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// Copyright 2013 Canonical Ltd. This software is licensed under the
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// GNU Lesser General Public License version 3 (see the file COPYING).
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// Generic poller interface/methods.
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// A poller exposes two methods to query a remote server and decide when
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// the response given by the server means that the polling is finished.
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type poller interface {
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poll() (*x509Response, error)
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isDone(*x509Response, error) (bool, error)
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// performPolling calls the poll() method of the given 'poller' object every
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// 'interval' until poller.isDone() returns true.
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func performPolling(poller poller, interval time.Duration, timeout time.Duration) (*x509Response, error) {
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timeoutChannel := time.After(timeout)
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ticker := time.Tick(interval)
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// Function to do a single poll, checking for timeout. The bool returned
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// indicates if polling is finished, one way or another.
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poll := func() (bool, *x509Response, error) {
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// This may need to tolerate some transient failures, such as network
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// failures that may go away after a few retries.
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case <-timeoutChannel:
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return true, nil, fmt.Errorf("polling timed out waiting for an asynchronous operation")
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response, pollerErr := poller.poll()
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done, err := poller.isDone(response, pollerErr)
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return true, response, nil
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return false, nil, nil
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// Do an initial poll.
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done, response, err := poll()
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// Poll every interval.
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for _ = range ticker {
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done, response, err := poll()
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// This code cannot be reached but Go insists on having a return or a panic
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// statement at the end of this method. Sigh.
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panic("invalid poller state!")
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// Operation poller structs/methods.
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// performOperationPolling calls performPolling on the given arguments and converts
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// the returned object into an *Operation.
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func performOperationPolling(poller poller, interval time.Duration, timeout time.Duration) (*Operation, error) {
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response, err := performPolling(poller, interval, timeout)
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operation := Operation{}
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err = operation.Deserialize(response.Body)
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return &operation, err
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// operationPoller is an object implementing the poller interface, used to
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// poll the Window Azure server until the operation referenced by the given
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// operationID is completed.
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type operationPoller struct {
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var _ poller = &operationPoller{}
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// newOperationPoller returns a poller object associated with the given
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// management API object and the given operationID. It can track (by polling
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// the server) the status of the operation associated with the provided
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// operationID string.
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func newOperationPoller(api *ManagementAPI, operationID string) poller {
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return operationPoller{api: api, operationID: operationID}
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// Poll issues a blocking request to microsoft Azure to fetch the information
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// related to the operation associated with the poller.
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// See http://msdn.microsoft.com/en-us/library/windowsazure/ee460783.aspx
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func (poller operationPoller) poll() (*x509Response, error) {
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URI := "operations/" + poller.operationID
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return poller.api.session.get(URI, "2009-10-01")
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// IsDone returns true if the given response has a status code indicating
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// success and if the returned XML response corresponds to a valid Operation
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// with a status indicating that the operation is completed.
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func (poller operationPoller) isDone(response *x509Response, pollerError error) (bool, error) {
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// TODO: Add a timeout so that polling won't continue forever if the
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// server cannot be reached.
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if pollerError != nil {
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return true, pollerError
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if response.StatusCode >= 200 && response.StatusCode < 300 {
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operation := Operation{}
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err := operation.Deserialize(response.Body)
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status := operation.Status
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done := (status != "" && status != InProgressOperationStatus)
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removed
poller.go
