Merge pull request kubernetes#11395 from akutz/feature/boskos-acquire…

…-wait

boskos-client: AcquireWait/AcquireByStateWait

boskos/client/README.md

@@ -12,13 +12,22 @@ The client object looks like:
 
 ```
 type Client struct {
+	// RetryCount is the number of times an HTTP request issued by this client
+	// is retried when the initial request fails due an inaccessible endpoint.
+	RetryCount uint
+
+	// RetryDuration is the interval to wait before retrying an HTTP operation
+	// that failed due to an inaccessible endpoint.
+	RetryWait time.Duration
+
 	url       string
 	resources []string
 	owner     string
 }
 ```
 
-To create a boskos client, use NewClient func, specify boskos server url, and owner of the client:
+To create a boskos client, use `NewClient` and specify the Boskos endpoint URL and resource owner.
+The `NewClient` function also sets the client's `RetryCount` to `3` and `RetryWait` interval to `10s`.
 ```
 func NewClient(url string, owner string) *Client
 ```
@@ -30,6 +39,18 @@ func NewClient(url string, owner string) *Client
 // Acquire asks boskos for a resource of certain type in certain state, and set the resource to dest state.
 func (c *Client) Acquire(rtype string, state string, dest string) (string, error)
 
+// AcquireWait blocks until Acquire returns the specified resource or the
+// provided context is cancelled or its deadline exceeded.
+func (c *Client) AcquireWait(rtype string, state string, dest string) (string, error)
+
+// AcquireByState asks boskos for a resources of certain type, and set the resource to dest state.
+// Returns a list of resources on success.
+func (c *Client) AcquireByState(state, dest string, names []string) ([]common.Resource, error)
+
+// AcquireByStateWait blocks until AcquireByState returns the specified
+// resource(s) or the provided context is cancelled or its deadline exceeded.
+func (c *Client) AcquireByStateWait(ctx context.Context, state, dest string, names []string) ([]common.Resource, error)
+
 // ReleaseAll returns all resources hold by the client back to boskos and set them to dest state.
 func (c *Client) ReleaseAll(dest string) error
 

boskos/client/client.go

@@ -44,6 +44,9 @@ var (
 	ErrNotFound = errors.New("resources not found")
 	// ErrAlreadyInUse is returned by Acquire when resources are already being requested.
 	ErrAlreadyInUse = errors.New("resources already used by another user")
+	// ErrContextRequired is returned by AcquireWait and AcquireByStateWait when
+	// they are invoked with a nil context.
+	ErrContextRequired = errors.New("context required")
 )
 
 // Client defines the public Boskos client object
@@ -120,6 +123,31 @@ func (c *Client) Acquire(rtype, state, dest string) (*common.Resource, error) {
 	return r, nil
 }
 
+// AcquireWait blocks until Acquire returns the specified resource or the
+// provided context is cancelled or its deadline exceeded.
+func (c *Client) AcquireWait(ctx context.Context, rtype, state, dest string) (*common.Resource, error) {
+	if ctx == nil {
+		return nil, ErrContextRequired
+	}
+	// Try to acquire the resource until available or the context is
+	// cancelled or its deadline exceeded.
+	for {
+		r, err := c.Acquire(rtype, state, dest)
+		if err != nil {
+			if err == ErrAlreadyInUse || err == ErrNotFound {
+				select {
+				case <-ctx.Done():
+					return nil, err
+				case <-time.After(3 * time.Second):
+					continue
+				}
+			}
+			return nil, err
+		}
+		return r, nil
+	}
+}
+
 // AcquireByState asks boskos for a resources of certain type, and set the resource to dest state.
 // Returns a list of resources on success.
 func (c *Client) AcquireByState(state, dest string, names []string) ([]common.Resource, error) {
@@ -135,6 +163,32 @@ func (c *Client) AcquireByState(state, dest string, names []string) ([]common.Re
 	return resources, nil
 }
 
+// AcquireByStateWait blocks until AcquireByState returns the specified
+// resource(s) or the provided context is cancelled or its deadline
+// exceeded.
+func (c *Client) AcquireByStateWait(ctx context.Context, state, dest string, names []string) ([]common.Resource, error) {
+	if ctx == nil {
+		return nil, ErrContextRequired
+	}
+	// Try to acquire the resource(s) until available or the context is
+	// cancelled or its deadline exceeded.
+	for {
+		r, err := c.AcquireByState(state, dest, names)
+		if err != nil {
+			if err == ErrAlreadyInUse || err == ErrNotFound {
+				select {
+				case <-ctx.Done():
+					return nil, err
+				case <-time.After(3 * time.Second):
+					continue
+				}
+			}
+			return nil, err
+		}
+		return r, nil
+	}
+}
+
 // ReleaseAll returns all resources hold by the client back to boskos and set them to dest state.
 func (c *Client) ReleaseAll(dest string) error {
 	c.lock.Lock()
@@ -286,7 +340,8 @@ func (c *Client) acquire(rtype, state, dest string) (*common.Resource, error) {
 	}
 	defer resp.Body.Close()
 
-	if resp.StatusCode == http.StatusOK {
+	switch resp.StatusCode {
+	case http.StatusOK:
 		body, err := ioutil.ReadAll(resp.Body)
 		if err != nil {
 			return nil, err
@@ -301,7 +356,9 @@ func (c *Client) acquire(rtype, state, dest string) (*common.Resource, error) {
 			return nil, fmt.Errorf("unable to parse resource")
 		}
 		return &res, nil
-	} else if resp.StatusCode == http.StatusNotFound {
+	case http.StatusUnauthorized:
+		return nil, ErrAlreadyInUse
+	case http.StatusNotFound:
 		return nil, ErrNotFound
 	}
 	return nil, fmt.Errorf("status %s, status code %v", resp.Status, resp.StatusCode)