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https://issues.apache.org/jira/browse/TINKERPOP-1490?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15554888#comment-15554888
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Marko A. Rodriguez commented on TINKERPOP-1490:
-----------------------------------------------
There are numerous "action/terminal"-methods off of {{Traversal}}.
* {{next()}}
* {{hasNext()}}
* {{nextTraverser()}}
* {{toList()}}
* {{toSet()}}
* {{iterate()}}
* {{explain()}}
* ...
If we want asyncrhonous support for all terminal methods, then I think we
shouldn't go down the route of {{nextAsync()}}, {{toListAsync()}}, etc. That is
a bit dirty. Instead, I think we should have one method --- call it what we
want --- that is basically a "future" that takes a {{Function<Traversal,V>}}.
Thus, we can do:
{code}
g.V().out().future(Traversal::toList)
g.V().out().future(Traversal::next)
...
{code}
In Java, its called a {{Future}}. Moreover, you can do {{CompletableFutures}}
(https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/CompletableFuture.html).
Thus, I think we kill many birds with one stone here. We get "async" and
"callback" support using one (and only one) method. Lets call it
{{Traversal.future()}} given the status of the term "async." Thus, I propose
that we add:
{code}
Future<T> Traversal.future(Function<Traversal,T>)
{code}
Lets get more specific and allow both "async" and "callback" via
https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/FutureTask.html.
{code}
OurFuture<T> Traversal.future(Function<Traversal,T>)
void OurFuture.then(Consume<T>)
{code}
...where {{OurFuture}} will be a custom class based off of {{FutureTask}}. In
sum total, you would then be able to do two things:
{code}
OurFuture<List<String>> result =
g.V().out().values("name").future(Traversal::List)
// some other stuff in parallel
List<String> list = result.get()
{code}
...and
{code}
g.V().out().values("name").future(Traversal::List).then(names ->
System.out.println("Here are the names of everyone: " + names))
// some other stuff in parallel
{code}
Both async and callback support across all terminal {{Traversal}} methods.
*** NOTE: I'm not married to {{future}} and {{then}} method names...so
whateves.
> Provider a Future based Traversal.async(Function<Traversal,V>) terminal step
> ----------------------------------------------------------------------------
>
> Key: TINKERPOP-1490
> URL: https://issues.apache.org/jira/browse/TINKERPOP-1490
> Project: TinkerPop
> Issue Type: Improvement
> Components: language-variant, process
> Affects Versions: 3.2.2
> Reporter: Marko A. Rodriguez
>
> [~mbroecheler] had the idea of adding a {{Traversal.async()}} method. This is
> important for not only avoiding thread locking on a query in Gremlin, but
> also, it will allow single threaded language variants like Gremlin-JavaScript
> to use callbacks for processing query results.
> {code}
> Future<List<String>> result =
> g.V().out().values("name").async(Traversal::toList)
> {code}
> {code}
> Future<List<String>> result = g.V().out().name.async{it.toList()}
> {code}
> {code}
> g.V().out().values('name').async((err,names) => {
> // I don't know JavaScript, but ...
> return list(names);
> })
> {code}
> ...
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