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fix(chart): cap per-pod backend concurrency at the frontproxy (maxconn) #99

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Merged
ServerSideHannes merged 1 commit into from
Jun 30, 2026
+14 −1
Merged

fix(chart): cap per-pod backend concurrency at the frontproxy (maxconn) #99

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6 changes: 5 additions & 1 deletion chart/templates/frontproxy/configmap.yaml
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,7 @@ data:
timeout connect {{ .Values.frontproxy.timeouts.connect }}
timeout client {{ .Values.frontproxy.timeouts.client }}
timeout server {{ .Values.frontproxy.timeouts.server }}
timeout queue {{ .Values.frontproxy.timeouts.queue }}

frontend http_in
bind *:{{ .Values.frontproxy.containerPort }}
Expand All @@ -32,7 +33,10 @@ data:
# Use the FQDN: HAProxy's resolver does NOT apply /etc/resolv.conf search
# domains, so a bare service name NXDOMAINs and leaves 0 backends (503 <NOSRV>).
option redispatch
server-template pod 1-{{ int .Values.replicaCount }} {{ .Chart.Name }}-headless.{{ .Release.Namespace }}.svc.cluster.local:{{ .Values.service.port }} check resolvers k8s init-addr none
# maxconn per pod bounds in-flight requests on each backend so uvicorn can't
# accumulate request-body buffers and OOM; excess connections queue (timeout
# queue) and redispatch instead of overrunning a pod.
server-template pod 1-{{ int .Values.replicaCount }} {{ .Chart.Name }}-headless.{{ .Release.Namespace }}.svc.cluster.local:{{ .Values.service.port }} check resolvers k8s init-addr none maxconn {{ int .Values.frontproxy.maxConnPerPod }}

resolvers k8s
parse-resolv-conf
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9 changes: 9 additions & 0 deletions chart/values.yaml
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Expand Up @@ -209,6 +209,15 @@ frontproxy:
client: "1h"
server: "1h"
connect: "10s"
# How long a connection waits in the per-pod queue for a free slot before 503.
queue: "30s"
# Max concurrent connections HAProxy sends to EACH backend pod. This is the
# real bound on a pod's memory: uvicorn buffers each in-flight request body off
# the socket before our app's limiter runs, so without a per-pod cap a backup
# flood piles up bodies and OOMs the pod. Excess connections queue here (up to
# timeouts.queue) and redispatch to a less-loaded pod instead of hard-failing.
# ~40 x worst-case part size stays well under the pod memory limit.
maxConnPerPod: 40
resources:
requests:
cpu: "50m"
Expand Down