Install on Istio

When installing Loki on Istio service mesh you must complete some additional steps. Without these steps, the ingester, querier, etc. might start, but you will see logs like the following:

loki level=debug ts=2021-11-24T11:33:37.352544925Z caller=broadcast.go:48 msg="Invalidating forwarded broadcast" key=collectors/distributor version=123 oldVersion=122 content=[loki-distributor-59c4896444-t9t6g[] oldContent=[loki-distributor-59c4896444-t9t6g[]

This means that the pod is failing to join the ring.

If you try to add loki to Grafana data sources, you will see logs like (empty ring):

loki level=warn ts=2021-11-24T08:02:42.08262122Z caller=logging.go:72 traceID=3fc821042d8ada1a orgID=fake msg="GET /loki/api/v1/labels?end=1637740962079859431&start=1637740361925000000 (500) 97.4µs Response: \"empty ring\\n\" ws: false; X-Scope-Orgid: fake; uber-trace-id: 3fc821042d8ada1a:1feed8872deea75c:1180f95a8235bb6c:0; "

When you enable istio-injection on the namespace where Loki is running, you need to also modify the configuration for the Loki services. Given that Istio will not allow a pod to resolve another pod using an IP address, you must also modify the memberlist service.

Required changes

Query frontend service

Make the following modifications to the file for the Loki Query Frontend service.

Change the name of grpc port to grpclb. This is used by the grpc load balancing strategy which relies on SRV records. Otherwise the querier will not be able to reach the query-frontend. See https://github.com/grafana/loki/blob/0116aa61c86fa983ddcbbd5e30a2141d2e89081a/production/ksonnet/loki/common.libsonnet#L19 and https://grpc.github.io/grpc/core/md_doc_load-balancing.html
Set the appProtocol of grpclb to tcp
Set publishNotReadyAddresses to true

apiVersion: v1
kind: Service
metadata:
  labels:
    app: loki-query-frontend
    app.kubernetes.io/instance: observability
    app.kubernetes.io/name: loki-query-frontend
spec:
  ports:
  - appProtocol: http
    name: http
    port: 3100
    protocol: TCP
    targetPort: http
  - appProtocol: tcp
    name: grpclb
    port: 9095
    protocol: TCP
    targetPort: grpc
  publishNotReadyAddresses: true
  selector:
    app: loki-query-frontend
    app.kubernetes.io/instance: observability
    app.kubernetes.io/name: loki-query-frontend
  type: ClusterIP

Querier service

Make the following modifications to the file for the Loki Querier service.

Set the appProtocol of the grpc service to tcp

apiVersion: v1
kind: Service
metadata:
  labels:
    app: loki-querier
    app.kubernetes.io/instance: observability
    app.kubernetes.io/name: loki-querier
  name: loki-querier
  namespace: observability
spec:
  ports:
  - appProtocol: http
    name: http
    port: 3100
    protocol: TCP
    targetPort: http
  - appProtocol: tcp
    name: grpc
    port: 9095
    protocol: TCP
    targetPort: grpc
  selector:
    app: loki-querier
    app.kubernetes.io/instance: observability
    app.kubernetes.io/name: loki-querier
  type: ClusterIP

Ingester service and Ingester headless service

Make the following modifications to the file for the Loki Query Ingester and Ingester Headless service.

Set the appProtocol of the grpc port to tcp.

apiVersion: v1
kind: Service
metadata:
  labels:
    app: loki-ingester-(headless)
    app.kubernetes.io/instance: observability
    app.kubernetes.io/name: loki-ingester
  name: loki-ingester-headless
spec:  
  clusterIP: None (if headless)
  ports:
  - name: http
    port: 3100
    protocol: TCP
    targetPort: http
  - appProtocol: tcp
    name: grpc
    port: 9095
    protocol: TCP
    targetPort: grpc
  selector:
    app: loki-ingester
    app.kubernetes.io/instance: observability
    app.kubernetes.io/name: loki-ingester
  type: ClusterIP

Distributor service

Make the following modifications to the file for the Loki Distributor service.

Set the appProtocol of the grpc port to tcp.

apiVersion: v1
kind: Service
metadata:
  labels:
    app: loki-distributor
    app.kubernetes.io/instance: observability
    app.kubernetes.io/name: loki-distributor
spec:
  ports:
  - name: http
    port: 3100
    protocol: TCP
    targetPort: http
  - name: grpc
    port: 9095
    protocol: TCP
    targetPort: grpc
    appProtocol: tcp
  selector:
    app: loki-distributor
    app.kubernetes.io/instance: observability
    app.kubernetes.io/name: loki-distributor
  sessionAffinity: None
  type: ClusterIP

Memberlist service

Make the following modifications to the file for the Memberlist service.

Set the appProtocol of the http port to tcp.

apiVersion: v1
kind: Service
metadata:
  labels:
    app.kubernetes.io/instance: observability
  name: loki-memberlist
  namespace: observability
spec:
  clusterIP: None
  ports:
    - name: http
      port: 7946
      protocol: TCP
      targetPort: 7946
      appProtocol: tcp
  selector:
    app.kubernetes.io/instance: observability
    app.kubernetes.io/part-of: memberlist