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From "Tzu-Li (Gordon) Tai" <tzuli...@apache.org>
Subject Re: BucketingSink never closed
Date Wed, 13 Sep 2017 08:56:02 GMT
Hi Flavio,

Let me try to understand / look at some of the problems you have encountered.
checkpointing: it's not clear which checkpointing system to use and how to tune/monitor it
and avoid OOM exceptions.
What do you mean be which "checkpointing system” to use? Do you mean state backends? Typically,
you would only get OOM exceptions for memory-backed state backends if the state size exceeds
the memory capacity. State sizes can be queried from the REST APIs / Web UI.
cleanup: BucketingSink doesn't always move to final state
This sounds like a bug that we should look into. Do you have any logs on which you observed
this?

missing output formats: parquet support to write generic Rows not very well supported (at
least out of the box) [1]
Would you be up to opening up JIRAs for what you think is missing (if there isn’t one already)?

progress monitoring: for example in the ES connector there's no way (apart from using accumulators)
to monitor the progress of the indexing
Maybe we can add some built-in metric in the ES sink connector that tracks the number of successfully
indexed elements, which can then be queried from the REST API / Web UI. That wouldn’t be
too much effort. What do you think, would that be useful for your case?

Would be happy to hear your thoughts on this!

Cheers,
Gordon


On 12 September 2017 at 11:36:27 AM, Flavio Pompermaier (pompermaier@okkam.it) wrote:

For the moment I give up with streaming...too many missing/unclear features wrt batch. 
For example:
checkpointing: it's not clear which checkpointing system to use and how to tune/monitor it
and avoid OOM exceptions. Moreover is it really necessary to use it? For example if I read
a file from HDFS and I don't have a checkpoint it could be ok to re-run the job on all the
data in case of errors (i.e. the stream is managed like a batch)
cleanup: BucketingSink doesn't always move to final state
missing output formats: parquet support to write generic Rows not very well supported (at
least out of the box) [1]
progress monitoring: for example in the ES connector there's no way (apart from using accumulators)
to monitor the progress of the indexing
[1] https://stackoverflow.com/questions/41144659/flink-avro-parquet-writer-in-rollingsink

Maybe I'm wrong with those points but the attempt to replace my current batch system with
a streaming one had no luck with those points.

Best,
Flavio

On Fri, Sep 8, 2017 at 5:29 PM, Aljoscha Krettek <aljoscha@apache.org> wrote:
Hi,

Expanding a bit on Kostas' answer. Yes, your analysis is correct, the problem is that the
job is shutting down before a last checkpoint can "confirm" the written bucket data by moving
it to the final state. The problem, as Kostas noted is that a user function (and thus also
BucketingSink) does not know whether close() is being called because of a failure or because
normal job shutdown. Therefore, we cannot move data to the final stage there.

Once we have the issue that Kostas posted resolve we can also resolve this problem for the
BucketingSink.

Best,
Aljoscha

On 8. Sep 2017, at 16:48, Kostas Kloudas <k.kloudas@data-artisans.com> wrote:

Hi Flavio,

If I understand correctly, I think you bumped into this issue: https://issues.apache.org/jira/browse/FLINK-2646

There is also a similar discussion on the BucketingSink here: 
http://apache-flink-mailing-list-archive.1008284.n3.nabble.com/DISCUSS-Adding-a-dispose-method-in-the-RichFunction-td14466.html#a14468

Kostas

On Sep 8, 2017, at 4:27 PM, Flavio Pompermaier <pompermaier@okkam.it> wrote:

Hi to all,
I'm trying to test a streaming job but the files written by the BucketingSink are never finalized
(remains into the pending state).
Is this caused by the fact that the job finishes before the checkpoint?
Shouldn't the sink properly close anyway?

This is my code:

  @Test
  public void testBucketingSink() throws Exception {
    final StreamExecutionEnvironment senv = StreamExecutionEnvironment.getExecutionEnvironment();
    final StreamTableEnvironment tEnv = TableEnvironment.getTableEnvironment(senv);
    senv.enableCheckpointing(5000);
    DataStream<String> testStream = senv.fromElements(//
        "1,aaa,white", //
        "2,bbb,gray", //
        "3,ccc,white", //
        "4,bbb,gray", //
        "5,bbb,gray" //
    );
    final RowTypeInfo rtf = new RowTypeInfo(
        BasicTypeInfo.STRING_TYPE_INFO,
        BasicTypeInfo.STRING_TYPE_INFO, 
        BasicTypeInfo.STRING_TYPE_INFO);
    DataStream<Row> rows = testStream.map(new MapFunction<String, Row>() {

      private static final long serialVersionUID = 1L;

      @Override
      public Row map(String str) throws Exception {
        String[] split = str.split(Pattern.quote(","));
        Row ret = new Row(3);
        ret.setField(0, split[0]);
        ret.setField(1, split[1]);
        ret.setField(2, split[2]);
        return ret;
      }
    }).returns(rtf);

    String columnNames = "id,value,state";
    final String dsName = "test";
    tEnv.registerDataStream(dsName, rows, columnNames);
    final String whiteAreaFilter = "state = 'white'";
    DataStream<Row> grayArea = rows;
    DataStream<Row> whiteArea = null;
    if (whiteAreaFilter != null) {
      String sql = "SELECT *, (%s) as _WHITE FROM %s";
      sql = String.format(sql, whiteAreaFilter, dsName);
      Table table = tEnv.sql(sql);
      grayArea = tEnv.toDataStream(table.where("!_WHITE").select(columnNames), rtf);
      DataStream<Row> nw = tEnv.toDataStream(table.where("_WHITE").select(columnNames),
rtf);
      whiteArea = whiteArea == null ? nw : whiteArea.union(nw);
    }
    Writer<Row> bucketSinkwriter = new RowCsvWriter("UTF-8", "\t", "\n");

    String datasetWhiteDir = "/tmp/bucket/white";
    BucketingSink<Row> whiteAreaSink = new BucketingSink<>(datasetWhiteDir.toString());
    whiteAreaSink.setWriter(bucketSinkwriter);
    whiteAreaSink.setBatchSize(10);
    whiteArea.addSink(whiteAreaSink);

    String datasetGrayDir = "/tmp/bucket/gray";
    BucketingSink<Row> grayAreaSink = new BucketingSink<>(datasetGrayDir.toString());
    grayAreaSink.setWriter(bucketSinkwriter);
    grayAreaSink.setBatchSize(10);
    grayArea.addSink(grayAreaSink);

    JobExecutionResult jobInfo = senv.execute("Buketing sink test ");
    System.out.printf("Job took %s minutes", jobInfo.getNetRuntime(TimeUnit.MINUTES));
  }







public class RowCsvWriter extends StreamWriterBase<Row> {
  private static final long serialVersionUID = 1L;

  private final String charsetName;
  private transient Charset charset;
  private String fieldDelimiter;
  private String recordDelimiter;
  private boolean allowNullValues = true;
  private boolean quoteStrings = false;

  /**
   * Creates a new {@code StringWriter} that uses {@code "UTF-8"} charset to convert strings
to
   * bytes.
   */
  public RowCsvWriter() {
    this("UTF-8", CsvOutputFormat.DEFAULT_FIELD_DELIMITER, CsvOutputFormat.DEFAULT_LINE_DELIMITER);
  }

  /**
   * Creates a new {@code StringWriter} that uses the given charset to convert strings to
bytes.
   *
   * @param charsetName Name of the charset to be used, must be valid input for
   *        {@code Charset.forName(charsetName)}
   */
  public RowCsvWriter(String charsetName, String fieldDelimiter, String recordDelimiter)
{
    this.charsetName = charsetName;
    this.fieldDelimiter = fieldDelimiter;
    this.recordDelimiter = recordDelimiter;
  }

  @Override
  public void open(FileSystem fs, Path path) throws IOException {
    super.open(fs, path);

    try {
      this.charset = Charset.forName(charsetName);
    } catch (IllegalCharsetNameException ex) {
      throw new IOException("The charset " + charsetName + " is not valid.", ex);
    } catch (UnsupportedCharsetException ex) {
      throw new IOException("The charset " + charsetName + " is not supported.", ex);
    }
  }

  @Override
  public void write(Row element) throws IOException {
    FSDataOutputStream outputStream = getStream();
    writeRow(element, outputStream);
  }

  private void writeRow(Row element, FSDataOutputStream out) throws IOException {
    int numFields = element.getArity();

    for (int i = 0; i < numFields; i++) {
      Object obj = element.getField(i);
      if (obj != null) {
        if (i != 0) {
          out.write(this.fieldDelimiter.getBytes(charset));
        }

        if (quoteStrings) {
          if (obj instanceof String || obj instanceof StringValue) {
            out.write('"');
            out.write(obj.toString().getBytes(charset));
            out.write('"');
          } else {
            out.write(obj.toString().getBytes(charset));
          }
        } else {
          out.write(obj.toString().getBytes(charset));
        }
      } else {
        if (this.allowNullValues) {
          if (i != 0) {
            out.write(this.fieldDelimiter.getBytes(charset));
          }
        } else {
          throw new RuntimeException("Cannot write tuple with <null> value at position:
" + i);
        }
      }
    }

    // add the record delimiter
    out.write(this.recordDelimiter.getBytes(charset));
  }

  @Override
  public Writer<Row> duplicate() {
    return new RowCsvWriter(charsetName, fieldDelimiter, recordDelimiter);
  }
}



Any help is appreciated,
Flavio




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