测试是功能上线之前的重要环节。
测试过程中，要尽量覆盖各种场景。故障情况或异常情况下的场景测试，也是必不可少的。
如何模拟故障呢？
在FreeBSD 中, failpoints经常用来模拟故障。
在golang，也有failpoint的实现，就是目前pingcap 公司的开源项目failpoint.
下面介绍golang中的failpoint的实现。
1.安装failpoint工具
cd $GOPATH/src
mkdir -p github.com/pingcap
cd github.com/pingcap
git clone https://github.com/pingcap/failpoint.git
cd failpoint
make
GO111MODULE=on CGO_ENABLED=0 GO111MODULE=on go build -ldflags '-X "github.com/pingcap/failpoint/failpoint-ctl/version.releaseVersion=12f4ac2-dev" -X "github.com/pingcap/failpoint/failpoint-ctl/version.buildTS=2019-11-15 09:41:49" -X "github.com/pingcap/failpoint/failpoint-ctl/version.gitHash=12f4ac2fd11dfc6b2f7018b00bb90f61a5b6b692" -X "github.com/pingcap/failpoint/failpoint-ctl/version.gitBranch=master" -X "github.com/pingcap/failpoint/failpoint-ctl/version.goVersion=go version go1.13 darwin/amd64"' -o bin/failpoint-ctl failpoint-ctl/main.go
failpoint-ctl build successfully :-) !
注意：仔细确认这些步骤。如果搞错，会出现无法转换代码的情况。
编译后，生成可执行文件failpoint-ctl：
ll bin
total 6840
-rwxr-xr-x 1 lanyang staff 3.3M 11 15 17:41 failpoint-ctl
2. 测试代码
代码结构如下：
cd $GOPATH/src
mkdir fp_example
cd fp_example
# tree ./
./
├── fruit
│ └── banana.go
├── main.go
└── util
├── apple.go
└── orange.go
其中，main.go文件内容：
package main
import (
"fmt"
"fp_example/hot_fruit"
"fp_example/fruit"
)
func main() {
hot_fruit.Apple()
hot_fruit.Orange()
fruit.Banana()
fmt.Println("main end")
}
fruit/banana.go：
package fruit
import (
"fmt"
"github.com/pingcap/failpoint"
)
func Banana() {
fmt.Println("banana....")
failpoint.Inject("bananaPanic", func() {
panic("banana failpoint triggerd")
})
}
注入一个panic。
hot_fruit/apple.go：
package hot_fruit
import (
"fmt"
"github.com/pingcap/failpoint"
)
func Apple() {
fmt.Println("apple....")
failpoint.Inject("applePanic", func() {
panic("apple failpoint triggerd")
})
}
再次注入一个panic。
hot_fruit/orange.go：
package hot_fruit
import (
"fmt"
"github.com/pingcap/failpoint"
)
func Orange() {
fmt.Println("orange....")
failpoint.Inject("orangePanic", func() {
panic("orange failpoint triggerd")
})
}
再次注入一个panic。
3. 使用failpoint转换代码
$GOPATH/src/github.com/pingcap/failpoint/bin/failpoint-ctl enable
代码转换之后，看下代码文件结构：
tree ./
./
├── fruit
│ ├── banana.go
│ ├── banana.go__failpoint_stash__
│ └── binding__failpoint_binding__.go
├── hot_fruit
│ ├── apple.go
│ ├── apple.go__failpoint_stash__
│ ├── binding__failpoint_binding__.go
│ ├── orange.go
│ └── orange.go__failpoint_stash__
├── main.go
2 directories, 10 files
可以看到多了几个文件。
如果执行disable，这些文件又会消失。
$GOPATH/src/github.com/pingcap/failpoint/bin/failpoint-ctl disable
4.编译和执行
使用装换之后的代码，进行编译：
go build -o simple main.go
生成可执行文件simple.
正常执行:
./simple
apple....
orange....
banana....
main end
触发bananaPanic故障执行：
GO_FAILPOINTS="fp_example/fruit/bananaPanic=return(true)" ./simple
apple....
orange....
banana....
panic: banana failpoint triggerd
goroutine 1 [running]:
fp_example/fruit.Banana()
/Users/lanyang/workspace/go_projects/src/fp_example/fruit/banana.go:12 +0x10e
main.main()
/Users/lanyang/workspace/go_projects/src/fp_example/main.go:13 +0x2c
其中，fp_example/fruit 是package名称, bananaPanic是注入的故障名称。
触发applePanic故障执行：
GO_FAILPOINTS="fp_example/hot_fruit/applePanic=return(true)" ./simple
apple....
panic: apple failpoint triggerd
goroutine 1 [running]:
fp_example/hot_fruit.Apple()
/Users/lanyang/workspace/go_projects/src/fp_example/hot_fruit/apple.go:12 +0x10e
main.main()
/Users/lanyang/workspace/go_projects/src/fp_example/main.go:11 +0x22
触发orangePanic故障执行：
GO_FAILPOINTS="fp_example/hot_fruit/orangePanic=return(true)" ./simple
apple....
orange....
panic: orange failpoint triggerd
goroutine 1 [running]:
fp_example/hot_fruit.Orange()
/Users/lanyang/workspace/go_projects/src/fp_example/hot_fruit/orange.go:12 +0x10e
main.main()
/Users/lanyang/workspace/go_projects/src/fp_example/main.go:12 +0x27