Tutorial

How To Scale Your Infrastructure with DigitalOcean

Published on February 27, 2013

Scaling

Bulat Khamitov

How To Scale Your Infrastructure with DigitalOcean

This tutorial is out of date and no longer maintained.

With DigitalOcean’s simple interface with API access, and full root level access, here is a great opportunity to create an automated setup that scales itself on-demand. You can have your websites scale up or down automatically to meet the traffic demands.

Both vertical and horizontal scalability is possible with this API, which can be accessed with just a bash script. It is best to create an admin droplet which has its public key on all other droplets. This would allow you to push webpage updates with rsync, as well as issue commands to other droplets, and query them for Nagios, NRPE, and SNMPD vitals. You would need to create your own level of logic to determine how and when you wish to scale things – for example if a server reaches 85% CPU usage, double the RAM (vertical scaling) or create a clone (horizontal scaling). The choice is a price-benefit analysis and is left to the reader.

Here is a bash script to get things started. Make sure to modify Client_Key and API_Key to your own variables from API Access Page - click “Generate a new API Key”. For our example we have the following:

Client Key: A2a9SfT4NeFBl6df5cu42
API Key: mnqWGdu4OfLBwwJPee6cpjkeY70qv9mKicqZYvtHJ

Scaler.sh :

#!/bin/bash
# Be Sure To Change This!
Client_Key=A2a9SfT4NeFBl6df5cu42
API_Key=mnqWGdu4OfLBwwJPee6cpjkeY70qv9mKicqZYvtHJ

droplets()
{
echo "Your current droplets:"
All_Droplets=`curl -s "https://api.digitalocean.com/droplets/?client_id=$Client_Key&api_key=$API_Key"`
echo $All_Droplets | sed -e 's/,/\n/g' | sed -e 's/{/\n/g' | sed -e 's/}/\n/g' | sed -e 's/"//g'
}

spinup()
{
Droplet_Name=$1
Size_ID=$2
Image_ID=$3
Region_ID=$4
echo "Spinning up a new droplet $Droplet_Name"
curl -s "https://api.digitalocean.com/droplets/new?name=$Droplet_Name&size_id=$Size_ID&image_id=$Image_ID®ion_id=$Region_ID&client_id=$Client_Key&api_key=$API_Key"
}

resize()
{
Droplet_ID=$1
Size_ID=$2
echo "Resizing a droplet ID: $Droplet_ID to Size ID: $2"
curl -s "https://api.digitalocean.com/droplets/$Droplet_ID/resize/?size_id=$Size_ID&client_id=$Client_Key&api_key=$API_Key"
}

sizes()
{
sizes=`curl -s "https://api.digitalocean.com/sizes/?client_id=$Client_Key&api_key=$API_Key"`
echo $sizes | sed -e 's/,/\n/g' | sed -e 's/{//g' | sed -e 's/}//g' | sed -e 's/"//g' | sed -e 's/\[/\n/g'
}

snapshot()
{
Droplet_ID=$1
Snapshot_Name=$2
echo "Taking a snapshot of Droplet $1 with Name: $Snapshot_Name"
curl -s "https://api.digitalocean.com/droplets/$Droplet_ID/snapshot/?name=$Snapshot_Name&client_id=$Client_Key&api_key=$API_Key"
}


go()
{
# Display all current droplets.  Region_ID: 1 for US, 2 for Amsterdam.
droplets

# Show possible Size IDs, for RAM, also tied to amount of CPU cores and HDD allocated - refer to https://www.digitalocean.com/pricing
echo "Possible droplets sizes by RAM:"
sizes

# Take a snapshot of an existing droplet
# The syntax is: snapshot Droplet_ID Snapshot_Name
# For example to take a snapshot of droplet with ID "72100":
#snapshot 72100 domain.com

# Vertical Scaling - Increase RAM, CPU, Disk
# The syntax is: resize Droplet_ID New_Size_ID
# For example to resize a 512MB droplet to a 1GB droplet with ID "72100":
#resize 72100 63

# Horizontal Scaling - Clone a server from a snapshot
# The syntax is: spinup Droplet_Name Size_ID Image_ID Region_ID
# For example, to spinup a 512MB clone of domain.com webserver with image ID "12573" in New York datacenter (Region 1):
#spinup domain.com 66 12574 1
}

go

Suppose we have created a webserver droplet that has the Nginx/Apache/Memcached stack with Nagios, NRPE, SNMPD configured. Our admin droplet’s SSH key in /root/.ssh/authorized_keys and iptables rules in place, only allowing admin droplet to connect via SSH. The domain being hosted is domain.com.

A sample output of the script, with this webserver droplet being displayed:

id:72100
name:domain.com
image_id:12574
size_id:66
region_id:1
backups_active:null
ip_address:192.34.56.29
status:active

Note the Droplet_ID is 72100 and Image_ID (snapshot) is 12574 To take a snapshot of this droplet, uncomment the following line and run it:

snapshot 72100 domain.com

Taking a snapshot of Droplet 72100 with Name: domain.com

{"status":"OK","event_id":473473}

This creates a snapshot of our droplet and saves it as “domain.com” :

To scale this droplet vertically from 512MB to 1GB uncomment the following line and run:

resize 72100 63

Resizing a droplet ID: 72100 to Size ID: 63
{"status":"OK","event_id":473530}

To scale this droplet horizontally, we will spin up a new one by uncommenting this line and running Scaler.sh :

spinup domain.com 66 12574 1

Spinning up a new droplet domain.com

{"status":"OK","droplet":{"id":72124,"name":"domain.com","image_id":12574,"size_id":66,"event_id":473545}}

Latest DigitalOcean droplet sizes and IDs:

ID	Name
66	512MB
63	1GB
62	2GB
64	4GB
65	8GB
61	16GB
60	32GB
70	48GB
70	48GB
69	64GB
68	96GB

Recently DigitalOcean has upgraded to SSD drives, and the smallest droplet comes with 512MB of RAM and 1 CPU core. The next step up is 1GB of RAM and 1 CPU core. You can run Nginx on backend with PHP-FPM handling PHP requests, and Varnish cache in front of Nginx.

Benchmarks of Varnish cache with Nginx and PHP+FPM reveal 420 requests/second compared against 22.25 requests/second served by Nginx and PHP-FPM alone.

As far as droplets are concerned, there is also an interesting concept of a self-replicating VM. A host can be self-aware of being ‘overloaded’ and decide to clone itself and add the clone into DNS rotation. There are many ways of implementing this, and simplest way would be to use SNMPD and Nagios for polling data.

You can even setup an orchestration VM that has its public key on all VMs. A level of automation depends on your imagination and desire for complexity.

Having essential monitoring tools like Nagios, SNMPD, NRPE, and your SSH keys on the droplet that you are cloning is important. It will allow you to sync new content to this server down the line, further automating the process. You can setup an admin droplet to which you’ll upload webpages and from which all syncs will be done with a crontab. This admin droplet should have its key placed on all your droplets, and SSH port allowed only from that admin droplet’s IP address. Whether you choose to have an OpenVPN connection to this admin droplet is up to you.

Once you have spun up your new webserver from a snapshot, you’ll need to place the server into rotation. This can be accomplished by DNS round robin, Nginx reverse proxy, a dedicated load balancer setup, and so on. The choice would depend on your infrastructure needs and budget.

By Bulat Khamitov

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Bulat Khamitov

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balajidl • February 27, 2013

Do you also provide dedicated load balancer as your service ?

mobile • February 27, 2013

do you guys have windows server OS SNAPSHOT?

Mitch Wainer

DigitalOcean Employee

• February 27, 2013

Not at this time. Sorry. :(

whoughton • August 2, 2013

Is it me, or do the sed linebreaks not work on OS X?

Kamal Nasser

DigitalOcean Employee

• August 2, 2013

@whoughton: Try replacing the single-quotes with double-quotes so that they are parsed properly, does that fix it?

George • September 11, 2013

Nice glad I found this example script. Thanks for sharing. I’m going to do my own spin on the script and later share it here if folks want it.

For $sizes format, maybe use this instead

echo $sizes | awk -F ‘{"’ ‘{print $3"\n" $4"\n" $5"\n" $6"\n" $7"\n" $8"\n" $9"\n" $10"\n" $11"\n" $12}’ | sed -e ‘s/}//g’ | sed -e ‘s/]//g’ | sed -e ‘s/,/\n/g’ | sed -e ‘s/"//g’

it breaks the format down by {" divisions so each size gets it’s own grouped line and then formats it a bit more nicely as such

id:66 name:512MB slug:null memory:512 cpu:1 disk:20 cost_per_hour:0.00744 cost_per_month:5.0

id:63 name:1GB slug:null memory:1024 cpu:1 disk:30 cost_per_hour:0.01488 cost_per_month:10.0

id:62 name:2GB slug:null memory:2048 cpu:2 disk:40 cost_per_hour:0.02976 cost_per_month:20.0

id:64 name:4GB slug:null memory:4096 cpu:2 disk:60 cost_per_hour:0.05952 cost_per_month:40.0

id:65 name:8GB slug:null memory:8192 cpu:4 disk:80 cost_per_hour:0.11905 cost_per_month:80.0

id:61 name:16GB slug:null memory:16384 cpu:8 disk:160 cost_per_hour:0.2381 cost_per_month:160.0

id:60 name:32GB slug:null memory:32768 cpu:12 disk:320 cost_per_hour:0.47619 cost_per_month:320.0

id:70 name:48GB slug:null memory:49152 cpu:16 disk:480 cost_per_hour:0.71429 cost_per_month:480.0

id:69 name:64GB slug:null memory:65536 cpu:20 disk:640 cost_per_hour:0.95238 cost_per_month:640.0

id:68 name:96GB slug:null memory:94208 cpu:24 disk:960 cost_per_hour:1.42857 cost_per_month:960.0

going to have fun playing with this :)

Kamal Nasser

DigitalOcean Employee

• September 11, 2013

Great job George! Good luck :]

Make sure you put it on github so people can contribute as well!

thehazzard • September 12, 2013

How can I Install a dinamic Load Balancer between my instances?

George • September 12, 2013

Thanks Kamal, maybe this is best place to ask as I tried DO support ticket and was asked and directed to read the api doc page heh.

Now I have question with regards to that bash script example above of creating a snapshot, is that valid ? As from the control panel on snapshot page it says to power off droplet from command line BEFORE creating snapshot ?

Does api snapshot command automatically power off the droplet or do I need to first run api command to shutdown or power off the droplet BEFORE running api cmd to create snapshot ?

also is it shutdown ?

https://api.digitalocean.com/droplets/[droplet_id]/power_off/?client_id=[your_client_id]&api_key=[your_api_key]

or power off ?

https://api.digitalocean.com/droplets/[droplet_id]/shutdown/?client_id=[your_client_id]&api_key=[your_api_key]

that i need to run before running snapshor command ?

For powering off at command line that is

shutdown -P now

shutdown -h now

Only then after powering off, then create snapshot

https://api.digitalocean.com/droplets/[droplet_id]/snapshot/?name=[snapshot_name]&client_id=[your_client_id]&api_key=[your_api_key]

Would be great to get some clarification for proper way to create a snapshot via command line and via api. If indeed need to power off, then the above bash script article needs updating or correcting for proper way to create snapshots :)

George • September 12, 2013

Did the same for formatting image output too

i.e.

allimages() { curl -s “${APIBASEURL}/images/?client_id=${CLIENTID}&api_key=${APIKEY}” | awk -F ‘{"’ ‘{for(i=1;i<=NF;i++) print $i}’ | sed -e ‘s/}//g’ | sed -e ‘s/]//g’ | sed -e ‘s/,/ | /g’ | sed -e ‘s/"//g’ echo }

ends up outputting like

./doapi.sh imglist

for regions

listregions() { curl -s “${APIBASEURL}/regions/?client_id=${CLIENTID}&api_key=${APIKEY}” | awk -F ‘{"’ ‘{for(i=1;i<=NF;i++) print $i"\n"}’ | sed -e ‘s/}//g’ | sed -e ‘s/]//g’ | sed -e ‘s/,/\n/g’ | sed -e ‘s/"//g’ echo }

./doapi.sh regions

status:OK regions:[

id:2 name:Amsterdam 1 slug:ams1

id:3 name:San Francisco 1 slug:sfo1

id:4 name:New York 2 slug:nyc2

still working things out like proper snapshot procedure etc. If it’s indeed power off then snapshot run then i’ll have 2 functions to process when snapshot command is called

snapshot) poff snapshotdroplet ;;

so far

./doapi.sh /root/tools/doapi/doapi.sh reboot /root/tools/doapi/doapi.sh recycle /root/tools/doapi/doapi.sh poweron /root/tools/doapi/doapi.sh poweroff /root/tools/doapi/doapi.sh listdroplets /root/tools/doapi/doapi.sh dropletinfo /root/tools/doapi/doapi.sh spinup /root/tools/doapi/doapi.sh resize /root/tools/doapi/doapi.sh snapshot /root/tools/doapi/doapi.sh regions /root/tools/doapi/doapi.sh imglist /root/tools/doapi/doapi.sh imgid /root/tools/doapi/doapi.sh transferimgid /root/tools/doapi/doapi.sh listsizes /root/tools/doapi/doapi.sh listdomains /root/tools/doapi/doapi.sh showdomain /root/tools/doapi/doapi.sh listrecords