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fb085186b7
Fixes #16517 Given a 3 Server cluster with at least 1 Client connected to Follower 1: If a NodeMeta.{Apply,Read} for the Client request is received by Follower 1 with `AllowStale = false` the Follower will forward the request to the Leader. The Leader, not being connected to the target Client, will forward the RPC to Follower 1. Follower 1, seeing AllowStale=false, will forward the request to the Leader. The Leader, not being connected to... well hoppefully you get the picture: an infinite loop occurs.
58 lines
2.8 KiB
Markdown
58 lines
2.8 KiB
Markdown
# New/Updated RPC Endpoint Checklist
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Prefer adding a new message to changing any existing RPC messages.
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## Code
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* [ ] `Request` struct and `*RequestType` constant in
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`nomad/structs/structs.go`. Append the constant, old constant
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values must remain unchanged
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* [ ] In `nomad/fsm.go`, add a dispatch case to the switch statement in `(n *nomadFSM) Apply`
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* `*nomadFSM` method to decode the request and call the state method
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* [ ] State method for modifying objects in a `Txn` in `nomad/state/state_store.go`
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* `nomad/state/state_store_test.go`
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* [ ] Handler for the request in `nomad/foo_endpoint.go`
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* RPCs are resolved by matching the method name for bound structs
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[net/rpc](https://golang.org/pkg/net/rpc/)
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* Check ACLs for security, list endpoints filter by ACL
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* Register new RPC struct in `nomad/server.go`
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* Check ACLs to enforce security
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* [ ] Wrapper for the HTTP request in `command/agent/foo_endpoint.go`
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* Backwards compatibility requires a new endpoint, an upgraded
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client or server may be forwarding this request to an old server,
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without support for the new RPC
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* RPCs triggered by an internal process may not need support
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* Check ACLs as an optimization
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* [ ] Endpoint added/updated in the [`nomad-openapi`](https://github.com/hashicorp/nomad-openapi) repository.
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* New endpoints will need to be configured in that repository's `generator` package.
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* Updated endpoints may require the `generator` configuration to change, especially if parameters or headers change.
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* If the accepted or returned `struct` schema changes, the Nomad version references in `generator/go.mod` will need
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to be updated. Once the version is updated, regenerate the spec and all all clients so that the new schema is
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reflected in the spec and thus the generated models.
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* If `QueryOptions`, `QueryMeta`, `WriteOptions`, or `WriteMeta` change, the `v1` framework will need to updated to
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support the change.
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* [ ] `nomad/core_sched.go` sends many RPCs
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* `ServersMeetMinimumVersion` asserts that the server cluster is
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upgraded, so use this to guard sending the new RPC, else send the old RPC
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* Version must match the actual release version!
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* [ ] If implementing a Client RPC...
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* Use `QueryOptions` instead of `WriteRequest` in the Request struct as
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`WriteRequest` is only for *Raft* writes.
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* Set `QueryOptions.AllowStale = true` in the *Server* RPC forwarder to avoid
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an infinite loop between leaders and followers when a Client RPC is
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forwarded through a follower. See
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https://github.com/hashicorp/nomad/issues/16517
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## Docs
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* [ ] Changelog
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* [ ] [Metrics](https://www.nomadproject.io/docs/operations/metrics#server-metrics)
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* [ ] [API docs](https://www.nomadproject.io/api-docs) for RPCs with an HTTP endpoint, include ACLs, params, and example response body.
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