From f940b709d99e522286afd648d8390cd67325bed7 Mon Sep 17 00:00:00 2001 From: Jared Date: Mon, 15 May 2017 17:15:20 -0700 Subject: [PATCH] access-clusters docs revamp (#3779) * access-clusters docs revamp Fix the accessing clusters docs, bring them into the right templates and put them in the right parts of the site. * Update proxies.md * Update concepts.yml * Update tasks.yml --- _data/concepts.yml | 3 + _data/tasks.yml | 2 + .../cluster-administration/proxies.md | 58 +++++ .../administer-cluster/access-cluster-api.md | 202 ++++++++++++++++++ .../access-cluster-services.md | 115 ++++++++++ 5 files changed, 380 insertions(+) create mode 100644 docs/concepts/cluster-administration/proxies.md create mode 100644 docs/tasks/administer-cluster/access-cluster-api.md create mode 100644 docs/tasks/administer-cluster/access-cluster-services.md diff --git a/_data/concepts.yml b/_data/concepts.yml index ea4fc8fa74..5c4b60e498 100644 --- a/_data/concepts.yml +++ b/_data/concepts.yml @@ -60,6 +60,9 @@ toc: - docs/concepts/cluster-administration/kubelet-garbage-collection.md - docs/concepts/cluster-administration/federation.md - docs/concepts/cluster-administration/sysctl-cluster.md + - docs/concepts/cluster-administration/authenticate-across-clusters-kubeconfig.md + - docs/concepts/cluster-administration/master-node-communication.md + - docs/concepts/cluster-administration/proxies.md - title: Storage section: diff --git a/_data/tasks.yml b/_data/tasks.yml index eacd6e5a09..1f99c6bed4 100644 --- a/_data/tasks.yml +++ b/_data/tasks.yml @@ -97,6 +97,8 @@ toc: - title: Administering a Cluster section: + - docs/tasks/administer-cluster/access-cluster-api.md + - docs/tasks/administer-cluster/access-cluster-services.md - docs/tasks/administer-cluster/configure-upgrade-etcd.md - docs/tasks/administer-cluster/apply-resource-quota-limit.md - docs/tasks/administer-cluster/out-of-resource.md diff --git a/docs/concepts/cluster-administration/proxies.md b/docs/concepts/cluster-administration/proxies.md new file mode 100644 index 0000000000..2f7dbe400f --- /dev/null +++ b/docs/concepts/cluster-administration/proxies.md @@ -0,0 +1,58 @@ +--- +title: Proxies in Kubernetes +redirect_from: +- "/docs/user-guide/accessing-the-cluster/" +- "/docs/user-guide/accessing-the-cluster.html" +--- + +{% capture overview %} +This page explains proxies used with Kubernetes. +{% endcapture %} + +{% capture body %} + +## Proxies + +There are several different proxies you may encounter when using Kubernetes: + + 1. The [kubectl proxy](#directly-accessing-the-rest-api): + - runs on a user's desktop or in a pod + - proxies from a localhost address to the Kubernetes apiserver + - client to proxy uses HTTP + - proxy to apiserver uses HTTPS + - locates apiserver + - adds authentication headers + 1. The [apiserver proxy](#discovering-builtin-services): + - is a bastion built into the apiserver + - connects a user outside of the cluster to cluster IPs which otherwise might not be reachable + - runs in the apiserver processes + - client to proxy uses HTTPS (or http if apiserver so configured) + - proxy to target may use HTTP or HTTPS as chosen by proxy using available information + - can be used to reach a Node, Pod, or Service + - does load balancing when used to reach a Service + 1. The [kube proxy](/docs/user-guide/services/#ips-and-vips): + - runs on each node + - proxies UDP and TCP + - does not understand HTTP + - provides load balancing + - is just used to reach services + 1. A Proxy/Load-balancer in front of apiserver(s): + - existence and implementation varies from cluster to cluster (e.g. nginx) + - sits between all clients and one or more apiservers + - acts as load balancer if there are several apiservers. + 1. Cloud Load Balancers on external services: + - are provided by some cloud providers (e.g. AWS ELB, Google Cloud Load Balancer) + - are created automatically when the Kubernetes service has type `LoadBalancer` + - use UDP/TCP only + - implementation varies by cloud provider. + +Kubernetes users will typically not need to worry about anything other than the first two types. The cluster admin +will typically ensure that the latter types are setup correctly. + +## Requesting redirects + +Proxies have replaced redirect capabilities. Redirects have been deprecated. + +{% endcapture %} + +{% include templates/concept.md %} diff --git a/docs/tasks/administer-cluster/access-cluster-api.md b/docs/tasks/administer-cluster/access-cluster-api.md new file mode 100644 index 0000000000..f83b48483c --- /dev/null +++ b/docs/tasks/administer-cluster/access-cluster-api.md @@ -0,0 +1,202 @@ +--- +title: Accessing Clusters Using the Kubernetes API +redirect_from: +- "/docs/user-guide/accessing-the-cluster/" +- "/docs/user-guide/accessing-the-cluster.html" +- "/docs/concepts/cluster-administration/access-cluster/" +--- + +{% capture overview %} +This page shows how to access clusters using the Kubernetes API. +{% endcapture %} + +{% capture prerequisites %} + +{% include task-tutorial-prereqs.md %} +{% endcapture %} + +{% capture steps %} + +## Accessing the cluster API + +### Accessing for the first time with kubectl + +When accessing the Kubernetes API for the first time, use the +Kubernetes command-line tool, `kubectl`. + +To access a cluster, you need to know the location of the cluster and have credentials +to access it. Typically, this is automatically set-up when you work through +a [Getting started guide](/docs/getting-started-guides/), +or someone else setup the cluster and provided you with credentials and a location. + +Check the location and credentials that kubectl knows about with this command: + +```shell +$ kubectl config view +``` + +Many of the [examples](https://github.com/kubernetes/kubernetes/tree/{{page.githubbranch}}/examples/) provide an introduction to using +kubectl. omplete documentation is found in the [kubectl manual](/docs/user-guide/kubectl/index). + +### Directly accessing the REST API + +Kubectl handles locating and authenticating to the apiserver. If you want to directly access the REST API with an http client like +`curl` or `wget`, or a browser, there are multiple ways you can locate and authenticate against the apiserver: + + 1. Run kubectl in proxy mode (recommended). This method is recommended, since it uses the stored apiserver location abd verifies the identity of the apiserver using a self-signed cert. No Man-in-the-middle (MITM) attack is possible using this method . + 1. Alternatively, you can provide the location and credentials directly to the http client. This works with for client code that is confused by proxies. To protect against man in the middle attacks, you'll need to import a root cert into your browser. + + Using the Go or Python client libraries provides accessing kubectl in proxy mode. + +#### Using kubectl proxy + +The following command runs kubectl in a mode where it acts as a reverse proxy. It handles +locating the apiserver and authenticating. + +Run it like this: + +```shell +$ kubectl proxy --port=8080 & +``` + +See [kubectl proxy](/docs/user-guide/kubectl/v1.6/#proxy) for more details. + +Then you can explore the API with curl, wget, or a browser, like so: + +```shell +$ curl http://localhost:8080/api/ +{ + "versions": [ + "v1" + ] +} +``` + +#### Without kubectl proxy + +It is possible to avoid using kubectl proxy by passing an authentication token +directly to the apiserver, like this: + +``` shell +$ APISERVER=$(kubectl config view | grep server | cut -f 2- -d ":" | tr -d " ") +$ TOKEN=$(kubectl describe secret $(kubectl get secrets | grep default | cut -f1 -d ' ') | grep -E '^token' | cut -f2 -d':' | tr -d '\t') +$ curl $APISERVER/api --header "Authorization: Bearer $TOKEN" --insecure +{ + "kind": "APIVersions", + "versions": [ + "v1" + ], + "serverAddressByClientCIDRs": [ + { + "clientCIDR": "0.0.0.0/0", + "serverAddress": "10.0.1.149:443" + } + ] +} +``` + +The above example uses the `--insecure` flag. This leaves it subject to MITM +attacks. When kubectl accesses the cluster it uses a stored root certificate +and client certificates to access the server. (These are installed in the +`~/.kube` directory). Since cluster certificates are typically self-signed, it +may take special configuration to get your http client to use root +certificate. + +On some clusters, the apiserver does not require authentication; it may serve +on localhost, or be protected by a firewall. There is not a standard +for this. [Configuring Access to the API](/docs/admin/accessing-the-api) +describes how a cluster admin can configure this. Such approaches may conflict +with future high-availability support. + +### Programmatic access to the API + +Kubernetes supports [Go](#go-client) and [Python](#python-client) client libraries. + +#### Go client + +* To get the library, run the following command: `go get k8s.io/client-go//kubernetes` See [https://github.com/kubernetes/client-go](https://github.com/kubernetes/client-go) to see which versions are supported. +* Write an application atop of the client-go clients. Note that client-go defines its own API objects, so if needed, please import API definitions from client-go rather than from the main repository, e.g., `import "k8s.io/client-go/1.4/pkg/api/v1"` is correct. + +The Go client can use the same [kubeconfig file](/docs/concepts/cluster-administration/authenticate-across-clusters-kubeconfig/) +as the kubectl CLI does to locate and authenticate to the apiserver. See this [example](https://github.com/kubernetes/client-go/blob/master/examples/out-of-cluster/main.go): + +```golang +import ( + "fmt" + "k8s.io/client-go/1.4/kubernetes" + "k8s.io/client-go/1.4/pkg/api/v1" + "k8s.io/client-go/1.4/tools/clientcmd" +) +... + // uses the current context in kubeconfig + config, _ := clientcmd.BuildConfigFromFlags("", "path to kubeconfig") + // creates the clientset + clientset, _:= kubernetes.NewForConfig(config) + // access the API to list pods + pods, _:= clientset.Core().Pods("").List(v1.ListOptions{}) + fmt.Printf("There are %d pods in the cluster\n", len(pods.Items)) +... +``` + +If the application is deployed as a Pod in the cluster, please refer to the [next section](#accessing-the-api-from-a-pod). + +#### Python client + +To use [Python client](https://github.com/kubernetes-incubator/client-python), run the following command: `pip install kubernetes` See [Python Client Library page](https://github.com/kubernetes-incubator/client-python) for more installation options. + +The Python client can use the same [kubeconfig file](/docs/user-guide/kubeconfig-file) +as the kubectl CLI does to locate and authenticate to the apiserver. See this [example](https://github.com/kubernetes-incubator/client-python/tree/master/examples/example1.py): + +```python +from kubernetes import client, config + +config.load_kube_config() + +v1=client.CoreV1Api() +print("Listing pods with their IPs:") +ret = v1.list_pod_for_all_namespaces(watch=False) +for i in ret.items: + print("%s\t%s\t%s" % (i.status.pod_ip, i.metadata.namespace, i.metadata.name)) +``` + +#### Other languages + +There are [client libraries](https://github.com/kubernetes/kubernetes/tree/{{page.githubbranch}}/docs/devel/client-libraries.md) for accessing the API from other languages. See documentation for other libraries for how they authenticate. + +### Accessing the API from a Pod + +When accessing the API from a pod, locating and authenticating +to the api server are somewhat different. + +The recommended way to locate the apiserver within the pod is with +the `kubernetes` DNS name, which resolves to a Service IP which in turn +will be routed to an apiserver. + +The recommended way to authenticate to the apiserver is with a +[service account](/docs/user-guide/service-accounts) credential. By kube-system, a pod +is associated with a service account, and a credential (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 apiserver. + +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. + +From within a pod the recommended ways to connect to API are: + + - run a kubectl proxy as one of the containers in the pod, or as a background + process within a container. This proxies the + Kubernetes API to the localhost interface of the pod, so that other processes + in any container of the pod can access it. See this [example of using kubectl proxy + in a pod](https://github.com/kubernetes/kubernetes/tree/{{page.githubbranch}}/examples/kubectl-container/). + - use the Go client library, and create a client using the `rest.InClusterConfig()` and `kubernetes.NewForConfig()` functions. + They handle locating and authenticating to the apiserver. [example](https://github.com/kubernetes/client-go/blob/master/examples/in-cluster/main.go) + +In each case, the credentials of the pod are used to communicate securely with the apiserver. + +{% endcapture %} + +{% include templates/task.md %} \ No newline at end of file diff --git a/docs/tasks/administer-cluster/access-cluster-services.md b/docs/tasks/administer-cluster/access-cluster-services.md new file mode 100644 index 0000000000..46025c6ec0 --- /dev/null +++ b/docs/tasks/administer-cluster/access-cluster-services.md @@ -0,0 +1,115 @@ +--- +title: Accessing Services Running on Clusters +redirect_from: +- "/docs/user-guide/accessing-the-cluster/" +- "/docs/user-guide/accessing-the-cluster.html" +--- + +{% capture overview %} +This page shows how to connect to services running on the Kubernetes cluster. +{% endcapture %} + +{% capture prerequisites %} + +{% include task-tutorial-prereqs.md %} +{% endcapture %} + +{% capture steps %} + +## Accessing services running on the cluster + +In Kubernetes, [nodes](/docs/admin/node), [pods](/docs/user-guide/pods) and [services](/docs/user-guide/services) all have +their own IPs. In many cases, the node IPs, pod IPs, and some service IPs on a cluster will not be +routable, so they will not be reachable from a machine outside the cluster, +such as your desktop machine. + +### Ways to connect + +You have several options for connecting to nodes, pods and services from outside the cluster: + + - Access services through public IPs. + - Use a service with type `NodePort` or `LoadBalancer` to make the service reachable outside + the cluster. See the [services](/docs/user-guide/services) and + [kubectl expose](/docs/user-guide/kubectl/v1.6/#expose) documentation. + - Depending on your cluster environment, this may just expose the service to your corporate network, + or it may expose it to the internet. Think about whether the service being exposed is secure. + Does it do its own authentication? + - Place pods behind services. To access one specific pod from a set of replicas, such as for debugging, + place a unique label on the pod it and create a new service which selects this label. + - In most cases, it should not be necessary for application developer to directly access + nodes via their nodeIPs. + - Access services, nodes, or pods using the Proxy Verb. + - Does apiserver authentication and authorization prior to accessing the remote service. + Use this if the services are not secure enough to expose to the internet, or to gain + access to ports on the node IP, or for debugging. + - Proxies may cause problems for some web applications. + - Only works for HTTP/HTTPS. + - Described [here](#manually-constructing-apiserver-proxy-urls). + - Access from a node or pod in the cluster. + - Run a pod, and then connect to a shell in it using [kubectl exec](/docs/user-guide/kubectl/v1.6/#exec). + Connect to other nodes, pods, and services from that shell. + - Some clusters may allow you to ssh to a node in the cluster. From there you may be able to + access cluster services. This is a non-standard method, and will work on some clusters but + not others. Browsers and other tools may or may not be installed. Cluster DNS may not work. + +### Discovering builtin services + +Typically, there are several services which are started on a cluster by kube-system. Get a list of these +with the `kubectl cluster-info` command: + +```shell +$ kubectl cluster-info + + Kubernetes master is running at https://104.197.5.247 + elasticsearch-logging is running at https://104.197.5.247/api/v1/namespaces/kube-system/services/elasticsearch-logging/proxy + kibana-logging is running at https://104.197.5.247/api/v1/namespaces/kube-system/services/kibana-logging/proxy + kube-dns is running at https://104.197.5.247/api/v1/namespaces/kube-system/services/kube-dns/proxy + grafana is running at https://104.197.5.247/api/v1/namespaces/kube-system/services/monitoring-grafana/proxy + heapster is running at https://104.197.5.247/api/v1/namespaces/kube-system/services/monitoring-heapster/proxy +``` + +This shows the proxy-verb URL for accessing each service. +For example, this cluster has cluster-level logging enabled (using Elasticsearch), which can be reached +at `https://104.197.5.247/api/v1/namespaces/kube-system/services/elasticsearch-logging/proxy/` if suitable credentials are passed, or through a kubectl proxy at, for example: +`http://localhost:8080/api/v1/namespaces/kube-system/services/elasticsearch-logging/proxy/`. +(See [above](#accessing-the-cluster-api) for how to pass credentials or use kubectl proxy.) + +#### Manually constructing apiserver proxy URLs + +As mentioned above, you use the `kubectl cluster-info` command to retrieve the service's proxy URL. To create proxy URLs that include service endpoints, suffixes, and parameters, you simply append to the service's proxy URL: +`http://`*`kubernetes_master_address`*`/api/v1/namespaces/`*`namespace_name`*`/services/`*`service_name[:port_name]`*`/proxy` + +If you haven't specified a name for your port, you don't have to specify *port_name* in the URL + +##### Examples + + * To access the Elasticsearch service endpoint `_search?q=user:kimchy`, you would use: `http://104.197.5.247/api/v1/namespaces/kube-system/services/elasticsearch-logging/proxy/_search?q=user:kimchy` + * To access the Elasticsearch cluster health information `_cluster/health?pretty=true`, you would use: `https://104.197.5.247/api/v1/namespaces/kube-system/services/elasticsearch-logging/proxy/_cluster/health?pretty=true` + +```json + { + "cluster_name" : "kubernetes_logging", + "status" : "yellow", + "timed_out" : false, + "number_of_nodes" : 1, + "number_of_data_nodes" : 1, + "active_primary_shards" : 5, + "active_shards" : 5, + "relocating_shards" : 0, + "initializing_shards" : 0, + "unassigned_shards" : 5 + } +``` + +#### Using web browsers to access services running on the cluster + +You may be able to put an apiserver proxy url into the address bar of a browser. However: + + - Web browsers cannot usually pass tokens, so you may need to use basic (password) auth. Apiserver can be configured to accept basic auth, + but your cluster may not be configured to accept basic auth. + - Some web apps may not work, particularly those with client side javascript that construct urls in a + way that is unaware of the proxy path prefix. + +{% endcapture %} + +{% include templates/task.md %} \ No newline at end of file