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forest.go
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forest.go
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// 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.
// forest is an example that shows that pipeline construction is normal Go
// code -- the pipeline "forest" is created recursively and uses a global
// variable -- and that a pipeline may contain non-connected parts.
//
// The pipeline generated has the shape of a forest where the output of each
// singleton leaf is flattened together over several rounds. This is most
// clearly seen via a visual representation of the pipeline, such as the one
// produced by the 'dot' runner.
//
// Running the pipeline logs "1", "2", "3", etc for each leaf in the forest.
// Note that different runners may produces different or non-deterministic
// orders.
package main
import (
"context"
"flag"
"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"
"github.com/apache/beam/sdks/go/pkg/beam/x/debug"
)
var (
n = flag.Int("count", 2, "Number of trees")
depth = flag.Int("depth", 3, "Depth of each tree")
)
func tree(s beam.Scope, depth int) beam.PCollection {
if depth <= 0 {
return leaf(s)
}
a := tree(s, depth-1)
b := tree(s, depth-1)
c := tree(s, depth-2)
return beam.Flatten(s, a, b, c)
}
var count = 0
func leaf(s beam.Scope) beam.PCollection {
count++
return beam.Create(s, count) // singleton PCollection<int>
}
func main() {
flag.Parse()
beam.Init()
ctx := context.Background()
log.Info(ctx, "Running forest")
// Build a forest of processing nodes with flatten "branches".
p := beam.NewPipeline()
s := p.Root()
for i := 0; i < *n; i++ {
t := tree(s, *depth)
debug.Print(s, t)
}
if err := beamx.Run(ctx, p); err != nil {
log.Exitf(ctx, "Failed to execute job: %v", err)
}
}