⇩ Markdown

kubernetes-glossary

^maps

* master * TODO - * AKA master **node** (or nodes in an HA setup). Contrast this with **worker** * `kubectl cluster-info` gives "Kubernetes **master** is running at https://172.17.4.99:443" *
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At 8:35 master /can/ run containers, but usually doesn't. ^master-containers

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At 30:54 - When you run kubectl get nodes if it says SchedulingDisabled on the master node, it will not run containers ^scheduling-disabled

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Node controller is a component in Kubernetes master which manages Node objects. ^node-controller

* minikube * a tool that makes it easy to run Kubernetes locally. It runs Kubernetes in a VM on your local machine. * minion * the *deprecated* name for a **node** * network namespace * TODO - is one way **pod** is isolated * name *
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An explicitly documented name and identifier ^name-and-identifier

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An explicitly documented name and identifier ^name-and-identifier

* http://kubernetes.io/docs/user-guide/identifiers/ * client-provided. * only one object of a given kind can have a given name at a time (i.e., they are spatially unique). * used to refer to an object in a resource URL, such as /api/v1/pods/some-name * naked pod *
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... naked pods (i.e., pods not bound to a replication controller ), go with the alternative. Naked pods will not be rescheduled in the event of node failure. ^naked-pods

* namespaces * TODO - there are a bunch of these, but I don't understand them yet * by default, everything is in the default namespace *
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At 6:20 - namespaces... different ones for environments: test/staging/production or for tenants ^namespace-for-environment

* From [video-kubernetes-architecture](video-kubernetes-architecture.html) - **Process ID (PID) namespace** * From [video-kubernetes-architecture](video-kubernetes-architecture.html) - **Network namespace** * From [video-kubernetes-architecture](video-kubernetes-architecture.html) - **Interprocess communication (IPC) namespace** * From [video-kubernetes-architecture](video-kubernetes-architecture.html) - **Unix Timesharing (UTS) namespace** *
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kubectl --namespace=demos get events ^namespace-get-events

* node * from [kubernetes-kubectl-commands](kubernetes-kubectl-commands.html) "Update the **taint**s on one or more nodes" * from [kubernetes-docs-ingress](kubernetes-docs-ingress.html) "A single virtual or physical machine in a Kubernetes cluster." *
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node is a worker machine in Kubernetes, previously known as minion. ^node-is-worker

* node affinity * TODO - [kubernetes-docs-assigning-pods-to-nodes](kubernetes-docs-assigning-pods-to-nodes.html) * node controller *
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Node controller is a component in Kubernetes master which manages Node objects. ^node-controller

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node controller receiving heartbeats ^node-controller-receives-heartbeats

(TODO - who sends these?) * [kubernetes-docs-node](kubernetes-docs-node.html) * node pools * TODO * node port *
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At 24:40 - A Node Port is an external service. Called node port because every node in the cluster makes the service available on the same port. ^node-port

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At 46:15 - the node ports fall within a specific range ^node-ports-range

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At 48:10 - if you access a service at the right port, but wrong node, kube proxy will bounce it to the right node ^kube-proxy-gets-request-to-right-node

* object * TODO - same as **resource**? * seems to be referred to much more often than resources. *
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every Kubernetes object has three basic fields in its description: Object Metadata, Specification (or Spec), and Status. ^three-basic-fields

* persistent volume * attached to the node prior to running the pod itself on the node *
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"Unlike volumes, persistent volumes are not associated with any specific pod or containers when they are created" ^persistent-volumes-no-association

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networked storage resource of the cluster that has been provisioned by an administrator. It is a resource in the cluster just like a node is a cluster resource. Are volume plugins like Volumes, but they have a distinct lifecycle that is independent of any individual pod that consumes the PV. ^persistent-volume-definition

* Types:
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Are implemented as plugins. Kubernetes supports popular backends and distributed file systems including Amazon EBS, GCE Persistent Disks, Cinder, Azure File System, NFS, iSCSI, Gluster, and Ceph among other types. ^persistent-volume-types

* pet sets *
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Pet Sets, an evolving concept in Kubernetes for running highly available stateful workloads. ^pet-sets

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Pet Sets, soon to be replaced by Stateful Sets in Kubernetes v1.5, give you deterministic order of initialization of pods. ^pet-set-stateful-set

* pod * The atomic unit of a kubernetes **cluster** * A collection of one of more containers that work well together * from [kubernetes-code-readme](kubernetes-code-readme.html) "a colocated group of application containers with shared volumes. They're the smallest deployable units that can be created, scheduled, and managed with Kubernetes. Pods can be created individually, but it's recommended that you use a replication controller even if creating a single pod." * A set of **data-volume**s * **namespaces** * **labels** * The atomic unit of scheduling. "It doesn't make any sense for those two containers to land on different machines" [talk-technical-overview-of-kubernetes](talk-technical-overview-of-kubernetes.html) * can be connected together on localhost (different containers on a pod can all see each other because they share a network namespace) * From [kubernetes-docs-services](kubernetes-docs-services.html) - "Each **pod** gets an IP addresses, but it cannot be relied upon to be stable over time." * From [video-kubernetes-architecture](video-kubernetes-architecture.html) - "Alternative to VM with multiple processes" * From [video-kubernetes-architecture](video-kubernetes-architecture.html) - Each pod is isolated by **Process ID (PID) namespace**, **Network namespace**, **Interprocess communication (IPC) namespace**, **Unix Timesharing (UTS) namespace** *
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At 18:20 "Every pod is completely autonomous. There is no notion of an 'application' that brings multiple pods together" ^pods-are-autonomous

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always runs an application container inside a top-level pod, even if the pod contains a single container ^always-in-a-pod

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it's easy to add a new small support service, because it operates in the private execution environment provided by its own container ^pod-makes-it-easy-to-add-support-service

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we decided that Kubernetes would allocate an IP address per pod, thus aligning network identity (IP address) with application identity ^ip-address-per-pod

* podmaster * TODO * name from diagram in [kubernetes-docs-high-availability](kubernetes-docs-high-availability.html) on **master** * port name *
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An explicitly documented name and identifier ^name-and-identifier

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port name (IANA_SVC_NAME): An alphanumeric (a-z, and 0-9) string, with a maximum length of 15 characters, with the '-' character allowed anywhere except the first or the last character or adjacent to another '-' character, it must contain at least a (a-z) character. ^port-name

* Process ID (PID) namespace * TODO - is one way **pod** is isolated * Prometheus * A way of monitoring a Kubernetes cluster * resource * TODO - seems to be a pretty generic term. What can it refer to? *
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Allow idempotent creation of API resources (#148) and enforcement of space-uniqueness of singleton objects. ^api-resources

(In same doc other things are referred to as objects) * reconciliation loop * Name from [talk-technical-overview-of-kubernetes](talk-technical-overview-of-kubernetes.html) at 14:20 * Same loop can be used for create, update, and delete * replica set * run X copies of a pod * handle **pod** failures (health checks) - TODO, what actually does this? * replication controller * combination of a **template** (a desired state template), some **labels**, and a number (like I want three) * From [kubernetes-code-readme](kubernetes-code-readme.html) "manage the lifecycle of pods. They ensure that a specified number of pods are running at any given time, by creating or killing pods as required." * scheduler * A small binary that lives on the "master side of the house" * Responsible for scheduling pods onto machines * modifies cluster state, and can get a **lease-lock** from the **API Server** to ensure single actor modifying cluster state - [kubernetes-docs-high-availability](kubernetes-docs-high-availability.html) *
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The scheduler binds unscheduled pods to nodes via the /binding API. The scheduler is pluggable, and we expect to support multiple cluster schedulers and even user-provided schedulers in the future. ^scheduler

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The scheduler needs to take into account individual and collective resource requirements, quality of service requirements, hardware/software/policy constraints, affinity and anti-affinity specifications, data locality, inter-workload interference, deadlines, and so on ^scheduler

* schedulable * A **node**-level attribute that determines whether **pod**s will be scheduled onto the node. * `cordon` marks a **node** as un**schedulable** * `uncordon` marks a **node** as **schedulable** * `drain` removes **pod**s from a node and marks is as un**schedulable**. * secret * exposed by data volume or ENV vars * managed by the **API Server** * selector * TODO (it's in the **spec** section in the yml file - what is that yml file called?) * same as **label selector**, or are there additional types of selectors? * service * From [kubernetes-code-readme](kubernetes-code-readme.html) "Services provide a single, stable name and address for a set of pods. They act as basic load balancers." * From [kubernetes-docs-services](kubernetes-docs-services.html) "A Kubernetes Service is an abstraction which defines a logical set of Pods and a policy by which to access them." * Get a known, static, fixed IP address * They get a DNS entry that's associated with that known, static, fixed IP address * The IP address only exists in the routing tables in the machines in the cluster (otherwise it's fake) * Has a name, some ports, and a label query. * The load balancer sends traffic to the dynamic set of pods that match the label query * TODO in **expose**, it says you can expose a service as a new Kubernetes Service. What does that mean? * from [kubernetes-docs-ingress](kubernetes-docs-ingress.html) "A Kubernetes Service that identifies a set of pods using label selectors. Unless mentioned otherwise, Services are assumed to have virtual IPs only routable within the **cluster network**." *
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At 22:15 an abstraction to define a logical set of pods, bound by a policy to access them. ^service-abstraction

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At 22:15 services are exposed through internal and external endpoints ^service-internal-external-enpoints

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At 22:15 can also point to a non-kubernetes endpoint through a Virtual-IP-Bridge ^service-non-kubernetes-endpoints

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At 22:15 supports TCP and UDP ^service-tcp-and-udp

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Interfaces with kube-proxy to manipulate IP tables ^service-interfaces-with-kube-proxy

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At 39:40 - there is a default kubernetes service when you do kubectl get svc ^default-kubernetes-service

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At 51:50 - If you scale a service by using a replication controller, the service will route to the right nodes using a load balancing scheme ^scale-service

* simple load balancing including session affinity * service port * The port specified in the **spec** of a **service** **manifest**. *
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At 37:50 - The default option is exposing the service port as a cluster IP ^service-port-as-cluster-ip

* service proxy * that lives on the "machines" themselves * provides load balancing * spec * TODO the spec section within the **manifest**. * Stateful sets *
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Pet Sets, soon to be replaced by Stateful Sets in Kubernetes v1.5, give you deterministic order of initialization of pods. ^pet-set-stateful-set

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runs database using statefulsets ^runs-database-using-statefulsets

* storage class *
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Enables administrators to create multiple tiers or classes of storage they offer. Different classes map to different levels of quality-of-service, backup policies, and arbitrary policies as defined by the administrators. ^storage-class

* storage pools * TODO - [blog-post-running-stateful-application-in-kubernetes](blog-post-running-stateful-application-in-kubernetes.html) * subdomain *
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An explicitly documented name and identifier ^name-and-identifier

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subdomain (DNS_SUBDOMAIN): One or more lowercase rfc1035/rfc1123 labels separated by '.' with a maximum length of 253 characters. ^subdomain

* supervisord *
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At 8:35 supervisord runs docker and kubelet ^supervisord-docker-kubelet

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At 10:20 supervisord ensures that docker and kublet remain running ^supervisord-ensures-docker-and-kublet-running

* taint * TODO - what is this? * from [kubernetes-kubectl-commands](kubernetes-kubectl-commands.html) "Update the **taint**s on one or more nodes" * template * TODO * UID *
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An explicitly documented name and identifier ^name-and-identifier

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UID: A non-empty, opaque, system-generated value guaranteed to be unique in time and space; intended to distinguish between historical occurrences of similar entities. ^uid

* UUID *
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An explicitly documented name and identifier ^name-and-identifier

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universally unique identifier (UUID): A 128 bit generated value that is extremely unlikely to collide across time and space and requires no central coordination. ^uuid

* In the case of Kubernetes, a UUID is one type of **UID** * Unix Timesharing (UTS) namespace * TODO - is one way **pod** is isolated * Virtual-IP-Bridge * TODO - a way that services can point to non-Kubernetes **endpoint**s. * worker * AKA worker node *
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At 12:25 the node is also called a minion or a slave (TODO is that only the worker node?) ^minion-slave

^glossary

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