[docs] Add KafkaDataset User Doc.

docs/KafkaDataset.md

@@ -0,0 +1,59 @@
+# KafkaDataset
+
+## 功能
+
+1. kafka dataset支持配置多partition，并按时序消费kafka 消息
+1. kafka dataset支持保存/恢复状态信息
+
+## 接口介绍
+
+### API说明
+
+```python
+class KafkaDataset(dataset_ops.Dataset):
+    def __init__(
+        self,
+        topics,
+        servers="localhost",
+        group="",
+        eof=False,
+        timeout=1000,
+        config_global=None,
+        config_topic=None,
+        message_key=False,
+)
+```
+
+### 参数说明
+
+- topics: A tf.string tensor containing one or more subscriptions, in the format of [topic:partition:offset:length], by default length is -1 for unlimited. 
+- servers: A list of bootstrap servers.
+- group: The consumer group id.
+- eof: If True, the kafka reader will stop on EOF.
+- timeout: The timeout value for the Kafka Consumer to wait (in millisecond). 
+- config_global: A tf.string tensor containing global configuration properties in [Key=Value] format, eg. ["enable.auto.commit=false", "heartbeat.interval.ms=2000"], please refer to 'Global configuration properties' in librdkafka doc. 
+- config_topic: A tf.string tensor containing topic configuration properties in [Key=Value] format, eg. ["auto.offset.reset=earliest"], please refer to 'Topic configuration properties' in librdkafka doc. 
+- message_key: If True, the kafka will output both message value and key. 
+
+## 使用示例
+
+```python
+import tensorflow as tf
+from tensorflow.python.data.ops import iterator_ops
+
+kafka_dataset = tf.data.KafkaDataset(topics=["dewu_1_partition:0:0:-1"],
+                                     group="test_group1",
+                                     timeout=100,
+                                     eof=False)
+iterator = iterator_ops.Iterator.from_structure(batch_dataset.output_types)
+init_op = iterator.make_initializer(kafka_dataset)
+get_next = iterator.get_next()
+saveable_obj = tf.data.experimental.make_saveable_from_iterator(iterator)
+tf.add_to_collection(tf.GraphKeys.SAVEABLE_OBJECTS, saveable_obj)
+saver=tf.train.Saver()
+with tf.Session() as sess:
+  sess.run(init_op)
+  for i in range(100):
+    print("Data", sess.run(get_next))
+  saver.save(sess, "ckpt/1")
+```

docs/index.md

@@ -80,4 +80,5 @@ oneDNN
 :caption: 样本读取及Dataset
 
 WorkQueue
-```
+KafkaDataset
+```