Github user zentol commented on a diff in the pull request:
https://github.com/apache/flink/pull/1640#discussion_r52990687
--- Diff: docs/apis/streaming/connectors/cassandra.md ---
@@ -0,0 +1,100 @@
+---
+title: "Apache Cassandra Connector"
+
+# Sub-level navigation
+sub-nav-group: streaming
+sub-nav-parent: connectors
+sub-nav-pos: 1
+sub-nav-title: Cassandra
+---
+<!--
+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 data into a
[Cassandra](https://cassandra.apache.org/) database.
+
+The Flink Cassandra sink integrates with Flink's checkpointing mechanism
to provide
+exactly-once processing semantics. To achieve that, Flink buffers incoming
records
+and commits them only when a checkpoint completes.
+
+To use this connector, add the following dependency to your project:
+
+{% highlight xml %}
+<dependency>
+ <groupId>org.apache.flink</groupId>
+ <artifactId>flink-connector-cassandra{{ site.scala_version_suffix
}}</artifactId>
+ <version>{{site.version }}</version>
+</dependency>
+{% endhighlight %}
+
+Note that the streaming connectors are currently not part of the binary
distribution. See how to link with them for cluster execution [here]({{
site.baseurl}}/apis/cluster_execution.html#linking-with-modules-not-contained-in-the-binary-distribution).
+
+#### Installing RabbitMQ
+Follow the instructions from the [Cassandra Getting Started
page](http://wiki.apache.org/cassandra/GettingStarted).
+
+#### Cassandra Sink
+
+Flink's Cassandra sink is called `CassandraExactlyOnceSink`.
+
+The constructor accepts the following arguments:
+
+1. The Host address
+2. query to create a new table to write into (optional)
+3. query to insert data the a table
+4. checkpoint committer
+
+A checkpoint committer stores additional information about completed
checkpoints
+in some resource. You can use a `CassandraCommitter` to store these in a
separate
+table in cassandra. Note that this table will NOT be cleaned up by Flink.
+
+The CassandraCommitter constructor accepts the following arguments:
+1. Host address
+2. Keyspace
+3. Table name
+
+The CassandraExactlyOnceSink is implemented as a custom operator
+instead of a sink, and as such is a bit more unwieldy than other sinks.
+
+Example:
+
+<div class="codetabs" markdown="1">
+<div data-lang="java" markdown="1">
+{% highlight java %}
+stream.transform(
+ "Cassandra Sink",
+ TypeExtractor.getForObject(new Tuple2<>("", 0)),
--- End diff --
seems like you can pass null, would have expected some sanity check to
catch that.
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