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task.go
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task.go
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/*
Copyright 2014 CoreOS, Inc.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package agent
import (
"fmt"
"github.com/coreos/fleet/job"
)
const (
taskTypeLoadUnit = "LoadUnit"
taskTypeUnloadUnit = "UnloadUnit"
taskTypeStartUnit = "StartUnit"
taskTypeStopUnit = "StopUnit"
taskReasonScheduledButNotRunnable = "unit scheduled locally but unable to run"
taskReasonScheduledButUnloaded = "unit scheduled here but not loaded"
taskReasonLoadedButNotScheduled = "unit loaded but not scheduled here"
taskReasonLoadedButHashDiffers = "unit loaded but hash differs to expected"
taskReasonLoadedDesiredStateLaunched = "unit currently loaded but desired state is launched"
taskReasonLaunchedDesiredStateLoaded = "unit currently launched but desired state is loaded"
taskReasonPurgingAgent = "purging agent"
)
type task struct {
typ string
reason string
unit *job.Unit
}
var taskTypeSortOrder = map[string]int{
taskTypeUnloadUnit: 1,
taskTypeLoadUnit: 2,
taskTypeStopUnit: 3,
taskTypeStartUnit: 4,
}
type sortableTasks []task
func (st sortableTasks) Len() int { return len(st) }
func (st sortableTasks) Swap(i, j int) { st[i], st[j] = st[j], st[i] }
func (st sortableTasks) Less(i, j int) bool {
return taskTypeSortOrder[st[i].typ] < taskTypeSortOrder[st[j].typ]
}
type taskResult struct {
task task
err error
}
type taskManager struct {
mapper taskMapperFunc
}
func newTaskManager() *taskManager {
return &taskManager{
mapper: mapTaskToFunc,
}
}
// Do attempts to complete a series of tasks against an Agent. Each task
// is executed in order. If any task is unable to be attempted, or is able
// to be attempted but fails, Do will halt execution. The returned slice
// will contain a taskResult for every task that was attempted. Do is not
// threadsafe.
func (tm *taskManager) Do(tasks []task, a *Agent) []taskResult {
results := make([]taskResult, 0, len(tasks))
for _, t := range tasks {
taskFunc, err := tm.mapper(t, a)
if err == nil {
err = taskFunc()
}
results = append(results, taskResult{task: t, err: err})
if err != nil {
break
}
}
return results
}
type taskMapperFunc func(t task, a *Agent) (func() error, error)
func mapTaskToFunc(t task, a *Agent) (fn func() error, err error) {
switch t.typ {
case taskTypeLoadUnit:
fn = func() error { return a.loadUnit(t.unit) }
case taskTypeUnloadUnit:
fn = func() error { a.unloadUnit(t.unit.Name); return nil }
case taskTypeStartUnit:
fn = func() error { a.startUnit(t.unit.Name); return nil }
case taskTypeStopUnit:
fn = func() error { a.stopUnit(t.unit.Name); return nil }
default:
err = fmt.Errorf("unrecognized task type %q", t.typ)
}
return
}