service

Schemas

• Service
  • Container
    • Filespec
    • LifeCycle
    • Probe
      • Exec
      • Http
      • Tcp
  • Secret

Schema Service

Service is a kind of workload profile that describes how to run your application code. This
is typically used for long-running web applications that should "never" go down, and handle
short-lived latency-sensitive web requests, or events.

Attributes

name	type	description	default value
annotations	{str:str}	Annotations are key/value pairs that attach arbitrary non-identifying metadata to the workload.
containers required	{str:}	Containers defines the templates of containers to be ran. More info: https://kubernetes.io/docs/concepts/containers
labels	{str:str}	Labels are key/value pairs that are attached to the workload.
replicas	int	Number of container replicas based on this configuration that should be ran.
secrets	{str:Secret}	Secrets can be used to store small amount of sensitive data e.g. password, token.

Examples

# Instantiate a long-running service and its image is "nginx:v1"

import kam.workload as wl
import kam.workload.container as c

nginxSvc : wl.Service {
    containers: {
        "nginx": c.Container {
            image: "nginx:v1"
        }
    }
}

Base Schema

WorkloadBase

Schema Container

Container describes how the Application's tasks are expected to be run. Depending on
the replicas parameter 1 or more containers can be created from each template.

Attributes

name	type	description	default value
args	[str]	Arguments to the entrypoint. Args will overwrite the CMD value set in the Dockfile, otherwise the Docker image's CMD is used if this is not provided.
command	[str]	Entrypoint array. Not executed within a shell. Command will overwrite the ENTRYPOINT value set in the Dockfile, otherwise the Docker image's ENTRYPOINT is used if this is not provided.
dirs	{str:str}	Collection of volumes mount into the container's filesystem. The dirs parameter is a dict with the key being the folder name in the container and the value being the referenced volume.
env	{str:str}	List of environment variables to set in the container. The value of the environment variable may be static text or a value from a secret.
files	{str:FileSpec}	List of files to create in the container. The files parameter is a dict with the key being the file name in the container and the value being the target file specification.
image required	str	Image refers to the Docker image name to run for this container. More info: https://kubernetes.io/docs/concepts/containers/images
lifecycle	lc.Lifecycle	Lifecycle refers to actions that the management system should take in response to container lifecycle events.
livenessProbe	p.Probe	LivenessProbe indicates if a running process is healthy. Container will be restarted if the probe fails.
readinessProbe	p.Probe	ReadinessProbe indicates whether an application is available to handle requests.
resources	{str:str}	Map of resource requirements the container should run with. The resources parameter is a dict with the key being the resource name and the value being the resource value.
startupProbe	p.Probe	StartupProbe indicates that the container has started for the first time. Container will be restarted if the probe fails.
workingDir	str	The working directory of the running process defined in entrypoint. Default container runtime will be used if this is not specified.

Examples

import kam.workload.container as c

web = c.Container {
    image:   "nginx:latest"
    command: ["/bin/sh", "-c", "echo hi"]
    env: {
        "name": "value"
    }
    resources: {
        "cpu": "2"
        "memory": "4Gi"
    }
}

Schema FileSpec

FileSpec defines the target file in a Container.

Attributes

name	type	description	default value
content	str	File content in plain text.
contentFrom	str	Source for the file content, reference to a secret of configmap value.
mode required	str	Mode bits used to set permissions on this file, must be an octal value between 0000 and 0777 or a decimal value between 0 and 511	"0644"

Examples

import kam.workload.container as c

tmpFile = c.FileSpec {
    content: "some file contents"
    mode: "0777"
}

Schema Lifecycle

Lifecycle describes actions that the management system should take in response to container lifecycle events.

Attributes

name	type	description	default value
postStart			The action to be taken after a container is created. More info: https://kubernetes.io/docs/concepts/containers/container-lifecycle-hooks/#container-hooks
preStop			The action to be taken before a container is terminated due to an API request or management event such as liveness/startup probe failure, preemption, resource contention, etc. More info: https://kubernetes.io/docs/concepts/containers/container-lifecycle-hooks/#container-hooks

Examples

import kam.workload.container.probe as p
import kam.workload.container.lifecycle as lc

lifecycleHook = lc.Lifecycle {
    preStop: p.Exec {
        command: ["preStop.sh"]
    }
    postStart: p.Http {
        url: "http://localhost:80"
    }
}

Schema Exec

Exec describes a "run in container" action.

Attributes

name	type	description	default value
command required	[str]	The command line to execute inside the container.

Examples

import kam.workload.container.probe as p

execProbe = p.Exec {
    command: ["probe.sh"]
}

Schema Http

Http describes an action based on HTTP Get requests.

Attributes

name	type	description	default value
headers	{str:str}	Collection of custom headers to set in the request
url required	str	The full qualified url to send HTTP requests.

Examples

import kam.workload.container.probe as p

httpProbe = p.Http {
    url: "http://localhost:80"
    headers: {
        "X-HEADER": "VALUE"
    }
}

Schema Probe

Probe describes a health check to be performed against a container to determine whether it is alive or ready to receive traffic. There are three probe types: readiness, liveness, and startup.

Attributes

name	type	description	default value
failureThreshold	int	Minimum consecutive failures for the probe to be considered failed after having succeeded.
initialDelaySeconds	int	The number of seconds before health checking is activated. More info: https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probes
periodSeconds	int	How often (in seconds) to perform the probe.
probeHandler required	Exec	Http	Tcp
successThreshold	int	Minimum consecutive successes for the probe to be considered successful after having failed.
terminationGracePeriod	int	Duration in seconds before terminate gracefully upon probe failure.
timeoutSeconds	int	The number of seconds after which the probe times out. More info: https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probes

Examples

import kam.workload.container.probe as p

probe = p.Probe {
    probeHandler: p.Http {
        path: "/healthz"
    }
    initialDelaySeconds: 10
}

Schema Tcp

Tcp describes an action based on opening a socket.

Attributes

name	type	description	default value
url required	str	The full qualified url to open a socket.

Examples

import kam.workload.container.probe as p

tcpProbe = p.Tcp {
    url: "tcp://localhost:1234"
}

Schema Secret

Secret can be used to store sensitive data.

Attributes

name	type	description	default value
data	{str:str}	Data contains the non-binary secret data in string form.
immutable	bool	Immutable, if set to true, ensures that data stored in the Secret cannot be updated.
params	{str:str}	Collection of parameters used to facilitate programmatic handling of secret data.
type required	"basic"	"token"	"opaque"

Examples

import kam.workload.secret as sec

basicAuth = sec.Secret {
    type: "basic"
    data: {
        "username": ""
        "password": ""
    }
}