Hi Liu Bo,
If you haven't customize serializations through the configuration item
"io.serializations", the default serializer for Writable objects is
org.apache.hadoop.io.serializer.WritableSerialization.WritableSerializer. As
you said, when WritableSerializer serialize the NullWritable object, it doesn't
actually write anything. So I suspect that "(null)" you saw may be part of the
value, not the key.
Best,
Haibo
At 2019-07-27 11:43:47, "Liu Bo" <diabl...@gmail.com> wrote:
The file header says key is NullWritable:
SEQ^F!org.apache.hadoop.io.NullWritable^Yorg.apache.hadoop.io.Text^A^A)org.apache.hadoop.io.compress.SnappyCodec
Might be a hadoop -text problem?
On Sat, 27 Jul 2019 at 11:07, Liu Bo <diabl...@gmail.com> wrote:
Dear flink users,
We're trying to switch from StringWriter to SequenceFileWriter to turn on
compression. StringWriter writes value only and we want to keep that way.
AFAIK, you can use NullWritable in Hadoop writers to escape key so you only
write the values.
So I tried with NullWritable as following code:
BucketingSink<Tuple2<NullWritable, Text>> hdfsSink = new
BucketingSink("/data/cjv");
hdfsSink.setBucketer(new DateTimeBucketer<>("yyyy-MM-dd/HH", ZoneOffset.UTC));
hdfsSink.setWriter(new SequenceFileWriter<NullWritable,
Text>("org.apache.hadoop.io.compress.SnappyCodec",
SequenceFile.CompressionType.BLOCK));
hdfsSink.setBatchSize(1024 * 1024 * 250);
hdfsSink.setBatchRolloverInterval(20 * 60 * 1000);
joinedResults.map(new MapFunction<Tuple2<String, String>,
Tuple2<NullWritable, Text>>() {
@Override
public Tuple2<NullWritable, Text> map(Tuple2<String, String> value) throws
Exception {
return Tuple2.of(NullWritable.get(), new Text(value.f1));
}
}).addSink(hdfsSink).name("hdfs_sink").uid("hdfs_sink");
But out put file has key as string value (null)
eg:
(null) {"ts":1564168038,"os":"android",...}
So my question is how to escape the key completely and write value only in
SequenceFileWriter?
Your help will be much of my appreciation.
--
All the best
Liu Bo
--
All the best
Liu Bo
