infra/stacks/monitoring/modules/monitoring/alloy.yaml

alloy:
  configMap:
    content: |-
      // Write your Alloy config here:
      logging {
        level = "info"
        format = "logfmt"
      }
      loki.write "default" {
        endpoint {
          url = "http://loki.monitoring.svc.cluster.local:3100/loki/api/v1/push"
        }
      }

      // discovery.kubernetes allows you to find scrape targets from Kubernetes resources.
      // It watches cluster state and ensures targets are continually synced with what is currently running in your cluster.
      discovery.kubernetes "pod" {
        role = "pod"
      }

      // discovery.relabel rewrites the label set of the input targets by applying one or more relabeling rules.
      // If no rules are defined, then the input targets are exported as-is.
      discovery.relabel "pod_logs" {
        targets = discovery.kubernetes.pod.targets

        // Label creation - "namespace" field from "__meta_kubernetes_namespace"
        rule {
          source_labels = ["__meta_kubernetes_namespace"]
          action = "replace"
          target_label = "namespace"
        }

        // Label creation - "pod" field from "__meta_kubernetes_pod_name"
        rule {
          source_labels = ["__meta_kubernetes_pod_name"]
          action = "replace"
          target_label = "pod"
        }

        // Label creation - "container" field from "__meta_kubernetes_pod_container_name"
        rule {
          source_labels = ["__meta_kubernetes_pod_container_name"]
          action = "replace"
          target_label = "container"
        }

        // Label creation -  "app" field from "__meta_kubernetes_pod_label_app_kubernetes_io_name"
        rule {
          source_labels = ["__meta_kubernetes_pod_label_app_kubernetes_io_name"]
          action = "replace"
          target_label = "app"
        }

        // Label creation -  "job" field from "__meta_kubernetes_namespace" and "__meta_kubernetes_pod_container_name"
        // Concatenate values __meta_kubernetes_namespace/__meta_kubernetes_pod_container_name
        rule {
          source_labels = ["__meta_kubernetes_namespace", "__meta_kubernetes_pod_container_name"]
          action = "replace"
          target_label = "job"
          separator = "/"
          replacement = "$1"
        }

        // Label creation - "container" field from "__meta_kubernetes_pod_uid" and "__meta_kubernetes_pod_container_name"
        // Concatenate values __meta_kubernetes_pod_uid/__meta_kubernetes_pod_container_name.log
        rule {
          source_labels = ["__meta_kubernetes_pod_uid", "__meta_kubernetes_pod_container_name"]
          action = "replace"
          target_label = "__path__"
          separator = "/"
          replacement = "/var/log/pods/*$1/*.log"
        }

        // Label creation -  "container_runtime" field from "__meta_kubernetes_pod_container_id"
        rule {
          source_labels = ["__meta_kubernetes_pod_container_id"]
          action = "replace"
          target_label = "container_runtime"
          regex = "^(\\S+):\\/\\/.+$"
          replacement = "$1"
        }
      }

      // loki.source.file tails pod logs from /var/log/pods/* on the host filesystem.
      // Previously used loki.source.kubernetes (apiserver streaming) which drove
      // kube-apiserver `CONNECT pods/log` to ~13 req/s + ~2200 sec/s of streams.
      // discovery.relabel.pod_logs already sets __path__ to the kubelet log path.
      loki.source.file "pod_logs" {
        targets    = discovery.relabel.pod_logs.output
        forward_to = [loki.process.pod_logs.receiver]
      }

      // loki.process receives log entries from other Loki components, applies one or more processing stages,
      // and forwards the results to the list of receivers in the component's arguments.
      loki.process "pod_logs" {
        stage.static_labels {
            values = {
              cluster = "default",
            }
        }

        forward_to = [loki.write.default.receiver]
      }

      // Node-level journal log collection for kernel panics, OOMs, hung tasks, etc.
      // Ships system logs off-node so they survive hard resets.
      loki.source.journal "node_journal" {
        forward_to = [loki.process.journal.receiver]
        relabel_rules = loki.relabel.journal.rules
        labels = {
          job = "node-journal",
        }
        max_age = "12h"
      }

      loki.relabel "journal" {
        forward_to = []

        rule {
          source_labels = ["__journal__hostname"]
          target_label  = "node"
        }
        rule {
          source_labels = ["__journal__systemd_unit"]
          target_label  = "unit"
        }
        rule {
          source_labels = ["__journal_priority_keyword"]
          target_label  = "level"
        }
        rule {
          source_labels = ["__journal__transport"]
          target_label  = "transport"
        }
      }

      // Forward warning+ journal entries (priority 0-4: emerg, alert, crit, err, warning)
      // Also forwards kernel transport entries regardless of priority for OOM/panic detection.
      loki.process "journal" {
        stage.static_labels {
          values = {
            cluster = "default",
          }
        }

        // Drop info/debug/notice entries that aren't from the kernel transport
        stage.match {
          selector = "{job=\"node-journal\", level=~\"info|notice|debug\", transport!=\"kernel\"}"
          action   = "drop"
        }

        forward_to = [loki.write.default.receiver]
      }

      // Kubernetes audit log collection from /var/log/kubernetes/audit.log
      // Requires alloy.mounts.varlog=true to mount /var/log from the host
      local.file_match "audit_logs" {
        path_targets = [{
          __path__ = "/var/log/kubernetes/audit.log",
          job      = "kubernetes-audit",
          node     = env("HOSTNAME"),
        }]
      }

      loki.source.file "audit_logs" {
        targets    = local.file_match.audit_logs.targets
        forward_to = [loki.write.default.receiver]
      }

  # Mount /var/log from the host for file-based log collection (audit logs)
  mounts:
    varlog: true
    # Mount journal directories for loki.source.journal
    extra:
      - name: journal-run
        mountPath: /run/log/journal
        readOnly: true
      - name: journal-var
        mountPath: /var/log/journal
        readOnly: true
      - name: machine-id
        mountPath: /etc/machine-id
        readOnly: true

controller:
  volumes:
    extra:
      - name: journal-run
        hostPath:
          path: /run/log/journal
          type: DirectoryOrCreate
      - name: journal-var
        hostPath:
          path: /var/log/journal
          type: DirectoryOrCreate
      - name: machine-id
        hostPath:
          path: /etc/machine-id
          type: File

  # Schedule on control-plane node too so we can tail /var/log/kubernetes/audit.log
  # from kube-apiserver. Without this, K8s audit log shipping (wave 1 K2-K9 alert
  # rules) has no source. control-plane has the standard NoSchedule taint.
  tolerations:
    - key: "node-role.kubernetes.io/control-plane"
      operator: "Exists"
      effect: "NoSchedule"

  # Resource limits for DaemonSet pods
  # Alloy tails logs from all containers on the node via K8s API and batches
  # them to Loki. Memory scales with number of active log streams (~30-50 per node).
  # 128Mi was OOMKilled; steady-state usage is ~400-450Mi per pod.
  resources:
    requests:
      cpu: 50m
      memory: 512Mi
    limits:
      memory: 1Gi