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https://issues.apache.org/jira/browse/BEAM-8292?focusedWorklogId=408534&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-408534
]
ASF GitHub Bot logged work on BEAM-8292:
----------------------------------------
Author: ASF GitHub Bot
Created on: 24/Mar/20 04:20
Start Date: 24/Mar/20 04:20
Worklog Time Spent: 10m
Work Description: youngoli commented on pull request #11197: [BEAM-8292]
Portable Reshuffle for Go SDK
URL: https://github.com/apache/beam/pull/11197#discussion_r396856077
##########
File path: sdks/go/pkg/beam/core/runtime/exec/reshuffle.go
##########
@@ -0,0 +1,170 @@
+// 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 exec
+
+import (
+ "bytes"
+ "context"
+ "fmt"
+ "io"
+ "math/rand"
+
+ "github.com/apache/beam/sdks/go/pkg/beam/core/graph/coder"
+ "github.com/apache/beam/sdks/go/pkg/beam/internal/errors"
+)
+
+// ReshuffleInput is a Node.
+type ReshuffleInput struct {
+ UID UnitID
+ SID StreamID
+ Coder *coder.Coder // Coder for the input PCollection.
+ Seed int64
+ Out Node
+
+ r *rand.Rand
+ enc ElementEncoder
+ wEnc WindowEncoder
+ b bytes.Buffer
+ // ret is a cached allocations for passing to the next Unit. Units
never modify the passed in FullValue.
+ ret FullValue
+}
+
+// ID returns the unit debug id.
+func (n *ReshuffleInput) ID() UnitID {
+ return n.UID
+}
+
+// Up initializes the value and window encoders, and the random source.
+func (n *ReshuffleInput) Up(ctx context.Context) error {
+ n.enc = MakeElementEncoder(coder.SkipW(n.Coder))
+ n.wEnc = MakeWindowEncoder(n.Coder.Window)
+ n.r = rand.New(rand.NewSource(n.Seed))
+ return nil
+}
+
+// StartBundle is a no-op.
+func (n *ReshuffleInput) StartBundle(ctx context.Context, id string, data
DataContext) error {
+ return MultiStartBundle(ctx, id, data, n.Out)
+}
+
+func (n *ReshuffleInput) ProcessElement(ctx context.Context, value *FullValue,
values ...ReStream) error {
+ n.b.Reset()
+ if err := EncodeWindowedValueHeader(n.wEnc, value.Windows,
value.Timestamp, &n.b); err != nil {
+ return err
+ }
+ if err := n.enc.Encode(value, &n.b); err != nil {
+ return errors.WithContextf(err, "encoding element %v with coder
%v", value, n.Coder)
+ }
+ n.ret = FullValue{Elm: n.r.Int(), Elm2: n.b.Bytes(), Timestamp:
value.Timestamp}
+ if err := n.Out.ProcessElement(ctx, &n.ret); err != nil {
+ return err
+ }
+ return nil
+}
+
+// FinishBundle propagates finish bundle, and clears cached state.
+func (n *ReshuffleInput) FinishBundle(ctx context.Context) error {
+ n.b = bytes.Buffer{}
+ n.ret = FullValue{}
+ return MultiFinishBundle(ctx, n.Out)
+}
+
+// Down is a no-op.
+func (n *ReshuffleInput) Down(ctx context.Context) error {
+ return nil
+}
+
+func (n *ReshuffleInput) String() string {
+ return fmt.Sprintf("ReshuffleInput[%v] Coder:%v", n.SID, n.Coder)
+}
+
+// ReshuffleOutput is a Node.
+type ReshuffleOutput struct {
+ UID UnitID
+ SID StreamID
+ Coder *coder.Coder // Coder for the receiving PCollection.
+ Out Node
+
+ b bytes.Buffer
+ dec ElementDecoder
+ wDec WindowDecoder
+ ret FullValue
+}
+
+// ID returns the unit debug id.
+func (n *ReshuffleOutput) ID() UnitID {
+ return n.UID
+}
+
+// Up initializes the value and window encoders, and the random source.
+func (n *ReshuffleOutput) Up(ctx context.Context) error {
+ n.dec = MakeElementDecoder(coder.SkipW(n.Coder))
+ n.wDec = MakeWindowDecoder(n.Coder.Window)
+ return nil
+}
+
+// StartBundle is a no-op.
+func (n *ReshuffleOutput) StartBundle(ctx context.Context, id string, data
DataContext) error {
+ return MultiStartBundle(ctx, id, data, n.Out)
+}
+
+func (n *ReshuffleOutput) ProcessElement(ctx context.Context, value
*FullValue, values ...ReStream) error {
+ // Marshal the pieces into a temporary buffer since they must be
transmitted on FnAPI as a single
+ // unit.
+ vs, err := values[0].Open()
Review comment:
It's strange to me that `values[]` can have multiple elements, but this
method ends up actually reading all the values from the first element of it.
Could you explain why that happens? Are there sometimes multiple ReStreams
representing different things?
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Issue Time Tracking
-------------------
Worklog Id: (was: 408534)
> Add a Reshuffle PTransform preventing fusion of the surrounding transforms
> --------------------------------------------------------------------------
>
> Key: BEAM-8292
> URL: https://issues.apache.org/jira/browse/BEAM-8292
> Project: Beam
> Issue Type: New Feature
> Components: sdk-go
> Reporter: John Patoch
> Assignee: Robert Burke
> Priority: Minor
> Time Spent: 2h
> Remaining Estimate: 0h
>
> Reshuffle is a PTransform that takes a PCollection<A> and shuffles the data
> to help increase parallelism.
> Reshuffle adds a temporary random key to each element, performs a
> GroupByKey, and finally removes the temporary key.
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