[GitHub] [beam] jrmccluskey commented on a diff in pull request #17955: Add native PubSub IO prototype to Go

[GitBox <gi...@apache.org>]

jrmccluskey commented on code in PR #17955:
URL: https://github.com/apache/beam/pull/17955#discussion_r889280034


##########
sdks/go/examples/native_wordcap/nativepubsubio/subscriptiontracker.go:
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@@ -0,0 +1,80 @@
+// Licensed to the Apache Software Foundation (ASF) under one or more
+// contributor license agreements.  See the NOTICE file distributed with
+// this work for additional information regarding copyright ownership.
+// The ASF licenses this file to You under the Apache License, Version 2.0
+// (the "License"); you may not use this file except in compliance with
+// the License.  You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package nativepubsubio
+
+import "math"
+
+// The SubscriptionRTracker maintains a single entry string to keep up with
+// the PubSub subscription being used in the NativeRead SDF.
+type SubscriptionRTracker struct {
+	Subscription string
+	Done         bool
+}
+
+// NewSubscriptionRTracker returns an RTracker wrapping the
+// provided subscription and a "Done" boolean.
+func NewSubscriptionRTracker(entry string) *SubscriptionRTracker {
+	return &SubscriptionRTracker{Subscription: entry, Done: false}
+}
+
+// TryClaim returns true iff the given position is a string and matches the underlying
+// subscription ID.
+func (s *SubscriptionRTracker) TryClaim(pos interface{}) bool {
+	posString, ok := pos.(string)
+	return ok && posString == s.Subscription
+}
+
+// TrySplit is a no-op for the StaticRTracker in the normal case and moves the subscription
+// to the residual in the checkpointing case, marking itself as done to keep the logical checks
+// around SDF data loss happy.
+func (s *SubscriptionRTracker) TrySplit(frac float64) (primary, residual interface{}, err error) {
+	if math.Abs(frac-0.000) < 0.0001 {

Review Comment:
   It's likely overkill in this case but I usually err on the side of not fully trusting floating point numbers. 



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