# Golang 输出插件

Fluent Bit 当前仅支持将 Golang 插件集成为仅用于输出插件的共享库。Golang 插件的接口目前正在开发中，但可以使用。

Fluent Bit当前仅支持将 Golang 插件集成为仅用于输出插件的共享库。Golang 插件的接口目前正在开发中，但可以使用。

## Getting Started

启用 Golang 支持选项编译 Fluent Bit，如:

```
$ cd build/
$ cmake -DFLB_DEBUG=On -DFLB_PROXY_GO=On ../
$ make
```

编译后，我们可以在二进制中看到新选项 `-e`，它代表扩展插件，例如:

```
$ bin/fluent-bit -h
Usage: fluent-bit [OPTION]

Available Options
  -c  --config=FILE    specify an optional configuration file, 指定可选的配置文件
  -d, --daemon        run Fluent Bit in background mode, 以后台方式运行 Fluent Bit
  -f, --flush=SECONDS    flush timeout in seconds (default: 5), 刷新数据到输出的超时时间(默认 5 秒)
  -i, --input=INPUT    set an input, 设置输入
  -m, --match=MATCH    set plugin match, same as '-p match=abc', 设置插件匹配的标签模式，与 '-p match=abc' 相同
  -o, --output=OUTPUT    set an output, 设置输出
  -p, --prop="A=B"    set plugin configuration property, 设置插件配置参数
  -e, --plugin=FILE    load an external plugin (shared lib), 加载扩展插件(共享库)
  ...
```

## Build a Go Plugin

**`fluent-bit-go`** 软件包可用于帮助开发人员创建 Go 插件

<https://github.com/fluent/fluent-bit-go>

作为最小形式，Go 插件至少如下所示：

```go
package main

import "github.com/fluent/fluent-bit-go/output"

//export FLBPluginRegister
func FLBPluginRegister(def unsafe.Pointer) int {
    // Gets called only once when the plugin.so is loaded
    return output.FLBPluginRegister(ctx, "gstdout", "Stdout GO!")
}

//export FLBPluginInit
func FLBPluginInit(plugin unsafe.Pointer) int {
    // Gets called only once for each instance you have configured.
    return output.FLB_OK
}

//export FLBPluginFlushCtx
func FLBPluginFlushCtx(ctx, data unsafe.Pointer, length C.int, tag *C.char) int {
    // Gets called with a batch of records to be written to an instance.
    return output.FLB_OK
}

//export FLBPluginExit
func FLBPluginExit() int {
    return output.FLB_OK
}

func main() {
}
```

上面的代码是编写输出插件的模板，将包名称设置为 `main` 并添加显式的 `main()` 函数非常重要。这是必需的，因为代码将被构建为共享库。

要构建上面的代码，请使用以下命令行:

```bash
$ go build -buildmode=c-shared -o out_gstdout.so out_gstdout.go
```

构建完成后，共享库 `out_gstdout.so` 将可被使用。仔细检查最终的 .so 文件确实是我们所期望的，这非常重要。对库执行 `ldd` 命令，我们应该看到类似于如下的内容:

```
$ ldd out_gstdout.so
    linux-vdso.so.1 =>  (0x00007fff561dd000)
    libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007fc4aeef0000)
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fc4aeb27000)
    /lib64/ld-linux-x86-64.so.2 (0x000055751a4fd000)
```

## Run Fluent Bit with the new plugin

```bash
$ bin/fluent-bit -e /path/to/out_gstdout.so -i cpu -o gstdout
```


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