Github user tdas commented on a diff in the pull request:
https://github.com/apache/spark/pull/17246#discussion_r106722120
--- Diff: docs/structured-streaming-kafka-integration.md ---
@@ -373,11 +375,204 @@ The following configurations are optional:
</tr>
</table>
+## Producing Data to Kafka
+
+### Writing Streaming Queries to Kafka
+
+<div class="codetabs">
+<div data-lang="scala" markdown="1">
+{% highlight scala %}
+
+// Write key-value data from a DataFrame to a specific Kafka topic
specified in an option
+val s1 = df1
+ .selectExpr("CAST(key AS STRING)", "CAST(value AS STRING)")
+ .writeStream
+ .format("kafka")
+ .option("kafka.bootstrap.servers", "host1:port1,host2:port2")
+ .option("topic", "topic1")
+ .start()
+
+// Write key-value data from a DataFrame to Kafka using a topic specified
in the data
+val s2 = df2
+ .selectExpr("topic", "CAST(key AS STRING)", "CAST(value AS STRING)")
+ .writeStream
+ .format("kafka")
+ .option("kafka.bootstrap.servers", "host1:port1,host2:port2")
+ .start()
+
+{% endhighlight %}
+</div>
+<div data-lang="java" markdown="1">
+{% highlight java %}
+
+// Write key-value data from a DataFrame to a specific Kafka topic
specified in an option
+StreamingQuery s1 = df1
+ .selectExpr("CAST(key AS STRING)", "CAST(value AS STRING)")
+ .writeStream()
+ .format("kafka")
+ .option("kafka.bootstrap.servers", "host1:port1,host2:port2")
+ .option("topic", "topic1")
+ .start()
+
+// Write key-value data from a DataFrame to Kafka using a topic specified
in the data
+StreamingQuery s2 = df1
+ .selectExpr("topic", "CAST(key AS STRING)", "CAST(value AS STRING)")
+ .writeStream()
+ .format("kafka")
+ .option("kafka.bootstrap.servers", "host1:port1,host2:port2")
+ .start()
+
+{% endhighlight %}
+</div>
+<div data-lang="python" markdown="1">
+{% highlight python %}
+
+# Write key-value data from a DataFrame to a specific Kafka topic
specified in an option
+s1 = df1 \
+ .selectExpr("CAST(key AS STRING)", "CAST(value AS STRING)") \
+ .writeStream \
+ .format("kafka") \
+ .option("kafka.bootstrap.servers", "host1:port1,host2:port2") \
+ .option("topic", "topic1") \
+ .start()
+
+# Write key-value data from a DataFrame to Kafka using a topic specified
in the data
+s2 = df2 \
+ .selectExpr("topic", "CAST(key AS STRING)", "CAST(value AS STRING)") \
+ .writeStream \
+ .format("kafka") \
+ .option("kafka.bootstrap.servers", "host1:port1,host2:port2") \
+ .start()
+
+{% endhighlight %}
+</div>
+</div>
+
+### Writing Batch Queries to Kafka
+
+<div class="codetabs">
+<div data-lang="scala" markdown="1">
+{% highlight scala %}
+
+// Write key-value data from a DataFrame to a specific Kafka topic
specified in an option
+df1.selectExpr("CAST(key AS STRING)", "CAST(value AS STRING)")
+ .write
+ .format("kafka")
+ .option("kafka.bootstrap.servers", "host1:port1,host2:port2")
+ .option("topic", "topic1")
+ .save()
+
+// Write key-value data from a DataFrame to Kafka using a topic specified
in the data
+df2.selectExpr("topic", "CAST(key AS STRING)", "CAST(value AS STRING)")
+ .write
+ .format("kafka")
+ .option("kafka.bootstrap.servers", "host1:port1,host2:port2")
+ .save()
+
+{% endhighlight %}
+</div>
+<div data-lang="java" markdown="1">
+{% highlight java %}
+
+// Write key-value data from a DataFrame to a specific Kafka topic
specified in an option
+df1.selectExpr("CAST(key AS STRING)", "CAST(value AS STRING)")
+ .write()
+ .format("kafka")
+ .option("kafka.bootstrap.servers", "host1:port1,host2:port2")
+ .option("topic", "topic1")
+ .save()
+
+// Write key-value data from a DataFrame to Kafka using a topic specified
in the data
+df1.selectExpr("topic", "CAST(key AS STRING)", "CAST(value AS STRING)")
+ .write()
+ .format("kafka")
+ .option("kafka.bootstrap.servers", "host1:port1,host2:port2")
+ .save()
+
+{% endhighlight %}
+</div>
+<div data-lang="python" markdown="1">
+{% highlight python %}
+
+# Write key-value data from a DataFrame to a specific Kafka topic
specified in an option
+df1.selectExpr("CAST(key AS STRING)", "CAST(value AS STRING)") \
+ .write \
+ .format("kafka") \
+ .option("kafka.bootstrap.servers", "host1:port1,host2:port2") \
+ .option("topic", "topic1") \
+ .save()
+
+# Write key-value data from a DataFrame to Kafka using a topic specified
in the data
+df2.selectExpr("topic", "CAST(key AS STRING)", "CAST(value AS STRING)") \
+ .write \
+ .format("kafka") \
+ .option("kafka.bootstrap.servers", "host1:port1,host2:port2") \
+ .save()
+
+{% endhighlight %}
+</div>
+</div>
+
+Each row being written to Kafka has the following schema:
+<table class="table">
+<tr><th>Column</th><th>Type</th></tr>
+<tr>
+ <td>key (optional)</td>
+ <td>string or binary</td>
+</tr>
+<tr>
+ <td>value (required)</td>
+ <td>string or binary</td>
+</tr>
+<tr>
+ <td>topic (*optional)</td>
+ <td>string</td>
+</tr>
+</table>
+\* The topic column is required if the "topic" configuration option is not
specified.<br>
+
+The value column is the only required option. If a key column is not
specified then
+a ```null``` valued key column will be automatically added (see Kafka
semantics on
+how ```null``` valued key values are handled). If a topic column exists
then its value
+is used as the topic when writing the given row to Kafka, unless the
"topic" configuration
+option is set i.e., the "topic" configuration option overrides the topic
column.
+
+The following options must be set for the Kafka sink
+for both batch and streaming queries.
+
+<table class="table">
+<tr><th>Option</th><th>value</th><th>meaning</th></tr>
+<tr>
+ <td>kafka.bootstrap.servers</td>
+ <td>A comma-separated list of host:port</td>
+ <td>The Kafka "bootstrap.servers" configuration.</td>
+</tr>
+</table>
+
+The following configurations are optional:
+
+<table class="table">
+<tr><th>Option</th><th>value</th><th>default</th><th>query
type</th><th>meaning</th></tr>
+<tr>
+ <td>topic</td>
+ <td>string</td>
+ <td>none</td>
+ <td>streaming and batch</td>
+ <td>Sets the topic that all rows will be written to in Kafka. This
option overrides any
+ topic column that may exist in the data.</td>
+</tr>
+</table>
+
+
+## Kafka Specific Configurations
+
Kafka's own configurations can be set via `DataStreamReader.option` with
`kafka.` prefix, e.g,
`stream.option("kafka.bootstrap.servers", "host:port")`. For possible
kafkaParams, see
--- End diff --
kafkaParams -> kafka parameters
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