kl0u commented on a change in pull request #6532: [FLINK-10109] Add 
documentation for StreamingFileSink
URL: https://github.com/apache/flink/pull/6532#discussion_r209176266
 
 

 ##########
 File path: docs/dev/connectors/streamfile_sink.md
 ##########
 @@ -0,0 +1,120 @@
+---
+title: "Streaming File Sink"
+nav-title: Streaming File Sink
+nav-parent_id: connectors
+nav-pos: 5
+---
+<!--
+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.
+-->
+
+This connector provides a Sink that writes partitioned files to filesystems
+supported by the Flink `FileSystem` abstraction. Since in streaming the input
+is potentially infinite, the streaming file sink writes data into buckets. The
+bucketing behaviour is configurable but a useful default is time-based
+bucketing where we start writing a new bucket every hour and thus get
+individual files that each contain a part of the infinite output stream.
+
+Within a bucket, we further split the output into smaller part files based on a
+rolling policy. This is useful to prevent individual bucket files from getting
+too big. This is also configurable but the default policy rolls files based on
+file size and a timeout, i.e if no new data was written to a part file. 
+
+#### Usage
+
+The only required configuration are the base path were we want to output our
+data and an
+[Encoder](http://flink.apache.org/docs/latest/api/java/org/apache/flink/api/common/serialization/Encoder.html)
+that is used for serializing records to the `OutputStream` for each file.
+
+Basic usage thus looks like this:
+
+
+<div class="codetabs" markdown="1">
+<div data-lang="java" markdown="1">
+{% highlight java %}
+import org.apache.flink.api.common.serialization.Encoder;
+import org.apache.flink.core.fs.Path;
+import 
org.apache.flink.streaming.api.functions.sink.filesystem.StreamingFileSink;
+
+DataStream<String> input = ...;
+
+final StreamingFileSink<String> sink = StreamingFileSink
+       .forRowFormat(new Path(outputPath), (Encoder<String>) (element, stream) 
-> {
+               PrintStream out = new PrintStream(stream);
+               out.println(element.f1);
+       })
+       .build();
+
+input.addSink(sink);
+
+{% endhighlight %}
+</div>
+<div data-lang="scala" markdown="1">
+{% highlight scala %}
+import org.apache.flink.api.common.serialization.Encoder
+import org.apache.flink.core.fs.Path
+import 
org.apache.flink.streaming.api.functions.sink.filesystem.StreamingFileSink
+
+val input: DataStream[String] = ...
+
+final StreamingFileSink[String] sink = StreamingFileSink
+       .forRowFormat(new Path(outputPath), (element, stream) => {
+               val out = new PrintStream(stream)
+               out.println(element.f1)
+       })
+       .build()
+
+input.addSink(sink)
+
+{% endhighlight %}
+</div>
+</div>
+
+This will create a streaming sink that creates hourly buckets and uses a
+default rolling policy. The default bucket assigner is
+[DateTimeBucketAssigner](http://flink.apache.org/docs/latest/api/java/org/apache/flink/streaming/api/functions/sink/filesystem/bucketassigners/DateTimeBucketAssigner.html)
+and the default rolling policy is
+[DefaultRollingPolicy](http://flink.apache.org/docs/latest/api/java/org/apache/flink/streaming/api/functions/sink/filesystem/rollingpolicies/DefaultRollingPolicy.html).
+You can specify a custom
+[BucketAssigner](http://flink.apache.org/docs/latest/api/java/org/apache/flink/streaming/api/functions/sink/filesystem/BucketAssigner.html)
+and
+[RollingPolicy](http://flink.apache.org/docs/latest/api/java/org/apache/flink/streaming/api/functions/sink/filesystem/RollingPolicy.html)
+on the sink builder. Please check out the JavaDoc for
+[StreamingFileSink](http://flink.apache.org/docs/latest/api/java/org/apache/flink/streaming/api/functions/sink/filesystem/StreamingFileSink.html)
+for more configuration options and more documentation about the workings and
+interactions of bucket assigners and rolling policies.
+
+#### Using Bulk-encoded Output Formats
+
+In the above example we used an `Encoder` that can encode or serialize each
+record individually. The streaming file sink also supports bulk-encoded output
+formats such as [Apache Parquet](http://parquet.apache.org). To use these,
+instead of `StreamingFileSink.forRowFormat()` you would use
+`StreamingFileSink.forBulkFormat()` and specify a `BulkWriter.Factory`.
+
+[ParquetAvroWriters](http://flink.apache.org/docs/latest/api/java/org/apache/flink/formats/parquet/avro/ParquetAvroWriters.html)
+has static methods for creating a `BulkWriter.Factory` for various types.
+
+<div class="alert alert-info">
+  <strong>Note:</strong> With Bulk Writers, only the
+  <code>OnCheckpointRollingPolicy</code>, which rolls the part file on every
+  checkpoint, is supported.
+</div>
+
 
 Review comment:
   And this:
   
   ```
   <b>IMPORTANT:</b> Bulk-encoding formats can only be combined with the
   `OnCheckpointRollingPolicy`, which rolls the in-progress part file on
   every checkpoint.
   ```

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