Refer other host to get facts when running in a host

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1

Hi,

I’m using Ansible to provision an application deployment.

here is my structure

hosts
[dbservers]
db.local

[memcached]
mc.local

[appservers]
app1.local
#app2.local

I’m using Tomcat and have a context like this in appservers ( app1.local)
roles/tomcat/templates/context.j2

<Manager className="de.javakaffee.web.msm.MemcachedBackupSessionManager"

<Resource name=“jdbc/postgres/configuration”

url=“jdbc:postgresql://db.local:5432/configuration”
/>

My questions are:

  • How can I resolve mc.local ( db.local) to IP?
    Doing this, I don’t have to set hosts in appservers like
    /etc/hosts
    192.168… mc.local
    …

  • In case of using dymamic inventory ( Ec2), how can I refer a db ( from db tags), resolve its ip and resolve the template.

  • Or is there another way to accomplish this?

I guess this model is trivial and should have a normal way out there ( but I’m still a Ansible newbie to get it)

Thanks,
Pilgrim

2

this seems a basic question and have a simple answer.

{% for host in groups[‘dbservers’] %}
{{ hostvars[host][‘ansible_eth1’][‘ipv4’][‘address’] }}
{% endfor %}

the interesting point is I normally run a specfic roles/tasks by tagging
like this

ansible-playbook site.yml --limit=appservers --tags=sb_tomcat

note: since we limit appservers only then Ansible have no idea to get facts from other servers ( dbserver, memcache) in this case.

I have to do cheat like this

ansible-playbook site.yml --limit=dbservers, appservers --tags=sb_tomcat ( add dbservers to gather facts)
but it’s not enough, I have to add a fake task like this for dbservers with tag sb_tomcat

  • name: Dont fool me
    command: echo “can you hear me”
    tags:
  • sb_tomcat

Doing this to tell Ansible to gather dbserver facts and

{% for host in groups[‘dbservers’] %}
{{ hostvars[host][‘ansible_eth1’][‘ipv4’][‘address’] }}
{% endfor %}

works.

Questions:

  • In real case, we really need a specfic tag. Do we have another way to gather fact explitcitly without modifying --limit or add fake tasks?

Regards,
Pilgrim