Firefox Bug or Configuration? Network Monitor Limit

(se316) #1

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.


(Harald Kirschner) #2

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?


(se316) #3

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.