Firefox Bug or Configuration? Network Monitor Limit

Context: I’ve been using Network Monitor from the Developer Tools to save my requests in a .HAR file for further analysis via Right Click>Save All As Har

Case: When approaching around 300MB transferred, instead of exporting JSON formatted text into the .HAR file, it returns a 9 byte download and when opening the file it contains a string that says ‘undefined’.

Troubleshooting: I initially thought there might be a request limit, but when artificially inflating the request count past the initial amount of requests around the point of failure I did not experience the same issue - but did notice that the amount of data I was trying to save was considerably less.

Organically reaching the amount where things stop working I noticed it was around 300MB when I’d experience this issue. I was using an older version of firefox then updated to the most recent version to see if it was specific to that old version or a general issue, it was the latter.

I saw that when firefox saves logs per about:networking#logging, it chooses the ~/appdata/ directory, and after looking through that, /appdata/local/Temp, and the Mozilla folder+subfolders in each /appdata/ directory I did not see a log that was relevant to the issue Network Monitor was having.

Additional Information:


 Win X
 Major  Minor  Build  Revision
 -----  -----  -----  --------
 10     0      16299  0


60.3.0esr (32-bit)

Question: Is this a bug, a known limitation, or does anyone know what is not defined upstream resulting in a ‘blank’ file? Is this something where I’d be able to look through a configuration file and set something in it to resolve this error when it happens? I haven’t found anything on this issue nor have I seen a data cap in the documentation.

1 Like

This would not be a known limitation that was added on purpose.

I build a quick example that generates up to 500Mb of data and can’t reproduce the issue in Nightly:

ESR fails with a memory issue which leads to just exporting undefined.

InternalError: allocation size overflow
Stack trace:
stringify@resource://devtools/shared/base-loader.js -> resource://devtools/client/netmonitor/src/har/har-exporter.js:228:14
fetchHarData/<@resource://devtools/shared/base-loader.js -> resource://devtools/client/netmonitor/src/har/har-exporter.js:164:24

ESR is a few versions behind, and since then we have spend cycles to speed up HAR export. Are you able to update to DevEdition?

Installed Dev Edition and tested it out, was able to export up to 370MB (current amount). Thank you for the insight and recommendation! I suspected something like that may be happening but I’m not as savvy on windows.