Add transactional examples to docs

Author: dpkp

README.rst

@@ -94,6 +94,14 @@ that expose basic message attributes: topic, partition, offset, key, and value:
     for msg in consumer:
         print (msg.headers)
 
+.. code-block:: python
+
+    # Read only committed messages from transactional topic
+    consumer = KafkaConsumer(isolation_level='read_committed')
+    consumer.subscribe(['txn_topic'])
+    for msg in consumer:
+        print(msg)
+
 .. code-block:: python
 
     # Get consumer metrics
@@ -153,6 +161,21 @@ for more details.
     for i in range(1000):
         producer.send('foobar', b'msg %d' % i)
 
+.. code-block:: python
+
+    # Use transactions
+    producer = KafkaProducer(transactional_id='fizzbuzz')
+    producer.init_transactions()
+    producer.begin_transaction()
+    future = producer.send('txn_topic', value=b'yes')
+    future.get() # wait for successful produce
+    producer.commit_transaction() # commit the transaction
+
+    producer.begin_transaction()
+    future = producer.send('txn_topic', value=b'no')
+    future.get() # wait for successful produce
+    producer.abort_transaction() # abort the transaction
+
 .. code-block:: python
 
     # Include record headers. The format is list of tuples with string key

docs/index.rst

@@ -80,6 +80,26 @@ that expose basic message attributes: topic, partition, offset, key, and value:
     for msg in consumer:
         assert isinstance(msg.value, dict)
 
+.. code-block:: python
+
+    # Access record headers. The returned value is a list of tuples
+    # with str, bytes for key and value
+    for msg in consumer:
+        print (msg.headers)
+
+.. code-block:: python
+
+    # Read only committed messages from transactional topic
+    consumer = KafkaConsumer(isolation_level='read_committed')
+    consumer.subscribe(['txn_topic'])
+    for msg in consumer:
+        print(msg)
+
+.. code-block:: python
+
+    # Get consumer metrics
+    metrics = consumer.metrics()
+
 
 KafkaProducer
 *************
@@ -133,6 +153,32 @@ client. See `KafkaProducer <apidoc/KafkaProducer.html>`_ for more details.
     for i in range(1000):
         producer.send('foobar', b'msg %d' % i)
 
+.. code-block:: python
+
+    # Use transactions
+    producer = KafkaProducer(transactional_id='fizzbuzz')
+    producer.init_transactions()
+    producer.begin_transaction()
+    future = producer.send('txn_topic', value=b'yes')
+    future.get() # wait for successful produce
+    producer.commit_transaction() # commit the transaction
+
+    producer.begin_transaction()
+    future = producer.send('txn_topic', value=b'no')
+    future.get() # wait for successful produce
+    producer.abort_transaction() # abort the transaction
+
+.. code-block:: python
+
+    # Include record headers. The format is list of tuples with string key
+    # and bytes value.
+    producer.send('foobar', value=b'c29tZSB2YWx1ZQ==', headers=[('content-encoding', b'base64')])
+
+.. code-block:: python
+
+    # Get producer performance metrics
+    metrics = producer.metrics()
+
 
 Thread safety
 *************