How to Poll for Large Response Payloads
If you're building a polling integration that has response payloads larger than 5MB then you'll need to save them as attachments and adapt your response processing.
Sometimes a polling integration that is fetching data from another system is required to handle response payloads larger than the 5MB limit imposed by ServiceNow. The normal setup for a Poll Processor includes the response payload being returned as a string in the Request script. Here we look at an alternative approach which avoids handling the response payload as a string and so avoids the 5MB string limit.
Alternative approach for response payloads > 5MB:
Make the request (using RESTMessageV2()).
Save the response as an attachment on a record (using saveResponseBodyAsAttachment()).
Pass the attachment
sys_id
through (using getResponseAttachmentSysid()).Fetch it and do something with the newly generated attachment - passing the stream of the attachment on to be processed however required, e.g. text/xml processing.
Don't pass the response body from the request script to the response script. Use saveResponseBodyAsAttachment() and getResponseAttachmentSysid() instead.
Example Use Case
The following example is taken from our Incident Attachment Poller Guide.
Request Script
// Process the request e.g. by executing a web service and returning the response
(function (poll_request, poller, connection, params) {
var request, response;
request = new sn_ws.RESTMessageV2();
request.setHttpMethod('GET');
request.setEndpoint(poll_request.endpoint_url);
request.setRequestHeader('Content-Type','application/json');
request.setBasicAuth(connection.getBasicAuthUser(), connection.getBasicAuthPassword());
// Save the response as a new attachment (on the poll request)
request.saveResponseBodyAsAttachment(
poll_request.getTableName(), poll_request.sys_id, params.attachment.file_name
);
response = request.execute();
poll_request.response_code = response.getStatusCode();
poll_request.response_status = response.getErrorMessage();
if (response.haveError()) {
throw '\nResponse Code: ' + response.getErrorCode() + '\nResponse error: ' + response.getErrorMessage();
}
// Return the sys_id of the saved attachment
answer = response.getResponseAttachmentSysid() + '';
})(poll_request, poller, connection, params);
Response Script
// Process the response returned by the request script
// The 'answer' variable from the request script is passed in here as the 'response' parameter
(function (poll_request, poller, response, params) {
// Establish the environment
var poll_helper = new x_snd_eb.PollHelper(poll_request);
var info = [
'Incident : ' + params.int_ref,
'- Attachment file name: ' + params.attachment.file_name,
'- Attachment id: ' + response
];
// The response should be the sys_id of the created attachment
params.attachment.data = '<x-attachment-data sys_id="' + response + '" />';
// Build the payload for Unifi
var payload = {
sys_id : params.ext_ref,
correlation_id : params.int_ref,
attachment : params.attachment
};
// Submit the message into Unifi
poll_helper.processInbound({
message_name : 'AddAttachmentInbound',
payload : JSON.stringify(payload)
});
poll_request.response_status = info.join('\n');
})(poll_request, poller, response, params);
In our example we've taken the inbound attachment, built a payload and passed it to Unifi to process.
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