Github user tzulitai commented on a diff in the pull request:
https://github.com/apache/flink/pull/3964#discussion_r117913544
--- Diff: docs/dev/connectors/index.md ---
@@ -25,22 +25,54 @@ specific language governing permissions and limitations
under the License.
-->
-Connectors provide code for interfacing with various third-party systems.
+* toc
+{:toc}
-Currently these systems are supported: (Please select the respective
documentation page from the navigation on the left.)
+## Predefined Sources and Sinks
- * [Apache Kafka](https://kafka.apache.org/) (sink/source)
- * [Elasticsearch](https://elastic.co/) (sink)
- * [Hadoop FileSystem](http://hadoop.apache.org) (sink)
- * [RabbitMQ](http://www.rabbitmq.com/) (sink/source)
- * [Amazon Kinesis Streams](http://aws.amazon.com/kinesis/streams/)
(sink/source)
- * [Twitter Streaming API](https://dev.twitter.com/docs/streaming-apis)
(source)
- * [Apache NiFi](https://nifi.apache.org) (sink/source)
- * [Apache Cassandra](https://cassandra.apache.org/) (sink)
+A few basic data sources and sinks are built into Flink and are always
available.
+The [predefined data sources]({{ site.baseurll
}}/dev/datastream_api.html#data-sources) include reading from files,
directories, and sockets, and
+ingesting data from collections and iterators.
+The [predefined data sinks]({{ site.baseurl
}}/dev/datastream_api.html#data-sinks) support writing to files, to stdout and
stderr, and to sockets.
+## Bundled Connectors
+Connectors provide code for interfacing with various third-party systems.
Currently these systems are supported:
-To run an application using one of these connectors, additional third party
-components are usually required to be installed and launched, e.g. the
servers
-for the message queues. Further instructions for these can be found in the
-corresponding subsections.
+ * [Apache Kafka](kafka.html) (sink/source)
+ * [Apache Cassandra](cassandra.html) (sink)
+ * [Amazon Kinesis Streams](kinesis.html) (sink/source)
+ * [Elasticsearch](elasticsearch.html) (sink)
+ * [Hadoop FileSystem](filesystem_sink.html) (sink)
+ * [RabbitMQ](rabbitmq.html) (sink/source)
+ * [Apache NiFi](nifi.html) (sink/source)
+ * [Twitter Streaming API](twitter.html) (source)
+
+Keep in mind that to use one of these connectors in an application,
additional third party
+components are usually required, e.g. servers for the data stores or
message queues.
+Note also that while the streaming connectors listed in this section are
part of the
+Flink project and are included in source releases, they are not included
in the binary distributions.
+Further instructions can be found in the corresponding subsections.
+
+## Related Topics
+
+### Data Enrichment via Async I/O
+
+Streaming applications sometimes need to pull in data from external
services and databases
+in order to enrich their event streams.
+Flink offers an API for [Asynchronous I/O]({{ site.baseurl
}}/dev/stream/asyncio.html)
+to make it easier to do this efficiently and robustly.
+
+### Side Outputs
+
+You can always connect an input stream to as many sinks as you like, but
sometimes it is
+useful to emit additional result streams "on the side," as it were.
+[Side Outputs]({{ site.baseurl }}/dev/stream/side_output.html) allow you
to flexibily
+split and filter your datastream in a typesafe way.
+
+### Queryable State
+
+Rather than always pushing data to external data stores, it is also
possible for external applications to query Flink,
+and read from the partitioned state it manages on demand.
+In some cases this [Queryable State]({{ site.baseurl
}}/dev/stream/queryable_state.html) interface can
+eliminate what would otherwise be a bottleneck.
--- End diff --
Not sure if its just me, but it was a bit unclear to me at a first glance
what "would otherwise be a bottleneck" refers to. Perhaps move the "bottleneck"
aspect directly after "always pushing data to external data store" to make this
more clear?
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