https://github.com/akihirosuda/go-replay

record-less semi-deterministic replayer for Go programs
https://github.com/akihirosuda/go-replay

Last synced: 3 months ago
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record-less semi-deterministic replayer for Go programs

• Host: GitHub
• URL: https://github.com/akihirosuda/go-replay
• Owner: AkihiroSuda
• License: apache-2.0
• Created: 2016-04-21T10:50:17.000Z (over 9 years ago)
• Default Branch: master
• Last Pushed: 2016-09-30T05:13:37.000Z (about 9 years ago)
• Last Synced: 2024-04-19T21:03:46.830Z (over 1 year ago)
• Language: Go
• Size: 22.5 KB
• Stars: 11
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

          
# GoReplay: record-less semi-deterministic replayer for Go programs

[![GoDoc](https://godoc.org/github.com/AkihiroSuda/go-replay?status.svg)](https://godoc.org/github.com/AkihiroSuda/go-replay)

[![Build Status](https://travis-ci.org/AkihiroSuda/go-replay.svg?branch=master)](https://travis-ci.org/AkihiroSuda/go-replay)

[![Go Report Card](https://goreportcard.com/badge/github.com/AkihiroSuda/go-replay)](https://goreportcard.com/report/github.com/AkihiroSuda/go-replay)

GoReplay replays concurrent Go programs _semi-deterministically_ without recording concrete events.

## How it works

GoReplay injects `time.Sleep(time.Duration(hash(seed, context, stack)) % maxInterval)` to arbitrary execution points of the target Go program.

 * `seed`: environmental variable `GRSEED`. You can replay the execution by remembering and setting `GRSEED`. The default value is empty value and it disables GoReplay.

 * `context`: optional `[]byte` slice.

 * `stack`: runtime stack. (planned)

 * `maxInterval`: environmental variable `GRMAX` (should be `time.Duration` string). The default value is `10ms`.

Name|Type|Default|Description

---|---|---|---

`GRSEED`|`string`|(empty)|The seed value for determining the delay. An empty value disables GoReplay.

`GRMAX`|`time.Duration`|`10ms`|Max delay.

`GRZBIAS`|`float64`|`0.0`|Probability of enforcing the delay to be zero. must be in `[0.0, 1.0)`.

## Usage

Follow the example: [`example/ex01`](example/ex01).

```go

package main

import (

	"fmt"

	"sync"

	"github.com/AkihiroSuda/go-replay"

)

func main() {

	n := 8

	var wg sync.WaitGroup

	for i := 0; i < n; i++ {

		wg.Add(1)

		go func(i interface{}) {

			msg := fmt.Sprintf("i=%d", i)

			replay.Inject([]byte(msg))

			fmt.Printf("%s\n", msg)

			wg.Done()

		}(i)

	}

	wg.Wait()

}

```

The result is non-deterministic without GoReplay:

```

$ go run example/ex01/main.go

i=7

i=5

i=1

i=6

i=0

i=2

i=3

i=4

$ (for f in $(seq 1 10);do go run example/ex01/main.go | sha512sum -; done) | sort | uniq | wc -l

4

```

If you set `GRSEED`, the result becomes deterministic:

```

$ (for f in $(seq 1 10);do GRSEED=foo go run example/ex01/main.go | sha512sum -; done) | sort | uniq

7ea818bd9e800609ab8e360688d975189033a9b9277d1ad9c9c96c9013f4ffeb1cf05c16ace9de737dcedaa68bc99162d611ac60b7169a43b4f9b17b1665f121  -

$ (for f in $(seq 1 10);do GRSEED=bar go run example/ex01/main.go | sha512sum -; done) | sort | uniq

fc1c177ebbc58baa7e4960102cf26da25173559de0d7a08e00c37a4512eb0a579fc6b4b70f2c708fe1166a1c0641e8839305d5fe7e26624cabbce2cb8274d963  -

```

## Practical Examples

 - [example/etcd-5155](example/etcd-5155): data race ([coreos/etcd#5155](https://github.com/coreos/etcd/issues/5155))

## Hint

You may use [AspectGo](https://github.com/AkihiroSuda/aspectgo)(WIP) for automatic instrumentation.

## Related project

 * [Namazu: a programmable fuzzy scheduler for testing distributed systems](https://github.com/osrg/namazu)

GoReplay is planned to be merged to Namazu.