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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-10109) Add documentation for StreamingFileSink
Date Tue, 14 Aug 2018 09:44:00 GMT

    [ https://issues.apache.org/jira/browse/FLINK-10109?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16579544#comment-16579544

ASF GitHub Bot commented on FLINK-10109:

aljoscha closed pull request #6532: [FLINK-10109] Add documentation for StreamingFileSink
URL: https://github.com/apache/flink/pull/6532

This is a PR merged from a forked repository.
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diff --git a/docs/dev/connectors/streamfile_sink.md b/docs/dev/connectors/streamfile_sink.md
new file mode 100644
index 00000000000..3db5577f67c
--- /dev/null
+++ b/docs/dev/connectors/streamfile_sink.md
@@ -0,0 +1,123 @@
+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
+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. 
+The `StreamingFileSink` supports both row-wise encoding formats and
+bulk-encoding formats, such as [Apache Parquet](http://parquet.apache.org).
+#### Using Row-encoded Output Formats
+The only required configuration are the base path where we want to output our
+data and an
+[Encoder]({{ site.baseurl }}/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();
+{% endhighlight %}
+<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()
+{% endhighlight %}
+This will create a streaming sink that creates hourly buckets and uses a
+default rolling policy. The default bucket assigner is
+[DateTimeBucketAssigner]({{ site.baseurl }}/api/java/org/apache/flink/streaming/api/functions/sink/filesystem/bucketassigners/DateTimeBucketAssigner.html)
+and the default rolling policy is
+[DefaultRollingPolicy]({{ site.baseurl }}/api/java/org/apache/flink/streaming/api/functions/sink/filesystem/rollingpolicies/DefaultRollingPolicy.html).
+You can specify a custom
+[BucketAssigner]({{ site.baseurl }}/api/java/org/apache/flink/streaming/api/functions/sink/filesystem/BucketAssigner.html)
+[RollingPolicy]({{ site.baseurl }}/api/java/org/apache/flink/streaming/api/functions/sink/filesystem/RollingPolicy.html)
+on the sink builder. Please check out the JavaDoc for
+[StreamingFileSink]({{ site.baseurl }}/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]({{ site.baseurl }}/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">
+    <b>IMPORTANT:</b> Bulk-encoding formats can only be combined with the
+    `OnCheckpointRollingPolicy`, which rolls the in-progress part file on
+    every checkpoint.
+{% top %}


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> Add documentation for StreamingFileSink
> ---------------------------------------
>                 Key: FLINK-10109
>                 URL: https://issues.apache.org/jira/browse/FLINK-10109
>             Project: Flink
>          Issue Type: Sub-task
>          Components: Streaming Connectors
>    Affects Versions: 1.6.0
>            Reporter: Aljoscha Krettek
>            Assignee: Aljoscha Krettek
>            Priority: Major
>              Labels: pull-request-available

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