How can I enable client side LB in Python ?

[tom.h...@gmail.com]

Hi,

I would like to enable round robin load balancing on my python client.

I setup my channel as follows:

 opts = [("grpc.lb_policy_name", "round_robin",)]
 channel = grpc.insecure_channel('localhost:50051' , opts)

However, after sending 1 message succesfully, my client blocks.  Am I creating the channel incorrectly ? Can you offer a hint ?

I updated the hello world example to repoduce this issue: 

https://github.com/tomhostyn/grpc/blob/round_robin_issue/examples/cpp/helloworld/greeter_client.cc

when executed, the output is as expected until :

========  with round robin =======

Connection OK

Greeter client received: Hello you

Connection OK

I tried to reproduce the same issue in the cpp client, but that works as expected

https://github.com/tomhostyn/grpc/blob/round_robin_issue/examples/cpp/helloworld/greeter_client.cc

environment:

$ uname -a

Linux instance-3 4.9.0-6-amd64 #1 SMP Debian 4.9.88-1+deb9u1 (2018-05-07) x86_64 

GNU/Linux

$ python --version

Python 2.7.13

$ pip freeze  (selected lines)

grpcio==1.12.0

protobuf==3.5.2.post1

 Thanks,

Tom

[tom.h...@gmail.com]

Hi,

in addition to the previous data - below output with 

export GRPC_VERBOSITY=debug

========  with round robin =======
Connection OK
D0619 10:22:38.353257384   17694 dns_resolver.cc:280]        Start resolving.
I0619 10:22:38.353954551   17696 subchannel.cc:608]          New connected subchannel at 0x7fe32c014de0 for subchannel 0x7fe32c012370
I0619 10:22:38.354072358   17696 subchannel.cc:608]          New connected subchannel at 0x7fe32c015140 for subchannel 0x7fe32c012dc0
Greeter client received: Hello you
Connection OK
D0619 10:22:38.354897819   17694 dns_resolver.cc:280]        Start resolving.

[Srini Polavarapu]

Can you enable tracing using GRPC_TRACE and collect more debug data to see if there is any issue with subchannels getting disconnected.

[Tom Hostyn]

Thanks for your reply and link, Srini.

$ env | grep 

GRPC

GRPC_TRACE=all

GRPC_VERBOSITY=DEBUG

$ python greeter_client.py &> log

^C^C^C

log output at https://pastebin.com/rxyp6huv

for this log, I updated the previous test code not to do the 10 messages with default options:

 

from __future__ import print_functionimport grpcimport helloworld_pb2import helloworld_pb2_grpcdef run(round_robin=False): if round_robin: opts = [("grpc.lb_policy_name", "round_robin",)] channel = grpc.insecure_channel('localhost:50051' , opts) else: channel = grpc.insecure_channel('localhost:50051') print ("Connection OK") stub = helloworld_pb2_grpc.GreeterStub(channel) response = stub.SayHello(helloworld_pb2.HelloRequest(name='you')) print("Greeter client received: " + response.message)if __name__ == '__main__': print("========= without options ========") for _ in range (0): run() print("======== with round robin =======") for _ in range (10): run(True)

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[Srini Polavarapu]

Looks like this broke in 1.12 release when channel.close() was introduced. It is not necessary to call channel.close() explicitly but looks like there is some issue cleaning up the previous channel. Can you try adding channel.close() before returning from run(). I tried and it works.

[Tom Hostyn]

Thanks a lot Psrini!

Closing the channel works both on my linux host, and on the kubernetes cluster.

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[Srini Polavarapu]

Also, it is not necessary to create a new channel for each RPC. Create the the channel once per host and reuse it for all the RPCs. gRPC manages the channel internally and reconnects if there is any connectivity issue. 

[tom.h...@gmail.com]

Thanks a lot for your help!!

I opened ticket https://github.com/grpc/grpc/issues/15892 

On Tuesday, 19 June 2018 10:08:46 UTC+2, tom.h...@gmail.com wrote: