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service.go
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service.go
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// Copyright 2020-2021 Changkun Ou. All rights reserved.
// Use of this source code is governed by a GPL-3.0
// license that can be found in the LICENSE file.
// Package service provides a simple way to create a system service.
// Currently supports Linux/(systemd | Upstart | SysV), and OSX/Launchd.
package service
// Service represents a generic way to interact with the system's service.
type Service interface {
Installer
Controller
Runner
Logger
}
// Installer is a simple install and remove commands.
type Installer interface {
// Installs this service on the system. May return an
// error if this service is already installed.
Install() error
// Removes this service from the system. May return an
// error if this service is not already installed.
Remove() error
}
// Controller is a service that implements ServiceController is able to
// start and stop itself.
type Controller interface {
// Starts this service on the system.
Start() error
// Stops this service on the system.
Stop() error
}
// Runner is a Generic way to stop and start a service.
type Runner interface {
// Call quickly after initial entry point. Does not return until
// service is ready to stop. onStart is called when the service is
// starting, returning an error will fail to start the service.
// If an error is returned from onStop, the service will still stop.
// An error passed from onStart or onStop will be returned as
// an error from Run.
// Both callbacks should return quickly and not block.
Run(onStart, onStop func() error) error
}
// Logger is a service that implements ServiceLogger can perform simple
// system logging.
type Logger interface {
// Basic log functions in the context of the service.
Error(format string, a ...interface{}) error
Warning(format string, a ...interface{}) error
Info(format string, a ...interface{}) error
}
// NewService creates a new service. name is the internal name
// and should not contain spaces. Display name is the pretty print
// name. The description is an arbitrary string used to describe the
// service.
func NewService(name, displayName, description string, args []string) (Service, error) {
return newService(&config{
Name: name,
DisplayName: displayName,
Description: description,
Args: args,
})
}
type config struct {
Name string
DisplayName string
Description string
Args []string
// System specific parameters.
KV KeyValue
}
// KeyValue is a key value mapping that offers a few handy utilities.
type KeyValue map[string]interface{}
// bool returns the value of the given name, assuming the value is a boolean.
// If the value isn't found or is not of the type, the defaultValue is returned.
func (kv KeyValue) bool(name string, defaultValue bool) bool {
if v, found := kv[name]; found {
if castValue, is := v.(bool); is {
return castValue
}
}
return defaultValue
}
// int returns the value of the given name, assuming the value is an int.
// If the value isn't found or is not of the type, the defaultValue is returned.
func (kv KeyValue) int(name string, defaultValue int) int {
if v, found := kv[name]; found {
if castValue, is := v.(int); is {
return castValue
}
}
return defaultValue
}
// string returns the value of the given name, assuming the value is a string.
// If the value isn't found or is not of the type, the defaultValue is returned.
func (kv KeyValue) string(name string, defaultValue string) string {
if v, found := kv[name]; found {
if castValue, is := v.(string); is {
return castValue
}
}
return defaultValue
}
// float64 returns the value of the given name, assuming the value is a float64.
// If the value isn't found or is not of the type, the defaultValue is returned.
func (kv KeyValue) float64(name string, defaultValue float64) float64 {
if v, found := kv[name]; found {
if castValue, is := v.(float64); is {
return castValue
}
}
return defaultValue
}