Remote callbacks functionality in gadgets.rpc
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Key: SHINDIG-442
URL: https://issues.apache.org/jira/browse/SHINDIG-442
Project: Shindig
Issue Type: Improvement
Components: Features (Javascript)
Reporter: John Hjelmstad
Assignee: John Hjelmstad
Priority: Minor
Attachments: rpc.remotecallbacks.patch
At present, passing a function as an argument to a gadgets.rpc service handler
has undefined behavior (in practice, it probably stringifies the function in
some odd ways).
In order to support asynchronous callback of multiple methods, I propose
automatically wrapping function parameters in "remote callbacks". This would
allow something like the following:
Service definition (as by container):
function myServiceHandler(foo, onSuccess, onError) {
var result = doSomethingWithFoo(foo);
if (resultIsError(result)) {
onError(result);
} else {
onSuccess(result);
}
}
gadgets.rpc.register('my-service', myServiceHandler);
Service use (as by gadget):
gadgets.rpc.call('..', 'my-service', null, foo, function(result) { /* success
code */ }, function(result) { /* error code */ });
This allows intuitive definition of services using callbacks, and intuitive use
of them in turn.
This proposal is in many ways complementary to SHINDIG-441, as that proposal
provides an async way to call the single "default" callback mechanism in
gadgets.rpc. That there are two is somewhat confusing - there's an argument
that having only one would be better, but since there's already a default I
feel it's worthwhile to consider defining ad hoc versions.
Pros:
- Intuitive use of function arguments
- Provides flexible asynchronous callback functionality to gadgets.rpc without
changing any existing functionality
Cons:
- Somewhat conflated with "default" callback mechanism
- Need to figure out memory-management policies for dynamically-generated
remote callbacks.
Regarding the latter, I propose later adding an optional API to mark remote
callbacks with how long they last: oneTimeUse, timeoutInMs, etc.
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