lostluck commented on a change in pull request #11499:
URL: https://github.com/apache/beam/pull/11499#discussion_r414160152
##########
File path: sdks/go/examples/stringsplit/offsetrange/offsetrange.go
##########
@@ -0,0 +1,107 @@
+package offsetrange
+
+import (
+ "errors"
+ "math"
+ "reflect"
+
+ "github.com/apache/beam/sdks/go/pkg/beam"
+)
+
+func init() {
+ beam.RegisterType(reflect.TypeOf((*Tracker)(nil)))
+ beam.RegisterType(reflect.TypeOf((*Restriction)(nil)))
+}
+
+type Restriction struct {
+ Start, End int64 // Half-closed interval with boundaries [start, end).
+}
+
+// Tracker tracks a restriction that can be represented as a range of integer
values,
+// for example for byte offsets in a file, or indices in an array. Note that
this tracker makes
+// no assumptions about the positions of blocks within the range, so users
must handle validation
+// of block positions if needed.
+type Tracker struct {
+ Rest Restriction
+ Claimed int64 // Tracks the last claimed position.
+ Stopped bool // Tracks whether TryClaim has already indicated to stop
processing elements for
+ // any reason.
+ Err error
+}
+
+// NewTracker is a constructor for an Tracker given a start and end range.
+func NewTracker(rest Restriction) *Tracker {
+ return &Tracker{
+ Rest: rest,
+ Claimed: rest.Start - 1,
+ Stopped: false,
+ Err: nil,
+ }
+}
+
+// TryClaim accepts an int64 position and successfully claims it if that
position is greater than
+// the previously claimed position and less than the end of the restriction.
Note that the
+// Tracker is not considered done until a position >= tracker.end tries to be
claimed,
+// at which point this method signals to end processing.
+func (tracker *Tracker) TryClaim(rawPos interface{}) bool {
+ if tracker.Stopped == true {
+ tracker.Err = errors.New("cannot claim work after restriction
tracker returns false")
+ return false
+ }
+
+ pos := rawPos.(int64)
+
+ if pos < tracker.Rest.Start {
+ tracker.Stopped = true
+ tracker.Err = errors.New("position claimed is out of bounds of
the restriction")
+ return false
+ }
+ if pos <= tracker.Claimed {
+ tracker.Stopped = true
+ tracker.Err = errors.New("cannot claim a position lower than
the previously claimed position")
+ return false
+ }
+
+ tracker.Claimed = pos
+ if pos >= tracker.Rest.End {
+ tracker.Stopped = true
+ return false
+ }
+ return true
+}
+
+// IsDone returns true if the most recent claimed element is past the end of
the restriction.
Review comment:
Please update the method documentation to match the new semantics.
##########
File path: sdks/go/examples/stringsplit/stringsplit.go
##########
@@ -0,0 +1,230 @@
+// 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.
+
+// An example of using a Splittable DoFn in the Go SDK with a portable runner.
+//
+// The following instructions describe how to execute this example in the
+// Flink local runner.
+//
+// 1. From a command line, navigate to the top-level beam/ directory and run
+// the Flink job server:
+// ./gradlew :runners:flink:1.10:job-server:runShadow -Djob-host=localhost
-Dflink-master=local
+//
+// 2. The job server is ready to receive jobs once it outputs a log like the
+// following: `JobService started on localhost:8099`. Take note of the endpoint
+// in that log message.
+//
+// 3. While the job server is running in one command line window, create a
+// second one in the same directory and run this example with the following
+// command, using the endpoint you noted from step 2:
+// go run sdks/go/examples/stringsplit/stringsplit.go --runner=universal
--endpoint=localhost:8099
+//
+// 4. Once the pipeline is complete, the job server can be closed with ctrl+C.
+// To check the output of the pipeline, search the job server logs for the
+// phrase "StringSplit Output".
+package main
+
+import (
+ "context"
+ "flag"
+ "reflect"
+
+ "github.com/apache/beam/sdks/go/examples/stringsplit/offsetrange"
+ "github.com/apache/beam/sdks/go/pkg/beam"
+ "github.com/apache/beam/sdks/go/pkg/beam/log"
+ "github.com/apache/beam/sdks/go/pkg/beam/x/beamx"
+)
+
+func init() {
+ beam.RegisterType(reflect.TypeOf((*StringSplitFn)(nil)).Elem())
+}
+
+// StringSplitFn is a Splittable DoFn that splits strings into substrings of
the
+// specified size (for example, to be able to fit them in a small buffer).
+// See ProcessElement for more details.
+type StringSplitFn struct {
+ BufSize int64
+}
+
+// CreateInitialRestriction creates an offset range restriction for each
element
+// with the size of the restriction corresponding to the length of the string.
+func (fn *StringSplitFn) CreateInitialRestriction(s string)
offsetrange.Restriction {
+ return offsetrange.Restriction{Start: 0, End: int64(len(s))}
+}
+
+// SplitRestriction performs initial splits so that each restriction is split
+// into 5.
+func (fn *StringSplitFn) SplitRestriction(s string, rest
offsetrange.Restriction) []offsetrange.Restriction {
+ size := rest.End - rest.Start
+ splitPts := []int64{
+ rest.Start,
+ rest.Start + (size / 5),
Review comment:
Do we know if it's a mistake to have duplicated restrictions in the
returned list?
##########
File path: sdks/go/examples/stringsplit/stringsplit.go
##########
@@ -0,0 +1,249 @@
+// 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.
+
+// An example of using a Splittable DoFn in the Go SDK with a portable runner.
+//
+// The following instructions describe how to execute this example in the
+// Flink local runner.
+//
+// 1. From a command line, navigate to the top-level beam/ directory and run
+// the Flink job server:
+// ./gradlew :runners:flink:1.10:job-server:runShadow -Djob-host=localhost
-Dflink-master=local
+//
+// 2. The job server is ready to receive jobs once it outputs a log like the
+// following: `JobService started on localhost:8099`. Take note of the endpoint
+// in that log message.
+//
+// 3. While the job server is running in one command line window, create a
+// second one in the same directory and run this example with the following
+// command, using the endpoint you noted from step 2:
+// go run sdks/go/examples/stringsplit/stringsplit.go --runner=universal
--endpoint=localhost:8099
+//
+// 4. Once the pipeline is complete, the job server can be closed with ctrl+C.
+// To check the output of the pipeline, search the job server logs for the
+// phrase "StringSplit Output".
+package main
+
+import (
+ "context"
+ "flag"
+ "reflect"
+ "time"
+
+ "github.com/apache/beam/sdks/go/examples/stringsplit/offsetrange"
+ "github.com/apache/beam/sdks/go/pkg/beam"
+ "github.com/apache/beam/sdks/go/pkg/beam/log"
+ "github.com/apache/beam/sdks/go/pkg/beam/x/beamx"
+)
+
+func init() {
+ beam.RegisterType(reflect.TypeOf((*StringSplitFn)(nil)).Elem())
+ beam.RegisterType(reflect.TypeOf((*LogFn)(nil)).Elem())
+}
+
+// StringSplitFn is a Splittable DoFn that splits strings into substrings of
the
+// specified size (for example, to be able to fit them in a small buffer).
+// See ProcessElement for more details.
+type StringSplitFn struct {
+ BufSize int64
+}
+
+// CreateInitialRestriction creates an offset range restriction for each
element
+// with the size of the restriction corresponding to the length of the string.
+func (fn *StringSplitFn) CreateInitialRestriction(s string)
offsetrange.Restriction {
+ rest := offsetrange.Restriction{Start: 0, End: int64(len(s))}
+ log.Debugf(context.Background(), "StringSplit CreateInitialRestriction:
%v", rest)
+ return rest
+}
+
+// SplitRestriction performs initial splits so that each restriction is split
+// into 5.
+func (fn *StringSplitFn) SplitRestriction(s string, rest
offsetrange.Restriction) []offsetrange.Restriction {
+ size := rest.End - rest.Start
+ splitPts := []int64{
+ rest.Start,
+ rest.Start + (size / 5),
+ rest.Start + (size * 2 / 5),
+ rest.Start + (size * 3 / 5),
+ rest.Start + (size * 4 / 5),
+ rest.End,
+ }
+ var splits []offsetrange.Restriction
+ for i := 0; i < len(splitPts)-1; i++ {
+ splits = append(splits, offsetrange.Restriction{Start:
splitPts[i], End: splitPts[i+1]})
+ }
+ log.Debugf(context.Background(), "StringSplit SplitRestrictions: %v ->
%v", rest, splits)
+ return splits
+}
+
+// RestrictionSize returns the size as the difference between the restriction's
+// start and end.
+func (fn *StringSplitFn) RestrictionSize(s string, rest
offsetrange.Restriction) float64 {
+ size := float64(rest.End - rest.Start)
+ log.Debugf(context.Background(), "StringSplit RestrictionSize: %v ->
%v", rest, size)
+ return size
+}
+
+// CreateTracker creates an offset range restriction tracker out of the offset
+// range restriction.
+func (fn *StringSplitFn) CreateTracker(rest offsetrange.Restriction)
*offsetrange.Tracker {
+ return offsetrange.NewTracker(rest)
+}
+
+// ProcessElement splits a string into substrings of a specified size (set in
+// StringSplitFn.BufSize).
+//
+// Note that the substring blocks are not guaranteed to line up with the
+// restriction boundaries. ProcessElement is expected to emit any substring
+// block that begins in its restriction, even if it extends past the end of the
+// restriction.
+//
+// Example: If BufSize is 100, then a restriction of 75 to 325 should emit the
+// following substrings: [100, 200], [200, 300], [300, 400]
+func (fn *StringSplitFn) ProcessElement(rt *offsetrange.Tracker, elem string,
emit func(string)) error {
+ log.Debugf(context.Background(), "StringSplit ProcessElement: Tracker =
%v", rt)
+ i := rt.Rest.Start
+ if rem := i % fn.BufSize; rem != 0 {
+ i += fn.BufSize - rem // Skip to next multiple of BufSize.
+ }
+ strEnd := int64(len(elem))
+
+ for ok := rt.TryClaim(i); ok == true; ok = rt.TryClaim(i) {
+ if i+fn.BufSize > strEnd {
+ emit(elem[i:])
+ } else {
+ emit(elem[i : i+fn.BufSize])
+ }
+ i += fn.BufSize
+ }
+ // TODO(BEAM-9799): Remove this check once error checking is automatic.
+ if err := rt.GetError(); err != nil {
+ return err
+ }
+ return nil
Review comment:
Consider just returning rt.GetError() instead of the extra block.
Having the rt.GetError() automatically checked is feasible given we already
have the tracker pointer. We can just
```
if ge, ok := rt.(interface{GetError() error}); ok {
err := ge.GetError()
... handle error...
}
```
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