WSO2 Complex Event Processor is succeeded by WSO2 Stream Processor. To view the latest documentation for WSO2 SP, see WSO2 Stream Processor Documentation.

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Siddhi language has a wide verity of extension variety of extensions ranging from string processing to natural language processing. These extensions can be utilized in numerous scenarios to manipulate attributes with ease. When using extensions within Siddhi queries, you need to follow the convention of extensionName:functionName to refer to a particular extension. If the extension is of the Function type you can refer to it as shown in the following example in different parts of the query.




<returnType r1> functionName   ( < paramType> p1) (FOR ONE RETURN TYPE & ONE PARAMETER TYPE)
< returnType | returnType functionName(<paramType|paramType> p1, <paramType|paramType> p2) (FOR ONE RETURN TYPE & MANY PARAMETER TYPES)
[< returnType | returnType r1, < returnType | returnType >  r2 functionName(<paramType|paramType> p1) (FOR MANY RETURN TYPES & ONE PARAMETER TYPE)
  • Extension TypeFunction | Aggregate  Function | Stream Function | Stream Processor | Window
  • Description
  • Parameter p1
  • Return  Parameter :  r1
  • Example:


<returnType> functionName   ( < paramType> p1)(FOR ONE RETURN TYPE & ONE PARAMETER TYPE)

<returnType|returnType>  functionName(<paramType|paramType> p1, <paramType|paramType> p2)(FOR ONE RETURN TYPE & MANY PARAMETER TYPES)

[< returnType | returnType r1, < returnType | returnType >  r2 functionName(<paramType|paramType> p1)(FOR MANY RETURN TYPES & ONE PARAMETER TYPE)

  • Extension Type: Function | Aggregate  Function | Stream Function | Aggregate Stream Function | Window
  • Description
  • Parameter p1
  • Return  Parameter :  r1
  • Example



This extension provides the capability to send a map object inside Siddhi stream definitions and use it inside queries. The following are the functions of the map extension.



<Object> create()


<Object> create(<Object> key1, <Object> value1,<Object> key2, <Object> value2,...<Object> keyN, <Object> valueN)

Extension TypeFunction
DescriptionReturns the created map object.
  • create() returns an empty map.
  • create(1 , ”one” ,  2 , ”two” , 3 , ”three”) returns a map with keys 1, 2, 3 and corresponding values "one", "two", "three".


Syntax<Object> get(<Map> map, <Object> key)
Extension TypeFunction
DescriptionReturns the value object from the map that is related to the given key.
Exampleget(company,1) returns the value that is related to the key 1 from the map named company.


Syntax<bool> isMap(<Object> object)
Extension TypeFunction
DescriptionReturns true if the object is a map or false otherwise.
ExampleisMap(students) returns true if the students object is a map. It returns false if the students object is not a map.


SyntaxObject> put(<Object> map, <Object> key,<Object> value)
Extension TypeFunction
DescriptionReturns the updated map after adding the given key-value pair.
Exampleput(students , 1234 , ”sam”) returns the updated map named students after adding the object "sam" with key 1234.


Syntax<Object> remove(<Object> map, <Object> key)
Extension TypeFunction
DescriptionReturns the updated map after removing the element with key.
Exampleremove(students , 1234) returns the updated map students after removing the element with the key 1234.


Syntax<Object> createFromJSON(<string> JSONstring)
Extension TypeFunction
DescriptionReturns the map created with the key values pairs given in the JSONstring.
ExamplecreateFromJSON(“{‘symbol' : 'IBM' , 'price' : 200, 'volume' : 100}”) returns a map with the keys "symbol""price", "volume", and with the values "IBM"200 and 100 respectively.


Syntax<Object> createFromXML(<string> XMLstring)
Extension TypeFunction
DescriptionReturns the map created with the key values pairs given in the XMLstring.
ExamplecreateFromXML(“<company> <symbol> wso2 </symbol> <price> <100> </price> <volume> 200 </volume> </company>”) returns a map with the keys "symbol""price""volume", and with the values WSO2100 and 200 respectively.


Syntax<String> toJSON(<Object> map)
Extension TypeFunction
DescriptionConverts a map into a JSON object and returns the definition of that JSON object as a string.
ExampleIf "company" is a map with key value pairs ("symbol" : wso2)("volume" : 100), and ("price",200), toJSON(company) returns the string “{“symbol” : “wso2” , “volume” : 100 , “price” : 200}”.



<String> toXML(<Object> map)


<String> toXML(<Object> map, <String> rootElementName)

Extension TypeFunction
DescriptionReturns the map as an XML string.

If "company" is a map with key value pairs (“symbol” : wso2)(“volume” : 100), and (“price” : 200),

toXML(company) returns the string “<symbol>wso2</symbol><volume><100></volume><price>200</price>".

toXML(company, "abcCompany") returns the string “<abcCompany><symbol>wso2</symbol><volume><100></volume><price>200</price></abcCompany>".


Reorder extension is implemented using the K-Slack algorithm. The K-Slack Siddhi extension is used for reordering events from an unordered event stream. The following is an example of a query with the reorder extension.

Code Block
@info(name = 'query1') 
from inputStream#reorder:kslack(eventTimestamp) 
select eventTimestamp, price, volume 
insert into outputStream;

There are several important variations of the K-slack API of which the details are described below.



<bool> kslack(<long> timestamp)

Extension TypeStreamProcessor
DescriptionThis is the most basic version. The events are sorted by the timestamp parameter.

<bool> kslack(<long> timestamp, <long> timeOut )

Extension TypeStreamProcessor
DescriptionThe second argument shown in the above syntax corresponds to a fixed time-out value set at the beginning of the process. Once the time-out value expires, the extension drains all the events that are buffered within the reorder extension to outside. The time out has been implemented internally using a timer. The events buffered within the extension are released each time the timer ticks.
<bool> kslack(<long> timestamp, <long> timeOut, <long> maxValue )
Extension TypeStreamProcessor
DescriptionThe third argument in the above syntax is the maximum value for K. This is the amount to which the K value of the K-Slack algorithm will be increased.
  • kslack(timestamp, -1l, 1000000)
    In the above example, the algorithm execution starts when K=0 and it gets increased up to 1000000. The value of the K-slack does not increase from that point onwards. Hence, this leads to lower latency compared to the version shown in the first (i.e., single parameter) example of this list. Note that the second argument is set to -1l which effectively disables the timer based draining of the internal buffer.
  • kslack(timestamp, 1000l, 1000000)
    The above is another variation of the third category. Here, a time-out value is specified for the second argument (i.e. 1000 ms). In this case, the K-slack algorithm buffers events until the 1000ms time period expires. The maximum K value is 1000000. The K-value cannot exceed the specified amount.


<bool> kslack(<long> timestamp, <long> timeOut, <bool> expireFlag )

Extension TypeStreamProcessor
DescriptionThe fourth argument in the above syntax is a flag that indicates whether the out-of order events that appear after the expiration of the K-slack window should be discarded or not.
Examplekslack(timestamp, -1l, -1l, true)