content: /*
   * 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 org.apache.beam.sdk.testutils.metrics;
  
  import org.apache.beam.sdk.metrics.Counter;
  import org.apache.beam.sdk.metrics.Metrics;
  import org.apache.beam.sdk.transforms.DoFn;
  import org.apache.beam.sdk.values.KV;
  
  /**
   * Monitor that records the number of bytes flowing through a PCollection.
   *
   * <p>To use: apply a monitor in a desired place in the pipeline. This will capture how many bytes
   * flew through this DoFn. Such information can be then collected and written out and queried using
   * {@link org.apache.beam.sdk.testutils.metrics.MetricsReader}.
   */
  public class ByteMonitor extends DoFn<KV<byte[], byte[]>, KV<byte[], byte[]>> {
  
    private Counter totalBytes;
  
    public ByteMonitor(String namespace, String name) {
      this.totalBytes = Metrics.counter(namespace, name);
    }
  
    @ProcessElement
    public void processElement(ProcessContext c) {
      totalBytes.inc(c.element().getKey().length + c.element().getValue().length);
      c.output(c.element());
    }
  }
  