Getting Plugged in with Go 1.8 Plugins @ GopherCon India

Go 1.8 will include a plugin package that allows you to define plugins that can be loaded at runtime. This talk will cover plugins in detail, discuss some use cases, and best practices for using the package.

Transcript

1. 2/25/2017 Go 1.8 Plugins
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   Go 1.8 Plugins
   Ian Lewis
   

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2. 2/25/2017 Go 1.8 Plugins
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   Go 1.8 Plugins
   

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   Go 1.5
   Go 1.5 introduced shared libraries using the -buildmode=shared option.
   // filename: calc.go
   package calc
   func Sum(x, y int) int {
   return x + y
   }
   

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4. 2/25/2017 Go 1.8 Plugins
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   Go shared libraries
   First you need to build Go stdlib as a shared library
   $ go install -buildmode=shared -linkshared std
   Build the shared library
   calc$ go install -buildmode=shared -linkshared calc
   

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5. 2/25/2017 Go 1.8 Plugins
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   Go shared libraries
   // package: cashier
   // filename: main.go
   package main
   import "calc"
   import "fmt"
   func main() {
   fmt.Println("Cashier Application")
   fmt.Printf("Result: %d\n", calc.Sum(5, 10))
   }
   & link it to another app
   cashier$ go build -linkshared
   

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   Go shared libraries
   Good for distributing binary code as a re-usable library
   Still need to link at compile time
   

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7. 2/25/2017 Go 1.8 Plugins
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   Go 1.8
   New plugin package
   New -buildmode=plugin
   Load shared code at runtime!
   

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8. 2/25/2017 Go 1.8 Plugins
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   Prior Art
   Exec Plugins (https://github.com/kelseyhightower/kube-cert-manager/blob/master/docs/plugins.md)
   Hashicorp Plugins (https://github.com/hashicorp/go-plugin)
   

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   Go Plugins
   Write a main package without main() func
   package main
   import "fmt"
   var V int
   func F() { fmt.Printf("Hello, number %d\n", V) }
   

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10. 2/25/2017 Go 1.8 Plugins
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    Build a Plugin
    Build to an .so file
    $ go build -buildmode=plugin adder
    

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11. 2/25/2017 Go 1.8 Plugins
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    Load a Plugin
    Load the plugin by passing the path to the .so to plugin.Open()
    func main() {
    p, err := plugin.Open("adder-plugin/adder-plugin.so")
    if err != nil {
    panic(err)
    }
    v, err := p.Lookup("V")
    if err != nil {
    panic(err)
    }
    f, err := p.Lookup("F")
    if err != nil {
    panic(err)
    }
    *v.(*int) = 7
    f.(func())() // prints "Hello, number 7"
    }
    

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12. 2/25/2017 Go 1.8 Plugins
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    Build the Main App
    Apps that use plugins can be built normally
    $ go build
    

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13. 2/25/2017 Go 1.8 Plugins
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    Use Cases
    Exposing API w/o source code (closed source)
    Abstract Backends (e.g. Cloud providers)
    

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14. 2/25/2017 Go 1.8 Plugins
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    Pros/Cons
    Pro: Easy loading at runtime
    Pro: Single process to maintain/monitor
    Con: Can't unload plugin, no hot reloading
    Con: It's new
    

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15. 2/25/2017 Go 1.8 Plugins
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    Testing
    

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    Testing
    

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    More Testing
    

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    Wrapping Up
    Moral of the Story: Testing is contribution!
    Provide ways for your users to extend
    Know the tradeoffs
    

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19. 2/25/2017 Go 1.8 Plugins
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    Thank you
    Ian Lewis
    Gopher/Kubernaut@Google (mailto:Gopher/Kubernaut@Google)
    @IanMLewis (http://twitter.com/IanMLewis)
    ianlewis@google.com (mailto:ianlewis@google.com)
    

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