Loki: Add a ring to the query scheduler to allow discovery via the ring as an alternative to DNS

CHANGELOG.md

@@ -5,6 +5,7 @@
 * [4443](https://github.com/grafana/loki/pull/4443) **DylanGuedes**: Loki: Change how push API checks for contentType
 * [4415](https://github.com/grafana/loki/pull/4415) **DylanGuedes**: Change default limits to common values
 * [4473](https://github.com/grafana/loki/pull/4473) **trevorwhitney**: Config: add object storage configuration to common config
+* [4425](https://github.com/grafana/loki/pull/4425) **trevorwhitney** and **slim-bean**: Add a ring for the query scheduler
 
 # 2.3.0 (2021/08/06)
 

docs/sources/configuration/_index.md

@@ -97,6 +97,10 @@ Pass the `-config.expand-env` flag at the command line to enable this way of set
 # just the querier.
 [querier: <querier_config>]
 
+# The query_scheduler block configures the Loki query scheduler.
+# When configured it separates the tenant query queues from the query-frontend
+[query_scheduler: <query_scheduler_config>]
+
 # The query_frontend_config configures the Loki query-frontend.
 [frontend: <query_frontend_config>]
 
@@ -282,6 +286,106 @@ engine:
   [max_look_back_period: <duration> | default = 30s]
 ```
 
+## query_scheduler_config
+
+The `query_scheduler_config` block configures the Loki query scheduler.
+
+```yaml
+# Maximum number of outstanding requests per tenant per query-scheduler.
+# In-flight requests above this limit will fail with HTTP response status code
+# 429.
+# CLI flag: -query-scheduler.max-outstanding-requests-per-tenant
+[max_outstanding_requests_per_tenant: <int> | default = 100]
+
+# This configures the gRPC client used to report errors back to the
+# query-frontend.
+[grpc_client_config: <grpc_client_config>]
+
+# Set to true to have the query schedulers create and place themselves in a ring.
+# If no frontend_address or scheduler_address are present 
+# anywhere else in the configuration, Loki will toggle this value to true.
+[use_scheduler_ring: <boolean> | default = false]
+
+# The hash ring configuration. This option is required only if use_scheduler_ring is true
+scheduler_ring:
+  # The key-value store used to share the hash ring across multiple instances.
+  kvstore:
+    # Backend storage to use for the ring. Supported values are: consul, etcd,
+    # inmemory, memberlist, multi.
+    # CLI flag: -scheduler.ring.store
+    [store: <string> | default = "memberlist"]
+
+    # The prefix for the keys in the store. Should end with a /.
+    # CLI flag: -scheduler.ring.prefix
+    [prefix: <string> | default = "schedulers/"]
+
+    # The consul_config configures the consul client.
+    # The CLI flags prefix for this block config is: scheduler.ring
+    [consul: <consul_config>]
+
+    # The etcd_config configures the etcd client.
+    # The CLI flags prefix for this block config is: scheduler.ring
+    [etcd: <etcd_config>]
+
+    multi:
+      # Primary backend storage used by multi-client.
+      # CLI flag: -scheduler.ring.multi.primary
+      [primary: <string> | default = ""]
+
+      # Secondary backend storage used by multi-client.
+      # CLI flag: -scheduler.ring.multi.secondary
+      [secondary: <string> | default = ""]
+
+      # Mirror writes to secondary store.
+      # CLI flag: -scheduler.ring.multi.mirror-enabled
+      [mirror_enabled: <boolean> | default = false]
+
+      # Timeout for storing value to secondary store.
+      # CLI flag: -scheduler.ring.multi.mirror-timeout
+      [mirror_timeout: <duration> | default = 2s]
+
+  # Interval between heartbeats sent to the ring. 0 = disabled.
+  # CLI flag: -scheduler.ring.heartbeat-period
+  [heartbeat_period: <duration> | default = 15s]
+
+  # The heartbeat timeout after which store gateways are considered unhealthy
+  # within the ring. 0 = never (timeout disabled). This option needs be set both
+  # on the store-gateway and querier when running in microservices mode.
+  # CLI flag: -scheduler.ring.heartbeat-timeout
+  [heartbeat_timeout: <duration> | default = 1m]
+
+  # File path where tokens are stored. If empty, tokens are neither stored at
+  # shutdown nor restored at startup.
+  # CLI flag: -scheduler.ring.tokens-file-path
+  [tokens_file_path: <string> | default = ""]
+
+  # True to enable zone-awareness and replicate blocks across different
+  # availability zones.
+  # CLI flag: -scheduler.ring.zone-awareness-enabled
+  [zone_awareness_enabled: <boolean> | default = false]
+
+  # Name of network interface to read addresses from.
+  # CLI flag: -scheduler.ring.instance-interface-names
+  [instance_interface_names: <list of string> | default = [eth0 en0]]
+
+  # IP address to advertise in the ring.
+  # CLI flag: -scheduler.ring.instance-addr
+  [instance_addr: <list of string> | default = first from instance_interface_names]
+
+  # Port to advertise in the ring
+  # CLI flag: -scheduler.ring.instance-port
+  [instance_port: <list of string> | default = server.grpc-listen-port]
+
+  # Instance ID to register in the ring.
+  # CLI flag: -scheduler.ring.instance-id
+  [instance_id: <list of string> | default = os.Hostname()]
+
+  # The availability zone where this instance is running. Required if
+  # zone-awareness is enabled.
+  # CLI flag: -scheduler.ring.instance-availability-zone
+  [instance_availability_zone: <string> | default = ""]
+```
+
 ## query_frontend_config
 
 The query_frontend_config configures the Loki query-frontend.
@@ -315,8 +419,9 @@ The query_frontend_config configures the Loki query-frontend.
 
 # How often to resolve the scheduler-address, in order to look for new
 # query-scheduler instances.
+# Also used to determine how often to poll the scheduler-ring for addresses if configured.
 # CLI flag: -frontend.scheduler-dns-lookup-period
-[scheduler_dns_lookup_period: <duration> | default = 10s]
+[scheduler_dns_lookup_period: <duration> | default = 3s]
 
 # Number of concurrent workers forwarding queries to single query-scheduler.
 # CLI flag: -frontend.scheduler-worker-concurrency
@@ -776,9 +881,10 @@ The `frontend_worker_config` configures the worker - running within the Loki que
 # CLI flag: -querier.worker-parallelism
 [parallelism: <int> | default = 10]
 
-# How often to query DNS.
+# How often to query the frontend_address DNS to resolve frontend addresses.
+# Also used to determine how often to poll the scheduler-ring for addresses if configured.
 # CLI flag: -querier.dns-lookup-period
-[dns_lookup_duration: <duration> | default = 10s]
+[dns_lookup_duration: <duration> | default = 3s]
 
 # The CLI flags prefix for this block config is: querier.frontend-client
 [grpc_client_config: <grpc_client_config>]

go.mod

@@ -31,6 +31,7 @@ require (
 	github.com/felixge/fgprof v0.9.1
 	github.com/fluent/fluent-bit-go v0.0.0-20190925192703-ea13c021720c
 	github.com/fsouza/fake-gcs-server v1.7.0
+	github.com/go-kit/kit v0.11.0 // indirect
 	github.com/go-kit/log v0.2.0
 	github.com/go-logfmt/logfmt v0.5.1
 	github.com/go-redis/redis/v8 v8.11.4
@@ -147,7 +148,6 @@ require (
 	github.com/edsrzf/mmap-go v1.0.0 // indirect
 	github.com/felixge/httpsnoop v1.0.1 // indirect
 	github.com/fsnotify/fsnotify v1.4.9 // indirect
-	github.com/go-kit/kit v0.11.0 // indirect
 	github.com/go-logr/logr v0.4.0 // indirect
 	github.com/go-openapi/analysis v0.20.0 // indirect
 	github.com/go-openapi/errors v0.20.0 // indirect

pkg/loki/config_wrapper.go

@@ -73,14 +73,22 @@ func (c *ConfigWrapper) ApplyDynamicConfig() cfg.Source {
 			}
 		}
 
+		// If nobody has defined any frontend address or scheduler address
+		// we can default to using the query scheduler ring for scheduler discovery.
+		if r.Worker.FrontendAddress == "" &&
+			r.Worker.SchedulerAddress == "" &&
+			r.Frontend.FrontendV2.SchedulerAddress == "" {
+			r.QueryScheduler.UseSchedulerRing = true
+		}
+
 		applyMemberlistConfig(r)
 		applyStorageConfig(r, &defaults)
 
 		return nil
 	}
 }
 
-// applyMemberlistConfig will change the default ingester, distributor, and ruler ring configurations to use memberlist
+// applyMemberlistConfig will change the default ingester, distributor, ruler, and query scheduler ring configurations to use memberlist
 // if the -memberlist.join_members config is provided. The idea here is that if a user explicitly configured the
 // memberlist configuration section, they probably want to be using memberlist for all their ring configurations.
 // Since a user can still explicitly override a specific ring configuration (for example, use consul for the distributor),
@@ -90,6 +98,7 @@ func applyMemberlistConfig(r *ConfigWrapper) {
 		r.Ingester.LifecyclerConfig.RingConfig.KVStore.Store = memberlistStr
 		r.Distributor.DistributorRing.KVStore.Store = memberlistStr
 		r.Ruler.Ring.KVStore.Store = memberlistStr
+		r.QueryScheduler.SchedulerRing.KVStore.Store = memberlistStr
 	}
 }
 

pkg/loki/loki.go

@@ -8,11 +8,9 @@ import (
 	"net/http"
 
 	cortex_tripper "github.com/cortexproject/cortex/pkg/querier/queryrange"
-	"github.com/cortexproject/cortex/pkg/querier/worker"
 	"github.com/cortexproject/cortex/pkg/ring"
 	cortex_ruler "github.com/cortexproject/cortex/pkg/ruler"
 	"github.com/cortexproject/cortex/pkg/ruler/rulestore"
-	"github.com/cortexproject/cortex/pkg/scheduler"
 	"github.com/cortexproject/cortex/pkg/util"
 	"github.com/cortexproject/cortex/pkg/util/fakeauth"
 	util_log "github.com/cortexproject/cortex/pkg/util/log"
@@ -38,8 +36,10 @@ import (
 	"github.com/grafana/loki/pkg/lokifrontend"
 	"github.com/grafana/loki/pkg/querier"
 	"github.com/grafana/loki/pkg/querier/queryrange"
+	"github.com/grafana/loki/pkg/querier/worker"
 	"github.com/grafana/loki/pkg/ruler"
 	"github.com/grafana/loki/pkg/runtime"
+	"github.com/grafana/loki/pkg/scheduler"
 	"github.com/grafana/loki/pkg/storage"
 	"github.com/grafana/loki/pkg/storage/chunk"
 	"github.com/grafana/loki/pkg/storage/stores/shipper/compactor"
@@ -224,6 +224,7 @@ type Loki struct {
 	MemberlistKV             *memberlist.KVInitService
 	compactor                *compactor.Compactor
 	QueryFrontEndTripperware cortex_tripper.Tripperware
+	queryScheduler           *scheduler.Scheduler
 
 	HTTPAuthMiddleware middleware.Interface
 }
@@ -435,13 +436,13 @@ func (t *Loki) setupModuleManager() error {
 		Querier:                  {Store, Ring, Server, IngesterQuerier, TenantConfigs},
 		QueryFrontendTripperware: {Server, Overrides, TenantConfigs},
 		QueryFrontend:            {QueryFrontendTripperware},
-		QueryScheduler:           {Server, Overrides},
+		QueryScheduler:           {Server, Overrides, MemberlistKV},
 		Ruler:                    {Ring, Server, Store, RulerStorage, IngesterQuerier, Overrides, TenantConfigs},
 		TableManager:             {Server},
 		Compactor:                {Server, Overrides},
 		IndexGateway:             {Server},
 		IngesterQuerier:          {Ring},
-		All:                      {QueryFrontend, Querier, Ingester, Distributor, TableManager, Ruler},
+		All:                      {QueryScheduler, QueryFrontend, Querier, Ingester, Distributor, Ruler},
 	}
 
 	// Add IngesterQuerier as a dependency for store when target is either ingester or querier.

pkg/loki/modules.go

@@ -12,13 +12,10 @@ import (
 
 	"github.com/NYTimes/gziphandler"
 	"github.com/cortexproject/cortex/pkg/cortex"
-	"github.com/cortexproject/cortex/pkg/frontend"
-	"github.com/cortexproject/cortex/pkg/frontend/transport"
 	"github.com/cortexproject/cortex/pkg/frontend/v1/frontendv1pb"
 	"github.com/cortexproject/cortex/pkg/frontend/v2/frontendv2pb"
 	"github.com/cortexproject/cortex/pkg/ring"
 	cortex_ruler "github.com/cortexproject/cortex/pkg/ruler"
-	"github.com/cortexproject/cortex/pkg/scheduler"
 	"github.com/cortexproject/cortex/pkg/scheduler/schedulerpb"
 	util_log "github.com/cortexproject/cortex/pkg/util/log"
 	"github.com/go-kit/log/level"
@@ -37,10 +34,13 @@ import (
 	"github.com/grafana/loki/pkg/ingester"
 	"github.com/grafana/loki/pkg/logproto"
 	"github.com/grafana/loki/pkg/logql"
+	"github.com/grafana/loki/pkg/lokifrontend/frontend"
+	"github.com/grafana/loki/pkg/lokifrontend/frontend/transport"
 	"github.com/grafana/loki/pkg/querier"
 	"github.com/grafana/loki/pkg/querier/queryrange"
 	"github.com/grafana/loki/pkg/ruler"
 	"github.com/grafana/loki/pkg/runtime"
+	"github.com/grafana/loki/pkg/scheduler"
 	loki_storage "github.com/grafana/loki/pkg/storage"
 	"github.com/grafana/loki/pkg/storage/chunk"
 	"github.com/grafana/loki/pkg/storage/chunk/cache"
@@ -210,6 +210,7 @@ func (t *Loki) initQuerier() (services.Service, error) {
 		QuerierWorkerConfig:   &t.Cfg.Worker,
 		QueryFrontendEnabled:  t.Cfg.isModuleEnabled(QueryFrontend),
 		QuerySchedulerEnabled: t.Cfg.isModuleEnabled(QueryScheduler),
+		SchedulerRing:         t.queryScheduler.SafeReadRing(),
 	}
 
 	var queryHandlers = map[string]http.Handler{
@@ -414,12 +415,20 @@ func (t *Loki) initQueryFrontendTripperware() (_ services.Service, err error) {
 func (t *Loki) initQueryFrontend() (_ services.Service, err error) {
 	level.Debug(util_log.Logger).Log("msg", "initializing query frontend", "config", fmt.Sprintf("%+v", t.Cfg.Frontend))
 
-	roundTripper, frontendV1, frontendV2, err := frontend.InitFrontend(frontend.CombinedFrontendConfig{
+	combinedCfg := frontend.CombinedFrontendConfig{
 		Handler:       t.Cfg.Frontend.Handler,
 		FrontendV1:    t.Cfg.Frontend.FrontendV1,
 		FrontendV2:    t.Cfg.Frontend.FrontendV2,
 		DownstreamURL: t.Cfg.Frontend.DownstreamURL,
-	}, disabledShuffleShardingLimits{}, t.Cfg.Server.GRPCListenPort, util_log.Logger, prometheus.DefaultRegisterer)
+	}
+	roundTripper, frontendV1, frontendV2, err := frontend.InitFrontend(
+		combinedCfg,
+		t.queryScheduler.SafeReadRing(),
+		disabledShuffleShardingLimits{},
+		t.Cfg.Server.GRPCListenPort,
+		util_log.Logger,
+		prometheus.DefaultRegisterer)
+
 	if err != nil {
 		return nil, err
 	}
@@ -660,13 +669,19 @@ func (t *Loki) initIndexGateway() (services.Service, error) {
 }
 
 func (t *Loki) initQueryScheduler() (services.Service, error) {
+	// Set some config sections from other config sections in the config struct
+	t.Cfg.QueryScheduler.SchedulerRing.ListenPort = t.Cfg.Server.GRPCListenPort
+	t.Cfg.QueryScheduler.SchedulerRing.KVStore.MemberlistKV = t.MemberlistKV.GetMemberlistKV
+
 	s, err := scheduler.NewScheduler(t.Cfg.QueryScheduler, t.overrides, util_log.Logger, prometheus.DefaultRegisterer)
 	if err != nil {
 		return nil, err
 	}
 
 	schedulerpb.RegisterSchedulerForFrontendServer(t.Server.GRPC, s)
 	schedulerpb.RegisterSchedulerForQuerierServer(t.Server.GRPC, s)
+	t.Server.HTTP.Handle("/scheduler/ring", s)
+	t.queryScheduler = s
 	return s, nil
 }
 

pkg/lokifrontend/config.go

@@ -3,9 +3,9 @@ package lokifrontend
 import (
 	"flag"
 
-	"github.com/cortexproject/cortex/pkg/frontend/transport"
-	v1 "github.com/cortexproject/cortex/pkg/frontend/v1"
-	v2 "github.com/cortexproject/cortex/pkg/frontend/v2"
+	"github.com/grafana/loki/pkg/lokifrontend/frontend/transport"
+	v1 "github.com/grafana/loki/pkg/lokifrontend/frontend/v1"
+	v2 "github.com/grafana/loki/pkg/lokifrontend/frontend/v2"
 )
 
 type Config struct {