I have a question about AppSync error handling. I would like to send errorInfo
object along with the error response and I tried with $util.error
. Per the document:
https://docs.aws.amazon.com/appsync/latest/devguide/resolver-util-reference.html
$util.error(String, String, Object, Object)
Throws a custom error. This can be used in request or response mapping templates if the template detects an error with the request or with the invocation result. Additionally, an errorType field, a data field, and a errorInfo field can be specified. The data value will be added to the corresponding error block inside errors in the GraphQL response. Note: data will be filtered based on the query selection set. The errorInfo value will be added to the corresponding error block inside errors in the GraphQL response. Note: errorInfo will NOT be filtered based on the query selection set.
And here is what my ResponseMappingTemplate look like:
#if( $context.result && $context.result.errorMessage )
$utils.error($context.result.errorMessage, $context.result.errorType, $context.result.data), $context.result.errorInfo)
#else
$utils.toJson($context.result.data)
#end
Here is what I did on the resolver:
var result = {
data: null,
errorMessage: 'I made this error',
errorType: 'ALWAYS_ERROR',
errorInfo: {
errorCode: 500,
validations: [
{
fieldName: '_',
result: false,
reasons: [
'Failed! Yay!'
]
}
],
}
};
callback(null, result);
And here is what I see in CloudWatch log:
{
"errors": [
"CustomTemplateException(message=I made this error, errorType=ALWAYS_ERROR, data=null, errorInfo={errorCode=500, validations=[{fieldName=_, result=false, reasons=[Failed! Yay!]}]})"
],
"mappingTemplateType": "Response Mapping",
"path": "[getError]",
"resolverArn": "arn:aws:appsync:ap-southeast-1:....",
"context": {
"arguments": {},
"result": {
"errorMessage": "I made this error",
"errorType": "ALWAYS_ERROR",
"errorInfo": {
"errorCode": 500,
"validations": [
{
"fieldName": "_",
"result": false,
"reasons": [
"Failed! Yay!"
]
}
]
}
},
"stash": {},
"outErrors": []
},
"fieldInError": true
}
And here is what I got in the response:
{
"data": {
"getError": null
},
"errors": [
{
"path": [
"getError"
],
"data": null,
"errorType": "ALWAYS_ERROR",
"errorInfo": null,
"locations": [
{
"line": 2,
"column": 3,
"sourceName": null
}
],
"message": "I made this error"
}
]
}
Notice that errorInfo
is null and I some how got CustomTemplateException. I suspect that is because of the 4th parameter to $utils.error
. But I don’t know why. Could anyone help to point out the error or tell me whether sending custom errorInfo
is possible
Turn out that I used the code from some tutorial which is not up to date. There are 2 versions of the Resolver Mapping Template: 2018-05-29
and 2017-02-28
. So I need to change the template version to 2018-05-29
for it to work.
RequestMappingTemplate: |
{
"version": "2018-05-29",
"operation": "Invoke",
"payload": {
"field": "getError",
"arguments": $utils.toJson($context.arguments)
}
}
See the changes between 2 versions here: https://docs.aws.amazon.com/appsync/latest/devguide/resolver-mapping-template-changelog.html#changing-the-version-on-a-function