Kubeclient

A Ruby client for Kubernetes REST api. The client supports GET, POST, PUT, DELETE on all the entities available in kubernetes in both the core and group apis. The client currently supports Kubernetes REST api version v1. To learn more about groups and versions in kubernetes refer to k8s docs

VULNERABILITY in <= v4.9.2❗

If you use Kubeclient::Config, all gem versions <= v4.9.3 can return incorrect ssl_options[:verify_ssl], allowing MITM attacks on your connection and thereby stealing your cluster credentials. See #554 for details and which versions got a fix.

Installation

Add this line to your application's Gemfile:

gem 'kubeclient'

And then execute:

bundle

Or install it yourself as:

gem install kubeclient

Usage

Initialize the client:

client = Kubeclient::Client.new('http://localhost:8080/api', 'v1')

For A Group Api:

client = Kubeclient::Client.new('http://localhost:8080/apis/batch', 'v1')

Another option is to initialize the client with URI object:

uri = URI::HTTP.build(host: "somehostname", port: 8080)
client = Kubeclient::Client.new(uri, 'v1')

SSL

It is also possible to use https and configure ssl with:

ssl_options = {
  client_cert: OpenSSL::X509::Certificate.new(File.read('/path/to/client.crt')),
  client_key:  OpenSSL::PKey::RSA.new(File.read('/path/to/client.key')),
  ca_file:     '/path/to/ca.crt',
  verify_ssl:  OpenSSL::SSL::VERIFY_PEER
}
client = Kubeclient::Client.new(
  'https://localhost:8443/api', 'v1', ssl_options: ssl_options
)

As an alternative to the ca_file it's possible to use the cert_store:

cert_store = OpenSSL::X509::Store.new
cert_store.add_cert(OpenSSL::X509::Certificate.new(ca_cert_data))
ssl_options = {
  cert_store: cert_store,
  verify_ssl: OpenSSL::SSL::VERIFY_PEER
}
client = Kubeclient::Client.new(
  'https://localhost:8443/api', 'v1', ssl_options: ssl_options
)

For testing and development purpose you can disable the ssl check with:

ssl_options = { verify_ssl: OpenSSL::SSL::VERIFY_NONE }
client = Kubeclient::Client.new(
  'https://localhost:8443/api', 'v1', ssl_options: ssl_options
)

Authentication

If you are using basic authentication or bearer tokens as described here then you can specify one of the following:

auth_options = {
  username: 'username',
  password: 'password'
}
client = Kubeclient::Client.new(
  'https://localhost:8443/api', 'v1', auth_options: auth_options
)

or (fixed token, if it expires it's up to you to create a new Client object):

auth_options = {
  bearer_token: 'MDExMWJkMjItOWY1Ny00OGM5LWJlNDEtMjBiMzgxODkxYzYz'
}
client = Kubeclient::Client.new(
  'https://localhost:8443/api', 'v1', auth_options: auth_options
)

or (will automatically re-read the token if file is updated):

auth_options = {
  bearer_token_file: '/path/to/token_file'
}
client = Kubeclient::Client.new(
  'https://localhost:8443/api', 'v1', auth_options: auth_options
)

Middleware

The Faraday HTTP client used by kubeclient allows configuration of custom middlewares. For example, you may want to add instrumentation, or add custom retry options. Kubeclient provides a hook for injecting these custom middlewares into the request/response chain, via Client#configure_faraday(&block). This provides an access point to the Faraday::Connection object during initialization. As an example, the following code adds retry options to client requests:

client = Kubeclient::Client.new('http://localhost:8080/api', 'v1')
retry_options = { max: 2, interval: 0.05, interval_randomness: 0.5, backoff_factor: 2 }
client.configure_faraday { |conn| conn.request(:retry, retry_options) }

For more examples and documentation, consult the Faraday docs. Note that certain middlewares (e.g. :raise_error) are always included since Kubeclient is dependent on their behaviour to function correctly.

Inside a Kubernetes cluster

The recommended way to locate the API server within the pod is with the kubernetes.default.svc DNS name, which resolves to a Service IP which in turn will be routed to an API server.

The recommended way to authenticate to the API server is with a service account. kube-system associates a pod with a service account and a bearer token for that service account is placed into the filesystem tree of each container in that pod at /var/run/secrets/kubernetes.io/serviceaccount/token.

If available, a certificate bundle is placed into the filesystem tree of each container at /var/run/secrets/kubernetes.io/serviceaccount/ca.crt, and should be used to verify the serving certificate of the API server.

For example:

auth_options = {
  bearer_token_file: '/var/run/secrets/kubernetes.io/serviceaccount/token'
}
ssl_options = {}
if File.exist?("/var/run/secrets/kubernetes.io/serviceaccount/ca.crt")
  ssl_options[:ca_file] = "/var/run/secrets/kubernetes.io/serviceaccount/ca.crt"
end
client = Kubeclient::Client.new(
  'https://kubernetes.default.svc',
  'v1',
  auth_options: auth_options,
  ssl_options:  ssl_options
)

Finally, the default namespace to be used for namespaced API operations is placed in a file at /var/run/secrets/kubernetes.io/serviceaccount/namespace in each container. It is recommended that you use this namespace when issuing API commands below.

namespace = File.read('/var/run/secrets/kubernetes.io/serviceaccount/namespace')

You can find information about tokens in this guide and in this reference.

Non-blocking IO

You can also use kubeclient with non-blocking sockets such as Celluloid::IO, see here for details. For example:

require 'celluloid/io'
socket_options = {
  socket_class: Celluloid::IO::TCPSocket,
  ssl_socket_class: Celluloid::IO::SSLSocket
}
client = Kubeclient::Client.new(
  'https://localhost:8443/api', 'v1', socket_options: socket_options
)

This affects only .watch_* sockets, not one-off actions like .get_*, .delete_* etc.

Proxies

You can also use kubeclient with an http proxy server such as tinyproxy. It can be entered as a string or a URI object. For example:

proxy_uri = URI::HTTP.build(host: "myproxyhost", port: 8443)
client = Kubeclient::Client.new(
  'https://localhost:8443/api', 'v1', http_proxy_uri: proxy_uri
)

Redirects

You can optionally not allow redirection with kubeclient. For example:

client = Kubeclient::Client.new(
  'https://localhost:8443/api', 'v1', http_max_redirects: 0
)

Timeouts

Watching configures the socket to never time out (however, sooner or later all watches terminate).

One-off actions like .get_*, .delete_* have a configurable timeout:

timeouts = {
  open: 10,  # unit is seconds
  read: nil  # nil means never time out
}
client = Kubeclient::Client.new(
  'https://localhost:8443/api', 'v1', timeouts: timeouts
)

Default timeouts match Net::HTTP and RestClient:

• open is 60 seconds
• read is 60 seconds.

If you want ruby-independent behavior, always specify :open.

Errors

If an error occurs while performing a request to the API server, Kubeclient::HttpError will be raised.

There are also certain case-specific errors that can be raised (which also inherit from Kubeclient::HttpError):

• Kubeclient::ResourceNotFoundError when attempting to fetch a resource that does not exist or any other situation that results in the API server returning a 404.
• Kubeclient::ResourceAlreadyExistsError when attempting to create a resource that already exists.

Discovery

Discovery from the kube-apiserver is done lazily on method calls so it would not change behavior.

It can also be done explicitly:

client = Kubeclient::Client.new('http://localhost:8080/api', 'v1')
client.discover

It is possible to check the status of discovery

unless client.discovered
  client.discover
end

Kubeclient::Config

If you've been using kubectl and have a .kube/config file (possibly referencing other files in fields such as client-certificate), you can auto-populate a config object using Kubeclient::Config:

# assuming $KUBECONFIG is one file, won't merge multiple like kubectl
config = Kubeclient::Config.read(ENV['KUBECONFIG'] || '/path/to/.kube/config')

This will lookup external files; relative paths will be resolved relative to the file's directory, if config refers to them with relative path. This includes external exec: credential plugins to be executed.

You can also construct Config directly from nested data. For example if you have JSON or YAML config data in a variable:

config = Kubeclient::Config.new(YAML.safe_load(yaml_text), nil)
# or
config = Kubeclient::Config.new(JSON.parse(json_text), nil)

The 2nd argument is a base directory for finding external files, if config refers to them with relative path. Setting it to nil disables file lookups, and exec: execution - such configs will raise an exception. (A config can be self-contained by using inline fields such as client-certificate-data.)

To create a client based on a Config object:

# default context according to `current-context` field:
context = config.context
# or to use a specific context, by name:
context = config.context('default/192-168-99-100:8443/system:admin')

Kubeclient::Client.new(
  context.api_endpoint,
  'v1',
  ssl_options: context.ssl_options,
  auth_options: context.auth_options
)

Amazon EKS Credentials

On Amazon EKS by default the authentication method is IAM. When running kubectl a temporary token is generated by shelling out to the aws-iam-authenticator binary which is sent to authenticate the user. See aws-iam-authenticator. To replicate that functionality, the Kubeclient::AmazonEksCredentials class can accept a set of IAM credentials and contains a helper method to generate the authentication token for you.

This requires a set of gems which are not included in kubeclient dependencies (aws-sigv4) so you should add them to your bundle. You will also require either the aws-sdk v2 or aws-sdk-core v3 gems to generate the required Aws:Credentials object to pass to this method.

To obtain a token:

require 'aws-sdk-core'
# Use keys
credentials = Aws::Credentials.new(access_key, secret_key)
# Or a profile
credentials = Aws::SharedCredentials.new(profile_name: 'default').credentials

auth_options = {
  bearer_token: Kubeclient::AmazonEksCredentials.token(credentials, eks_cluster_name)
}
client = Kubeclient::Client.new(
  eks_cluster_https_endpoint, 'v1', auth_options: auth_options
)

Note that this returns a token good for one minute. If your code requires authorization for longer than that, you should plan to acquire a new one, see How to manually renew section.

Google GCP credential plugin

If kubeconfig file has user: {auth-provider: {name: gcp, cmd-path: ..., cmd-args: ..., token-key: ...}}, the command will be executed to obtain a token. (Normally this would be a gcloud config config-helper command.)

Note that this returns an expiring token. If your code requires authorization for a long time, you should plan to acquire a new one, see How to manually renew section.

Google's Application Default Credentials

On Google Compute Engine, Google App Engine, or Google Cloud Functions, as well as gcloud-configured systems with application default credentials, kubeclient can use googleauth gem to authorize.

This requires the googleauth gem that is not included in kubeclient dependencies so you should add it to your bundle.

If you use Config.context(...).auth_options and the kubeconfig file has user: {auth-provider: {name: gcp}}, but does not contain cmd-path key, kubeclient will automatically try this (raising LoadError if you don't have googleauth in your bundle).

Or you can obtain a token manually:

require 'googleauth'

auth_options = {
  bearer_token: Kubeclient::GoogleApplicationDefaultCredentials.token
}
client = Kubeclient::Client.new(
  'https://localhost:8443/api', 'v1', auth_options: auth_options
)

Note that this returns a token good for one hour. If your code requires authorization for longer than that, you should plan to acquire a new one, see How to manually renew section.

OIDC Auth Provider

If the cluster you are using has OIDC authentication enabled you can use the openid_connect gem to obtain id-tokens if the one in your kubeconfig has expired.

This requires the openid_connect gem which is not included in the kubeclient dependencies so should be added to your own applications bundle.

The OIDC Auth Provider will not perform the initial setup of your $KUBECONFIG file. You will need to use something like dexter in order to configure the auth-provider in your $KUBECONFIG file.

If you use Config.context(...).auth_options and the $KUBECONFIG file has user: {auth-provider: {name: oidc}}, kubeclient will automatically obtain a token (or use id-token if still valid)

Tokens are typically short-lived (e.g. 1 hour) and the expiration time is determined by the OIDC Provider (e.g. Google). If your code requires authentication for longer than that you should obtain a new token periodically, see How to manually renew section.

Note: id-tokens retrieved via this provider are not written back to the $KUBECONFIG file as they would be when using kubectl.

How to manually renew expired credentials

Kubeclient does not yet help with this.

The division of labor between Config and Context objects may change, for now please make no assumptions at which stage exec: and auth-provider: are handled and whether they're cached. The currently guaranteed way to renew is create a new Config object.

The more painful part is that you'll then need to create new Client object(s) with the credentials from new config. So repeat all of this:

config = Kubeclient::Config.read(ENV['KUBECONFIG'] || '/path/to/.kube/config')
context = config.context
ssl_options = context.ssl_options
auth_options = context.auth_options

client = Kubeclient::Client.new(
    context.api_endpoint, 'v1',
    ssl_options: ssl_options, auth_options: auth_options
)
# and additional Clients if needed...

Security: Don't use config from untrusted sources

Config.read is catastrophically unsafe — it will execute arbitrary command lines specified by the config!

Config.new(data, nil) is better but Kubeclient was never reviewed for behaving safely with malicious / malformed config. It might crash / misbehave in unexpected ways...

namespace

Additionally, the config.context object will contain a namespace attribute, if it was defined in the file. It is recommended that you use this namespace when issuing API commands below. This is the same behavior that is implemented by kubectl command.

You can read it as follows:

puts config.context.namespace

Impersonation

Impersonation is supported when loading a kubectl config and via the Ruby API, for example:

client = Kubeclient::Client.new(
  context.api_endpoint, 'v1',
  auth_options: {
    as: "admin",
    as_groups: ["system:masters"],
    as_uid: "123", # optional
    as_user_extra: {
      "reason" => ["admin access"]
    }
  }
)

Note that only one group and one value per each extra field are currently supported. Using list of multiple values will result in ArgumentError.

Supported kubernetes versions

We try to support the last 3 minor versions, matching the official support policy for Kubernetes. Kubernetes 1.2 and below have known issues and are unsupported. Kubernetes 1.3 presumed to still work although nobody is really testing on such old versions...

Supported actions & examples:

Summary of main CRUD actions:

get_foos(namespace: 'namespace', **opts)  # namespaced collection
get_foos(**opts)                          # all namespaces or global collection

get_foo('name', 'namespace', opts)  # namespaced
get_foo('name', nil, opts)          # global

watch_foos(namespace: ns, **opts)   # namespaced collection
watch_foos(**opts)                  # all namespaces or global collection
watch_foos(namespace: ns, name: 'name', **opts)   # namespaced single object
watch_foos(name: 'name', **opts)                  # global single object

delete_foo('name', 'namespace', opts)    # namespaced
delete_foo('name', nil, opts)            # global
delete_foos(namespace: 'ns', **opts)     # namespaced

create_foo(Kubeclient::Resource.new({metadata: {name: 'name', namespace: 'namespace', ...}, ...}))
create_foo(Kubeclient::Resource.new({metadata: {name: 'name', ...}, ...}))  # global

update_foo(Kubeclient::Resource.new({metadata: {name: 'name', namespace: 'namespace', ...}, ...}))
update_foo(Kubeclient::Resource.new({metadata: {name: 'name', ...}, ...}))  # global

patch_foo('name', patch, 'namespace')    # namespaced
patch_foo('name', patch)                 # global

apply_foo(Kubeclient::Resource.new({metadata: {name: 'name', namespace: 'namespace', ...}, ...}), field_manager: 'myapp', **opts)
apply_foo(Kubeclient::Resource.new({metadata: {name: 'name', ...}, ...}), field_manager: 'myapp', **opts)  # global

These grew to be quite inconsistent 😖, see #312 and #332 for improvement plans.

Get all instances of a specific entity type

Such as: get_pods, get_secrets, get_services, get_nodes, get_replication_controllers, get_resource_quotas, get_limit_ranges, get_persistent_volumes, get_persistent_volume_claims, get_component_statuses, get_service_accounts

pods = client.get_pods

Get all entities of a specific type in a namespace:

services = client.get_services(namespace: 'development')

You can get entities which have specific labels by specifying a parameter named label_selector (named labelSelector in Kubernetes server):

pods = client.get_pods(label_selector: 'name=redis-master')

You can specify multiple labels (that option will return entities which have both labels:

pods = client.get_pods(label_selector: 'name=redis-master,app=redis')

There is also a ability to filter by some fields. Which fields are supported is not documented, you can try and see if you get an error...

client.get_pods(field_selector: 'spec.nodeName=master-0')

You can ask for entities at a specific version by specifying a parameter named resource_version:

pods = client.get_pods(resource_version: '0')

but it's not guaranteed you'll get it. See https://kubernetes.io/docs/reference/using-api/api-concepts/#resource-versions to understand the semantics.

With default (as: :ros) return format, the returned object acts like an array of the individual pods, but also supports a .resourceVersion method.

With :parsed and :parsed_symbolized formats, the returned data structure matches kubernetes list structure: it's a hash containing metadata and items keys, the latter containing the individual pods.

Get all entities of a specific type in chunks

continue = nil
loop do
  entities = client.get_pods(limit: 1_000, continue: continue)
  continue = entities.continue

  break if entities.last?
end

See https://kubernetes.io/docs/reference/using-api/api-concepts/#retrieving-large-results-sets-in-chunks for more information.

The continue tokens expire after a short amount of time, so similar to a watch if you don't request a subsequent page within aprox. 5 minutes of the previous page being returned the server will return a 410 Gone error and the client must request the list from the start (i.e. omit the continue token for the next call).

Support for chunking was added in v1.9 so previous versions will ignore the option and return the full collection.

Get a specific instance of an entity (by name)

Such as: get_service "service name" , get_pod "pod name" , get_replication_controller "rc name", get_secret "secret name", get_resource_quota "resource quota name", get_limit_range "limit range name" , get_persistent_volume "persistent volume name" , get_persistent_volume_claim "persistent volume claim name", get_component_status "component name", get_service_account "service account name"

The GET request should include the namespace name, except for nodes and namespaces entities.

node = client.get_node "127.0.0.1"

service = client.get_service "guestbook", 'development'

Note - Kubernetes doesn't work with the uid, but rather with the 'name' property. Querying with uid causes 404.

Getting raw responses

To avoid overhead from parsing and building RecursiveOpenStruct objects for each reply, pass the as: :raw option when initializing Kubeclient::Client or when calling get_ / watch_ methods. The result can then be printed, or searched with a regex, or parsed via JSON.parse(r).

client = Kubeclient::Client.new(url, version, as: :raw)

or

pods = client.get_pods as: :raw
node = client.get_node "127.0.0.1", as: :raw

Other formats are:

• :ros (default) for RecursiveOpenStruct
• :parsed for JSON.parse
• :parsed_symbolized for JSON.parse(..., symbolize_names: true)
• a class of your choice (this will instantiate a new instance of that class with the raw value of the response body)

Watch — Receive entities updates

See https://kubernetes.io/docs/reference/using-api/api-concepts/#efficient-detection-of-changes for an overview.

It is possible to receive live update notices watching the relevant entities:

client.watch_pods do |notice|
  # process notice data
end

The notices have .type field which may be 'ADDED', 'MODIFIED', 'DELETED', or currently 'ERROR', and an .object field containing the object. UPCOMING CHANGE: In next major version, we plan to raise exceptions instead of passing on ERROR into the block.

For namespaced entities, the default watches across all namespaces, and you can specify client.watch_secrets(namespace: 'foo') to only watch in a single namespace.

You can narrow down using label_selector: and field_selector: params, like with get_pods methods.

You can also watch a single object by specifying name: e.g. client.watch_nodes(name: 'gandalf') (not namespaced so a name is enough) or client.watch_pods(namespace: 'foo', name: 'bar') (namespaced, need both params). Note the method name is still plural! There is no watch_pod, only watch_pods. The yielded "type" remains the same — watch notices, it's just they'll always refer to the same object.

You can use as: param to control the format of the yielded notices.

You can use allow_watch_bookmarks: true to get BOOKMARK events returned regularly, see watch bookmarks

client.watch_pods allow_watch_bookmarks: true do |notice|
  # process notice data
end

All watches come to an end!

While nominally the watch block looks like an infinite loop, that's unrealistic. Network connections eventually get severed, and kubernetes apiserver is known to terminate watches.

Unfortunately, this sometimes raises an exception and sometimes the loop just exits. UPCOMING CHANGE: In next major version, non-deliberate termination will always raise an exception; the block will only exit silenty if stopped deliberately.

Deliberately stopping a watch

You can use break or return inside the watch block.

It is possible to interrupt the watcher from another thread with:

watcher = client.watch_pods

watcher.each do |notice|
  # process notice data
end
# <- control will pass here after .finish is called

### In another thread ###
watcher.finish

Starting watch version

You can specify version to start from, commonly used in "List+Watch" pattern:

list = client.get_pods
collection_version = list.resourceVersion
# or with other return formats:
list = client.get_pods(as: :parsed)
collection_version = list['metadata']['resourceVersion']

# note spelling resource_version vs resourceVersion.
client.watch_pods(resource_version: collection_version) do |notice|
  # process notice data
end

It's important to understand the effects of unset/0/specific resource_version as it modifies the behavior of the watch — in some modes you'll first see a burst of synthetic 'ADDED' notices for all existing objects.

If you re-try a terminated watch again without specific resourceVersion, you might see previously seen notices again, and might miss some events.

To attempt resuming a watch from same point, you can try using last resourceVersion observed during the watch. Or do list+watch again.

Whenever you ask for a specific version, you must be prepared for an 410 "Gone" error if the server no longer recognizes it.

Watch events about a particular object

Events are entities in their own right. You can use the field_selector option as part of the watch methods.

client.watch_events(namespace: 'development', field_selector: 'involvedObject.name=redis-master') do |notice|
  # process notice date
end

Delete an entity (by name)

For example: delete_pod "pod name" , delete_replication_controller "rc name", delete_node "node name", delete_secret "secret name"

Input parameter - name (string) specifying service name, pod name, replication controller name.

deleted = client.delete_service("redis-service")

If you want to cascade delete, for example a deployment, you can use the delete_options parameter.

deployment_name = 'redis-deployment'
namespace = 'default'
delete_options = Kubeclient::Resource.new(
    apiVersion: 'meta/v1',
    gracePeriodSeconds: 0,
    kind: 'DeleteOptions',
    propagationPolicy: 'Foreground' # Orphan, Foreground, or Background
)
client.delete_deployment(deployment_name, namespace, delete_options: delete_options)

Delete all instances of a specific entity type in a namespace

Such as: delete_pods, delete_secrets, delete_services, delete_nodes, delete_replication_controllers, delete_resource_quotas, delete_limit_ranges, delete_persistent_volumes, delete_persistent_volume_claims, delete_component_statuses, delete_service_accounts

Delete all entities of a specific type in a namespace, entities are returned in the same manner as for get_services:

services = client.delete_services(namespace: 'development')

You can get entities which have specific labels by specifying a parameter named label_selector (named labelSelector in Kubernetes server):

pods = client.delete_pods(namespace: 'development', label_selector: 'name=redis-master')

You can specify multiple labels (that option will return entities which have both labels:

pods = client.delete_pods(namespace: 'default', label_selector: 'name=redis-master,app=redis')

There is also a ability to filter by some fields. Which fields are supported is not documented, you can try and see if you get an error...

client.delete_pods(namespace: 'development', field_selector: 'spec.nodeName=master-0')

With default (as: :ros) return format, the returned object acts like an array of the individual pods, but also supports a .resourceVersion method.

With :parsed and :parsed_symbolized formats, the returned data structure matches kubernetes list structure: it's a hash containing metadata and items keys, the latter containing the individual pods.

Create an entity

For example: create_pod pod_object, create_replication_controller rc_obj, create_secret secret_object, create_resource_quota resource_quota_object, create_limit_range limit_range_object, create_persistent_volume persistent_volume_object, create_persistent_volume_claim persistent_volume_claim_object, create_service_account service_account_object

Input parameter - object of type Service, Pod, ReplicationController.

The below example is for v1

service = Kubeclient::Resource.new
service.metadata = {}
service.metadata.name = "redis-master"
service.metadata.namespace = 'staging'
service.spec = {}
service.spec.ports = [{
  'port' => 6379,
  'targetPort' => 'redis-server'
}]
service.spec.selector = {}
service.spec.selector.name = "redis"
service.spec.selector.role = "master"
service.metadata.labels = {}
service.metadata.labels.app = 'redis'
service.metadata.labels.role = 'slave'
client.create_service(service)

Update an entity

For example: update_pod, update_service, update_replication_controller, update_secret, update_resource_quota, update_limit_range, update_persistent_volume, update_persistent_volume_claim, update_service_account

Input parameter - object of type Pod, Service, ReplicationController etc.

The below example is for v1

updated = client.update_service(service1)

Patch an entity (by name)

For example: patch_pod, patch_service, patch_secret, patch_resource_quota, patch_persistent_volume

Input parameters - name (string) specifying the entity name, patch (hash) to be applied to the resource, optional: namespace name (string)

The PATCH request should include the namespace name, except for nodes and namespaces entities.

The below example is for v1

patched = client.patch_pod("docker-registry", {metadata: {annotations: {key: 'value'}}}, "default")

patch_#{entity} is called using a strategic merge patch. json_patch_#{entity} and merge_patch_#{entity} are also available that use JSON patch and JSON merge patch, respectively. These strategies are useful for resources that do not support strategic merge patch, such as Custom Resources. Consult the Kubernetes docs for more information about the different patch strategies.

Apply an entity

This is similar to kubectl apply --server-side (kubeclient doesn't implement logic for client-side apply). See https://kubernetes.io/docs/reference/using-api/api-concepts/#server-side-apply

For example: apply_pod

Input parameters - resource (Kubeclient::Resource) representing the desired state of the resource, field_manager (String) to identify the system managing the state of the resource, force (Boolean) whether or not to override a field managed by someone else.

Example:

service = Kubeclient::Resource.new(
  metadata: {
    name: 'redis-master',
    namespace: 'staging',
  },
  spec: {
    ...
  }
)

client.apply_service(service, field_manager: 'myapp')

Get all entities of all types : all_entities

Makes requests for all entities of each discovered kind (in this client's API group). This method is a convenience method instead of calling each entity's get method separately.

Returns a hash with keys being the singular entity kind, in lowercase underscore style. For example for core API group may return keys "node', "secret", "service", "pod", "replication_controller", "namespace", "resource_quota", "limit_range", "endpoint", "event", "persistent_volume", "persistent_volume_claim", "component_status", "service_account". Each key points to an EntityList of same type.

client.all_entities

Get a proxy URL

You can get a complete URL for connecting a kubernetes entity via the proxy.

client.proxy_url('service', 'srvname', 'srvportname', 'ns')
# => "https://localhost.localdomain:8443/api/v1/proxy/namespaces/ns/services/srvname:srvportname"

Note the third parameter, port, is a port name for services and an integer for pods:

client.proxy_url('pod', 'podname', 5001, 'ns')
# => "https://localhost.localdomain:8443/api/v1/namespaces/ns/pods/podname:5001/proxy"

Get the logs of a pod

You can get the logs of a running pod, specifying the name of the pod and the namespace where the pod is running:

client.get_pod_log('pod-name', 'default')
# => "Running...\nRunning...\nRunning...\n"

If that pod has more than one container, you must specify the container:

client.get_pod_log('pod-name', 'default', container: 'ruby')
# => "..."

If a container in a pod terminates, a new container is started, and you want to retrieve the logs of the dead container, you can pass in the :previous option:

client.get_pod_log('pod-name', 'default', previous: true)
# => "..."

Kubernetes can add timestamps to every log line or filter by lines time:

client.get_pod_log('pod-name', 'default', timestamps: true, since_time: '2018-04-27T18:30:17.480321984Z')
# => "..."

since_time can be a a Time, DateTime or String formatted according to RFC3339

Kubernetes can fetch a specific number of lines from the end of the logs:

client.get_pod_log('pod-name', 'default', tail_lines: 10)
# => "..."

Kubernetes can fetch a specific number of bytes from the log, but the exact size is not guaranteed and last line may not be terminated:

client.get_pod_log('pod-name', 'default', limit_bytes: 10)
# => "..."

You can also watch the logs of a pod to get a stream of data:

client.watch_pod_log('pod-name', 'default', container: 'ruby') do |line|
  puts line
end

OpenShift: Process a template

Returns a processed template containing a list of objects to create. Input parameter - template (hash) Besides its metadata, the template should include a list of objects to be processed and a list of parameters to be substituted. Note that for a required parameter that does not provide a generated value, you must supply a value.

Note: This functionality is not supported by K8s at this moment. See the following issue

client.process_template template

Informer

A list that is always updated because it is it kept in sync by a watch in the background. Can also share a list+watch with multiple threads.

client = Kubeclient::Client.new('http://localhost:8080/api/', 'v1')
informer = Kubeclient::Informer.new(client, "pods", reconcile_timeout: 15 * 60, logger: Logger.new(STDOUT))
informer.start_worker

informer.list # all current pods
informer.watch { |notice|  } # watch for changes (hides restarts and errors)

To pass custom options to the list and watch request, like setting namespace, the initializer accepts options keyword:

informer = Kubeclient::Informer.new(
  client,
  "pods",
  options: { namespace: "some-namespace" },
  reconcile_timeout: 15 * 60,
  logger: Logger.new(STDOUT)
)

Contributing

1. Fork it ( https://github.com/[my-github-username]/kubeclient/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Test your changes with rake test rubocop, add new tests if needed.
4. If you added a new functionality, add it to README
5. Commit your changes (git commit -am 'Add some feature')
6. Push to the branch (git push origin my-new-feature)
7. Create a new Pull Request

Tests

This client is tested with Minitest and also uses VCR recordings in some tests. Please run all tests before submitting a Pull Request, and add new tests for new functionality.

Running tests:

rake test