helper/resource: add Retry function
This commit is contained in:
Mitchell Hashimoto
parent
65f5069616
commit
ef62fa80db
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@ -0,0 +1,120 @@
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package resource
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import (
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"errors"
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"fmt"
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"log"
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"math"
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"time"
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)
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// StateRefreshFunc is a function type used for StateChangeConf that is
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// responsible for refreshing the item being watched for a state change.
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//
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// It returns three results. `result` is any object that will be returned
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// as the final object after waiting for state change. This allows you to
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// return the final updated object, for example an EC2 instance after refreshing
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// it.
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//
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// `state` is the latest state of that object. And `err` is any error that
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// may have happened while refreshing the state.
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type StateRefreshFunc func() (result interface{}, state string, err error)
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// StateChangeConf is the configuration struct used for `WaitForState`.
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type StateChangeConf struct {
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Delay time.Duration // Wait this time before starting checks
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Pending []string // States that are "allowed" and will continue trying
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Refresh StateRefreshFunc // Refreshes the current state
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Target string // Target state
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Timeout time.Duration // The amount of time to wait before timeout
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MinTimeout time.Duration // Smallest time to wait before refreshes
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}
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// WaitForState watches an object and waits for it to achieve the state
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// specified in the configuration using the specified Refresh() func,
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// waiting the number of seconds specified in the timeout configuration.
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func (conf *StateChangeConf) WaitForState() (interface{}, error) {
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log.Printf("[DEBUG] Waiting for state to become: %s", conf.Target)
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notfoundTick := 0
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var result interface{}
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var resulterr error
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doneCh := make(chan struct{})
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go func() {
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defer close(doneCh)
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// Wait for the delay
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time.Sleep(conf.Delay)
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var err error
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for tries := 0; ; tries++ {
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// Wait between refreshes using an exponential backoff
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wait := time.Duration(math.Pow(2, float64(tries))) *
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100 * time.Millisecond
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if wait < conf.MinTimeout {
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wait = conf.MinTimeout
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} else if wait > 10*time.Second {
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wait = 10 * time.Second
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}
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log.Printf("[TRACE] Waiting %s before next try", wait)
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time.Sleep(wait)
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var currentState string
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result, currentState, err = conf.Refresh()
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if err != nil {
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resulterr = err
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return
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}
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// If we're waiting for the absence of a thing, then return
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if result == nil && conf.Target == "" {
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return
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}
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if result == nil {
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// If we didn't find the resource, check if we have been
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// not finding it for awhile, and if so, report an error.
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notfoundTick += 1
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if notfoundTick > 20 {
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resulterr = errors.New("couldn't find resource")
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return
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}
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} else {
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// Reset the counter for when a resource isn't found
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notfoundTick = 0
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if currentState == conf.Target {
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return
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}
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found := false
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for _, allowed := range conf.Pending {
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if currentState == allowed {
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found = true
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break
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}
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}
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if !found {
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resulterr = fmt.Errorf(
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"unexpected state '%s', wanted target '%s'",
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currentState,
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conf.Target)
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return
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}
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}
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}
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}()
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select {
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case <-doneCh:
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return result, resulterr
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case <-time.After(conf.Timeout):
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return nil, fmt.Errorf(
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"timeout while waiting for state to become '%s'",
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conf.Target)
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}
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}
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@ -0,0 +1,99 @@
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package resource
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import (
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"errors"
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"testing"
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"time"
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)
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func FailedStateRefreshFunc() StateRefreshFunc {
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return func() (interface{}, string, error) {
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return nil, "", errors.New("failed")
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}
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}
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func TimeoutStateRefreshFunc() StateRefreshFunc {
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return func() (interface{}, string, error) {
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time.Sleep(100 * time.Second)
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return nil, "", errors.New("failed")
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}
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}
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func SuccessfulStateRefreshFunc() StateRefreshFunc {
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return func() (interface{}, string, error) {
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return struct{}{}, "running", nil
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}
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}
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func TestWaitForState_timeout(t *testing.T) {
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conf := &StateChangeConf{
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Pending: []string{"pending", "incomplete"},
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Target: "running",
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Refresh: TimeoutStateRefreshFunc(),
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Timeout: 1 * time.Millisecond,
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}
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obj, err := conf.WaitForState()
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if err == nil && err.Error() != "timeout while waiting for state to become 'running'" {
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t.Fatalf("err: %s", err)
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}
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if obj != nil {
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t.Fatalf("should not return obj")
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}
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}
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func TestWaitForState_success(t *testing.T) {
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conf := &StateChangeConf{
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Pending: []string{"pending", "incomplete"},
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Target: "running",
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Refresh: SuccessfulStateRefreshFunc(),
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Timeout: 200 * time.Second,
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}
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obj, err := conf.WaitForState()
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if err != nil {
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t.Fatalf("err: %s", err)
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}
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if obj == nil {
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t.Fatalf("should return obj")
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}
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}
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func TestWaitForState_successEmpty(t *testing.T) {
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conf := &StateChangeConf{
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Pending: []string{"pending", "incomplete"},
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Target: "",
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Refresh: func() (interface{}, string, error) {
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return nil, "", nil
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},
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Timeout: 200 * time.Second,
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}
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obj, err := conf.WaitForState()
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if err != nil {
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t.Fatalf("err: %s", err)
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}
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if obj != nil {
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t.Fatalf("obj should be nil")
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}
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}
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func TestWaitForState_failure(t *testing.T) {
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conf := &StateChangeConf{
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Pending: []string{"pending", "incomplete"},
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Target: "running",
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Refresh: FailedStateRefreshFunc(),
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Timeout: 200 * time.Second,
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}
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obj, err := conf.WaitForState()
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if err == nil && err.Error() != "failed" {
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t.Fatalf("err: %s", err)
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}
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if obj != nil {
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t.Fatalf("should not return obj")
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}
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}
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@ -1,120 +1,31 @@
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package resource
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import (
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"errors"
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"fmt"
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"log"
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"math"
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"time"
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)
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// StateRefreshFunc is a function type used for StateChangeConf that is
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// responsible for refreshing the item being watched for a state change.
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//
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// It returns three results. `result` is any object that will be returned
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// as the final object after waiting for state change. This allows you to
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// return the final updated object, for example an EC2 instance after refreshing
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// it.
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//
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// `state` is the latest state of that object. And `err` is any error that
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// may have happened while refreshing the state.
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type StateRefreshFunc func() (result interface{}, state string, err error)
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// RetryFunc is the function retried until it succeeds.
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type RetryFunc func() error
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// StateChangeConf is the configuration struct used for `WaitForState`.
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type StateChangeConf struct {
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Delay time.Duration // Wait this time before starting checks
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Pending []string // States that are "allowed" and will continue trying
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Refresh StateRefreshFunc // Refreshes the current state
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Target string // Target state
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Timeout time.Duration // The amount of time to wait before timeout
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MinTimeout time.Duration // Smallest time to wait before refreshes
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}
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// WaitForState watches an object and waits for it to achieve the state
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// specified in the configuration using the specified Refresh() func,
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// waiting the number of seconds specified in the timeout configuration.
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func (conf *StateChangeConf) WaitForState() (interface{}, error) {
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log.Printf("[DEBUG] Waiting for state to become: %s", conf.Target)
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notfoundTick := 0
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var result interface{}
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var resulterr error
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doneCh := make(chan struct{})
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go func() {
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defer close(doneCh)
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// Wait for the delay
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time.Sleep(conf.Delay)
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var err error
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for tries := 0; ; tries++ {
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// Wait between refreshes using an exponential backoff
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wait := time.Duration(math.Pow(2, float64(tries))) *
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100 * time.Millisecond
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if wait < conf.MinTimeout {
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wait = conf.MinTimeout
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} else if wait > 10*time.Second {
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wait = 10 * time.Second
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}
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log.Printf("[TRACE] Waiting %s before next try", wait)
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time.Sleep(wait)
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var currentState string
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result, currentState, err = conf.Refresh()
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// Retry is a basic wrapper around StateChangeConf that will just retry
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// a function until it no longer returns an error.
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func Retry(timeout time.Duration, f RetryFunc) error {
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var err error
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c := &StateChangeConf{
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Pending: []string{"error"},
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Target: "success",
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Timeout: timeout,
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MinTimeout: 500 * time.Millisecond,
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Refresh: func() (interface{}, string, error) {
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err = f()
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if err != nil {
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resulterr = err
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return
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return 42, "error", nil
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}
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// If we're waiting for the absence of a thing, then return
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if result == nil && conf.Target == "" {
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return
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}
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if result == nil {
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// If we didn't find the resource, check if we have been
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// not finding it for awhile, and if so, report an error.
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notfoundTick += 1
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if notfoundTick > 20 {
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resulterr = errors.New("couldn't find resource")
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return
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}
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} else {
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// Reset the counter for when a resource isn't found
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notfoundTick = 0
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if currentState == conf.Target {
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return
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}
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found := false
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for _, allowed := range conf.Pending {
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if currentState == allowed {
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found = true
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break
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}
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}
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if !found {
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resulterr = fmt.Errorf(
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"unexpected state '%s', wanted target '%s'",
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currentState,
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conf.Target)
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return
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}
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}
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}
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}()
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select {
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case <-doneCh:
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return result, resulterr
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case <-time.After(conf.Timeout):
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return nil, fmt.Errorf(
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"timeout while waiting for state to become '%s'",
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conf.Target)
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return 42, "success", nil
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},
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}
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c.WaitForState()
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return err
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}
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@ -1,99 +1,39 @@
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package resource
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import (
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"errors"
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"fmt"
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"testing"
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"time"
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)
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func FailedStateRefreshFunc() StateRefreshFunc {
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return func() (interface{}, string, error) {
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return nil, "", errors.New("failed")
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}
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}
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func TestRetry(t *testing.T) {
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t.Parallel()
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func TimeoutStateRefreshFunc() StateRefreshFunc {
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return func() (interface{}, string, error) {
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time.Sleep(100 * time.Second)
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return nil, "", errors.New("failed")
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}
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}
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tries := 0
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f := func() error {
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tries++
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if tries == 1 {
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return nil
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}
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func SuccessfulStateRefreshFunc() StateRefreshFunc {
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return func() (interface{}, string, error) {
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return struct{}{}, "running", nil
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}
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}
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func TestWaitForState_timeout(t *testing.T) {
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conf := &StateChangeConf{
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Pending: []string{"pending", "incomplete"},
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Target: "running",
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Refresh: TimeoutStateRefreshFunc(),
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Timeout: 1 * time.Millisecond,
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return fmt.Errorf("error")
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}
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obj, err := conf.WaitForState()
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if err == nil && err.Error() != "timeout while waiting for state to become 'running'" {
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t.Fatalf("err: %s", err)
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}
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if obj != nil {
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t.Fatalf("should not return obj")
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}
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}
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func TestWaitForState_success(t *testing.T) {
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conf := &StateChangeConf{
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Pending: []string{"pending", "incomplete"},
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Target: "running",
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Refresh: SuccessfulStateRefreshFunc(),
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Timeout: 200 * time.Second,
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}
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obj, err := conf.WaitForState()
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err := Retry(2 * time.Second, f)
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if err != nil {
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t.Fatalf("err: %s", err)
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}
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if obj == nil {
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t.Fatalf("should return obj")
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}
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}
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func TestWaitForState_successEmpty(t *testing.T) {
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conf := &StateChangeConf{
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Pending: []string{"pending", "incomplete"},
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Target: "",
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Refresh: func() (interface{}, string, error) {
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return nil, "", nil
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},
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Timeout: 200 * time.Second,
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func TestRetry_timeout(t *testing.T) {
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t.Parallel()
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f := func() error {
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return fmt.Errorf("always")
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}
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obj, err := conf.WaitForState()
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if err != nil {
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t.Fatalf("err: %s", err)
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}
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if obj != nil {
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t.Fatalf("obj should be nil")
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}
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}
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func TestWaitForState_failure(t *testing.T) {
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conf := &StateChangeConf{
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Pending: []string{"pending", "incomplete"},
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Target: "running",
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Refresh: FailedStateRefreshFunc(),
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Timeout: 200 * time.Second,
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}
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obj, err := conf.WaitForState()
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if err == nil && err.Error() != "failed" {
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t.Fatalf("err: %s", err)
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}
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if obj != nil {
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t.Fatalf("should not return obj")
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err := Retry(1 * time.Second, f)
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if err == nil {
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t.Fatal("should error")
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}
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}
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