08 Nov 2019 12:52 AM
Hi Team,
Do you know maximum POST size of RUM beacon?
We saw 403 error of "/rb_<ID>".
We think it is because that there is maximum POST size rule on WAF.
We are planning to change maximum POST size from 4KB to 1MB.
Do you think it is enough to POST RUM beacon?
Best Regards,
Natsumi Tanaka
Solved! Go to Solution.
08 Nov 2019 07:37 AM
This depends on the data actually sent in the beacon and also depends if session replay is enabled for the application or not. But even a complex user action with many resource timing data might result in beacons with size over 4kB.
Why are you limiting post size to 4kB in the first place? Does this come from any security policy in your organization?
08 Nov 2019 09:04 AM
Thank you for your reply.
They use AWS WAF and dafault yaml.
https://s3.us-east-2.amazonaws.com/awswaf-owasp/owasp_10_base.yml
The default setting is the following
maxExpectedBodySize:
Type: Number
Description: Maximum number of bytes allowed in the body of the request. If you do not plan to allow large uploads, set it to the largest payload value that makes sense for your web application. Accepting unnecessarily large values can cause performance issues, if large payloads are used as an attack vector against your web application.
Default: 4096
They will change the setting from 4096 to 1000000
08 Nov 2019 09:00 AM
the default max size of a beacon is 30kb, if it would grow higher than that it's split into multiple requests. the default limit can be configured using the `custom configuration properties` textbox within the advanced application configuration. just enter `msl=<size-in-bytes>`, so in your case `msl=4000` to decrease this limit. expect an higher amount of beacons though, since the beacon will be split if the content grows beyond 4kb.
08 Nov 2019 09:50 AM
Thank you for your information.
I am released to hear that the max size is 30kb, so after our customer change maxExpectedBodySize from 4096 to 1000000 they will do not face to 403 error.
More, I do not know we can restrict beacon size using `custom configuration properties`.
It is very useful! Thank you!
08 Jan 2021 11:54 AM
Small detail, but Is this 4 kB (4000 bytes), or 4 KiB (kibibytes, or KB, 4096 bytes)