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raftlog: introduce & use in loqrecovery, kvserver
This commit introduces a new package `raftlog`. Aspirationally, this
will at some point become the de facto way of encapsulating the raft log
encoding and may play a role in programmatically constructing and
inspecting raft logs (e.g. for testing).
For now, we introduce two concepts:
- `raftlog.Entry`, which wraps a `raftpb.Entry` and all of the
information derived from it, such as the command ID, the
`kvserverpb.RaftCommand`, the configuration change (if any), etc.
- `raftlog.Iterator`, a way to iterate over the raft log in terms of
`raftlog.Entry` (as opposed to `raftpb.Entry` which requires lots of
manual processing).
Both are then applied across the codebase, concretely:
- `loqrecovery` is simplified via `raftlog.Iterator` to pull commit
triggers out of the raft log.
- debug pretty-printing is simpler thanks to use of `raftlog.Entry`.
- `decodedRaftEntry` is now structurally a `raftpb.Entry`, and again
lots manual custom unmarshaling code evaporates.
It's currently difficult to create "interesting" raft log entries if
trying to stay away from manual population of large datastructures
(which is prone to rotting), so there's zero unit testing of
`raftlog.Iterator`. However, the code is not new, instead it was
deduplicated from a few places, and is now tested through all of them;
so I don't feel to bad about it. I still think it is a priority to be
able to "comfortably" create at least "simple" raft logs, meaning we
need to be able to string together `batcheval` and entry creation at
least in a rudimentary fashion. I intend to look into this next and
add comprehensive unit tests for `raftlog.{Entry,Iterator}`.
Touches cockroachdb#75729.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,22 @@ | ||
| load("@io_bazel_rules_go//go:def.bzl", "go_library") | ||
|
|
||
| go_library( | ||
| name = "raftlog", | ||
| srcs = [ | ||
| "entry.go", | ||
| "iterator.go", | ||
| ], | ||
| importpath = "github.com/cockroachdb/cockroach/pkg/kv/kvserver/raftlog", | ||
| visibility = ["//visibility:public"], | ||
| deps = [ | ||
| "//pkg/keys", | ||
| "//pkg/kv/kvserver/kvserverbase", | ||
| "//pkg/kv/kvserver/kvserverpb", | ||
| "//pkg/roachpb:with-mocks", | ||
| "//pkg/storage", | ||
| "//pkg/storage/enginepb", | ||
| "//pkg/util/protoutil", | ||
| "@com_github_cockroachdb_errors//:errors", | ||
| "@io_etcd_go_etcd_raft_v3//raftpb", | ||
| ], | ||
| ) |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,101 @@ | ||
| // Copyright 2022 The Cockroach Authors. | ||
| // | ||
| // Use of this software is governed by the Business Source License | ||
| // included in the file licenses/BSL.txt. | ||
| // | ||
| // As of the Change Date specified in that file, in accordance with | ||
| // the Business Source License, use of this software will be governed | ||
| // by the Apache License, Version 2.0, included in the file | ||
| // licenses/APL.txt. | ||
|
|
||
| package raftlog | ||
|
|
||
| import ( | ||
| "github.com/cockroachdb/cockroach/pkg/kv/kvserver/kvserverbase" | ||
| "github.com/cockroachdb/cockroach/pkg/kv/kvserver/kvserverpb" | ||
| "github.com/cockroachdb/cockroach/pkg/storage" | ||
| "github.com/cockroachdb/cockroach/pkg/storage/enginepb" | ||
| "github.com/cockroachdb/cockroach/pkg/util/protoutil" | ||
| "github.com/cockroachdb/errors" | ||
| "go.etcd.io/etcd/raft/v3/raftpb" | ||
| ) | ||
|
|
||
| // Entry contains data related to the current raft log entry. | ||
| type Entry struct { | ||
| Meta enginepb.MVCCMetadata // optional | ||
| Ent raftpb.Entry | ||
| ID kvserverbase.CmdIDKey | ||
| CC1 *raftpb.ConfChange | ||
| CC2 *raftpb.ConfChangeV2 | ||
| CCC *kvserverpb.ConfChangeContext | ||
| Cmd kvserverpb.RaftCommand | ||
| } | ||
|
|
||
| func (e *Entry) CC() raftpb.ConfChangeI { | ||
| if e.CC1 != nil { | ||
| return e.CC1 | ||
| } | ||
| if e.CC2 != nil { | ||
| return e.CC2 | ||
| } | ||
| // NB: nil != interface{}(nil). | ||
| return nil | ||
| } | ||
|
|
||
| func (e *Entry) LoadFromRawValue(b []byte) error { | ||
| if err := protoutil.Unmarshal(b, &e.Meta); err != nil { | ||
| return errors.Wrap(err, "decoding raft log MVCCMetadata") | ||
| } | ||
|
|
||
| if err := storage.MakeValue(e.Meta).GetProto(&e.Ent); err != nil { | ||
| return errors.Wrap(err, "unmarshalling raft Entry") | ||
| } | ||
|
|
||
| return e.load() | ||
| } | ||
|
|
||
| func (e *Entry) Load() error { | ||
| e.Meta = enginepb.MVCCMetadata{} | ||
| return e.load() | ||
| } | ||
|
|
||
| func (e *Entry) load() error { | ||
| if len(e.Ent.Data) == 0 { | ||
| // Raft-proposed empty entry. | ||
| return nil | ||
| } | ||
|
|
||
| var payload []byte | ||
| switch e.Ent.Type { | ||
| case raftpb.EntryNormal: | ||
| e.ID, payload = kvserverbase.DecodeRaftCommand(e.Ent.Data) | ||
| case raftpb.EntryConfChange: | ||
| e.CC1 = &raftpb.ConfChange{} | ||
| if err := protoutil.Unmarshal(e.Ent.Data, e.CC1); err != nil { | ||
| return errors.Wrap(err, "unmarshalling ConfChange") | ||
| } | ||
| e.CCC = &kvserverpb.ConfChangeContext{} | ||
| if err := protoutil.Unmarshal(e.CC1.Context, e.CCC); err != nil { | ||
| return errors.Wrap(err, "unmarshalling ConfChangeContext") | ||
| } | ||
| payload = e.CCC.Payload | ||
| e.ID = kvserverbase.CmdIDKey(e.CCC.CommandID) | ||
| case raftpb.EntryConfChangeV2: | ||
| e.CC2 = &raftpb.ConfChangeV2{} | ||
| if err := protoutil.Unmarshal(e.Ent.Data, e.CC2); err != nil { | ||
| return errors.Wrap(err, "unmarshalling ConfChangeV2") | ||
| } | ||
| e.CCC = &kvserverpb.ConfChangeContext{} | ||
| if err := protoutil.Unmarshal(e.CC2.Context, e.CCC); err != nil { | ||
| return errors.Wrap(err, "unmarshalling ConfChangeContext") | ||
| } | ||
| payload = e.CCC.Payload | ||
| e.ID = kvserverbase.CmdIDKey(e.CCC.CommandID) | ||
| default: | ||
| return errors.AssertionFailedf("unknown entry type %d", e.Ent.Type) | ||
| } | ||
|
|
||
| // TODO(tbg): can len(payload)==0 if we propose an empty command to wake up leader? | ||
| // If so, is that a problem here? | ||
| return errors.Wrap(protoutil.Unmarshal(payload, &e.Cmd), "unmarshalling RaftCommand") | ||
| } |
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