I'm not personally a fan of RPC, at least for the sort of applications I write. I have lived through several generations of RPC—DCE, Corba, Java RMI, and so on. I'm sure GRPC is the best of the RCPs, but it is still RPC. The problem with RPC for me has always been that it results in wide interfaces that couple clients and servers tightly together. It might be the right choice for some applications, but if you value loose coupling over implementation efficiency, I think there are better options. I like all the non-functional properties—service discovery, client-side load balancing, well-factored monitoring, context propagation—can I have all that without the RPC interface model, please?

Martin

On Fri, Oct 21, 2016 at 10:44 AM, Ben Sigelman via cncf-toc <cncf-toc@...> wrote:

Hi all,

"I am not on the TOC, but" I did want to share a few thoughts about GRPC per the call the other day.

I was recently at one of those moderated VC dinners where everyone gets put on the spot to say something "insightful" (sic) – I'm sure we all know the scenario. Anyway, we had to go around the table and talk about "the one OSS project that's poised to change the way the industry functions". There were lots of mentions of Docker, k8s, etc, and for good reason. I had the bad luck of being last and felt like it wasn't useful to just +1 someone else's comment, and I realized that GRPC was in many ways an excellent answer.

Varun alluded to this in his presentation, but to restate it in different words: the value of an RPC system is mostly not actually about the RPC... it's the service discovery, client-side load balancing, well-factored monitoring, context propagation, and so on.

In that way, a high-quality RPC system is arguably the lynchpin of the "user-level OS" that sits just below the application code but above the actual (kernel) syscalls. An alternative approach moves things like RPC into its own process (a la linkerd(*)) and I think that makes sense in certain situations... but when the RPC system depends on data from its host process beyond the RPC payload and peer identity (which is often the case for more sophisticated microservice deployments), OR when "throughput matters" and extra copies are unacceptable, an in-process RPC subsystem is the right approach.

As for whether GRPC is the right in-process RPC system to incubate: I think that's a no-brainer. It has good momentum, the code is of a much higher quality and works in more languages than the alternatives, and Google's decision to adopt it internally will help to ensure that it works within scaled-out systems (both architecturally and in terms of raw performance). Apache Thrift moves quite slowly in my experience and has glaring problems in many languages; Finagle is mature but is limited to JVM (and perhaps bites off more than it can chew at times); other entrants that I'm aware of don't have a strong community behind them.

So yes, this is just an enthusiastic +1 from me. Hope the above makes sense and isn't blindingly obvious. :)

Comments / disagreements welcome –

Ben

(*): re linkerd specifically: I am a fan, and IMO this is a "both/and" situation, not "either/or"...

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Martin Nally, Apigee Engineering

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