Define ksonnet lib for query scheduler. (#4102)

* Define ksonnet definition for query scheduler.

* Enable query scheduler based on config flag.

production/ksonnet/loki/config.libsonnet

@@ -13,6 +13,7 @@
     using_boltdb_shipper: true,
 
     wal_enabled: false,
+    query_scheduler_enabled: false,
 
     // flags for running ingesters/queriers as a statefulset instead of deployment type.
     stateful_ingesters: false,

production/ksonnet/loki/loki.libsonnet

@@ -13,6 +13,10 @@
 (import 'query-frontend.libsonnet') +
 (import 'ruler.libsonnet') +
 
+// Query scheduler support
+// must be mixed in after frontend and querier so it can override their configuration.
+(import 'query-scheduler.libsonnet') + 
+
 // Supporting services
 (import 'memcached.libsonnet') +
 

production/ksonnet/loki/query-scheduler.libsonnet

@@ -0,0 +1,51 @@
+
+local k = import 'ksonnet-util/kausal.libsonnet';
+
+{
+  // Override frontend and querier configuration
+  _config +:: {
+    loki+: if $._config.query_scheduler_enabled then {
+      frontend+: {
+        scheduler_address: 'query-scheduler.%s.svc.cluster.local:9095' % $._config.namespace,
+      },
+      frontend_worker+: {
+        frontend_address: '',
+        scheduler_address: 'query-scheduler.%s.svc.cluster.local:9095' % $._config.namespace,
+      },
+    } else {},
+  },
+
+  query_scheduler_args:: if $._config.query_scheduler_enabled then
+    $._config.commonArgs {
+      target: 'query-scheduler',
+      'log.level': 'debug',
+    }
+  else {},
+
+  local container = k.core.v1.container,
+  query_scheduler_container:: if $._config.query_scheduler_enabled then
+    container.new('query-scheduler', $._images.query_frontend) +
+    container.withPorts($.util.defaultPorts) +
+    container.withArgsMixin(k.util.mapToFlags($.query_scheduler_args)) +
+    $.jaeger_mixin +
+    k.util.resourcesRequests('2', '600Mi') +
+    k.util.resourcesLimits(null, '1200Mi')
+  else {},
+
+  local deployment = k.apps.v1.deployment,
+  query_scheduler_deployment: if $._config.query_scheduler_enabled then
+    deployment.new('query-scheduler', 2, [$.query_scheduler_container]) +
+    $.config_hash_mixin +
+    k.util.configVolumeMount('loki', '/etc/loki/config') +
+    k.util.configVolumeMount(
+      $._config.overrides_configmap_mount_name,
+      $._config.overrides_configmap_mount_path,
+    ) +
+    k.util.antiAffinity
+  else {},
+
+  local service = k.core.v1.service,
+  query_scheduler_service: if $._config.query_scheduler_enabled then
+    k.util.serviceFor($.query_scheduler_deployment)
+  else {},
+}