sample-alloy-config.alloy

// Alloy configuration for collecting JSON logs and sending to Loki
// This configuration captures logs from the trace-test-app and forwards them to Loki

// Discover Kubernetes pods with specific labels
discovery.kubernetes "pods" {
  role = "pod"
  namespaces {
    names = ["default"]
  }
}

// Relabel discovered targets to filter for trace-test-app
discovery.relabel "trace_test_app" {
  targets = discovery.kubernetes.pods.targets

  // Keep only pods with app=trace-test label
  rule {
    source_labels = ["__meta_kubernetes_pod_label_app"]
    regex         = "trace-test"
    action        = "keep"
  }

  // Set the pod name as a label
  rule {
    source_labels = ["__meta_kubernetes_pod_name"]
    target_label  = "pod"
  }

  // Set the namespace as a label
  rule {
    source_labels = ["__meta_kubernetes_namespace"]
    target_label  = "namespace"
  }

  // Set the container name as a label
  rule {
    source_labels = ["__meta_kubernetes_pod_container_name"]
    target_label  = "container"
  }

  // Set the node name as a label
  rule {
    source_labels = ["__meta_kubernetes_pod_node_name"]
    target_label  = "node"
  }
}

// Source logs from discovered pods
loki.source.kubernetes "trace_test_logs" {
  targets    = discovery.relabel.trace_test_app.output
  forward_to = [loki.process.json_parser.receiver]
}

// Process and parse JSON logs
loki.process "json_parser" {
  // Parse JSON log lines
  stage.json {
    expressions = {
      level       = "levelname",
      timestamp   = "asctime",
      message     = "message",
      name        = "name",
      component   = "component",
      operation   = "operation",
      item_id     = "item_id",
      trace_id    = "trace_id",
      span_id     = "span_id",
      error_type  = "error_type",
      endpoint    = "endpoint",
      method      = "method",
      user_id     = "user_id",
      environment = "environment",
    }
  }

  // Convert level to lowercase for consistency
  stage.template {
    source   = "level"
    template = "{{ ToLower .Value }}"
  }

  // Set the log level as a label
  stage.labels {
    values = {
      level     = "level",
      component = "component",
      operation = "operation",
    }
  }

  // Use the parsed timestamp
  stage.timestamp {
    source = "timestamp"
    format = "2006-01-02 15:04:05,000"
  }

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

// Write logs to Loki
loki.write "local_loki" {
  endpoint {
    url = "http://loki.loki.svc:3100/loki/api/v1/push"

    // Optional: Add basic auth if required
    // basic_auth {
    //   username = "user"
    //   password = "pass"
    // }
  }

  external_labels = {
    cluster = "demo-cluster",
    job     = "trace-test-app",
  }
}