pfSense

Problem :
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Status, Monitoring, failed to display the quality Graph

The GUI display the error "Error: [object XMLHttpRequest]" in place of the graph.

Steps to reproduce :
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2.4.4-RELEASE-p2 AMD64 deployed on VMware 6.0

pfSense WEB-GUI > Status > Monitoring > Settings > Left Axis : Quality > Clic "Update Graphs" button

After 10 seconds an error message is displayed in place off the graph :
Error: [object XMLHttpRequest]

We have tried to reproduce on two pfSense instance and obtained the same error.

HTTP Headers details for rrd_fetch_json.php :
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Request URL: https://x.x.x.x/rrd_fetch_json.php
Request Method: POST
Status Code: 502
Remote Address: x.x.x.x:443
Referrer Policy: no-referrer-when-downgrade
content-length: 568
content-type: text/html
date: Thu, 10 Jan 2019 16:39:24 GMT
server: nginx
status: 502
:authority: x.x.x.x
:method: POST
:path: /rrd_fetch_json.php
:scheme: https
accept: application/json,*/*
accept-encoding: gzip, deflate, br
accept-language: fr-FR,fr;q=0.9,en-US;q=0.8,en;q=0.7
content-length: 121
content-type: application/x-www-form-urlencoded
cookie: PHPSESSID=zzzzzzzzzzzzzzzzzzzzzzz
origin: https://x.x.x.x
referer: https://x.x.x.x/status_monitoring.php
user-agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/71.0.3578.98 Safari/537.36
left: GW_WAN-quality
right: null
start:
end:
resolution: 300
timePeriod: -1d
graphtype: line
invert: true
refreshInterval: 60000