinToExecute);
+
+            if (itty.isPresent())
+                handleIterator(gremlinContext, itty.get());
+        } catch (Exception ex) {
+            handleException(gremlinContext, ex);
+        }
+    }
+
+    protected void handleException(final Context gremlinContext, final 
Throwable t) throws RexsterException {
+        if (t instanceof RexsterException) throw (RexsterException) t;
+
+        final Optional<Throwable> possibleTemporaryException = 
determineIfTemporaryException(t);
+        if (possibleTemporaryException.isPresent()) {
+            final Throwable temporaryException = 
possibleTemporaryException.get();
+            throw new RexsterException(temporaryException.getMessage(), t,
+                    ResponseMessage.build(gremlinContext.getRequestMessage())
+                            .code(ResponseStatusCode.SERVER_ERROR_TEMPORARY)
+                            .statusMessage(temporaryException.getMessage())
+                            
.statusAttributeException(temporaryException).create());
+        }
+
+        final Throwable root = ExceptionUtils.getRootCause(t);
+
+        if (root instanceof TimedInterruptTimeoutException) {
+            // occurs when the TimedInterruptCustomizerProvider is in play
+            final String msg = String.format("A timeout occurred within the 
script during evaluation of [%s] - consider increasing the limit given to 
TimedInterruptCustomizerProvider",
+                    gremlinContext.getRequestMessage().getRequestId());
+            throw new RexsterException(msg, root, 
ResponseMessage.build(gremlinContext.getRequestMessage())
+                    .code(ResponseStatusCode.SERVER_ERROR_TIMEOUT)
+                    .statusMessage("Timeout during script evaluation triggered 
by TimedInterruptCustomizerProvider")
+                    .create());
+        }
+
+        if (root instanceof TimeoutException) {
+            final String errorMessage = String.format("Script evaluation 
exceeded the configured threshold for request [%s]",
+                    gremlinContext.getRequestMessage().getRequestId());
+            throw new RexsterException(errorMessage, root, 
ResponseMessage.build(gremlinContext.getRequestMessage())
+                    .code(ResponseStatusCode.SERVER_ERROR_TIMEOUT)
+                    .statusMessage(t.getMessage())
+                    .create());
+        }
+
+        if (root instanceof InterruptedException ||
+                root instanceof TraversalInterruptedException ||
+                root instanceof InterruptedIOException) {
+            String msg = "Processing interrupted but the reason why was not 
known";
+            switch (closeReason.get()) {
+                case CHANNEL_CLOSED:
+                    msg = "Processing interrupted because the channel was 
closed";
+                    break;
+                case SESSION_TIMEOUT:
+                    msg = String.format("Session closed - %s - 
sessionLifetimeTimeout of %s ms exceeded", sessionId, 
actualTimeoutLengthWhenClosed);
+                    break;
+                case REQUEST_TIMEOUT:
+                    msg = String.format("Evaluation exceeded timeout threshold 
of %s ms", actualTimeoutLengthWhenClosed);
+                    break;
+            }
+            final ResponseStatusCode code = closeReason.get() == 
CloseReason.SESSION_TIMEOUT || closeReason.get() == CloseReason.REQUEST_TIMEOUT 
?
+                    ResponseStatusCode.SERVER_ERROR_TIMEOUT : 
ResponseStatusCode.SERVER_ERROR;
+            throw new RexsterException(msg, root, 
ResponseMessage.build(gremlinContext.getRequestMessage())
+                    .code(code)
+                    .statusMessage(msg).create());
+        }
+
+        if (root instanceof MultipleCompilationErrorsException && 
root.getMessage().contains("Method too large") &&
+                ((MultipleCompilationErrorsException) 
root).getErrorCollector().getErrorCount() == 1) {
+            final String errorMessage = String.format("The Gremlin statement 
that was submitted exceeds the maximum compilation size allowed by the JVM, 
please split it into multiple smaller statements - %s", 
trimMessage(gremlinContext.getRequestMessage()));
+            logger.warn(errorMessage);
+            throw new RexsterException(errorMessage, root, 
ResponseMessage.build(gremlinContext.getRequestMessage())
+                    .code(ResponseStatusCode.SERVER_ERROR_EVALUATION)
+                    .statusMessage(errorMessage)
+                    .statusAttributeException(root).create());
+        }
+
+        // GroovyRuntimeException will hit a pretty wide range of eval type 
errors, like MissingPropertyException,
+        // CompilationFailedException, MissingMethodException, etc. If more 
specific handling is required then
+        // try to catch it earlier above.
+        if (root instanceof GroovyRuntimeException ||
+                root instanceof VerificationException ||
+                root instanceof ScriptException) {
+            throw new RexsterException(root.getMessage(), root, 
ResponseMessage.build(gremlinContext.getRequestMessage())
+                    .code(ResponseStatusCode.SERVER_ERROR_EVALUATION)
+                    .statusMessage(root.getMessage())
+                    .statusAttributeException(root).create());
+        }
+
+        throw new RexsterException(root.getClass().getSimpleName() + ": " + 
root.getMessage(), root,
+                ResponseMessage.build(gremlinContext.getRequestMessage())
+                        .code(ResponseStatusCode.SERVER_ERROR)
+                        .statusAttributeException(root)
+                        .statusMessage(root.getMessage()).create());
+    }
+
+    /**
+     * Used to decrease the size of a Gremlin script that triggered a "method 
too large" exception so that it
+     * doesn't log a massive text string nor return a large error message.
+     */
+    private RequestMessage trimMessage(final RequestMessage msg) {
+        final RequestMessage trimmedMsg = RequestMessage.from(msg).create();
+        if (trimmedMsg.getArgs().containsKey(Tokens.ARGS_GREMLIN))
+            trimmedMsg.getArgs().put(Tokens.ARGS_GREMLIN, 
trimmedMsg.getArgs().get(Tokens.ARGS_GREMLIN).toString().substring(0, 1021) + 
"...");
+
+        return trimmedMsg;
+    }
+
+    /**
+     * Check if any exception in the chain is TemporaryException then we 
should respond with the right error code so
+     * that the client knows to retry.
+     */
+    protected Optional<Throwable> determineIfTemporaryException(final 
Throwable ex) {
+        return Stream.of(ExceptionUtils.getThrowables(ex)).
+                filter(i -> i instanceof TemporaryException).findFirst();
+    }
+
+    @Override
+    public synchronized void close() {
+        // already closing/closed
+        if (!sessions.containsKey(sessionId)) return;
+
+        sessions.remove(sessionId);
+
+        if (sessionCancelFuture.get() != null) {
+            final ScheduledFuture<?> f = sessionCancelFuture.get();
+            if (!f.isDone()) f.cancel(true);
+        }
+    }
+
+    protected Iterator<?> fromScript(final Context gremlinContext, final 
String script) throws Exception {
+        final RequestMessage msg = gremlinContext.getRequestMessage();
+        final Map<String, Object> args = msg.getArgs();
+        final String language = args.containsKey(Tokens.ARGS_LANGUAGE) ? 
(String) args.get(Tokens.ARGS_LANGUAGE) : "gremlin-groovy";
+        return IteratorUtils.asIterator(getScriptEngine(gremlinContext, 
language).eval(
+                script, mergeBindingsFromRequest(gremlinContext, 
getWorkerBindings())));
+    }
+
+    protected Optional<Iterator<?>> fromBytecode(final Context gremlinContext, 
final Bytecode bytecode) throws Exception {
+        final RequestMessage msg = gremlinContext.getRequestMessage();
+
+        final Traversal.Admin<?, ?> traversal;
+        final Map<String, String> aliases = (Map<String, String>) 
msg.optionalArgs(Tokens.ARGS_ALIASES).get();
+        final GraphManager graphManager = gremlinContext.getGraphManager();
+        final String traversalSourceName = 
aliases.entrySet().iterator().next().getValue();
+        final TraversalSource g = 
graphManager.getTraversalSource(traversalSourceName);
+
+        // handle bytecode based graph operations like commit/rollback commands
+        if (BytecodeHelper.isGraphOperation(bytecode)) {
+            handleGraphOperation(gremlinContext, bytecode, g.getGraph());
+            return Optional.empty();
+        } else {
+
+            final Optional<String> lambdaLanguage = 
BytecodeHelper.getLambdaLanguage(bytecode);
+            if (!lambdaLanguage.isPresent())
+                traversal = JavaTranslator.of(g).translate(bytecode);
+            else {
+                final SimpleBindings bindings = new SimpleBindings();
+                bindings.put(traversalSourceName, g);
+                traversal = 
gremlinContext.getGremlinExecutor().getScriptEngineManager().getEngineByName(lambdaLanguage.get()).eval(bytecode,
 bindings, traversalSourceName);
+            }
+
+            // compile the traversal - without it getEndStep() has nothing in 
it
+            traversal.applyStrategies();
+
+            return Optional.of(new TraverserIterator(traversal));
+        }
+    }
+
+    protected Bindings getWorkerBindings() throws RexsterException {
+        return new SimpleBindings(graphManager.getAsBindings());
+    }
+
+    protected Bindings mergeBindingsFromRequest(final Context gremlinContext, 
final Bindings bindings) throws RexsterException {
+        // alias any global bindings to a different variable.
+        final RequestMessage msg = gremlinContext.getRequestMessage();
+        if (msg.getArgs().containsKey(Tokens.ARGS_ALIASES)) {
+            final Map<String, String> aliases = (Map<String, String>) 
msg.getArgs().get(Tokens.ARGS_ALIASES);
+            for (Map.Entry<String,String> aliasKv : aliases.entrySet()) {
+                boolean found = false;
+
+                // first check if the alias refers to a Graph instance
+                final Graph graph = 
gremlinContext.getGraphManager().getGraph(aliasKv.getValue());
+                if (null != graph) {
+                    bindings.put(aliasKv.getKey(), graph);
+                    found = true;
+                }
+
+                // if the alias wasn't found as a Graph then perhaps it is a 
TraversalSource - it needs to be
+                // something
+                if (!found) {
+                    final TraversalSource ts = 
gremlinContext.getGraphManager().getTraversalSource(aliasKv.getValue());
+                    if (null != ts) {
+                        bindings.put(aliasKv.getKey(), ts);
+                        found = true;
+                    }
+                }
+
+                // this validation is important to calls to 
GraphManager.commit() and rollback() as they both
+                // expect that the aliases supplied are valid
+                if (!found) {
+                    final String error = String.format("Could not alias [%s] 
to [%s] as [%s] not in the Graph or TraversalSource global bindings",
+                            aliasKv.getKey(), aliasKv.getValue(), 
aliasKv.getValue());
+                    throw new RexsterException(error, 
ResponseMessage.build(msg)
+                            
.code(ResponseStatusCode.REQUEST_ERROR_INVALID_REQUEST_ARGUMENTS).statusMessage(error).create());
+                }
+            }
+        } else {
+            // there's no bindings so determine if that's ok with Gremlin 
Server
+            if (gremlinContext.getSettings().strictTransactionManagement) {
+                final String error = "Gremlin Server is configured with 
strictTransactionManagement as 'true' - the 'aliases' arguments must be 
provided";
+                throw new RexsterException(error, ResponseMessage.build(msg)
+                        
.code(ResponseStatusCode.REQUEST_ERROR_INVALID_REQUEST_ARGUMENTS).statusMessage(error).create());
+            }
+        }
+
+        // add any bindings to override any other supplied
+        Optional.ofNullable((Map<String, Object>) 
msg.getArgs().get(Tokens.ARGS_BINDINGS)).ifPresent(bindings::putAll);
+        return bindings;
+    }
+
+    /**
+     * Provides a generic way of iterating a result set back to the client.
+     *
+     * @param gremlinContext The Gremlin Server {@link Context} object 
containing settings, request message, etc.
+     * @param itty The result to iterator
+     */
+    protected void handleIterator(final Context gremlinContext, final 
Iterator<?> itty) throws InterruptedException {
+        final ChannelHandlerContext nettyContext = 
gremlinContext.getChannelHandlerContext();
+        final RequestMessage msg = gremlinContext.getRequestMessage();
+        final Settings settings = gremlinContext.getSettings();
+        boolean warnOnce = false;
+
+        // sessionless requests are always transaction managed, but in-session 
requests are configurable.
+        final boolean managedTransactionsForRequest = transactionManaged ?
+                true : (Boolean) 
msg.getArgs().getOrDefault(Tokens.ARGS_MANAGE_TRANSACTION, false);
+
+        // we have an empty iterator - happens on stuff like: g.V().iterate()
+        if (!itty.hasNext()) {
+            final Map<String, Object> attributes = 
generateStatusAttributes(gremlinContext,ResponseStatusCode.NO_CONTENT, itty);
+            // 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
+            if (managedTransactionsForRequest)
+                closeTransaction(gremlinContext, Transaction.Status.COMMIT);
+
+            gremlinContext.writeAndFlush(ResponseMessage.build(msg)
+                    .code(ResponseStatusCode.NO_CONTENT)
+                    .statusAttributes(attributes)
+                    .create());
+            return;
+        }
+
+        // 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.
+            // todo: what implementation does this?! can we kill it going 
forward - seems always false
+            // final boolean forceFlush = isForceFlushed(nettyContext, msg, 
itty);
+            final boolean forceFlush = false;
+
+            // 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());
+
+            // Don't keep executor busy if client has already given up; there 
is no way to catch up if the channel is
+            // not active, and hence we should break the loop.
+            if (!nettyContext.channel().isActive()) {
+                if (managedTransactionsForRequest) {
+                    closeTransaction(gremlinContext, 
Transaction.Status.ROLLBACK);

Review comment:
       this code is gone now...removed as it is technically covered elsewhere 
on channel close.




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> Consolidate the executor for bytecode & string based client
> -----------------------------------------------------------
>
>                 Key: TINKERPOP-2245
>                 URL: https://issues.apache.org/jira/browse/TINKERPOP-2245
>             Project: TinkerPop
>          Issue Type: Improvement
>          Components: server
>    Affects Versions: 3.4.2
>            Reporter: Divij Vaidya
>            Assignee: Stephen Mallette
>            Priority: Minor
>
> We have two code paths in the server which perform (more or less) the same 
> functions. One is the executor for string based queries and other is the 
> executor for bytecode. This code can be refactored together so that the logic 
> to handle timeout, handle exception during execution, handle exception before 
> execution and others can consolidated. 
> [https://github.com/apache/tinkerpop/blob/master/gremlin-groovy/src/main/java/org/apache/tinkerpop/gremlin/groovy/engine/GremlinExecutor.java#L246]
> and
> [https://github.com/apache/tinkerpop/blob/master/gremlin-server/src/main/java/org/apache/tinkerpop/gremlin/server/op/traversal/TraversalOpProcessor.java#L333]



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