How to pass domain name to Nginx conf through chef - amazon-web-services

Question

I have installed Nginx through chef, but i have to pass "AWS instance Public IP to Chef Recipe"
I am creating AWS instance, and installed my application on that Instance through Chef.
I have to run nginx with my default installation method and my Nginx.conf configuration file
So how we can I take the newly created instance Public IP or EC-2 URL in my Nginx configuration i.e. in place of server_name so that I can browse the URL? OR How can I pass the domain name to Nginx.conf ?

Answer 1

You can use EC2 meta-data:
curl http://169.254.169.254/latest/meta-data/public-ipv4
curl http://169.254.169.254/latest/meta-data/public-hostname
To get the list of all available keys, try this:
curl http://169.254.169.254/latest/meta-data/
ami-id
ami-launch-index
ami-manifest-path
block-device-mapping/
hostname
instance-action
instance-id
instance-type
local-hostname
local-ipv4
mac
metrics/
network/
placement/
product-codes
profile
public-hostname
public-ipv4
public-keys/
reservation-id
security-groups
Nevertheless server_name can be empty, see the docs:
If no server_name is defined in a server block then nginx uses the
empty name as the server name. Nginx versions up to 0.8.48 used the machine’s hostname as the server
name in this case. If a server name is defined as “$hostname” (0.9.4),
the machine’s hostname is used.

Answer 2

You can take advantage of ohai plugin ec2 wich gives correct attributes, mainly node['ec2']['public_ipv4'] for this case.
the drawback is taht ohai can't guess itself you're on an AWS instance and does not run the plugin, for this you have to create a hint file, hoepfully there's a cookbook for this.
There's example to create the hints within a chef run too, but they're quite complex IMO, here's what I would do (untested, comment if it break):
# Resource to reload the ec2 plugin if the hint is created
ohai 'ec2' do
plugin 'ec2'
action :nothing
end
ohai_hint 'ec2' do
notifies :reload, 'ohai[ec2]', :immediately # to force ohai to run the ec2 plugin now
end
You nedd this recipe early in your run list, and this ercipe's cookbook must have a depends 'ohai' in it's metadata.rb for the ohai cookbook to be loaded.