Enhance housekeeping to add variety of tasks (#932)

This commit enhances Housekeeping to enable the addition of a variety
of tasks. Previously, Housekeeping was limited to only Client
Deactivation task.

In this update, the actual tasks are implemented in the service
package(e.g. clients), while housekeeping package is only
responsible for scheduling tasks. It is for separation of concerns.

go.mod

@@ -5,6 +5,7 @@ go 1.21
 require (
 	connectrpc.com/connect v1.12.0
 	connectrpc.com/grpchealth v1.3.0
+	github.com/go-co-op/gocron/v2 v2.10.1
 	github.com/go-playground/locales v0.14.0
 	github.com/go-playground/universal-translator v0.18.0
 	github.com/go-playground/validator/v10 v10.11.1
@@ -16,7 +17,7 @@ require (
 	github.com/rs/xid v1.5.0
 	github.com/spf13/cobra v1.5.0
 	github.com/spf13/viper v1.17.0
-	github.com/stretchr/testify v1.8.4
+	github.com/stretchr/testify v1.9.0
 	github.com/undefinedlabs/go-mpatch v1.0.6
 	go.mongodb.org/mongo-driver v1.11.7
 	go.uber.org/zap v1.23.0
@@ -35,10 +36,12 @@ require (
 	github.com/fsnotify/fsnotify v1.6.0 // indirect
 	github.com/golang/protobuf v1.5.3 // indirect
 	github.com/golang/snappy v0.0.4 // indirect
+	github.com/google/uuid v1.6.0 // indirect
 	github.com/hashicorp/go-immutable-radix v1.3.1 // indirect
 	github.com/hashicorp/golang-lru v0.5.4 // indirect
 	github.com/hashicorp/hcl v1.0.0 // indirect
 	github.com/inconshreveable/mousetrap v1.0.1 // indirect
+	github.com/jonboulle/clockwork v0.4.0 // indirect
 	github.com/klauspost/compress v1.17.0 // indirect
 	github.com/leodido/go-urn v1.2.1 // indirect
 	github.com/magiconair/properties v1.8.7 // indirect
@@ -53,6 +56,7 @@ require (
 	github.com/prometheus/common v0.37.0 // indirect
 	github.com/prometheus/procfs v0.8.0 // indirect
 	github.com/rivo/uniseg v0.4.2 // indirect
+	github.com/robfig/cron/v3 v3.0.1 // indirect
 	github.com/sagikazarmark/locafero v0.3.0 // indirect
 	github.com/sagikazarmark/slog-shim v0.1.0 // indirect
 	github.com/sourcegraph/conc v0.3.0 // indirect
@@ -66,8 +70,8 @@ require (
 	github.com/youmark/pkcs8 v0.0.0-20201027041543-1326539a0a0a // indirect
 	go.uber.org/atomic v1.10.0 // indirect
 	go.uber.org/multierr v1.9.0 // indirect
-	golang.org/x/exp v0.0.0-20230905200255-921286631fa9 // indirect
-	golang.org/x/sync v0.3.0 // indirect
+	golang.org/x/exp v0.0.0-20240613232115-7f521ea00fb8 // indirect
+	golang.org/x/sync v0.7.0 // indirect
 	golang.org/x/sys v0.15.0 // indirect
 	golang.org/x/text v0.14.0 // indirect
 	gopkg.in/ini.v1 v1.67.0 // indirect

go.sum

@@ -81,6 +81,8 @@ github.com/frankban/quicktest v1.14.4 h1:g2rn0vABPOOXmZUj+vbmUp0lPoXEMuhTpIluN0X
 github.com/frankban/quicktest v1.14.4/go.mod h1:4ptaffx2x8+WTWXmUCuVU6aPUX1/Mz7zb5vbUoiM6w0=
 github.com/fsnotify/fsnotify v1.6.0 h1:n+5WquG0fcWoWp6xPWfHdbskMCQaFnG6PfBrh1Ky4HY=
 github.com/fsnotify/fsnotify v1.6.0/go.mod h1:sl3t1tCWJFWoRz9R8WJCbQihKKwmorjAbSClcnxKAGw=
+github.com/go-co-op/gocron/v2 v2.10.1 h1:rlDqSrn+lcMCO4H2d/o+WxpeSTPNkcpW5oaJdeg1pnQ=
+github.com/go-co-op/gocron/v2 v2.10.1/go.mod h1:xY7bJxGazKam1cz04EebrlP4S9q4iWdiAylMGP3jY9w=
 github.com/go-gl/glfw v0.0.0-20190409004039-e6da0acd62b1/go.mod h1:vR7hzQXu2zJy9AVAgeJqvqgH9Q5CA+iKCZ2gyEVpxRU=
 github.com/go-gl/glfw/v3.3/glfw v0.0.0-20191125211704-12ad95a8df72/go.mod h1:tQ2UAYgL5IevRw8kRxooKSPJfGvJ9fJQFa0TUsXzTg8=
 github.com/go-gl/glfw/v3.3/glfw v0.0.0-20200222043503-6f7a984d4dc4/go.mod h1:tQ2UAYgL5IevRw8kRxooKSPJfGvJ9fJQFa0TUsXzTg8=
@@ -148,8 +150,8 @@ github.com/google/go-cmp v0.5.1/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/
 github.com/google/go-cmp v0.5.2/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-cmp v0.5.4/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
-github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
-github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
+github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
+github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/google/gofuzz v1.0.0/go.mod h1:dBl0BpW6vV/+mYPU4Po3pmUjxk6FQPldtuIdl/M65Eg=
 github.com/google/martian v2.1.0+incompatible/go.mod h1:9I4somxYTbIHy5NJKHRl3wXiIaQGbYVAs8BPL6v8lEs=
 github.com/google/martian/v3 v3.0.0/go.mod h1:y5Zk1BBys9G+gd6Jrk0W3cC1+ELVxBWuIGO+w/tUAp0=
@@ -166,11 +168,11 @@ github.com/google/pprof v0.0.0-20201203190320-1bf35d6f28c2/go.mod h1:kpwsk12EmLe
 github.com/google/pprof v0.0.0-20201218002935-b9804c9f04c2/go.mod h1:kpwsk12EmLew5upagYY7GY0pfYCcupk39gWOCRROcvE=
 github.com/google/renameio v0.1.0/go.mod h1:KWCgfxg9yswjAJkECMjeO8J8rahYeXnNhOm40UhjYkI=
 github.com/google/uuid v1.1.2/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
+github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
+github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/googleapis/gax-go/v2 v2.0.4/go.mod h1:0Wqv26UfaUD9n4G6kQubkQ+KchISgw+vpHVxEJEs9eg=
 github.com/googleapis/gax-go/v2 v2.0.5/go.mod h1:DWXyrwAJ9X0FpwwEdw+IPEYBICEFu5mhpdKc/us6bOk=
 github.com/googleapis/google-cloud-go-testing v0.0.0-20200911160855-bcd43fbb19e8/go.mod h1:dvDLG8qkwmyD9a/MJJN3XJcT3xFxOKAvTZGvuZmac9g=
-github.com/grpc-ecosystem/go-grpc-prometheus v1.2.0 h1:Ovs26xHkKqVztRpIrF/92BcuyuQ/YW4NSIpoGtfXNho=
-github.com/grpc-ecosystem/go-grpc-prometheus v1.2.0/go.mod h1:8NvIoxWQoOIhqOTXgfV/d3M/q6VIi02HzZEHgUlZvzk=
 github.com/hackerwins/go-memdb v1.3.3-0.20211225080334-513a74641622 h1:7UYuTq6zV83XV4zqn14gUuTtcywzbxGhUnj+hr/MUrE=
 github.com/hackerwins/go-memdb v1.3.3-0.20211225080334-513a74641622/go.mod h1:uBTr1oQbtuMgd1SSGoR8YV27eT3sBHbYiNm53bMpgSg=
 github.com/hashicorp/go-immutable-radix v1.3.0/go.mod h1:0y9vanUI8NX6FsYoO3zeMjhV/C5i9g4Q3DwcSNZ4P60=
@@ -191,6 +193,8 @@ github.com/inconshreveable/mousetrap v1.0.1 h1:U3uMjPSQEBMNp1lFxmllqCPM6P5u/Xq7P
 github.com/inconshreveable/mousetrap v1.0.1/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=
 github.com/jedib0t/go-pretty/v6 v6.4.9 h1:vZ6bjGg2eBSrJn365qlxGcaWu09Id+LHtrfDWlB2Usc=
 github.com/jedib0t/go-pretty/v6 v6.4.9/go.mod h1:Ndk3ase2CkQbXLLNf5QDHoYb6J9WtVfmHZu9n8rk2xs=
+github.com/jonboulle/clockwork v0.4.0 h1:p4Cf1aMWXnXAUh8lVfewRBx1zaTSYKrKMF2g3ST4RZ4=
+github.com/jonboulle/clockwork v0.4.0/go.mod h1:xgRqUGwRcjKCO1vbZUEtSLrqKoPSsUpK7fnezOII0kc=
 github.com/jpillora/backoff v1.0.0/go.mod h1:J/6gKK9jxlEcS3zixgDgUAsiuZ7yrSoa/FX5e0EB2j4=
 github.com/json-iterator/go v1.1.6/go.mod h1:+SdeFBvtyEkXs7REEP0seUULqWtbJapLOCVDaaPEHmU=
 github.com/json-iterator/go v1.1.10/go.mod h1:KdQUCv79m/52Kvf8AW2vK1V8akMuk1QjK/uOdHXbAo4=
@@ -279,6 +283,8 @@ github.com/prometheus/procfs v0.8.0/go.mod h1:z7EfXMXOkbkqb9IINtpCn86r/to3BnA0ua
 github.com/rivo/uniseg v0.2.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
 github.com/rivo/uniseg v0.4.2 h1:YwD0ulJSJytLpiaWua0sBDusfsCZohxjxzVTYjwxfV8=
 github.com/rivo/uniseg v0.4.2/go.mod h1:FN3SvrM+Zdj16jyLfmOkMNblXMcoc8DfTHruCPUcx88=
+github.com/robfig/cron/v3 v3.0.1 h1:WdRxkvbJztn8LMz/QEvLN5sBU+xKpSqwwUO1Pjr4qDs=
+github.com/robfig/cron/v3 v3.0.1/go.mod h1:eQICP3HwyT7UooqI/z+Ov+PtYAWygg1TEWWzGIFLtro=
 github.com/rogpeppe/go-internal v1.3.0/go.mod h1:M8bDsm7K2OlrFYOpmOWEs/qY81heoFRclV5y23lUDJ4=
 github.com/rogpeppe/go-internal v1.6.1/go.mod h1:xXDCJY+GAPziupqXw64V24skbSoqbTEfhy4qGm1nDQc=
 github.com/rogpeppe/go-internal v1.8.0/go.mod h1:WmiCO8CzOY8rg0OYDC4/i/2WRWAB6poM+XZ2dLUbcbE=
@@ -321,8 +327,9 @@ github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/
 github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/stretchr/testify v1.7.4/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
 github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
-github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
 github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
+github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
+github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
 github.com/subosito/gotenv v1.6.0 h1:9NlTDc1FTs4qu0DDq7AEtTPNw6SVm7uBMsUCUjABIf8=
 github.com/subosito/gotenv v1.6.0/go.mod h1:Dk4QP5c2W3ibzajGcXpNraDfq2IrhjMIvMSWPKKo0FU=
 github.com/tidwall/pretty v1.0.0 h1:HsD+QiTn7sK6flMKIvNmpqz1qrpP3Ps6jOKIKMooyg4=
@@ -352,8 +359,8 @@ go.opencensus.io v0.22.4/go.mod h1:yxeiOL68Rb0Xd1ddK5vPZ/oVn4vY4Ynel7k9FzqtOIw=
 go.opencensus.io v0.22.5/go.mod h1:5pWMHQbX5EPX2/62yrJeAkowc+lfs/XD7Uxpq3pI6kk=
 go.uber.org/atomic v1.10.0 h1:9qC72Qh0+3MqyJbAn8YU5xVq1frD8bn3JtD2oXtafVQ=
 go.uber.org/atomic v1.10.0/go.mod h1:LUxbIzbOniOlMKjJjyPfpl4v+PKK2cNJn91OQbhoJI0=
-go.uber.org/goleak v1.1.11 h1:wy28qYRKZgnJTxGxvye5/wgWr1EKjmUDGYox5mGlRlI=
-go.uber.org/goleak v1.1.11/go.mod h1:cwTWslyiVhfpKIDGSZEM2HlOvcqm+tG4zioyIeLoqMQ=
+go.uber.org/goleak v1.3.0 h1:2K3zAYmnTNqV73imy9J1T3WC+gmCePx2hEGkimedGto=
+go.uber.org/goleak v1.3.0/go.mod h1:CoHD4mav9JJNrW/WLlf7HGZPjdw8EucARQHekz1X6bE=
 go.uber.org/multierr v1.9.0 h1:7fIwc/ZtS0q++VgcfqFDxSBZVv/Xo49/SYnDFupUwlI=
 go.uber.org/multierr v1.9.0/go.mod h1:X2jQV1h+kxSjClGpnseKVIxpmcjrj7MNnI0bnlfKTVQ=
 go.uber.org/zap v1.23.0 h1:OjGQ5KQDEUawVHxNwQgPpiypGHOxo2mNZsOqTak4fFY=
@@ -381,8 +388,8 @@ golang.org/x/exp v0.0.0-20191227195350-da58074b4299/go.mod h1:2RIsYlXP63K8oxa1u0
 golang.org/x/exp v0.0.0-20200119233911-0405dc783f0a/go.mod h1:2RIsYlXP63K8oxa1u096TMicItID8zy7Y6sNkU49FU4=
 golang.org/x/exp v0.0.0-20200207192155-f17229e696bd/go.mod h1:J/WKrq2StrnmMY6+EHIKF9dgMWnmCNThgcyBT1FY9mM=
 golang.org/x/exp v0.0.0-20200224162631-6cc2880d07d6/go.mod h1:3jZMyOhIsHpP37uCMkUooju7aAi5cS1Q23tOzKc+0MU=
-golang.org/x/exp v0.0.0-20230905200255-921286631fa9 h1:GoHiUyI/Tp2nVkLI2mCxVkOjsbSXD66ic0XW0js0R9g=
-golang.org/x/exp v0.0.0-20230905200255-921286631fa9/go.mod h1:S2oDrQGGwySpoQPVqRShND87VCbxmc6bL1Yd2oYrm6k=
+golang.org/x/exp v0.0.0-20240613232115-7f521ea00fb8 h1:yixxcjnhBmY0nkL253HFVIm0JsFHwrHdT3Yh6szTnfY=
+golang.org/x/exp v0.0.0-20240613232115-7f521ea00fb8/go.mod h1:jj3sYF3dwk5D+ghuXyeI3r5MFf+NT2An6/9dOA95KSI=
 golang.org/x/image v0.0.0-20190227222117-0694c2d4d067/go.mod h1:kZ7UVZpmo3dzQBMxlp+ypCbDeSB+sBbTgSJuh5dn5js=
 golang.org/x/image v0.0.0-20190802002840-cff245a6509b/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=
 golang.org/x/lint v0.0.0-20181026193005-c67002cb31c3/go.mod h1:UVdnD1Gm6xHRNCYTkRU2/jEulfH38KcIWyp/GAMgvoE=
@@ -467,8 +474,8 @@ golang.org/x/sync v0.0.0-20200625203802-6e8e738ad208/go.mod h1:RxMgew5VJxzue5/jJ
 golang.org/x/sync v0.0.0-20201020160332-67f06af15bc9/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20201207232520-09787c993a3a/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.3.0 h1:ftCYgMx6zT/asHUrPw8BLLscYtGznsLAnjq5RH9P66E=
-golang.org/x/sync v0.3.0/go.mod h1:FU7BRWz2tNW+3quACPkgCx/L+uEAv1htQ0V83Z9Rj+Y=
+golang.org/x/sync v0.7.0 h1:YsImfSBoP9QPYL0xyKJPq0gcaJdG3rInoqxTWbfQu9M=
+golang.org/x/sync v0.7.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
 golang.org/x/sys v0.0.0-20180830151530-49385e6e1522/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20180905080454-ebe1bf3edb33/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20181116152217-5ac8a444bdc5/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=

server/backend/backend.go

@@ -43,16 +43,15 @@ import (
 // Backend manages Yorkie's backend such as Database and Coordinator. And it
 // has the server status such as the information of this Server.
 type Backend struct {
-	Config     *Config
-	serverInfo *sync.ServerInfo
+	Config           *Config
+	serverInfo       *sync.ServerInfo
+	AuthWebhookCache *cache.LRUExpireCache[string, *types.AuthWebhookResponse]
 
+	Metrics      *prometheus.Metrics
 	DB           database.Database
 	Coordinator  sync.Coordinator
-	Metrics      *prometheus.Metrics
 	Background   *background.Background
 	Housekeeping *housekeeping.Housekeeping
-
-	AuthWebhookCache *cache.LRUExpireCache[string, *types.AuthWebhookResponse]
 }
 
 // New creates a new instance of Backend.
@@ -62,6 +61,8 @@ func New(
 	housekeepingConf *housekeeping.Config,
 	metrics *prometheus.Metrics,
 ) (*Backend, error) {
+	// 01. Build the server info with the given hostname or the hostname of the
+	// current machine.
 	hostname := conf.Hostname
 	if hostname == "" {
 		hostname, err := os.Hostname()
@@ -77,10 +78,21 @@ func New(
 		UpdatedAt: time.Now(),
 	}
 
+	// 02. Create the auth webhook cache. The auth webhook cache is used to
+	// cache the response of the auth webhook.
+	// TODO(hackerwins): Consider to extend the cache for general purpose.
+	webhookCache, err := cache.NewLRUExpireCache[string, *types.AuthWebhookResponse](conf.AuthWebhookCacheSize)
+	if err != nil {
+		return nil, err
+	}
+
+	// 03. Create the background instance. The background instance is used to
+	// manage background tasks.
 	bg := background.New()
 
+	// 04. Create the database instance. If the MongoDB configuration is given,
+	// create a MongoDB instance. Otherwise, create a memory database instance.
 	var db database.Database
-	var err error
 	if mongoConf != nil {
 		db, err = mongo.Dial(mongoConf)
 		if err != nil {
@@ -93,23 +105,32 @@ func New(
 		}
 	}
 
+	// 05. Create the coordinator instance. The coordinator is used to manage
+	// the synchronization between the Yorkie servers.
 	// TODO(hackerwins): Implement the coordinator for a shard. For now, we
 	//  distribute workloads to all shards per document. In the future, we
 	//  will need to distribute workloads of a document.
 	coordinator := memsync.NewCoordinator(serverInfo)
 
-	authWebhookCache, err := cache.NewLRUExpireCache[string, *types.AuthWebhookResponse](conf.AuthWebhookCacheSize)
+	// 06. Create the housekeeping instance. The housekeeping is used
+	// to manage keeping tasks such as deactivating inactive clients.
+	keeping, err := housekeeping.New(housekeepingConf)
 	if err != nil {
 		return nil, err
 	}
 
-	keeping, err := housekeeping.Start(
-		housekeepingConf,
-		db,
-		coordinator,
-	)
-	if err != nil {
-		return nil, err
+	// 07. Ensure the default user and project. If the default user and project
+	// do not exist, create them.
+	if conf.UseDefaultProject {
+		_, _, err = db.EnsureDefaultUserAndProject(
+			context.Background(),
+			conf.AdminUser,
+			conf.AdminPassword,
+			conf.ClientDeactivateThreshold,
+		)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	dbInfo := "memory"
@@ -123,38 +144,37 @@ func New(
 		dbInfo,
 	)
 
-	_, _, err = db.EnsureDefaultUserAndProject(
-		context.Background(),
-		conf.AdminUser,
-		conf.AdminPassword,
-		conf.ClientDeactivateThreshold,
-	)
-	if err != nil {
-		return nil, err
-	}
-
 	return &Backend{
-		Config:     conf,
-		serverInfo: serverInfo,
+		Config:           conf,
+		serverInfo:       serverInfo,
+		AuthWebhookCache: webhookCache,
 
-		Background:   bg,
 		Metrics:      metrics,
 		DB:           db,
 		Coordinator:  coordinator,
+		Background:   bg,
 		Housekeeping: keeping,
-
-		AuthWebhookCache: authWebhookCache,
 	}, nil
 }
 
+// Start starts the backend.
+func (b *Backend) Start() error {
+	if err := b.Housekeeping.Start(); err != nil {
+		return err
+	}
+
+	logging.DefaultLogger().Infof("backend started: id: %s", b.serverInfo.ID)
+	return nil
+}
+
 // Shutdown closes all resources of this instance.
 func (b *Backend) Shutdown() error {
-	b.Background.Close()
-
 	if err := b.Housekeeping.Stop(); err != nil {
 		return err
 	}
 
+	b.Background.Close()
+
 	if err := b.Coordinator.Close(); err != nil {
 		logging.DefaultLogger().Error(err)
 	}

server/backend/housekeeping/config.go

@@ -14,6 +14,8 @@
  * limitations under the License.
  */
 
+// Package housekeeping is the package for housekeeping service. It cleans up
+// the resources and data that is no longer needed.
 package housekeeping
 
 import (
@@ -59,3 +61,13 @@ func (c *Config) Validate() error {
 
 	return nil
 }
+
+// ParseInterval parses the interval.
+func (c *Config) ParseInterval() (time.Duration, error) {
+	interval, err := time.ParseDuration(c.Interval)
+	if err != nil {
+		return 0, fmt.Errorf("parse interval %s: %w", c.Interval, err)
+	}
+
+	return interval, nil
+}