HTTP Health check and metrics

[viktorerlingsson]

Adds a health check over http on http://listen_address:http_port/healthz that returns 200 OK when amqproxy is up and running.
Supersedes #179

Also adds some simple prometheus style metrics. Just client_connections and upstream_connections for now, but this can be extended in the future (maybe some throughput stats and server resource information?).

[j-m-harris]

Thanks for implementing this!

[viktorerlingsson]

Fix for integration test failure in #185

[carlhoerberg]

Dockerfile EXPOSE for the http port should be added?

[carlhoerberg]

How much did memory usage increase with this? Probably little, but did we do any test?

…

On Wed, 23 Oct 2024, 10:24 Viktor Erlingsson, ***@***.***> wrote: Merged #184 <#184> into main. — Reply to this email directly, view it on GitHub <#184 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AABL6TVO72DRWJFXVYQOG3LZ45MNTAVCNFSM6AAAAABPWIE3V6VHI2DSMVQWIX3LMV45UABCJFZXG5LFIV3GK3TUJZXXI2LGNFRWC5DJN5XDWMJUHAYDINBVGE2DGMA> . You are receiving this because your review was requested.Message ID: ***@***.***>

[viktorerlingsson]

How much did memory usage increase with this? Probably little, but did we do any test?

No, didn't do any proper testing of that before, but here's a comparison between 2.0.2 and 2.0.3.
VmSize is ~17MB bigger, but RSS is just ~350kb extra.

2.0.2

VmPeak:    38204 kB
VmSize:    38136 kB
VmLck:         0 kB
VmPin:         0 kB
VmHWM:      6504 kB
VmRSS:      6484 kB
RssAnon:            1584 kB
RssFile:            4900 kB
RssShmem:              0 kB
VmData:    28340 kB
VmStk:       132 kB
VmExe:      1240 kB
VmLib:      4944 kB
VmPTE:        76 kB
VmSwap:        0 kB

2.0.3

VmPeak:    55144 kB
VmSize:    55144 kB
VmLck:         0 kB
VmPin:         0 kB
VmHWM:      6856 kB
VmRSS:      6836 kB
RssAnon:            1600 kB
RssFile:            5236 kB
RssShmem:              0 kB
VmData:    44732 kB
VmStk:       132 kB
VmExe:      1648 kB
VmLib:      5012 kB
VmPTE:        84 kB
VmSwap:        0 kB