Kubernetes Scheduler Startup and Configuration Sequence

K8S Scheduler Application Lifecycle.png

K8S Scheduler Application Lifecycle.svg

K8S Scheduler Configuration Handling.png

K8S Scheduler Configuration Handling.svg

scheduler-config-lifecycle.txt

title K8S Scheduler Configuration Handling
# Paste into https://sequencediagram.org/

participant "command line\nflags" as flags
participant "k8s.io/kubernetes/cmd/kube-scheduler/options\n++**Options**++" as Options
participant "k8s.io/kubernetes/cmd/kube-scheduler/config\n++**Config**++" as Config
participant "k8s.io/kubernetes/pkg/apis/componentconfig/v1alpha1\n++**KubeSchedulerConfiguration**++" as componentConfig
participant "k8s.io/kubernetes/cmd/kube-scheduler/config\n++**CompletedConfig**++" as CompletedConfig
participant "k8s.io/kubernetes/pkg/scheduler/api\n++**Policy**++" as Policy
participant "k8s.io/kubernetes/pkg/scheduler\n++**Configurator**++" as Configurator
participant "k8s.io/kubernetes/pkg/scheduler\n++**Config**++" as schedConfig
participant "k8s.io/kubernetes/pkg/scheduler\n++**Scheduler**++" as Scheduler


flags --> Options: parsed into fields of
destroysilent flags

Options -> *Config:
Options --> Config: ApplyTo() fills out some fields
Options -> *componentConfig: loadConfigFromFile()
componentConfig --> Options: member of
destroysilent componentConfig

Options --> Config: Config() fills out other fields
destroysilent Options

Config -> *CompletedConfig: Complete() applies some defaults
destroysilent Config

CompletedConfig -> *Configurator: NewConfigFactory()

abox left of CompletedConfig: Either a provider name or a Policy object is used

CompletedConfig -> *Policy: reads from ComponentConfig or separate file
destroysilent CompletedConfig

Configurator ->(3) *schedConfig: CreateFromProvider(string)\n               or\nCreateFromConfig(Policy)
destroysilent Configurator

space -7.1
Policy -> *schedConfig:
destroysilent Policy

schedConfig -> *Scheduler: NewFromConfig()
destroysilent schedConfig

note over Scheduler: now we can call Run()

==made with https://sequencediagram.org/==

scheduler-startup-sequence.txt

title K8S Scheduler Application Lifecycle
# Paste into https://sequencediagram.org/

participant "main()" as main
participant "command" as command
participant "anonymous\nfunc" as anonFunc
participant "k8s.io/kubernetes/cmd/kube-scheduler/options\n++**Options**++" as Options
participant "k8s.io/kubernetes/cmd/kube-scheduler/config\n++**Config**++" as Config
participant "k8s.io/kubernetes/cmd/kube-scheduler/config\n++**CompletedConfig**++" as CompletedConfig
participant "k8s.io/kubernetes/cmd/kube-scheduler/app\n++**func Run(CompletedConfig)**++" as appPkg
participant "k8s.io/client-go/tools/leaderelection\n++**LeaderElector**++" as LeaderElector
participant "k8s.io/kubernetes/pkg/scheduler\n++**Configurator**++" as Configurator
participant "k8s.io/kubernetes/pkg/scheduler\n++**Config**++" as schedulerConfig
participant "k8s.io/kubernetes/pkg/scheduler\n++**Scheduler**++" as scheduler


activate main
main->*command: NewSchedulerCommand()

note left of command:This is a\nCobra command
space -5
command->*anonFunc:value of `Run` field
#space -6
#rbox over main: flags get parsed\ninto `Options`

main->*Options: flags get parsed

main->command: Execute()
activate command
command->anonFunc:
activate anonFunc



anonFunc->>Options: Validate()

linear on
anonFunc->Options: Config()
space -5
Options->*Config:
destroysilent Options
linear off

linear on
anonFunc->Config:Complete()
space -5
Config->*CompletedConfig:
destroysilent Config
linear off

CompletedConfig-->(3)appPkg:
space -3
destroysilent CompletedConfig
activate appPkg


space -2
anonFunc->appPkg:
#activate appPkg

appPkg->*Configurator: NewConfigFactory(CompletedConfig)

abox over Configurator:++Informer event handlers\nare added here++

linear on
appPkg->Configurator: NewSchedulerConfig()
destroysilent Configurator
space -5
Configurator->*schedulerConfig:
schedulerConfig-->(4)*scheduler:
linear off




space -7.1
destroysilent schedulerConfig

appPkg->*scheduler:NewFromConfig(Config)

abox over appPkg:++Informers and broadcasters\nare started here++




appPkg->*LeaderElector:NewLeaderElector()
appPkg->LeaderElector: Run()
activate LeaderElector
LeaderElector->LeaderElector: acquire leadership
LeaderElector->scheduler: Run()
activate scheduler

rbox over scheduler:++This is the\n run loop!++

# Unroll the stack here
scheduler->LeaderElector: crash or lost leadership
deactivate scheduler
LeaderElector->appPkg:
deactivate LeaderElector
appPkg->anonFunc:
deactivate appPkg
anonFunc->command:
deactivate anonFunc
command->main:
deactivate command
deactivate main


==made with https://sequencediagram.org/==