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* WIP: add k8s grouper - This shares a great deal of behaviour with allGrouper. Once it's tested, refactor that to share as much as possible - Glide hell. Checked in the yaml and lock files but a glide i -v will be required to bring vendor/ up-to-date. Will address once this is ready. * Update README. Make the watch tracking work. (To follow: add the junk that was pulled in via the glide update.) * Vendor updates. * go fmt * Use the allGrouper with a k8s-backed DBStore instead. This is much tidier :-) * Fix up go vet
130 lines
3.9 KiB
Markdown
130 lines
3.9 KiB
Markdown
# Fn Load Balancer
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The Fn Load Balancer (Fn LB) allows operators to deploy clusters of Fn servers and route traffic to them intelligently. Most importantly, it will route traffic to nodes where hot functions are running to ensure optimal performance, as well as distribute load if traffic to a specific function increases. It also gathers information about the entire cluster which you can use to know when to scale out (add more Fn servers) or in (decrease Fn servers).
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## Load balancing several Fn servers
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You can run multiple Fn instances and balance the load amongst them using `fnlb` as follows:
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```sh
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fnlb --listen <address-for-incoming> --nodes <node1>,<node2>,<node3>
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```
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And redirect all traffic to the load balancer.
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**NOTE: For the load balancer to be of use, all function nodes need to be sharing the same DB.**
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## Running with docker
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To build a docker image for `fnlb` just run (in `fnlb/`):
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```
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make docker-build
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```
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To start the `fnlb` proxy with the addresses of functions nodes in a docker
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container:
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```sh
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docker run -d --name fnlb -p 8081:8081 fnproject/fnlb:latest --nodes <node1>,<node2>
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```
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If running locally with functions servers in docker, running with docker links
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can make things easier (can use local addresses). for example:
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```sh
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docker run -d --name fn-8080 --privileged -p 8080:8080 fnproject/fnserver:latest
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docker run -d --name fnlb --link fn-8080 -p 8081:8081 fnproject/fnlb:latest --nodes 127.0.0.1:8080
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```
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## Operating / usage
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To make functions requests against the lb with the cli:
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```sh
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FN_API_URL=http://<fnlb_address> fn call my/function
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```
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To add a functions node later:
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```sh
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curl -sSL -X PUT -d '{"node":"<node>"}' <fnlb_address>/1/lb/nodes
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```
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`<node>` should be the address of a functions server. The lb will health check
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this and log if it cannot reach that node as well as stop sending requests to
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that node until it begins passing health checks again. Any number of functions
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servers may be added to the load balancer.
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To permanently remove a functions node:
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```sh
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curl -sSL -X DELETE -d '{"node":"<node>"}' <fnlb_address>/1/lb/nodes
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```
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To list functions nodes and their state:
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```sh
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curl -sSL -X GET <fnlb_address>/1/lb/nodes
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```
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## Running under Kubernetes
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The fnlb supports a mode of operation which relies on Kubernetes to inform it as Fn pods come in and out of service. In order to run in this mode, some additional command-line flags are required. `-db=k8s` will select Kubernetes operation; in this mode, the `nodes` flag is ignored. `-label-selector=...` is a standard Kubernetes selector expression.
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A sample k8s configuration follows; this expects Fn pods to be labelled `app=fn,role=fn-service`. By default, the lb will look in its own namespace for Fn pods. This can be changed by explicitly passing the `-namespace=...` option.
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```yaml
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apiVersion: v1
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kind: Service
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metadata:
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name: fn-service
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namespace: fn
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labels:
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app: fn
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role: fn-lb
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spec:
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type: NodePort
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ports:
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- name: fn-service
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port: 8080
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targetPort: 8080
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nodePort: 32180
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selector:
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app: fn
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role: fn-lb
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---
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apiVersion: extensions/v1beta1
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kind: DaemonSet
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metadata:
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name: fn-lb
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namespace: fn
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spec:
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updateStrategy:
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type: RollingUpdate
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rollingUpdate:
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maxUnavailable: 1
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minReadySeconds: 30
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template:
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metadata:
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labels:
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app: fn
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role: fn-lb
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spec:
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containers:
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- name: fn-lb
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image: fnproject/fnlb
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imagePullPolicy: Always
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args:
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- "-db=k8s"
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- "-label-selector=app=fn,role=fn-service"
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- "-listen=:8080"
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- "-mgmt-listen=:8080"
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ports:
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- containerPort: 8080
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env:
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- name: LOG_LEVEL
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value: debug
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```
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In this mode, the shared database is not required; each lb will listen to the Kubernetes master independently to derive the same information. The lb nodes continue to health-check Fn pods *in addition* to the health checks running directly as part of a Pod definition. |