ec2hostsfile.ngs

#!/usr/bin/env ngs

# Builds a section of /etc/hosts file listing EC2 instances.
# Naming is based on "env" and "role" tags of the instances.

### sample output
### 172.XX.XX.XX     staging-api-gateway               #   i-b2XXXXXX   5X.XXX.XXX.XXX   api-gateway/66                                
### 172.XX.XX.XX     prod-compositor-1                 #   i-83XXXXXX   5X.XXX.XXX.XXX   compositor/978-1-7                            
### 172.XX.XX.XX     prod-compositor-2                 #   i-84XXXXXX   1XX.XX.XX.XXX    compositor/978-1-7                            
### 172.XX.XX.XX     prod-vdr-manager-1                #   i-90XXXXXX   5X.XX.XX.XXX     vdr-manager-vpc/683-4                         
### 172.XX.XX.XX     prod-vdr-manager-2                #   i-97XXXXXX   5X.XX.XXX.XX     vdr-manager-vpc/683-4                         
### 172.XX.XX.XX     staging-store                     #   i-79XXXXXX   5X.XX.XXX.XXX    store/257                                     
### 172.XX.XX.XX     staging-dsp-manager               #   i-acXXXXXX   5X.X.XX.XXX      dsp-manager/707-1-7                           
### ...

# For minimalistic output: NGS_table_ec2hosts='["PrivateIpAddress", "HostName"]' ./demo/ec2hostsfile.ngs

{
	# TODO: sorting of the instances

	F HostnameBase(i:Hash) "${i.Tags.env}-${i.Tags.role}"

	instances = ``aws ec2 describe-instances --filters Name=instance-state-name,Values=running``

	# Only look at instances with "env" and "role" tags
	instances = instances.filter(F(i) try HostnameBase(i))

	# stats - know which instances to suffix with sequential number and which not
	# stats = instances.map(HostnameBase).Stats()
	stats = Stats(instances / HostnameBase)
	debug("Names stats: ${stats}")

	# sequential numbering for instances with same "env" and "role" tags
	numbering = Stats()

	# Preparing the table
	instances.each(F(i) {
		hostname_base = HostnameBase(i)
		i.HostName = if stats[hostname_base] == 1 hostname_base else {
			numbering.push(hostname_base)
			"${hostname_base}-${numbering[hostname_base]}"
		}
		i.Comment = '#'
		i.Name = i.Tags.get('Name', '-')
	})

	config('table_ec2hosts', %[PrivateIpAddress HostName Comment InstanceId PublicIpAddress Name])
	config('output_format', 'text')
	config('output_title', false)
	config('output_headers', false)
	t = Table('ec2hosts', instances)
	echo(t)

}