Kubernetes Query Frontend Example
This aims to be a general purpose example; there are a number of substitutions to make for it to work correctly. These variables take the form of <variable_name>. You should override them with specifics to your environment.
It’s a common occurrence to start running Grafana Loki as a single binary while trying it out in order to simplify deployments and defer learning the (initially unnecessary) nitty gritty details. As we become more comfortable with its paradigms and begin migrating towards a more production ready deployment there are a number of things to be aware of. A common bottleneck is on the read path: queries that executed effortlessly on small data sets may churn to a halt on larger ones. Sometimes we can solve this with more queriers. However, that doesn’t help when our queries are too large for a single querier to execute. Then we need the query frontend.
One of the most important functions of the query frontend is the ability to split larger queries into smaller ones, execute them in parallel, and stitch the results back together. How often it splits them is determined by the
querier.split-queries-by-interval flag or the yaml config
query_range.split_queriers_by_interval. With this set to
1h, the frontend will dissect a day long query into 24 one hour queries, distribute them to the queriers, and collect the results. This is immensely helpful in production environments as it not only allows us to perform larger queries via aggregation, but also evens the work distribution across queriers so that one or two are not stuck with impossibly large queries while others are left idle.
Use this ConfigMap to get the benefits of query parallelisation and caching with the query-frontend component.
apiVersion: v1 kind: ConfigMap metadata: name: loki-frontend namespace: <namespace> data: config.yaml: | # Disable the requirement that every request to Loki has a # X-Scope-OrgID header. `fake` will be substituted in instead. auth_enabled: false # We don't want the usual /api/prom prefix. http_prefix: server: http_listen_port: 3100 query_range: # make queries more cache-able by aligning them with their step intervals align_queries_with_step: true max_retries: 5 cache_results: true results_cache: cache: # We're going to use the in-process "FIFO" cache enable_fifocache: true fifocache: size: 1024 validity: 24h limits_config: max_cache_freshness_per_query: '10m' # parallelize queries in 15min intervals split_queries_by_interval: 15m frontend: log_queries_longer_than: 5s downstream_url: http://querier.<namespace>.svc.cluster.local:3100 compress_responses: true
apiVersion: v1 kind: Service metadata: annotations: labels: name: query-frontend name: query-frontend namespace: <namespace> spec: ports: - name: query-frontend-http port: 3100 protocol: TCP targetPort: 3100 selector: name: query-frontend sessionAffinity: None type: ClusterIP ClusterIP: None publishNotReadyAddresses: true
apiVersion: extensions/v1beta1 kind: Deployment metadata: labels: name: query-frontend name: query-frontend namespace: <namespace> spec: minReadySeconds: 10 replicas: 2 selector: matchLabels: name: query-frontend template: metadata: labels: name: query-frontend spec: containers: - args: - -config.file=/etc/loki/config.yaml - -log.level=debug - -target=query-frontend image: grafana/loki:latest imagePullPolicy: Always name: query-frontend ports: - containerPort: 3100 name: http protocol: TCP resources: limits: memory: 1200Mi requests: cpu: "2" memory: 600Mi volumeMounts: - mountPath: /etc/loki name: loki-frontend restartPolicy: Always terminationGracePeriodSeconds: 30 volumes: - configMap: defaultMode: 420 name: loki-frontend name: loki-frontend
Once you’ve deployed these, point your Grafana datasource to the new frontend service. The service is available within the cluster at
GRPC Mode (Pull model)
The query frontend operates in one of two ways:
--frontend.downstream-urlor its YAML equivalent,
frontend.downstream_url. This proxies requests over HTTP to the specified URL.
--frontend.downstream-urlor its yaml equivalent
frontend.downstream_url, the query frontend defaults to a pull service. As a pull service, the frontend instantiates per-tenant queues that downstream queriers pull queries from via GRPC. To act as a pull service, queriers need to specify
-querier.frontend-addressor its YAML equivalent
ClusterIP=Nonefor the query frontend pull service. This causes DNS resolution of each query frontend pod IP address. It avoids wrongly resolving to the service IP.
publishNotReadyAddresses=trueon the query frontend pull service. Doing so eliminates a race condition in which the query frontend address is needed before the query frontend becomes ready when at least one querier connects.