Newsgroups: php.internals
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Date: Sat, 22 Jan 2022 21:00:15 +0100
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Subject: Best way to monitor php-fpm container liveness on Kubernetes
From: adam.hamsik@lablabs.io (Adam Hamsik)

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Hello,

We are using PHP for our application backends, this works very well as we=
 have developed s imple way to clone them with minimal effort(they can be=
 very similar). =46or our orchestration we are using Kubernetes (>=3D 1.2=
1). Our application pod generally contains NGINX + php-fpm and fluentbit =
for log shipping. We generally want to have LivenessProbe(for an simple e=
xplanation this is a simple check which is run against our pod to verify =
if it's alive, if it fails particular container will be restarted).

This works very we(we are also using swoole which is roughly 80-70% bette=
r)l, but in certain unstable situations when we see higher application la=
tency (db problem or a bug in our application). We often experience probl=
ems, because pods are falsely marked as dead (failed liveness probe and r=
estarted by kubelet). This happens all processes in our static pool are a=
llocated to application requests. =46or our livenessProbe we tried to use=
 both fpm.ping and fpm.status endpoints but both of them behave in a same=
 way as they are managed with worker processes.

I had a look at pgp-src repo if e.g. we can use signals to verify if appl=
ication server is running as a way to go around our issue. When looking a=
t this I saw fpm-systemd.c which is a SystemD specific check. This check =
reports fpm status every couple seconds(configurable to systemd). Would y=
ou be willing to integrate similar feature for kubernetes. This would be =
based on a pull model probably with and REST interface.

My idea is following:

1) During startup if this is enabled php-fpm master will open a secondary=
 port pm.health=5Fport(9001) and listen for a pm.health=5Fpath(/healtz)=5B=
2=5D.
2) If we receive GET request fpm master process will respond with HTTP co=
de 200 and string ok. If anything is wrong (we can later add some checks/=
metrics to make sure fpm is in a good state).=C2=A0=C2=A0If we do not res=
pond or fpm is not ok our LivenessProbe will fail. based on configuration=
 this will trigger container restart.

Would you be interested to integrate feature like this =3F or is there an=
y other way how we can achieve similar results =3F

=5B1=5D=C2=A0https://kubernetes.io/docs/concepts/workloads/pods/pod-lifec=
ycle/=23when-should-you-use-a-liveness-probe
=5B2=5D=C2=A0https://kubernetes.io/docs/reference/using-api/health-checks=
/


=C2=A0 =C2=A0Best Regards,

=C2=A0 =C2=A0Adam.



Adam Ham=C5=A1=C3=ADk
Co-founder & CEO
Mobile:=C2=A0+421-904-937-495
www.lablabs.io



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