How do you set a timeout in Python's gRPC Library

Question

I have a grpc server / client that today will occasionally hang, causing issues. This is being called from a Flask application which is checking in with a background worker process to make sure it's alive / functioning. To make the request to the gRPC server, I have:

try:
        health = self.grpc_client.Health(self.health_ping)
        if health.message == u'PONG':
            return {
                u'healthy': True,
                u'message': {
                    u'healthy': True,
                    u'message': u'success'
                },
                u'status_code': 200
            }
except Exception as e:
        if str(e.code()) == u'StatusCode.UNAVAILABLE':
            return {
                u'healthy': False,
                u'message': {
                    u'healthy': False,
                    u'message': (u'[503 Unavailable] connection to worker '
                                 u'failed')},
                u'status_code': 200}
        elif str(e.code()) == u'StatusCode.INTERNAL':
            return {
                u'healthy': False,
                u'message': {
                    u'healthy': False,
                    u'message': (u'[500 Internal] worker encountered '
                                 u'an error while responding')},
                u'status_code': 200}
        return {
            u'healthy': False,
            u'message': {u'healthy': False, u'message': e.message},
            u'status_code': 500
        }

the client is a stub:

channel = grpc.insecure_channel(address)
stub = WorkerStub(channel)
return stub

the proto is:

syntax = "proto3";

option java_multiple_files = true;
option java_package = "com.company.project.worker";
option java_outer_classname = "ProjectWorker";
option objc_class_prefix = "PJW";

package projectworker;

service Worker {
  rpc Health (Ping) returns (Pong) {}
}

// The request message containing PONG
message Ping {
  string message = 1;
}

// The response message containing PONG
message Pong {
  string message = 1;
}

Using this code, how would I then add a timeout to ensure that I can always respond rather than fail and hang?

score 29 · Accepted Answer · answered May 09 '17 at 15:11

29

timeout is an optional keyword parameter on RPC invocation so you should change

health = self.grpc_client.Health(self.health_ping)

to

health = self.grpc_client.Health(self.health_ping, timeout=my_timeout_in_seconds)

.

answered May 09 '17 at 15:11

Nathaniel Manista At Google

2,442
15
15

Ah, ok. Thank you so much for that information! Can't believe I missed that – kkirsche May 09 '17 at 19:04
Is there a synonymous setting for the channel options here https://github.com/grpc/grpc/blob/v1.36.x/include/grpc/impl/codegen/grpc_types.h? is it grpc.grpclb_call_timeout_ms? – spacether Mar 26 '21 at 01:03

score 8 · Answer 2 · answered Sep 20 '19 at 09:28

To define a timeout on client side, add an optional parameter timeout=<timeout in seconds> when you invoke a service function;

channel = grpc.insecure_channel(...)
stub = my_service_pb2_grpc.MyServiceStub(channel)
request = my_service_pb2.DoSomethingRequest(data='this is my data')
response = stub.DoSomething(request, timeout=0.5)

Note a timeout situation will raise an exception

score 5 · Answer 3 · answered Jul 19 '19 at 13:57

You may also want to catch and handle timeouts differently than other errors. Sadly the documentation is not quite good on this topic, so here's what you have:

try:
    health = self.grpc_client.Health(self.health_ping, timeout=my_timeout_in_seconds)
except grpc.RpcError as e:
    e.details()
    status_code = e.code()
    status_code.name
    status_code.value

Timeout will return DEADLINE_EXCEEDED status_code.value.

How do you set a timeout in Python's gRPC Library

3 Answers3

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