#grpc

hello folks

what's a good way of service discovery/load balancing grpc on kubernetes?

the recommended kubernetes method is through services, however, the grpc documentation recommends not using L4 LB

You can do gRPC with L4, but you'd want to configure a max channel age on server-side.

Otherwise you won't re-balance across backends.

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kubernetes also supports headless services, which adds mutliple A records with the same name, afaik grpc also supports that

how often is the dns service requeried though?

Yeah. I think people have experienced problems with staleness. Yeah.

gRPC won't pro-actively requery.

there is also https://github.com/sercand/kuberesolver but I don't see its benefits if grpc requeries the dns server

ah, i see

kuberesolver might solve my issue then, since it appears to watch for changes

There is some requerying that happens, but it won't pro-actively move clients away from a server that's going down.

gRPC does have support for nameresolvers that provide notifications.

(as in, they can notify gRPC and gRPC can handle that)

i've searched quite a bit, there appears to be one issue on grpc which recommends having a separate nameresolver for k8s

there are also some "service mesh" tools, but they just appear to be tooled L4 proxies

noonien: gRPC should requery DNS when reconnecting, so maybe people simply weren't specifying a max connection age. Or maybe we need to tweak one case of gRPC.

Hmm... maybe it's just grpc-go that doesn't re-query on reconnect. I'll glance some.

I do see naming.NewDNSResolverWithFreq, which seems like it would get you most of the way.

awesome, thanks for the info!

hi, if I'm consuming stremaing from server and putting every element into Map one by one, should I use blocking stub or async stub ? (java)

Hi. I am trying to connect to a GRPC server in a Celery task, and I keep getting a FutureTimeOutError. From the python shell, the same code is able to connect to the server. I am using the grpc.channel_ready_future method. Any ideas would be helpful :)

noonien: So, I talked with the Go folks. The "naming" package is the "old" API and will be going away if possible. "resolver" is the new one, and it doesn't allow specifying a polling frequency.

However, they're also already working on triggering re-resolutions when the connection fails (like C and Java). So after that lands (no issue or PR yet, but "soon") grpc-go+kube+DNS may be fine.