Errors are prone to happen, no matter how much we try to get rid of them. This is why it is very important to handle the errors gracefully when they happen.
In ReactiveSearch Pipelines, errors might be thrown by the system as well as user-defined stages can throw error and stop execution as well.
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continueOnError: what is it?
For pre-built stages, ReactiveSearch provides a way to handle errors automatically. This is done by the continueOnError
field.
This field indicates whether the execution should continue or not when there is an error. This will map to a Boolean value. The default value of this field is set to true.
Pre-Defined Stage Error Handling
Let's understand this with an example. Let's say we have a stage using the pre-built reactivesearchQuery
stage. It is defined in the following way:
- id: reactive search with error
use: reactivesearchQuery
continueOnError: false
Since the continueOnError
field is by default set to true
, we need to explicitly set it to false
when we want the execution to stop on error.
The above example will stop the execution of the pipeline when there is an error in that stage and will return the response body.
Set response body
Let's say we want to make sure that a custom response body is returned when there is error in the reactivesearchQuery
stage. For this, we can set the response body before that stage, so that when the error occurs, we can return that body.
This can be done in the following way with a custom user-defined script
function handleRequest() {
return {
response: {
body: JSON.stringify({"message": "error while executing reactivesearch"}),
code: 500
}
}
}
- id: set error
scriptRef: setError.js
- id: reactive search with error
use: reactivesearchQuery
continueOnError: false
Now, if there will be an error in the reactive search with error
step then the response will be the one we set in the setError.js
script.
Custom Errors
At times, there might be need to throw custom errors. This can be done by defining a custom stage that throws an error.
Example: Throw error if query
is not present
Let's understand this with an example. Let's say we want the query field to be present in the request body. If the field is not present, we cannot continue execution and want it to stop. We can do that in the following way with a custom script.
function handleRequest() {
const requestBody = JSON.parse(context.request.body);
if requestBody.query == null {
throw error("query is a required field!");
}
}
We can then use this script in the following way:
- id: check query field
scriptRef: checkQueryWithError.js
continueOnError: false
Note that we are setting the
continueOnError
field because we are throwing an error.
Complete Pipeline
Now that we have defined the stages we needed, let's get the whole pipeline
enabled: true
description: Handle errors gracefully
routes:
- path: /error-pipeline/_reactivesearch
method: POST
classify:
category: reactivesearch
stages:
- id: Authorize User
use: authorization
continueOnError: false
- id: check query field
scriptRef: checkQueryWithError.js
continueOnError: false
- id: set error
scriptRef: setError.js
- id: ReactiveSearch Query
use: reactivesearchQuery
continueOnError: false
- id: ElasticSearch Query
use: elasticsearchQuery
Create the pipeline
Now that we have the whole pipeline defined, we can create the pipeline by hitting the ReactiveSearch instance.
The URL we will hit is: /_pipeline
with a POST request.
The above endpoint expects a multipart/form-data
body with the pipeline
key containing the path to the pipeline file. All the scriptRef
files can be passed as a separate key in the form data and will be parsed by the API automatically. Read more about this endpoint here
We can create the pipeline in the following request:
Below request assumes all the files mentioned in this guide are present in the current directory
curl -X POST 'CLUSTER_ID/_pipeline' -H "Content-Type: multipart/form-data" --form "pipeline=pipeline.yaml" --form "checkQueryWithError.js=checkQueryWithError.js" --form "setError.js=setError.js"
Test the pipeline
We can hit the pipeline with no query
field to see if the error handling is working in the following way:
curl -X POST 'CLUSTER_ID/_reactivesearch' -H "Content-Type: application/json" -d '{"settings": {"backend": "elasticsearch"}}'
Above request does not contain the query
field and will make the pipeline throw an error.