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[wip] raft/rafttest: introduce datadriven testing
It has often been tedious to test the interactions between multi-member Raft groups, especially when many steps were required to reach a certain scenario. Often, this boilerplate was as boring as it is hard to write and hard to maintain, making it attractive to resort to shortcuts whenever possible, which in turn tended to undercut how meaningful and maintainable the tests ended up being - that is, if the tests were even written, which sometimes they weren't. This change introduces a datadriven framework specifically for testing deterministically the interaction between multiple members of a raft group with the goal of reducing the friction for writing these tests to near zero. In the near term, this will be used to add thorough testing for joint consensus (which is already available today, but wildly undertested), but just converting an existing test into this framework has shown that the concise representation and built-in inspection of log messages highlights unexpected behavior much more readily than the previous unit tests did (the test in question is `snapshot_succeed_via_app_resp`; the reader is invited to compare the old and new version of it). The main building block is `InteractionEnv`, which holds on to the state of the whole system and exposes various relevant methods for manipulating it, including but not limited to adding nodes, delivering and dropping messages, and proposing configuration changes. All of this is extensible so that in the future I hope to use it to explore the phenomena discussed in #7625 (comment) which requires injecting appropriate "crash points" in the Ready handling loop. Discussions of the "what if X happened in state Y" can quickly be made concrete by "scripting up an interaction test". Additionally, this framework is intentionally not kept internal to the raft package.. Though this is in its infancy, a goal is that it should be possible for a suite of interaction tests to allow applications to validate that their Storage implementation behaves accordingly, simply by running a raft-provided interaction suite against their Storage.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,17 @@ | ||
| package raft_test | ||
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| import ( | ||
| "testing" | ||
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| "github.com/cockroachdb/datadriven" | ||
| "go.etcd.io/etcd/raft/rafttest" | ||
| ) | ||
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| func TestInteraction(t *testing.T) { | ||
| datadriven.Walk(t, "testdata", func(t *testing.T, path string) { | ||
| env := rafttest.NewInteractionEnv(nil) | ||
| datadriven.RunTest(t, path, func(d *datadriven.TestData) string { | ||
| return env.Handle(t, *d) | ||
| }) | ||
| }) | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,94 @@ | ||
| // Copyright 2019 The etcd Authors | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
|
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| package rafttest | ||
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| import ( | ||
| "fmt" | ||
| "math" | ||
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| "go.etcd.io/etcd/raft" | ||
| pb "go.etcd.io/etcd/raft/raftpb" | ||
| ) | ||
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| // InteractionOpts blob | ||
| type InteractionOpts struct { | ||
| OnConfig func(*raft.Config) | ||
| } | ||
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| type State struct { | ||
| AppliedIndex uint64 | ||
| pb.ConfState | ||
| Content string | ||
| } | ||
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| type Storage interface { | ||
| raft.Storage | ||
| SetHardState(state pb.HardState) error | ||
| ApplySnapshot(pb.Snapshot) error | ||
| Compact(newFirstIndex uint64) error | ||
| Append([]pb.Entry) error | ||
| } | ||
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| type InteractionEnv struct { | ||
| Options *InteractionOpts | ||
| Nodes []*raft.RawNode | ||
| Storages []Storage | ||
| Configs []*raft.Config | ||
| Messages []pb.Message | ||
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| Histories [][]pb.Snapshot | ||
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| Output *RedirectLogger | ||
| } | ||
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| func NewInteractionEnv(opts *InteractionOpts) *InteractionEnv { | ||
| if opts == nil { | ||
| opts = &InteractionOpts{} | ||
| } | ||
| return &InteractionEnv{ | ||
| Options: opts, | ||
| Output: &RedirectLogger{}, | ||
| } | ||
| } | ||
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| func defaultRaftConfig(id uint64, applied uint64, s raft.Storage) *raft.Config { | ||
| return &raft.Config{ | ||
| ID: id, | ||
| Applied: applied, | ||
| ElectionTick: 3, | ||
| HeartbeatTick: 1, | ||
| Storage: s, | ||
| MaxSizePerMsg: math.MaxUint64, | ||
| MaxInflightMsgs: math.MaxInt32, | ||
| } | ||
| } | ||
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| func defaultEntryFormatter(b []byte) string { | ||
| return fmt.Sprintf("%q", b) | ||
| } | ||
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| type Store struct { | ||
| Storage | ||
| SnapshotOverride func() (pb.Snapshot, error) | ||
| } | ||
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| func (s Store) Snapshot() (pb.Snapshot, error) { | ||
| if s.SnapshotOverride != nil { | ||
| return s.SnapshotOverride() | ||
| } | ||
| return s.Storage.Snapshot() | ||
| } | ||
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| var _ raft.Storage = Store{} |
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