Kubernetes软件网络-Weave安装和配置

本文来源，https://www.weave.works/docs/net/latest/kubernetes/kube-addon/

The following topics are discussed:

Installation

Weave Net can be installed onto your CNI-enabled Kubernetes cluster with a single command:

$ kubectl apply -f "https://cloud.weave.works/k8s/net?k8s-version=$(kubectl version | base64 | tr -d '\n')"

After a few seconds, a Weave Net pod should be running on each Node and any further pods you create will be automatically attached to the Weave network.

Note: This command requires Kubernetes 1.4 or later, and we recommend your master node has at least two CPU cores.

CNI, the Container Network Interface, is a proposed standard for configuring network interfaces for Linux containers.

If you do not already have a CNI-enabled cluster, you can bootstrap one easily with kubeadm.

Alternatively, you can configure CNI yourself

Note: If using the Weave CNI Plugin from a prior full install of Weave Net with your cluster, you must first uninstall it before applying the Weave-kube addon. Shut down Kubernetes, and on all nodes perform the following:

weave reset
Remove any separate provisions you may have made to run Weave at boot-time, e.g. systemd units
rm /opt/cni/bin/weave-*

Then relaunch Kubernetes and install the addon as described above.

Upgrading Kubernetes to version 1.6

In version 1.6, Kubernetes has increased security, so we need to create a special service account to run Weave Net. This is done in the file weave-daemonset-k8s-1.6.yaml attached to the Weave Net release.

Also, the toleration required to let Weave Net run on master nodes has moved from an annotation to a field on the DaemonSet spec object.

If you have edited the Weave Net DaemonSet from a previous release, you will need to re-make your changes against the new version.

Upgrading the Daemon Sets

For Kubernetes 1.6 and above the DaemonSet definition specifies Rolling Updates, so when you apply a new version Kubernetes will automatically restart the Weave Net pods one by one.

Kubernetes v1.5 and below does not support rolling upgrades of daemon sets, and so you will need to perform the procedure manually:

Apply the updated addon manifest kubectl apply -f "https://cloud.weave.works/k8s/net?k8s-version=$(kubectl version | base64 | tr -d '\n')"
Kill each Weave Net pod with kubectl delete and then wait for it to reboot before moving on to the next pod.

Note: In versions prior to Weave Net 2.0, deleting all Weave Net pods at the same time will result in them losing track of IP address range ownership, possibly leading to duplicate IP addresses if you then start a new copy of Weave Net.

CPU and Memory Requirements

Kubernetes manages resources on each node, and only schedules pods to run on nodes that have enough free resources.

The components of a typical Kubernetes installation (with the master node running etcd, scheduler, api-server, etc.) take up about 95% of a CPU, which leaves little room to run anything else. For all of Weave Net’s features to work, it must run on every node, including the master.

The best way to resolve this issue is to use machines with at least two CPU cores. However if you are installing Kubernetes and Weave Net for the first time, you may not be aware of this requirement. For this reason, Weave Net launches as a DaemonSet with a specification that reserves at least 1% CPU for each container. This enables Weave Net to start up seamlessly on a single-CPU node.

Depending on the workload, Weave Net may need more than 1% of the CPU. The percentage set in the DaemonSet is the minimum and not a limit. This minimum setting allows Weave Net to take advantage of available CPU and “burst” above that limit if it needs to.

Pod Eviction

If a node runs out of CPU, memory or disk, Kubernetes may decide to evict one or more pods. It may choose to evict the Weave Net pod, which will disrupt pod network operations.

You can reduce the chance of eviction by changing the DaemonSet to have a much bigger request, and a limit of the same value.

This causes Kubernetes to apply a “guaranteed” rather than a “burstable” policy. However a similar request for disk space can not be made, and so please be aware of this issue and monitor your resources to ensure that they stay below 100%.

You can see when pods have been evicted via the kubectl get events command

LASTSEEN   COUNT     NAME          KIND    TYPE      REASON     SOURCE            MESSAGE
1m         1         mypod-09vkd   Pod     Warning   Evicted    kubelet, node-1   The node was low on resource: memory.

or kubectl get pods

NAME                READY     STATUS    RESTARTS   AGE       IP          NODE
mypod-09vkd         0/1       Evicted   0          1h        <none>      node-1

If you see this in your cluster, consider some of the above steps to reduce disruption.

Features

Pod Network

Weave Net provides a network to connect all pods together, implementing the Kubernetes model.

Kubernetes uses the Container Network Interface (CNI) to join pods onto Weave Net.

Kubernetes implements many network features itself on top of the pod network. This includes Services, Service Discovery via DNS and Ingress into the cluster. WeaveDNS is disabled when using the Kubernetes addon.

Network Policy

Kubernetes Network Policies let you securely isolate pods from each other based on namespaces and labels. For more information on configuring network policies in Kubernetes see the walkthrough and the NetworkPolicy API object definition

Note: as of version 1.9 of Weave Net, the Network Policy Controller allows all multicast traffic. Since a single multicast address may be used by multiple pods, we cannot implement rules to isolate them individually. You can turn this behaviour off (block all multicast traffic) by adding --allow-mcast=false as an argument to weave-npc in the YAML configuration.

Troubleshooting

Many Kubernetes network issues occur at a higher level than Weave Net. The [Kubernetes Service Debugging Guide] (https://kubernetes.io/docs/tasks/debug-application-cluster/debug-service/) has a detailed step-by-step guide.

The status of Weave Net can be checked by running its CLI commands. This can be done in various ways:

1. Install the weave script and run:

$ weave status
        Version: 2.0.1 (up to date; next check at 2017/07/10 13:49:29)

        Service: router
       Protocol: weave 1..2
           Name: 42:8e:e8:c4:52:1b(host-0)
     Encryption: disabled
  PeerDiscovery: enabled
        Targets: 3
    Connections: 3 (2 established, 1 failed)
          Peers: 3 (with 6 established connections)
 TrustedSubnets: none

        Service: ipam
         Status: ready
          Range: 10.32.0.0/12
  DefaultSubnet: 10.32.0.0/12

2. If you don’t want to install additional software onto your hosts, run via kubectl commands, which produce the exact same outcome as the previous example:

### Identify the Weave Net pods:

$ kubectl get pods -n kube-system -l name=weave-net -o wide
NAME              READY  STATUS   RESTARTS  AGE  IP           NODE
weave-net-1jkl6   2/2    Running  0         1d   10.128.0.4   host-0
weave-net-bskbv   2/2    Running  0         1d   10.128.0.5   host-1
weave-net-m4x1b   2/2    Running  0         1d   10.128.0.6   host-2

The above shows all Weave Net pods available in your cluster. You can see Kubernetes has deployed one Weave Net pod per host, in order to interconnect all hosts.

You then need to:

choose which pod you want to run your command from (in most cases it doesn’t matter which one you pick so just pick the first one, e.g. pod weave-net-1jkl6 here)
use kubectl exec to run the weave status command
specify the absolute path /home/weave/weave and add --local because it’s running inside a container

$ kubectl exec -n kube-system weave-net-1jkl6 -c weave -- /home/weave/weave --local status

        Version: 2.0.1 (up to date; next check at 2017/07/10 13:49:29)

        Service: router
       Protocol: weave 1..2
           Name: 42:8e:e8:c4:52:1b(host-0)
     Encryption: disabled
  PeerDiscovery: enabled
        Targets: 3
    Connections: 3 (2 established, 1 failed)
          Peers: 3 (with 6 established connections)
 TrustedSubnets: none

        Service: ipam
         Status: ready
          Range: 10.32.0.0/12
  DefaultSubnet: 10.32.0.0/12

3. Finally you could also use Weave Cloud and monitor all your pods, including Weave Net’s ones, from there.

Weave Net status screen in Weave Cloud

For more information see What is Weave Cloud?

Troubleshooting Blocked Connections

If you suspect that legitimate traffic is being blocked by the Weave Network Policy Controller, the first thing to do is check the weave-npc container’s logs.

To do this, first you have to find the name of the Weave Net pod running on the relevant host:

$ kubectl get pods -n kube-system -o wide | grep weave-net
weave-net-08y45                  2/2       Running   0          1m        10.128.0.2   host1
weave-net-2zuhy                  2/2       Running   0          1m        10.128.0.4   host3
weave-net-oai50                  2/2       Running   0          1m        10.128.0.3   host2

Select the relevant container, for example, if you want to look at host2 then pick weave-net-oai50 and run:

$ kubectl logs <weave-pod-name-as-above> -n kube-system weave-npc

When the Weave Network Policy Controller blocks a connection, it logs the following details about it:

protocol used,
source IP and port,
destination IP and port,

as per the below example:

TCP connection from 10.32.0.7:56648 to 10.32.0.11:80 blocked by Weave NPC.
UDP connection from 10.32.0.7:56648 to 10.32.0.11:80 blocked by Weave NPC.

Things to watch out for

Don’t turn on --masquerade-all on kube-proxy: this will change the source address of every pod-to-pod conversation which will make it impossible to correctly enforce network policies that restrict which pods can talk.
If you do set the --cluster-cidr option on kube-proxy, make sure it matches the IPALLOC_RANGE given to Weave Net (see below)

Changing Configuration Options

Using `cloud.weave.works`

You can customise the YAML you get from cloud.weave.works by passing some of Weave Net’s options, arguments and environment variables as query parameters:

version: Weave Net’s version. Default: latest, i.e. latest release. N.B.: This only changes the specified version inside the generated YAML file, it does not ensure that the rest of the YAML is compatible with that version. To freeze the YAML version save a copy of the YAML file from the release page and use that copy instead of downloading it each time from cloud.weave.works.

password-secret: name of the Kubernetes secret containing your password. N.B: The Kubernetes secret name must correspond to a name of a file containing your password. Example:

$ echo "s3cr3tp4ssw0rd" > /var/lib/weave/weave-passwd
$ kubectl create secret -n kube-system generic weave-passwd --from-file=/var/lib/weave/weave-passwd
$ kubectl apply -f "https://cloud.weave.works/k8s/net?k8s-version=$(kubectl version | base64 | tr -d '\n')&password-secret=weave-passwd"

known-peers: comma-separated list of hosts. Default: empty.
trusted-subnets: comma-separated list of CIDRs. Default: empty.
disable-npc: boolean (true|false). Default: false.
env.NAME=VALUE: add environment variable NAME and set it to VALUE.
seLinuxOptions.NAME=VALUE: add SELinux option NAME and set it to VALUE, e.g. seLinuxOptions.type=spc_t
use-legacy-netpol: use legacy NetworkPolicy semantics, boolean (true|false). Default: true for Kubernetes version <= 1.6, false for > 1.6.

The list of variables you can set is:

CHECKPOINT_DISABLE - if set to 1, disable checking for new Weave Net versions (default is blank, i.e. check is enabled)
CONN_LIMIT - soft limit on the number of connections between peers. Defaults to 30.
HAIRPIN_MODE - Weave Net defaults to enabling hairpin on the bridge side of the veth pair for containers attached. If you need to disable hairpin, e.g. your kernel is one of those that can panic if hairpin is enabled, then you can disable it by setting HAIRPIN_MODE=false.
IPALLOC_RANGE - the range of IP addresses used by Weave Net and the subnet they are placed in (CIDR format; default 10.32.0.0/12)
EXPECT_NPC - set to 0 to disable Network Policy Controller (default is on)
KUBE_PEERS - list of addresses of peers in the Kubernetes cluster (default is to fetch the list from the api-server)
IPALLOC_INIT - set the initialization mode of the IP Address Manager (defaults to consensus amongst the KUBE_PEERS)
WEAVE_EXPOSE_IP - set the IP address used as a gateway from the Weave network to the host network - this is useful if you are configuring the addon as a static pod.
WEAVE_MTU - Weave Net defaults to 1376 bytes, but you can set a smaller size if your underlying network has a tighter limit, or set a larger size for better performance if your network supports jumbo frames - see here for more details.

Example:

$ kubectl apply -f "https://cloud.weave.works/k8s/net?k8s-version=$(kubectl version | base64 | tr -d '\n')&env.WEAVE_MTU=1337"

This command – notice &env.WEAVE_MTU=1337 at the end of the URL – generates a YAML file containing, among others:

[...]
          containers:
            - name: weave
[...]
              env:
                - name: WEAVE_MTU
                  value: '1337'
[...]

Note: The YAML file can also be saved for later use or manual editing by using, for example:

$ curl -fsSLo weave-daemonset.yaml "https://cloud.weave.works/k8s/net?k8s-version=$(kubectl version | base64 | tr -d '\n')"

Manually editing the YAML file

Whether you saved the YAML file served from cloud.weave.works or downloaded a static YAML file from our releases page, you can manually edit it to suit your needs.

For example,

additional arguments may be supplied to the Weave router process by adding them to the command: array in the YAML file,
additional parameters can be set via the environment variables listed above; these can be inserted into the YAML file like this:

      containers:
        - name: weave
          env:
            - name: IPALLOC_RANGE
              value: 10.0.0.0/16