Script Processor
editScript Processor
editThe script
processor executes Javascript code to process an event. The processor
uses a pure Go implementation of ECMAScript 5.1 and has no external
dependencies. This can be useful in situations where one of the other processors
doesn’t provide the functionality you need to filter events.
The processor can be configured by embedding Javascript in your configuration file or by pointing the processor at external file(s).
processors: - script: lang: javascript source: > function process(event) { event.Tag("js"); }
This loads filter.js
from disk.
processors: - script: lang: javascript file: ${path.config}/filter.js
Parameters can be passed to the script by adding params
to the config.
This allows for a script to be made reusable. When using params
the
code must define a register(params)
function to receive the parameters.
processors: - script: lang: javascript tag: my_filter params: threshold: 15 source: > var params = {threshold: 42}; function register(scriptParams) { params = scriptParams; } function process(event) { if (event.Get("severity") < params.threshold) { event.Cancel(); } }
If the script defines a test()
function it will be invoked when the processor
is loaded. Any exceptions thrown will cause the processor to fail to load. This
can be used to make assertions about the behavior of the script.
function process(event) { if (event.Get("event.code") === 1102) { event.Put("event.action", "cleared"); } return event; } function test() { var event = process(new Event({event: {code: 1102}})); if (event.Get("event.action") !== "cleared") { throw "expected event.action === cleared"; } }
Configuration options
editThe script
processor has the following configuration settings:
-
lang
-
This field is required and its value must be
javascript
. -
tag
-
This is an optional identifier that is added to log messages. If defined
it enables metrics logging for this instance of the processor. The metrics
include the number of exceptions and a histogram of the execution times for
the
process
function. -
source
- Inline Javascript source code.
-
file
-
Path to a script file to load. Relative paths are interpreted as
relative to the
path.config
directory. Globs are expanded. -
files
-
List of script files to load. The scripts are concatenated together.
Relative paths are interpreted as relative to the
path.config
directory. And globs are expanded. -
params
-
A dictionary of parameters that are passed to the
register
of the script. -
tag_on_exception
-
Tag to add to events in case the Javascript code causes an
exception while processing an event. Defaults to
_js_exception
. -
timeout
-
This sets an execution timeout for the
process
function. When theprocess
function takes longer than thetimeout
period the function is interrupted. You can set this option to prevent a script from running for too long (like preventing an infinitewhile
loop). By default there is no timeout. -
max_cached_sessions
-
This sets the maximum number of Javascript VM sessions
that will be cached to avoid reallocation. The default is
4
.
Event API
editThe Event
object passed to the process
method has the following API.
Method | Description |
---|---|
|
Get a value from the event (either a scalar or an object). If the key does not
exist Example: |
|
Put a value into the event. If the key was already set then the previous value is returned. It throws an exception if the key cannot be set because one of the intermediate values is not an object. Example: |
|
Rename a key in the event. The target key must not exist. It returns true if the source key was successfully renamed to the target key. Example: |
|
Delete a field from the event. It returns true on success. Example: |
|
Flag the event as cancelled which causes the processor to drop event. Example: |
|
Append a tag to the Example: |
|
Example: |