Github user HeartSaVioR commented on a diff in the pull request:
https://github.com/apache/spark/pull/23195#discussion_r238090666
--- Diff: docs/structured-streaming-kafka-integration.md ---
@@ -624,3 +624,57 @@ For experimenting on `spark-shell`, you can also use
`--packages` to add `spark-
See [Application Submission Guide](submitting-applications.html) for more
details about submitting
applications with external dependencies.
+
+## Security
+
+Kafka 0.9.0.0 introduced several features that increases security in a
cluster. For detailed
+description about these possibilities, see [Kafka security
docs](http://kafka.apache.org/documentation.html#security).
+
+It's worth noting that security is optional and turned off by default.
+
+Spark supports the following ways to authenticate against Kafka cluster:
+- **Delegation token (introduced in Kafka broker 1.1.0)**: This way the
application can be configured
+ via Spark parameters and may not need JAAS login configuration (Spark
can use Kafka's dynamic JAAS
+ configuration feature). For further information about delegation tokens,
see
+ [Kafka delegation token
docs](http://kafka.apache.org/documentation/#security_delegation_token).
+
+ The process is initiated by Spark's Kafka delegation token provider.
This is enabled by default
+ but can be turned off with `spark.security.credentials.kafka.enabled`.
When
+ `spark.kafka.bootstrap.servers` set Spark looks for authentication
information in the following
+ order and choose the first available to log in:
+ - **JAAS login configuration**
+ - **Keytab file**, such as,
+
+ ./bin/spark-submit \
+ --keytab <KEYTAB_FILE> \
+ --principal <PRINCIPAL> \
+ --conf spark.kafka.bootstrap.servers=<KAFKA_SERVERS> \
+ ...
+
+ - **Kerberos credential cache**, such as,
+
+ ./bin/spark-submit \
+ --conf spark.kafka.bootstrap.servers=<KAFKA_SERVERS> \
+ ...
+
+ Spark supports the following authentication protocols to obtain token:
+ - **SASL SSL (default)**: With `GSSAPI` mechanism Kerberos used for
authentication and SSL for encryption.
+ - **SSL**: It's leveraging a capability from SSL called 2-way
authentication. The server authenticate
+ clients through certificates. Please note 2-way authentication must be
enabled on Kafka brokers.
+ - **SASL PLAINTEXT (for testing)**: With `GSSAPI` mechanism Kerberos
used for authentication but
+ because there is no encryption it's only for testing purposes.
+
+ After delegation token successfully obtained Spark spreads it across
nodes and renews it accordingly.
--- End diff --
nit: `After obtaining delegation token successfully,` sounds more natural
for me, but just adding `,` before `Spark` would be also fine.
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