configure the go runtime to honour the k8s memory and cpu resource li…

…mits

README.md

@@ -15,6 +15,7 @@ It will:
 * Show the containers running inside the container pod.
 * Show the container memory limits.
 * Show the container cgroups.
+* Configure [the Go runtime](https://pkg.go.dev/runtime) to honour the defined kubernetes container memory and cpu resource limits with the `GOMEMLIMIT` and `GOMAXPROCS` environment variables.
 * Expose as a Kubernetes `LoadBalancer` `Service`.
  * Note that this results in the creation of an [EC2 Classic Load Balancer (CLB)](https://docs.aws.amazon.com/elasticloadbalancing/latest/classic/introduction.html).
 * Use [Role and RoleBinding](https://kubernetes.io/docs/reference/access-authn-authz/rbac/).

main.go

@@ -204,6 +204,7 @@ table > tbody > tr:hover {
  <tr><th>Hostname</th><td>{{.Hostname}}</td></tr>
  <tr><th>Pod Containers</th><td>{{.PodContainers}}</td></tr>
  <tr><th>Cgroup</th><td>{{.Cgroup}}</td></tr>
+ <tr><th>Go Max CPUs</th><td>{{.GoMaxCPUs}}</td></tr>
  <tr><th>Memory Limit</th><td>{{.MemoryLimit}}</td></tr>
  <tr><th>Memory Usage</th><td>{{.MemoryUsage}}</td></tr>
  <tr><th>Os</th><td>{{.Os}}</td></tr>
@@ -297,6 +298,7 @@ type indexData struct {
  Gid int
  PodContainers string
  Cgroup string
+ GoMaxCPUs int
  MemoryLimit uint64
  MemoryUsage uint64
  Request string
@@ -493,6 +495,7 @@ func main() {
  Gid: os.Getgid(),
  PodContainers: podContainers,
  Cgroup: string(cgroup),
+ GoMaxCPUs: runtime.GOMAXPROCS(0),
  MemoryLimit: memoryInfo.Limit,
  MemoryUsage: memoryInfo.Usage,
  Request: fmt.Sprintf("%s %s%s", r.Method, r.Host, r.URL),

resources.yml

@@ -162,6 +162,22 @@ spec:
  memory: 20Mi
  cpu: '0.1'
  env:
+ # configure the go runtime to honour the k8s memory and cpu
+ # resource limits.
+ # NB resourceFieldRef will cast the limits to bytes and integer
+ # number of cpus (rounding up to the nearest integer).
+ # see https://pkg.go.dev/runtime
+ # see https://www.riverphillips.dev/blog/go-cfs/
+ # see https://github.com/golang/go/issues/33803
+ # see https://github.com/traefik/traefik-helm-chart/pull/1029
+ - name: GOMEMLIMIT
+ valueFrom:
+ resourceFieldRef:
+ resource: limits.memory
+ - name: GOMAXPROCS
+ valueFrom:
+ resourceFieldRef:
+ resource: limits.cpu
  # see https://github.com/kubernetes/kubernetes/blob/master/test/e2e/common/downward_api.go
  - name: POD_UID
  valueFrom: