116 lines
2.7 KiB
Markdown
116 lines
2.7 KiB
Markdown
# Secondly
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Secondly is a configuration management plugin for Go projects. It takes care of
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the app's configuration, specifically of updating it in runtime.
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## Configuration
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First, we need to define a struct that will hold the app's configuration. Let's
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make it simple for demonstration purposes.
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```go
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type Config struct {
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AppName string `json:"app_name"`
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Version float32 `json:"version"`
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}
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```
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Make sure you've added `json` tags to each field.
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Next, right where you will define your app's flags, ask Secondly to add one for
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configuration file.
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```go
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secondly.SetupFlags()
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flag.Parse()
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```
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Now you can pass a configuration file to your program like this:
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```
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./app -config=config.json
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```
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Now we need to ask Secondly to take care of your configuration:
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```go
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var conf Config
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secondly.Manage(&conf)
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// or asynchronously
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go secondly.Manage(&conf)
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```
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If you prefer to configure the app asynchronously, then you'll probably want to
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know when configuration is loaded, so there's a handy helper function just for
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that:
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```go
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secondly.OnLoad(func(){
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log.Println("Configuration initialized")
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})
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```
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Congratulations! You've just configured Secondly to read and initialize the
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configuration of your app. But this is not what you came for, right?
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If you want a configuration GUI, simply start Secondly's web server on a port
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you want.
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```go
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secondly.StartServer("", 5500)
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```
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Tired of restarting the app every time you modify the config? You're not alone.
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```go
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secondly.HandleFileSystemEvents()
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```
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Want some more control over when specifically the config will be reloaded? Ask
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Secondly to listen for SIGHUP syscalls.
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```go
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secondly.HandleSIGHUP()
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```
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You can also set up callback functions on specific fields and receive a call
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when this field's value changes.
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```go
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// Refer to a field using its json tag
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secondly.OnChange("num_workers", func(oldVal, newVal interface{}) {
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old := oldVal.(int)
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cur := newVal.(int)
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if cur > old {
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pool.AddWorkers(cur - old)
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} else {
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pool.StopWorkers(old - cur)
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}
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log.Println("Number of workers changed from %d to %d", old, cur)
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}
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})
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```
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Full example can be found [here](https://github.com/localhots/secondly/blob/master/demo/demo.go).
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## Demo Screenshot
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<img src="https://raw.githubusercontent.com/localhots/secondly/master/demo/screenshot.png" width="440">
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## Building
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The only thing to keep in mind when building Secondly is to convert assets into a
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binary form so they could be kept in memory of your app and would not require
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any additional web server configuration.
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```
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go get github.com/GeertJohan/go.rice/rice
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rice embed-go
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go build
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```
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## Licence
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Secondly is distributed under the [MIT Licence](https://github.com/localhots/secondly/blob/master/LICENCE).
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