doc<stream>: add concurrency and runAsync doc

docs/en_US/extension/source.md

@@ -4,9 +4,9 @@ Sources feed data into Kuiper from other systems. Kuiper has built-in source sup
 
 ## Developing
 
-### Develop a sink
+### Develop a source
 
-To develop a sink for Kuiper is to implement [api.Sink](../../../xstream/api/stream.go) interface and export it as a golang plugin.
+To develop a source for Kuiper is to implement [api.Source](../../../xstream/api/stream.go) interface and export it as a golang plugin.
 
 Before starting the development, you must [setup the environment for golang plugin](overview.md#setup-the-plugin-developing-environment). 
 
@@ -51,6 +51,10 @@ A configuration system is supported for Kuiper extension which will automaticall
  1. The name of your configuration file must be the same as the _.so_ file and must be camel case with upper case first letter. For example, MySource.yaml.
  2. The yaml file must be located inside _etc/sources_
  3. The format of the yaml file could be found [here](../rules/sources/mqtt.md)
+ 
+#### common configuration field
+
+There is a common configuration field ``concurrency`` to specify how many instances will be started to run the source.
 
 ### Package the source
 Build the implemented source as a go plugin and make sure the output so file resides in the plugins/sources folder.

docs/en_US/rules/overview.md

@@ -45,7 +45,12 @@ The sql query to run for the rule.
 
 ### actions
 
-Currently, 3 kinds of actions are supported: [log](sinks/logs.md), [mqtt](sinks/mqtt.md) and [rest](sinks/rest.md). Each action can define its own properties.
+Currently, 3 kinds of actions are supported: [log](sinks/logs.md), [mqtt](sinks/mqtt.md) and [rest](sinks/rest.md). Each action can define its own properties. There are 2 common properties:
+
+| property name | Type & Default Value | Description                                                  |
+| ------------- | -------- | ------------------------------------------------------------ |
+| concurrency | int: 1   | Specify how many instances of the sink will be run. |
+| runAsync        | bool:false   | Whether the sink will run asynchronously for better performance. If it is true, the sink result order is not promised.  |
 
 Actions could be customized to support different kinds of outputs, see [extension](../extension/overview.md) for more detailed info.
 

docs/en_US/rules/sources/mqtt.md

@@ -8,6 +8,7 @@ default:
   qos: 1
   sharedSubscription: true
   servers: [tcp://127.0.0.1:1883]
+  concurrency: 1
   #username: user1
   #password: password
   #certificationPath: /var/kuiper/xyz-certificate.pem
@@ -29,6 +30,9 @@ Use can specify the global MQTT settings here. The configuration items specified
 
 The default subscription QoS level.
 
+### concurrency
+How many instances will be started. By default, only an instance will be run. If more than one instance is specified, the topic must be a shared subscription topic.
+
 ### sharedSubscription
 
 Whether use the shared subscription mode or not. If using the shared subscription mode, then there are multiple Kuiper process can be load balanced.

docs/zh_CN/rules/overview.md

@@ -45,7 +45,12 @@
 
 ### 动作
 
-当前，支持两种操作： [log](sinks/logs.md) 、[mqtt](sinks/mqtt.md) 和 [rest](sinks/rest.md)。 每个动作可以定义自己的属性。
+当前，支持两种操作： [log](sinks/logs.md) 、[mqtt](sinks/mqtt.md) 和 [rest](sinks/rest.md)。 每个动作可以定义自己的属性。当前有两个公共属性:
+
+| 属性名 | 类型和默认值 | 描述                                                  |
+| ------------- | -------- | ------------------------------------------------------------ |
+| concurrency | int: 1   | 设置运行的线程数。 |
+| runAsync        | bool:false   | 设置是否异步运行输出操作以提升性能。请注意，异步运行的情况下，输出结果顺序不能保证。  |
 
 可以自定义动作以支持不同种类的输出，有关更多详细信息，请参见 [extension](../extension/overview.md) 。
 

docs/zh_CN/rules/sources/mqtt.md

@@ -8,6 +8,7 @@ default:
   qos: 1
   sharedsubscription: true
   servers: [tcp://127.0.0.1:1883]
+  concurrency: 1
   #username: user1
   #password: password
   #certificationPath: /var/kuiper/xyz-certificate.pem
@@ -28,6 +29,9 @@ demo: #Conf_key
 
 默认订阅QoS级别。
 
+### concurrency
+设置运行的线程数，默认值为1。如果设置进程数大于1，必须使用共享订阅模式。
+
 ### sharedsubscription
 
 是否使用共享订阅模式。 如果使用共享订阅模式，那么多个Kuiper进程可以进行负载平衡。