initial commit, but the application might be already complete ;-)

.gitea/workflows/build.yaml

@@ -0,0 +1,32 @@
+name: Build and Push
+
+on:
+  workflow_dispatch:
+    inputs:
+      tag:
+        description: 'Image tag'
+        required: true
+        default: 'latest'
+  push:
+    tags:
+      - '*'
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+      - uses: actions/checkout@v4
+      - name: Login to Gitea registry
+      - name: Build and push
+        run: |
+          TAG=${{ github.ref_name }}
+          if [ "${{ github.event_name }}" = "workflow_dispatch" ]; then
+            TAG=${{ inputs.tag }}
+          fi
+          IMAGE=gitea.home.hrajfrisbee.cz/${{ github.repository }}:$TAG
+          docker build -t $IMAGE .
+          docker push $IMAGE

.gitignore

@@ -0,0 +1 @@
+.idea

Dockerfile

@@ -0,0 +1,11 @@
+FROM golang:1.25-bookworm AS builder
+WORKDIR /app
+COPY go.mod go.sum ./
+RUN go mod download
+COPY main.go .
+RUN CGO_ENABLED=0 go build -ldflags="-s -w" -o memory-stress-test .
+
+FROM ubuntu:24.04
+RUN apt-get update && apt-get install -y --no-install-recommends ca-certificates && rm -rf /var/lib/apt/lists/*
+COPY --from=builder /app/memory-stress-test /usr/local/bin/
+ENTRYPOINT ["memory-stress-test"]

go.mod

@@ -0,0 +1,18 @@
+module memory-stress-test
+
+go 1.25
+
+require github.com/prometheus/client_golang v1.23.2
+
+require (
+	github.com/beorn7/perks v1.0.1 // indirect
+	github.com/cespare/xxhash/v2 v2.3.0 // indirect
+	github.com/kr/text v0.2.0 // indirect
+	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
+	github.com/prometheus/client_model v0.6.2 // indirect
+	github.com/prometheus/common v0.66.1 // indirect
+	github.com/prometheus/procfs v0.16.1 // indirect
+	go.yaml.in/yaml/v2 v2.4.2 // indirect
+	golang.org/x/sys v0.35.0 // indirect
+	google.golang.org/protobuf v1.36.8 // indirect
+)

go.sum

@@ -0,0 +1,46 @@
+github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
+github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
+github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
+github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
+github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
+github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
+github.com/klauspost/compress v1.18.0 h1:c/Cqfb0r+Yi+JtIEq73FWXVkRonBlf0CRNYc8Zttxdo=
+github.com/klauspost/compress v1.18.0/go.mod h1:2Pp+KzxcywXVXMr50+X0Q/Lsb43OQHYWRCY2AiWywWQ=
+github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=
+github.com/kr/pretty v0.3.1/go.mod h1:hoEshYVHaxMs3cyo3Yncou5ZscifuDolrwPKZanG3xk=
+github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
+github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
+github.com/kylelemons/godebug v1.1.0 h1:RPNrshWIDI6G2gRW9EHilWtl7Z6Sb1BR0xunSBf0SNc=
+github.com/kylelemons/godebug v1.1.0/go.mod h1:9/0rRGxNHcop5bhtWyNeEfOS8JIWk580+fNqagV/RAw=
+github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 h1:C3w9PqII01/Oq1c1nUAm88MOHcQC9l5mIlSMApZMrHA=
+github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822/go.mod h1:+n7T8mK8HuQTcFwEeznm/DIxMOiR9yIdICNftLE1DvQ=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/prometheus/client_golang v1.23.2 h1:Je96obch5RDVy3FDMndoUsjAhG5Edi49h0RJWRi/o0o=
+github.com/prometheus/client_golang v1.23.2/go.mod h1:Tb1a6LWHB3/SPIzCoaDXI4I8UHKeFTEQ1YCr+0Gyqmg=
+github.com/prometheus/client_model v0.6.2 h1:oBsgwpGs7iVziMvrGhE53c/GrLUsZdHnqNwqPLxwZyk=
+github.com/prometheus/client_model v0.6.2/go.mod h1:y3m2F6Gdpfy6Ut/GBsUqTWZqCUvMVzSfMLjcu6wAwpE=
+github.com/prometheus/common v0.66.1 h1:h5E0h5/Y8niHc5DlaLlWLArTQI7tMrsfQjHV+d9ZoGs=
+github.com/prometheus/common v0.66.1/go.mod h1:gcaUsgf3KfRSwHY4dIMXLPV0K/Wg1oZ8+SbZk/HH/dA=
+github.com/prometheus/procfs v0.16.1 h1:hZ15bTNuirocR6u0JZ6BAHHmwS1p8B4P6MRqxtzMyRg=
+github.com/prometheus/procfs v0.16.1/go.mod h1:teAbpZRB1iIAJYREa1LsoWUXykVXA1KlTmWl8x/U+Is=
+github.com/rogpeppe/go-internal v1.10.0 h1:TMyTOH3F/DB16zRVcYyreMH6GnZZrwQVAoYjRBZyWFQ=
+github.com/rogpeppe/go-internal v1.10.0/go.mod h1:UQnix2H7Ngw/k4C5ijL5+65zddjncjaFoBhdsK/akog=
+github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
+github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
+go.uber.org/goleak v1.3.0 h1:2K3zAYmnTNqV73imy9J1T3WC+gmCePx2hEGkimedGto=
+go.uber.org/goleak v1.3.0/go.mod h1:CoHD4mav9JJNrW/WLlf7HGZPjdw8EucARQHekz1X6bE=
+go.yaml.in/yaml/v2 v2.4.2 h1:DzmwEr2rDGHl7lsFgAHxmNz/1NlQ7xLIrlN2h5d1eGI=
+go.yaml.in/yaml/v2 v2.4.2/go.mod h1:081UH+NErpNdqlCXm3TtEran0rJZGxAYx9hb/ELlsPU=
+golang.org/x/sys v0.35.0 h1:vz1N37gP5bs89s7He8XuIYXpyY0+QlsKmzipCbUtyxI=
+golang.org/x/sys v0.35.0/go.mod h1:BJP2sWEmIv4KK5OTEluFJCKSidICx8ciO85XgH3Ak8k=
+google.golang.org/protobuf v1.36.8 h1:xHScyCOEuuwZEc6UtSOvPbAT4zRh0xcNRYekJwfqyMc=
+google.golang.org/protobuf v1.36.8/go.mod h1:fuxRtAxBytpl4zzqUh6/eyUujkJdNiuEkXntxiD/uRU=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

k8s/deploy.yaml

@@ -0,0 +1,68 @@
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: memconsumer
+  labels:
+    app: memconsumer
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: memconsumer
+  template:
+    metadata:
+      labels:
+        app: memconsumer
+      annotations:
+        prometheus.io/scrape: "true"
+        prometheus.io/port: "8080"
+        prometheus.io/path: "/metrics"
+    spec:
+      containers:
+        - name: memconsumer
+          image: memconsumer:latest
+          env:
+            - name: INITIAL_MB
+              value: "50"
+            - name: ALLOC_MB
+              value: "25"
+            - name: INTERVAL
+              value: "10s"
+            - name: MAX_MB
+              value: "200"
+          ports:
+            - containerPort: 8080
+              name: metrics
+          resources:
+            requests:
+              memory: "64Mi"
+              cpu: "50m"
+            limits:
+              memory: "256Mi"  # OOMKill trigger point
+              cpu: "100m"
+          livenessProbe:
+            httpGet:
+              path: /healthz
+              port: 8080
+            initialDelaySeconds: 3
+            periodSeconds: 5
+          readinessProbe:
+            httpGet:
+              path: /healthz
+              port: 8080
+            initialDelaySeconds: 3
+            periodSeconds: 5
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: memconsumer
+  labels:
+    app: memconsumer
+spec:
+  selector:
+    app: memconsumer
+  ports:
+    - port: 8080
+      targetPort: 8080
+      name: metrics

main.go

@@ -0,0 +1,131 @@
+package main
+
+import (
+	"flag"
+	"log"
+	"net/http"
+	"os"
+	"os/signal"
+	"strconv"
+	"syscall"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/collectors"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+var (
+	allocatedBytes = prometheus.NewGauge(prometheus.GaugeOpts{
+		Name: "memconsumer_allocated_bytes",
+		Help: "Total bytes allocated by the memory consumer",
+	})
+	allocationCount = prometheus.NewCounter(prometheus.CounterOpts{
+		Name: "memconsumer_allocations_total",
+		Help: "Total number of memory allocations performed",
+	})
+)
+
+// memoryHolder prevents GC from reclaiming allocations
+var memoryHolder [][]byte
+
+func envInt(key string, fallback int) int {
+	if v := os.Getenv(key); v != "" {
+		if i, err := strconv.Atoi(v); err == nil {
+			return i
+		}
+	}
+	return fallback
+}
+
+func envDuration(key string, fallback time.Duration) time.Duration {
+	if v := os.Getenv(key); v != "" {
+		if d, err := time.ParseDuration(v); err == nil {
+			return d
+		}
+	}
+	return fallback
+}
+
+func envString(key, fallback string) string {
+	if v := os.Getenv(key); v != "" {
+		return v
+	}
+	return fallback
+}
+
+func main() {
+	// Env vars set defaults, flags can override
+	initialMB := flag.Int("initial-mb", envInt("INITIAL_MB", 0), "Initial memory to allocate (MB) [env: INITIAL_MB]")
+	allocMB := flag.Int("alloc-mb", envInt("ALLOC_MB", 10), "Memory to allocate per iteration (MB) [env: ALLOC_MB]")
+	maxMB := flag.Int("max-mb", envInt("MAX_MB", 1000), "Max total memory to allocate, 0=unlimited (MB) [env: MAX_MB]")
+	interval := flag.Duration("interval", envDuration("INTERVAL", 5*time.Second), "Allocation interval [env: INTERVAL]")
+	metricsAddr := flag.String("metrics-addr", envString("METRICS_ADDR", ":8080"), "Prometheus metrics address [env: METRICS_ADDR]")
+	flag.Parse()
+
+	var totalAllocated int
+
+	reg := prometheus.NewRegistry()
+	reg.MustRegister(
+		collectors.NewGoCollector(),
+		collectors.NewProcessCollector(collectors.ProcessCollectorOpts{}),
+		allocatedBytes,
+		allocationCount,
+	)
+
+	// Initial allocation
+	if *initialMB > 0 {
+		allocate(*initialMB)
+		totalAllocated += *initialMB
+		log.Printf("Initial allocation: %d MB", *initialMB)
+	}
+
+	// Metrics server
+	http.Handle("/metrics", promhttp.HandlerFor(reg, promhttp.HandlerOpts{}))
+	http.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	})
+	go func() {
+		log.Printf("Metrics server listening on %s", *metricsAddr)
+		if err := http.ListenAndServe(*metricsAddr, nil); err != nil {
+			log.Fatalf("metrics server failed: %v", err)
+		}
+	}()
+
+	// Graceful shutdown
+	stop := make(chan os.Signal, 1)
+	signal.Notify(stop, syscall.SIGTERM, syscall.SIGINT)
+
+	ticker := time.NewTicker(*interval)
+	defer ticker.Stop()
+
+	log.Printf("Starting: alloc=%dMB interval=%v max=%dMB", *allocMB, *interval, *maxMB)
+
+	for {
+		select {
+		case <-ticker.C:
+			if *maxMB > 0 && totalAllocated+*allocMB > *maxMB {
+				log.Printf("Max limit reached (%d MB), skipping allocation", *maxMB)
+				continue
+			}
+			allocate(*allocMB)
+			totalAllocated += *allocMB
+			log.Printf("Allocated %d MB, total held: %d MB", *allocMB, totalAllocated)
+		case <-stop:
+			log.Println("Shutting down")
+			return
+		}
+	}
+}
+
+func allocate(mb int) {
+	size := mb * 1024 * 1024
+	buf := make([]byte, size)
+	// Touch pages to ensure RSS allocation
+	for i := 0; i < size; i += 4096 {
+		buf[i] = 1
+	}
+	memoryHolder = append(memoryHolder, buf)
+	allocatedBytes.Add(float64(size))
+	allocationCount.Inc()
+}