Form action wrong in snmp-exporter Docker container / version 0.28.0

[4N-TE]

Hi,

if I run SNMP Exporter as docker container like this:

docker run -p 9116:9116 -v ./snmp.yml:/etc/snmp_exporter/snmp.yml -d prom/snmp-exporter

and then connect to http://localhost:9116 using a browser I get a form where I can enter Target, Auth and Module to do a test run of polling SNMP data.

Once I click submit I get an error that hostname "snmp" cannot be resolved. I can see that the URL the brower (Firefox or Chrome) tries to open is this:

http://snmp/?target=1.2.3.4&auth=v3&module=if_mib

If I run snmp-exporter without using a docker container the URL is correctly generated as:

http://localhost:9116/snmp?target=1.2.3.4&auth=v3&module=if_mib

The version in the container is 0.28.0:
snmp_exporter, version 0.28.0 (branch: HEAD, revision: 9f9547f)

The version I have outside the container is slightly older at 0.26.0:
snmp_exporter, version 0.26.0 (branch: main, revision: e9a9866)

The reason for the error is that in the container (0.28.0) the HTML that displays the form reads

<form action="//snmp">

while outside the container (0.26.0) it reads:

<form action="/snmp">

If I user browser side tools to modify the HTML to just use /snmp as the form action then submitting my query also works with 0.28.0.

When manually entering the correctly formatted URL that works with 0.28.0, too - so at least Prometheus does not have issues scraping the metrics.

I assume the form HTML is wrong in 0.28.0.

Regards
Thomas

[bastischubert]

duplicate of #1366