127 lines
3.4 KiB
Go
127 lines
3.4 KiB
Go
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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NotFoundChecks int // Number of times to allow not found
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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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// Set a default for times to check for not found
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if conf.NotFoundChecks == 0 {
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conf.NotFoundChecks = 20
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}
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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 > conf.NotFoundChecks {
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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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