How does deadline work?

[pszemus]

I'm creating a blocking stub with deadline:

blockingStub = MyGrpc
        .newBlockingStub(channel)
        .withDeadlineAfter(3, TimeUnit.SECONDS);

and then I start calling method in a loop:

for (int i=0; i<100; i++) blockingStub.doSomething();

first 8 calls are handled correctly but others end with DEADLINE_EXCEEDED exception.
Looking at my gRPC server logs I can see that the 8th call (last succeeded call) is ~3 seconds after the 1st one, so I assume that the deadline I set is for all my calls.
How to set up a deadline per call ?

[ejona86]

A deadline is a fixed point in time, like 8:10 AM on Feb 29th. A timeout is a relative time, like 3 seconds. gRPC is using deadlines, not timeouts, as they work much better when you many things you need to do by a certain time.

To have each RPC last up to 3 seconds, you could do:

for (int i=0; i<100; i++)
    blockingStub.withDeadlineAfter(3, TimeUnit.SECONDS).doSomething();

There are some plans to support timeouts, but they are part of larger per-service configuration plans. It'll be a while until it is ready.

[pszemus]

Thank you. That's very explanatory.

[stephenh]

I just ran in to this as well; is there an issue open for the timeouts? I didn't see one (I went to look so I could subscribe for updates to see when it's available).

[odiszapc]

@ejona86 excuse me, what is defaul deadline value when deadline is not set?

[jmblakl]

Do I need to handle clock skew between servers manually?

[carl-mastrangelo]

@jmblakl No, it is converted to a relative time when transmitted on the wire.

In general you should ask such questions on Stack Overflow or on our support forum. We use the issues here to track bugs and feature requests.

[beninu]

@carl-mastrangelo If deadline converted to relative time on the wire, how the server figures out how long the request queued in TCP buffer?

[carl-mastrangelo]

@beninu it doesn't. You need to set TCP_NOTSENT_LOWAT if you want to avoid time in the TCP buffer.

[ejona86]

@odiszapc, there is no default deadline if one is not set. It is the equivalent of "infinite."

@beninu, the timeout on the server is known to be imprecise, because any precise solution would require a lot of infrastructure. The server's view of the deadline will not be before the client's view (other than cases of extreme clock speed differences). But we handle the various cases, best-effort.