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65 lines
2.4 KiB
Markdown
65 lines
2.4 KiB
Markdown
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## Worker Node
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can be a physical server, virtual machine, etc
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made up of........
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## pods
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- a wrapper over a container so that Kubernetes can replace them if necessary
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- there is usually 1 application per pod (or 1 application with a helper)
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**pods are EPHEMERAL** (they can die very easily)
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★ for example, if the app contained in the pod's wrapped container crashes, runs out of resources, etc
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when this happens, a new pod is created in it's place, with a new address.
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To work with this, we attach a.....
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## Service
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- a static IP address that is attatched to each pod/app
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- an app (stored in a node) will have it's own service/database, and every pod will have it's own service
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- the service lifetime is not connected to the pod's, so when the pod is replaced, the same internal IP can be used
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- also works as a load balancer when allocating requests to pods
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There are **two types of services**
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1. internal
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- this is the default type
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- can not be accessed externally
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2. external
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- you must specify this when creating a service
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- can communicate externally (i.e. via browser for a web app's endpoint)
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- can be accessed via http://[node_ip_addr][service_port_number]
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what if you want to access something, but it needs to be via some sort of domain?
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use.....
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## Ingress
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- exposes HTTP and HTTPS routes from outside the cluster to services within the cluster
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- you set **rules**, which will then decide how requests are routed (forewarded to services or otherwise)
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<hr>
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## ConfigMap
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- external configurations for your application (i.e. database urls)
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- connected to pods so that they have access to this data
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- this allows you to just change the value in the configMap without re-building the pods
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- stored in plaintext
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**HOWEVER**
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This type of storage is ***NOT*** secure, so kubernetes offers.....
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## Secret
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- just like configMap, but for secrets (i.e. usernames, passowrd, etc)
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- stored in base64-encoded format
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- is meant to be encrypted using third-party tools (perhaps given by the cloud provider)
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**BOTH** ConfigMap and Secret can be used inside of pods like env vars or as a properties file
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<hr>
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## Volume
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- used for data storage
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★ imagine there is a "database" pod. If that pod restarts, your data is gone
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- attaches physical storage to a pod
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- can be on the same machine the pod is running on or a remote source outside of the cluster
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- **kubernetes does not manage data persistance**
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