[jira] [Created] (TINKERPOP-2030) KeepAlive task executed for every Connection.write call

["Simone Rondelli (JIRA)" <ji...@apache.org>]

Simone Rondelli created TINKERPOP-2030:
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             Summary: KeepAlive task executed for every Connection.write call
                 Key: TINKERPOP-2030
                 URL: https://issues.apache.org/jira/browse/TINKERPOP-2030
             Project: TinkerPop
          Issue Type: Bug
          Components: driver
    Affects Versions: 3.3.2
            Reporter: Simone Rondelli


The Gremlin Driver communicates with the server via {{Connection.write()}}.

The {{write()}} method has a logic in the end to schedule a task to keep the connection alive, which by default is scheduled to be run after 30min, every 30 min.


{code:java}
  // try to keep the connection alive if the channel allows such things - websockets will
        if (channelizer.supportsKeepAlive() && keepAliveInterval > 0) {

            final ScheduledFuture oldKeepAliveFuture = keepAliveFuture.getAndSet(cluster.executor().scheduleAtFixedRate(() -> {
                logger.debug("Request sent to server to keep {} alive", thisConnection);
                try {
                    channel.writeAndFlush(channelizer.createKeepAliveMessage());
                } catch (Exception ex) {
                    // will just log this for now - a future real request can be responsible for the failure that
                    // marks the host as dead. this also may not mean the host is actually dead. more robust handling
                    // is in play for real requests, not this simple ping
                    logger.warn(String.format("Keep-alive did not succeed on %s", thisConnection), ex);
                }
            }, keepAliveInterval, keepAliveInterval, TimeUnit.MILLISECONDS));

            // try to cancel the old future if it's still un-executed - no need to ping since a new write has come
            // through on the connection
            if (oldKeepAliveFuture != null) oldKeepAliveFuture.cancel(true);
        }
{code}

The problem with this is that on every call of the {{wirte()}} method, which basically means on every query executed, the {[Connection}} schedule a KeepAlive task which won't be run for at least 30 minutes. This lead the {{Cluster.executor()}} queue to fill up with tasks waiting for completion.

One possible solution to fix this would be to schedule avoid this KeepAlive task to be instantiated more than once per connection:

{code:java}
final class Connection {
    ...
    private final AtomicBoolean keepAliveInitialized = new AtomicBoolean(false);

    public ChannelPromise write(final RequestMessage requestMessage, final CompletableFuture<ResultSet> future) {
    ...

        if (channelizer.supportsKeepAlive() && keepAliveInterval > 0 && keepAliveInitialized.compareAndSet(false, true)) {
        ...
        }
    ...
    }
   ...
}


}
{code}




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