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DocumentationCloud Log ServiceOperation GuideData Processing documentsData ProcessingData Processing FunctionsFlow Control

Flow Control

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Last updated: 2024-01-20 17:44:35

Overview

The writing method of the flow control logic in commonly used programming languages is different from that in DSL functions. See the figure below.




Function compose

Function definition

This function is used to combine multiple operation functions. Providing combination capabilities similar to those of branch code blocks, this function can combine multiple operation functions and execute them in sequence. It can be used in combination with branches and output functions.

Syntax description

compose(Function 1,Function 2, ...)

Parameter description

Parameter
Description
Parameter Type
Required
Default Value
Value Range
Variable parameter, function
The parameter must be a function whose return value type is LOG.
string
At least one function parameter
-
-

Example

Example 1. Call functions in sequence, executing the enrich function first and then the fields_set function Raw log:
{"status": "500"}
Processing rule: 
// 1. `enrich` function: use the data in `dict` to enrich the raw log, where `status` is `500`, and generate a field (field `message` with value `Failed`) after the enrichment.
//2. `fields_Set` function: add a field `new` and assign value `1` to it.
compose(enrich_dict("{\\"200\\":\\"SUCCESS\\",\\"500\\":\\"FAILED\\"}", "status", output="message"), fields_set("new", 1))
Processing result:
// The final log contains 3 fields:
{"new":"1","message":"FAILED","status":"500"}
Example 2 Raw log:
{"status": "500"}
Processing rule:
compose(fields_set("new", 1))
Processing result:
{"new":"1","status":"500"}
Example 3 Raw log:
{"condition1": 0,"condition2": 1, "status": "500"}
Processing rule:
t_if_else(v("condition2"), compose(fields_set("new", 1),log_output("target")), log_output("target2"))
Processing result, target output: 
{"new":"1","condition1":"0","condition2":"1","status":"500"}

Function t_if

Function definition

This function is used to execute a corresponding function if a condition is met and does not perform any processing if the condition is not met.

Syntax description

t_if(Condition 1, Function 1)

Parameter description

Parameter
Description
Parameter Type
Required
Default Value
Value Range
condition
Function expression whose return value is of bool type
bool
Yes
-
-
function
Function expression whose return value is of LOG type
string
Yes
-
-

Example

Example 1
Raw log:
{"condition": 1, "status": "500"}
Processing rule:
t_if(True, fields_set("new", 1))
Processing result:
{"new":"1","condition":"1","status":"500"}
Example 2 Raw log:
// If the value of `condition` is `1` (true), add a field `new` and assign value `1` to it.
{"condition": 1, "status": "500"}
Processing rule:
t_if(v("condition"), fields_set("new", 1))
Processing result:
{"new":"1","condition":"1","status":"500"}

Function t_if_not

Function definition

This function is used to execute a corresponding function if a condition is not met and does not perform any processing if the condition is met.

Syntax description

t_if_not(Condition 1, Function 1)

Parameter description

Parameter
Description
Parameter Type
Required
Default Value
Value Range
condition
Function expression whose return value is of bool type
bool
Yes
-
-
function
Function expression whose return value is of LOG type
string
Yes
-
-

Example

Raw log:
{"condition": 0, "status": "500"}
Processing rule:
t_if_not(v("condition"), fields_set("new", 1))
Processing result:
{"new":"1","condition":"0","status":"500"}

Function t_if_else

Function definition

This function is used to execute a function based on the evaluation result of a condition.

Syntax description

t_if_else("Condition 1", Function 1, Function 2)

Parameter description

Parameter
Description
Parameter Type
Required
Default Value
Value Range
condition
Function expression whose return value is of bool type
bool
Yes
-
-
function
Function expression whose return value is of LOG type
string
Yes
-
-
function
Function expression whose return value is of LOG type
string
Yes
-
-

Example

Raw log:
{"condition": 1, "status": "500"}
Processing rule:
t_if_else(v("condition"), fields_set("new", 1), fields_set("new", 2))
Processing result:
{"new":"1","condition":"1","status":"500"}

Function t_switch

Function definition

This function is used to execute different functions depending on whether branch conditions are met. If all conditions are not met, the data is deleted.

Syntax description

t_switch("Condition 1", Function 1, "Condition 2", Function 2, ...)

Parameter description

Parameter
Description
Parameter Type
Required
Default Value
Value Range
Variable parameter, which is a list of condition-function expression pairs
Similar to a combination of multiple t_if functions. For more information, see Function t_if.
-
-
-
-

Example

Raw log:
{"condition1": 0,"condition2": 1, "status": "500"}
Processing rule:
// If `condition1` is `1` (true), add a field `new` and assign value `1` to it. Here, `False` is returned for `condition1`, and therefore the `new` field (value: `1`) is not added; `True` is returned for `condition2`, and therefore the `new` field (value: `2`) is added.
t_switch(v("condition1"), fields_set("new", 1), v("condition2"), fields_set("new", 2))
Processing result:
{"new":"2","condition1":"0","condition2":"1","status":"500"}

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