Adding autopause APIs to future (#110)

* Updating thrift definitions to add autopause for batch based update strategies.

* Adding batch calculator utility and test cases for it.

* Adding PauseUpdateMonitor which allows users to poll Aurora for information on an active Update being carried out until it enters the ROLL_FORWARD_PAUSED state.

* Tests for PauseUpdateMonitor and VariableBatchStep added to the end to end tests.

* Adding TerminalUpdateStates function which returns a slice containing all terminal states for an update. Changed signature of JobUpdateStatus from using a map for desired states to a slice. A map is no longer necessary with the new version of thrift and only adds complexity.

util.go

@@ -25,6 +25,18 @@ var TerminalStates = make(map[aurora.ScheduleStatus]bool)
 // ActiveJobUpdateStates - States a Job Update may be in where it is considered active.
 var ActiveJobUpdateStates = make(map[aurora.JobUpdateStatus]bool)
 
+// TerminalJobUpdateStates returns a slice containing all the terminal states an update may end up in.
+// This is a function in order to avoid having a slice that can be accidentally mutated.
+func TerminalUpdateStates() []aurora.JobUpdateStatus {
+	return []aurora.JobUpdateStatus{
+		aurora.JobUpdateStatus_ROLLED_FORWARD,
+		aurora.JobUpdateStatus_ROLLED_BACK,
+		aurora.JobUpdateStatus_ABORTED,
+		aurora.JobUpdateStatus_ERROR,
+		aurora.JobUpdateStatus_FAILED,
+	}
+}
+
 // AwaitingPulseJobUpdateStates - States a job update may be in where it is waiting for a pulse.
 var AwaitingPulseJobUpdateStates = make(map[aurora.JobUpdateStatus]bool)
 
@@ -87,3 +99,22 @@ func validateAuroraURL(location string) (string, error) {
 
 	return u.String(), nil
 }
+
+func calculateCurrentBatch(updatingInstances int32, batchSizes []int32) int {
+	for i, size := range batchSizes {
+		updatingInstances -= size
+		if updatingInstances <= 0 {
+			return i
+		}
+	}
+
+	// Overflow batches
+	batchCount := len(batchSizes) - 1
+	lastBatchIndex := len(batchSizes) - 1
+	batchCount += int(updatingInstances / batchSizes[lastBatchIndex])
+
+	if updatingInstances%batchSizes[lastBatchIndex] != 0 {
+		batchCount++
+	}
+	return batchCount
+}