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Unreliable RPC Testing #178

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JMurph2015 opened this issue Mar 26, 2018 · 2 comments
Closed

Unreliable RPC Testing #178

JMurph2015 opened this issue Mar 26, 2018 · 2 comments

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@JMurph2015
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Hello!
I am working on a project that may require testing with an unreliable network. Probably the simplest way to do this is to gate the actual RPC sending functionality behind a probability or enable/disable flag. I don't quite understand the client side here well enough, so I was wondering if anyone could provide some guidance on this one.
Thanks!

@tikue
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tikue commented Mar 26, 2018

You'd probably want to be able to plug in a custom transport that replicates an unreliable network. Issue #38 is relevant, though there hasn't been any work here or new discussion in a long time. Basically tarpc would need to generate stubs that are generic over the transport.

@tikue
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tikue commented Sep 15, 2018

#199 will allow you to do this kind of thing.

tikue added a commit that referenced this issue Oct 16, 2018
#199)

# New Crates

- crate rpc contains the core client/server request-response framework, as well as a transport trait.
- crate bincode-transport implements a transport that works almost exactly as tarpc works today (not to say it's wire-compatible).
- crate trace has some foundational types for tracing. This isn't really fleshed out yet, but it's useful for in-process log tracing, at least.

All crates are now at the top level. e.g. tarpc-plugins is now tarpc/plugins rather than tarpc/src/plugins. tarpc itself is now a *very* small code surface, as most functionality has been moved into the other more granular crates.

# New Features
- deadlines: all requests specify a deadline, and a server will stop processing a response when past its deadline.
- client cancellation propagation: when a client drops a request, the client sends a message to the server informing it to cancel its response. This means cancellations can propagate across multiple server hops.
- trace context stuff as mentioned above
- more server configuration for total connection limits, per-connection request limits, etc.

# Removals
- no more shutdown handle.  I left it out for now because of time and not being sure what the right solution is.
- all async now, no blocking stub or server interface. This helps with maintainability, and async/await makes async code much more usable. The service trait is thusly renamed Service, and the client is renamed Client.
- no built-in transport. Tarpc is now transport agnostic (see bincode-transport for transitioning existing uses).
- going along with the previous bullet, no preferred transport means no TLS support at this time. We could make a tls transport or make bincode-transport compatible with TLS.
- a lot of examples were removed because I couldn't keep up with maintaining all of them. Hopefully the ones I kept are still illustrative.
- no more plugins!

# Open Questions

1. Should client.send() return `Future<Response>` or `Future<Future<Response>>`? The former appears more ergonomic but it doesn’t allow concurrent requests with a single client handle. The latter is less ergonomic but yields back control of the client once it’s successfully sent out the request. Should we offer fns for both?
2. Should rpc service! Fns take &mut self or &self or self? The service needs to impl Clone anyway, technically we only need to clone it once per connection, and then leave it up to the user to decide if they want to clone it per RPC. In practice, everyone doing nontrivial stuff will need to clone it per RPC, I think.
3. Do the request/response structs look ok?
4. Is supporting server shutdown/lameduck important?

Fixes #178 #155 #124 #104 #83 #38
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