Hello,
We noticed that remote traversals in Tinkerpop client only evaluate the
request exactly once, just wanted to check if its by design. For example
lets say if I have client code that looks like below (retryStrategy will
retry the supplied lambda if exceptions are thrown from it),
GraphTraversal buildQuery() {
return g.addV().
... // some more steps here
}
void execute(GraphTraversal gt) {
retryStrategy.apply(() -> {
gt.iterate();
}
}
As per this code [1], RemoteStep only submits the request the first time it
executes. After this it reuses the same future and for someone calling a
terminal step it will continue to give the same error if the first request
errored out. In above example code, retry strategy is ineffective since it
will continue to get the same exception.
I think this is misleading since it makes it seem like the server is
throwing the same exception even though no new requests are being enqueued.
Instead of this client can explicitly throw an error that indicates results
are already consumed for this traversal (say TraversalClosedException).
That way it clearly indicates to the user that they will need to create
another traversal for sending the request. Another alternative is to
resubmit the bytecode to the server every-time a terminal method is called
by making a copy of the traversal.
I would like to hear your thoughts on how to handle this or let me know if
I misunderstood anything here. In addition to this, it would be good to add
some documentation around client error handling to reference documentation.
Happy to contribute to both these areas.
Thanks,
-Sainath
[1]
https://github.com/apache/tinkerpop/blob/master/gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/remote/traversal/step/map/RemoteStep.java#L88
