72 lines
2.3 KiB
Markdown
72 lines
2.3 KiB
Markdown
# RPC
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This section is a work in progress.
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The RPC subsystem is exclusicely in Server Agents. It is comprised of two main components:
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1. the "RPC Server" (for lack of a better term) handles multiplexing of many different
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requests on a single TCP port.
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2. RPC endpoints handle RPC requests and return responses.
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The RPC subsystems handles requests from:
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1. Client Agents in the local DC
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2. (if the server is a leader) other Server Agents in the local DC
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3. Server Agents in other Datacenters
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4. in-process requests from other components running in the same process (ex: the HTTP API
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or DNS interface).
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## Routing
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The "RPC Server" accepts requests to the [server port] and routes the requests based on
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configuration of the Server and the the first byte in the request. The diagram below shows
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all the possible routing flows.
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[server port]: https://www.consul.io/docs/agent/config/config-files#server_rpc_port
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<sup>[source](./routing.mmd)</sup>
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The main entrypoint to RPC routing is `handleConn` in [agent/consul/rpc.go].
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[agent/consul/rpc.go]: https://github.com/hashicorp/consul/blob/main/agent/consul/rpc.go
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### Development
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Multiplexing several protocols over a single server port helps to reduce our
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network requirements, but also makes interacting with Consul using local
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development tools such as [grpcurl] difficult.
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[grpcurl]: https://github.com/fullstorydev/grpcurl
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You can get a "plain" TCP connection to the gRPC server using this proxy script:
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```
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$ go run tools/private-grpc-proxy/main.go localhost:8300
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Proxying connections to Consul's private gRPC server
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Use this address: 127.0.0.1:64077
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```
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Pass the returned proxy address to your tool of choice.
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## RPC Endpoints
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This section is a work in progress, it will eventually cover topics like:
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- net/rpc - (in the stdlib)
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- new grpc endpoints
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- [Streaming](./streaming)
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- [agent/structs](https://github.com/hashicorp/consul/tree/main/agent/structs) - contains definitions of all the internal RPC protocol request and response structures.
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## RPC connections and load balancing
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This section is a work in progress, it will eventually cover topics like:
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Routing RPC request to Consul servers and for connection pooling.
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- [agent/router](https://github.com/hashicorp/consul/tree/main/agent/router)
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- [agent/pool](https://github.com/hashicorp/consul/tree/main/agent/pool)
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