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Load Balancing with Fabio Guide (#4445)
* add load-balancing guide * restructure load balancing section * defining consul lb strategies inline and giving fabio its own bullet point * update docker image name and shorten job template * changing system scheduler link to relative link and moving load balancing navigation link right to right above Web UI
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Omar Khawaja
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website/source/guides/load-balancing/fabio.html.md
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---
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layout: "guides"
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page_title: "Load Balancing with Nomad"
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sidebar_current: "guides-load-balancing"
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description: |-
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There are multiple approaches to load balancing within a Nomad cluster.
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One approach involves using [fabio][fabio]. Fabio integrates natively
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with Consul and provides rich features with an optional Web UI.
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---
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# Load Balancing with Fabio
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[Fabio][fabio] integrates natively with Consul and provides an optional Web UI
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to visualize routing.
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The main use case for fabio is to distribute incoming HTTP(S) and TCP requests
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from the internet to frontend services that can handle these requests. This
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guide will show you one such example using [Apache][apache] web server.
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## Reference Material
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- [Fabio](https://github.com/fabiolb/fabio) on GitHub
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- [Load Balancing Strategies for Consul](https://www.hashicorp.com/blog/load-balancing-strategies-for-consul)
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- [Elastic Load Balancing][elb]
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## Estimated Time to Complete
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20 minutes
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## Challenge
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Think of a scenario where a Nomad operator needs to configure an environment to
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make Apache web server highly available behind an endpoint and distribute
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incoming traffic evenly.
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## Solution
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Deploy fabio as a
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[system][system]
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scheduler so that it can route incoming traffic evenly to the Apache web server
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group regardless of which client nodes Apache is running on. Place all client nodes
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behind an [AWS load balancer][elb] to
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provide the end user with a single endpoint for access.
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## Prerequisites
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To perform the tasks described in this guide, you need to have a Nomad
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environment with Consul installed. You can use this
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[repo](https://github.com/hashicorp/nomad/tree/master/terraform#provision-a-nomad-cluster-in-the-cloud)
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to easily provision a sandbox environment. This guide will assume a cluster with
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one server node and three client nodes.
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-> **Please Note:** This guide is for demo purposes and is only using a single server
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node. In a production cluster, 3 or 5 server nodes are recommended.
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## Steps
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### Step 1: Create a Job for Fabio
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Create a job for Fabio and name it `fabio.nomad`
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```hcl
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job "fabio" {
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datacenters = ["dc1"]
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type = "system"
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group "fabio" {
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task "fabio" {
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driver = "docker"
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config {
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image = "fabiolb/fabio"
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network_mode = "host"
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}
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resources {
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cpu = 200
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memory = 128
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network {
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mbits = 20
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port "lb" {
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static = 9999
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}
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port "ui" {
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static = 9998
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}
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}
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}
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}
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}
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}
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```
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Setting `type` to [system][system] will ensure that fabio is run on all clients.
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Please note that the `network_mode` option is set to `host` so that fabio can
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communicate with Consul which is also running on the client nodes.
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### Step 2: Run the Fabio Job
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We can now register our fabio job:
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```shell
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$ nomad job run fabio.nomad
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==> Monitoring evaluation "fba4f04a"
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Evaluation triggered by job "fabio"
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Allocation "6e6367d4" created: node "f3739267", group "fabio"
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Allocation "d17573b4" created: node "28d7f859", group "fabio"
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Allocation "f3ad9b16" created: node "510898b6", group "fabio"
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Evaluation status changed: "pending" -> "complete"
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==> Evaluation "fba4f04a" finished with status "complete"
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```
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At this point, you should be able to visit any one of your client nodes at port
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`9998` and see the web interface for fabio. The routing table will be empty
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since we have not yet deployed anything that fabio can route to.
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Accordingly, if you visit any of the client nodes at port `9999` at this
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point, you will get a `404` HTTP response. That will change soon.
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### Step 3: Create a Job for Apache Web Server
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Create a job for Apache and name it `webserver.nomad`
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```hcl
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job "webserver" {
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datacenters = ["dc1"]
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type = "service"
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group "webserver" {
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count = 3
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restart {
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attempts = 2
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interval = "30m"
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delay = "15s"
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mode = "fail"
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}
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ephemeral_disk {
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size = 300
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}
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task "apache" {
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driver = "docker"
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config {
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image = "httpd:latest"
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port_map {
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http = 80
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}
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}
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resources {
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network {
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mbits = 10
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port "http" {}
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}
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}
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service {
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name = "apache-webserver"
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tags = ["urlprefix-/"]
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port = "http"
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check {
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name = "alive"
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type = "http"
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path = "/"
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interval = "10s"
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timeout = "2s"
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}
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}
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}
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}
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}
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```
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Notice the tag in the service stanza begins with `urlprefix-`. This is how a
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path is registered with fabio. In this case, we are registering the path '/'
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with fabio (which will route us to the default page for Apache web server).
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### Step 4: Run the Job for Apache Web Server
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We can now register our job for Apache:
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```shell
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$ nomad job run webserver.nomad
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==> Monitoring evaluation "c7bcaf40"
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Evaluation triggered by job "webserver"
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Evaluation within deployment: "e3603b50"
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Allocation "20951ad4" created: node "510898b6", group "webserver"
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Allocation "43807686" created: node "28d7f859", group "webserver"
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Allocation "7b60eb24" created: node "f3739267", group "webserver"
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Evaluation status changed: "pending" -> "complete"
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==> Evaluation "c7bcaf40" finished with status "complete"
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```
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You have now deployed and registered your web servers with fabio! At this point,
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you should be able to visit any of the Nomad clients at port `9999` and
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see the default web page for Apache web server. If you visit fabio's web
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interface by going to any of the client nodes at port `9998`, you will see that
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the routing table has been populated as shown below (**Note:** your destination IP
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addresses will be different).
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[![Routing Table][routing-table]][routing-table]
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Feel free to reduce the `count` in `webserver.nomad` for testing purposes. You
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will see that you still get routed to the Apache home page by accessing
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any client node on port `9999`. Accordingly, the routing table
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in the web interface on port `9999` will reflect the changes.
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### Step 5: Place Nomad Client Nodes Behing AWS Load Balancer
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At this point, you are ready to place your Nomad client nodes behind an AWS load
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balancer. Your Nomad client nodes may change over time, and it is important
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to provide your end users with a single endpoint to access your services. This guide will use the [Classic Load Balancer][classic-lb].
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The AWS [documentation][classic-lb-doc] provides instruction on how to create a
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load balancer. The basic steps involve creating a load balancer, registering
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instances behind the load balancer (in our case these will be the Nomad client
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nodes), creating listeners, and configuring health checks.
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Once you are done
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with this, you should be able to hit the DNS name of your load balancer at port
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80 (or whichever port you configured in your listener) and see the home page of
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Apache web server. If you configured your listener to also foward traffic to
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the web interface at port `9998`, you should be able to access that as well.
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[![Home Page][lb-homepage]][lb-homepage]
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[![Routing Table][lb-routing-table]][lb-routing-table]
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[apache]: https://httpd.apache.org/
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[classic-lb]: https://docs.aws.amazon.com/elasticloadbalancing/latest/classic/introduction.html
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[classic-lb-doc]: https://docs.aws.amazon.com/elasticloadbalancing/latest/classic/elb-getting-started.html
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[elb]: https://aws.amazon.com/elasticloadbalancing/
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[fabio]: https://fabiolb.net/
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[lb-homepage]: /assets/images/lb-homepage.png
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[lb-routing-table]: /assets/images/lb-routing-table.png
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[routing-table]: /assets/images/routing-table.png
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[system]: /docs/runtime/schedulers.html#system
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20
website/source/guides/load-balancing/load-balancing.html.md
Normal file
20
website/source/guides/load-balancing/load-balancing.html.md
Normal file
@@ -0,0 +1,20 @@
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---
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||||
layout: "guides"
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page_title: "Load Balancing"
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sidebar_current: "guides-load-balancing"
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description: |-
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There are multiple approaches to load balancing within a Nomad cluster. This
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discusses the most popular strategies.
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||||
---
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# Load Balancing
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There are multiple approaches to set up load balancing across a Nomad cluster.
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Most of these methods assume Consul is installed alongside Nomad (see [Load
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Balancing Strategies for
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Consul](https://www.hashicorp.com/blog/load-balancing-strategies-for-consul)).
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- [Fabio](/guides/load-balancing/fabio.html)
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Please refer to the specific documentation above or in the sidebar for more
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detailed information about each strategy.
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@@ -200,6 +200,15 @@
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</ul>
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</li>
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<li<%= sidebar_current("guides-load-balancing") %>>
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<a href="/guides/load-balancing/load-balancing.html">Load Balancing</a>
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<ul class="nav">
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<li<%= sidebar_current("guides-fabio") %>>
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<a href="/guides/load-balancing/fabio.html">Fabio</a>
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</li>
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</ul>
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</li>
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<li<%= sidebar_current("guides-ui") %>>
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<a href="/guides/ui.html">Web UI</a>
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</li>
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