Upgrade go-marathon to dd6cbd4.

Fixes a problem with UnreachableStrategy being available now in two
type-incompatible formats (object and string).

We also upgrade the transitive dependency
github.com/donovanhide/eventsource.

vendor/github.com/gambol99/go-marathon/client.go

@@ -150,8 +150,6 @@ type Marathon interface {
 }
 
 var (
-	// ErrInvalidResponse is thrown when marathon responds with invalid or error response
-	ErrInvalidResponse = errors.New("invalid response from Marathon")
 	// ErrMarathonDown is thrown when all the marathon endpoints are down
 	ErrMarathonDown = errors.New("all the Marathon hosts are presently down")
 	// ErrTimeoutError is thrown when the operation has timed out
@@ -190,6 +188,11 @@ type httpClient struct {
 	config Config
 }
 
+// newRequestError signals that creating a new http.Request failed
+type newRequestError struct {
+	error
+}
+
 // NewClient creates a new marathon client
 //		config:			the configuration to use
 func NewClient(config Config) (Marathon, error) {
@@ -298,8 +301,7 @@ func (r *marathonClient) apiCall(method, path string, body, result interface{})
 		if response.StatusCode >= 200 && response.StatusCode <= 299 {
 			if result != nil {
 				if err := json.Unmarshal(respBody, result); err != nil {
-					r.debugLog.Printf("apiCall(): failed to unmarshall the response from marathon, error: %s\n", err)
-					return ErrInvalidResponse
+					return fmt.Errorf("failed to unmarshal response from Marathon: %s", err)
 				}
 			}
 			return nil
@@ -317,7 +319,8 @@ func (r *marathonClient) apiCall(method, path string, body, result interface{})
 	}
 }
 
-// buildAPIRequest creates a default API request
+// buildAPIRequest creates a default API request.
+// It fails when there is no available member in the cluster anymore or when the request can not be built.
 func (r *marathonClient) buildAPIRequest(method, path string, reader io.Reader) (request *http.Request, member string, err error) {
 	// Grab a member from the cluster
 	member, err = r.hosts.getMember()
@@ -328,7 +331,7 @@ func (r *marathonClient) buildAPIRequest(method, path string, reader io.Reader)
 	// Build the HTTP request to Marathon
 	request, err = r.client.buildMarathonRequest(method, member, path, reader)
 	if err != nil {
-		return nil, member, err
+		return nil, member, newRequestError{err}
 	}
 	return request, member, nil
 }

vendor/github.com/gambol99/go-marathon/group.go

@@ -209,7 +209,9 @@ func (r *marathonClient) WaitOnGroup(name string, timeout time.Duration) error {
 func (r *marathonClient) DeleteGroup(name string, force bool) (*DeploymentID, error) {
 	version := new(DeploymentID)
 	path := fmt.Sprintf("%s/%s", marathonAPIGroups, trimRootPath(name))
-	path = buildPathWithForceParam(path, force)
+	if force {
+		path += "?force=true"
+	}
 	if err := r.apiDelete(path, nil, version); err != nil {
 		return nil, err
 	}
@@ -224,7 +226,9 @@ func (r *marathonClient) DeleteGroup(name string, force bool) (*DeploymentID, er
 func (r *marathonClient) UpdateGroup(name string, group *Group, force bool) (*DeploymentID, error) {
 	deploymentID := new(DeploymentID)
 	path := fmt.Sprintf("%s/%s", marathonAPIGroups, trimRootPath(name))
-	path = buildPathWithForceParam(path, force)
+	if force {
+		path += "?force=true"
+	}
 	if err := r.apiPut(path, group, deploymentID); err != nil {
 		return nil, err
 	}

vendor/github.com/gambol99/go-marathon/health.go

@@ -27,7 +27,7 @@ type HealthCheck struct {
 	GracePeriodSeconds     int      `json:"gracePeriodSeconds,omitempty"`
 	IntervalSeconds        int      `json:"intervalSeconds,omitempty"`
 	TimeoutSeconds         int      `json:"timeoutSeconds,omitempty"`
-	IgnoreHTTP1xx          *bool    `json:"ignoreHttp1xx,ommitempty"`
+	IgnoreHTTP1xx          *bool    `json:"ignoreHttp1xx,omitempty"`
 }
 
 // SetCommand sets the given command on the health check.

vendor/github.com/gambol99/go-marathon/subscription.go

@@ -103,7 +103,8 @@ func (r *marathonClient) registerSubscription() error {
 	case EventsTransportCallback:
 		return r.registerCallbackSubscription()
 	case EventsTransportSSE:
-		return r.registerSSESubscription()
+		r.registerSSESubscription()
+		return nil
 	default:
 		return fmt.Errorf("the events transport: %d is not supported", r.config.EventsTransport)
 	}
@@ -162,40 +163,81 @@ func (r *marathonClient) registerCallbackSubscription() error {
 	return nil
 }
 
-func (r *marathonClient) registerSSESubscription() error {
-	// Prevent multiple SSE subscriptions
+// registerSSESubscription starts a go routine that continously tries to
+// connect to the SSE stream and to process the received events. To establish
+// the connection it tries the active cluster members until no more member is
+// active. When this happens it will retry to get a connection every 5 seconds.
+func (r *marathonClient) registerSSESubscription() {
 	if r.subscribedToSSE {
-		return nil
-	}
-
-	request, _, err := r.buildAPIRequest("GET", marathonAPIEventStream, nil)
-	if err != nil {
-		return err
-	}
-
-	// Try to connect to stream, reusing the http client settings
-	stream, err := eventsource.SubscribeWith("", r.config.HTTPClient, request)
-	if err != nil {
-		return err
+		return
 	}
 
 	go func() {
 		for {
-			select {
-			case ev := <-stream.Events:
-				if err := r.handleEvent(ev.Data()); err != nil {
-					// TODO let the user handle this error instead of logging it here
-					r.debugLog.Printf("registerSSESubscription(): failed to handle event: %v\n", err)
-				}
-			case err := <-stream.Errors:
-				// TODO let the user handle this error instead of logging it here
-				r.debugLog.Printf("registerSSESubscription(): failed to receive event: %v\n", err)
+			stream, err := r.connectToSSE()
+			if err != nil {
+				r.debugLog.Printf("Error connecting SSE subscription: %s", err)
+				<-time.After(5 * time.Second)
+				continue
 			}
+
+			err = r.listenToSSE(stream)
+			stream.Close()
+			r.debugLog.Printf("Error on SSE subscription: %s", err)
 		}
 	}()
 
 	r.subscribedToSSE = true
-	return nil
+}
+
+// connectToSSE tries to establish an *eventsource.Stream to any of the Marathon cluster members, marking the
+// member as down on connection failure, until there is no more active member in the cluster.
+// Given the http request can not be built, it will panic as this case should never happen.
+func (r *marathonClient) connectToSSE() (*eventsource.Stream, error) {
+	for {
+		request, member, err := r.buildAPIRequest("GET", marathonAPIEventStream, nil)
+		if err != nil {
+			switch err.(type) {
+			case newRequestError:
+				panic(fmt.Sprintf("Requests for SSE subscriptions should never fail to be created: %s", err.Error()))
+			default:
+				return nil, err
+			}
+		}
+
+		// The event source library manipulates the HTTPClient. So we create a new one and copy
+		// its underlying fields for performance reasons. See note that at least the Transport
+		// should be reused here: https://golang.org/pkg/net/http/#Client
+		httpClient := &http.Client{
+			Transport:     r.config.HTTPClient.Transport,
+			CheckRedirect: r.config.HTTPClient.CheckRedirect,
+			Jar:           r.config.HTTPClient.Jar,
+			Timeout:       r.config.HTTPClient.Timeout,
+		}
+
+		stream, err := eventsource.SubscribeWith("", httpClient, request)
+		if err != nil {
+			r.debugLog.Printf("Error subscribing to Marathon event stream: %s", err)
+			r.hosts.markDown(member)
+			continue
+		}
+
+		return stream, nil
+	}
+}
+
+func (r *marathonClient) listenToSSE(stream *eventsource.Stream) error {
+	for {
+		select {
+		case ev := <-stream.Events:
+			if err := r.handleEvent(ev.Data()); err != nil {
+				r.debugLog.Printf("listenToSSE(): failed to handle event: %v", err)
+			}
+		case err := <-stream.Errors:
+			return err
+
+		}
+	}
 }
 
 // Subscribe adds a URL to Marathon's callback facility

vendor/github.com/gambol99/go-marathon/unreachable_strategy.go

@@ -16,12 +16,54 @@ limitations under the License.
 
 package marathon
 
+import (
+	"encoding/json"
+	"fmt"
+)
+
+const UnreachableStrategyAbsenceReasonDisabled = "disabled"
+
 // UnreachableStrategy is the unreachable strategy applied to an application.
 type UnreachableStrategy struct {
+	EnabledUnreachableStrategy
+	AbsenceReason string
+}
+
+// EnabledUnreachableStrategy covers parameters pertaining to present unreachable strategies.
+type EnabledUnreachableStrategy struct {
 	InactiveAfterSeconds *float64 `json:"inactiveAfterSeconds,omitempty"`
 	ExpungeAfterSeconds  *float64 `json:"expungeAfterSeconds,omitempty"`
 }
 
+type unreachableStrategy UnreachableStrategy
+
+// UnmarshalJSON unmarshals the given JSON into an UnreachableStrategy. It
+// populates parameters for present strategies, and otherwise only sets the
+// absence reason.
+func (us *UnreachableStrategy) UnmarshalJSON(b []byte) error {
+	var u unreachableStrategy
+	var errEnabledUS, errNonEnabledUS error
+	if errEnabledUS = json.Unmarshal(b, &u); errEnabledUS == nil {
+		*us = UnreachableStrategy(u)
+		return nil
+	}
+
+	if errNonEnabledUS = json.Unmarshal(b, &us.AbsenceReason); errNonEnabledUS == nil {
+		return nil
+	}
+
+	return fmt.Errorf("failed to unmarshal unreachable strategy: unmarshaling into enabled returned error '%s'; unmarshaling into non-enabled returned error '%s'", errEnabledUS, errNonEnabledUS)
+}
+
+// MarshalJSON marshals the unreachable strategy.
+func (us *UnreachableStrategy) MarshalJSON() ([]byte, error) {
+	if us.AbsenceReason == "" {
+		return json.Marshal(us.EnabledUnreachableStrategy)
+	}
+
+	return json.Marshal(us.AbsenceReason)
+}
+
 // SetInactiveAfterSeconds sets the period after which instance will be marked as inactive.
 func (us UnreachableStrategy) SetInactiveAfterSeconds(cap float64) UnreachableStrategy {
 	us.InactiveAfterSeconds = &cap