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_test.go

@@ -63,3 +63,40 @@ func TestAuroraURLValidator(t *testing.T) {
 		assert.NoError(t, err)
 	})
 }
+
+func TestCurrentBatchCalculator(t *testing.T) {
+	t.Run("singleBatchOverflow", func(t *testing.T) {
+		curBatch := calculateCurrentBatch(10, []int32{2})
+		assert.Equal(t, 4, curBatch)
+	})
+
+	t.Run("noInstancesUpdating", func(t *testing.T) {
+		curBatch := calculateCurrentBatch(0, []int32{2})
+		assert.Equal(t, 0, curBatch)
+	})
+
+	t.Run("evenMatchSingleBatch", func(t *testing.T) {
+		curBatch := calculateCurrentBatch(2, []int32{2})
+		assert.Equal(t, 0, curBatch)
+	})
+
+	t.Run("moreInstancesThanBatches", func(t *testing.T) {
+		curBatch := calculateCurrentBatch(5, []int32{1, 2})
+		assert.Equal(t, 2, curBatch)
+	})
+
+	t.Run("moreInstancesThanBatchesDecreasing", func(t *testing.T) {
+		curBatch := calculateCurrentBatch(5, []int32{2, 1})
+		assert.Equal(t, 3, curBatch)
+	})
+
+	t.Run("unevenFit", func(t *testing.T) {
+		curBatch := calculateCurrentBatch(2, []int32{1, 2})
+		assert.Equal(t, 1, curBatch)
+	})
+
+	t.Run("halfWay", func(t *testing.T) {
+		curBatch := calculateCurrentBatch(1, []int32{1, 2})
+		assert.Equal(t, 0, curBatch)
+	})
+}