Rendering a template to the remote end and the rendered result should only contain information about the node on which the task is running

Question

Here is the background information for this question: I have a inventory which contains the information about remote nodes. I also have a template file. I'm trying to render this template to remote end and the rendered result should only contain the information about its target. For example, when I render my template to ops1, the result should only contain the information which defined in my Inventory file（[ceph_osd] - ops1 - rules）

This is my Inventory file:

[cluster]
ops1 ansible_host=192.168.15.80
ops2 ansible_host=192.168.15.81
ops3 ansible_host=192.168.15.82

[ceph_osd]
ops1 rules="{'rule1':{'bcache': '/dev/nvme1n1p7', 'disks': ['/dev/sdb']},'rule2':{'bcache': '/dev/nvme1n1p8', 'disks': ['/dev/sdc']}}"
ops2 rules="{'rule1':{'bcache': '/dev/nvme1n1p7', 'disks': ['/dev/sdb']},'rule2':{'bcache': '/dev/nvme1n1p8', 'disks': ['/dev/sdd']}}"
ops3 rules="{'rule1':{'bcache': '/dev/nvme1n1p7', 'disks': ['/dev/sdc']},'rule2':{'bcache': '/dev/nvme1n1p8', 'disks': ['/dev/sdf']}}"

This is my jinja2 template file:

# clean_bcache.sh.j2
#!/bin/sh

{% for host in groups['ceph_osd'] %}
{% for rule in hostvars[host].rules.values() %}
{% if rule.bcache != 'none' %}
    bcache_name=$(lsblk -o KNAME {{ rule.bcache }} | grep bcache)
    cset.uuid=$(bcache-super-show {{ rule.bcache }} | grep cset.uuid | awk -F' ' '{print $2}')
    echo ${cset.uuid} > /sys/block/$bcache_name/bcache/detach
    sleep 1
    echo 1 >/sys/fs/bcache/${cset.uuid}/unregister 
    sleep 1
{% for backing_dev in rule.disks %}
    echo 1 > /sys/block/{{backing_dev}}/bcache/stop
    
{% endfor %}
{% endif %}
{% endfor %}
{% endfor %}

My ansible task is as follows：

- hosts: cluster
  name: start bcache deployment
  gather_facts: False
  tasks:
  - name: template
    template: src=./clean_bcache.sh.j2 dest=/opt/clean_bcache.sh

After executing this task, all of the rendered files have the same content, which as shown below.

# clean_bcache.sh
#!/bin/sh
    #########################
    bcache_name=$(lsblk -o KNAME /dev/nvme1n1p9 | grep bcache)
    cset.uuid=$(bcache-super-show /dev/nvme1n1p9 | grep cset.uuid | awk -F' ' '{print $2}')
    echo ${cset.uuid} > /sys/block/$bcache_name/bcache/detach
    sleep 1
    echo 1 >/sys/fs/bcache/${cset.uuid}/unregister 
    sleep 1
    echo 1 > /sys/block//dev/sdg/bcache/stop
    
    bcache_name=$(lsblk -o KNAME /dev/nvme1n1p8 | grep bcache)
    cset.uuid=$(bcache-super-show /dev/nvme1n1p8 | grep cset.uuid | awk -F' ' '{print $2}')
    echo ${cset.uuid} > /sys/block/$bcache_name/bcache/detach
    sleep 1
    echo 1 >/sys/fs/bcache/${cset.uuid}/unregister 
    sleep 1
    echo 1 > /sys/block//dev/sdc/bcache/stop
    
    #########################
    bcache_name=$(lsblk -o KNAME /dev/nvme1n1p9 | grep bcache)
    cset.uuid=$(bcache-super-show /dev/nvme1n1p9 | grep cset.uuid | awk -F' ' '{print $2}')
    echo ${cset.uuid} > /sys/block/$bcache_name/bcache/detach
    sleep 1
    echo 1 >/sys/fs/bcache/${cset.uuid}/unregister 
    sleep 1
    echo 1 > /sys/block//dev/sdc/bcache/stop
    bcache_name=$(lsblk -o KNAME /dev/nvme1n1p8 | grep bcache)
    cset.uuid=$(bcache-super-show /dev/nvme1n1p8 | grep cset.uuid | awk -F' ' '{print $2}')
    echo ${cset.uuid} > /sys/block/$bcache_name/bcache/detach
    sleep 1
    echo 1 >/sys/fs/bcache/${cset.uuid}/unregister 
    sleep 1
    echo 1 > /sys/block//dev/sdd/bcache/stop
  
    #########################
    bcache_name=$(lsblk -o KNAME /dev/nvme1n1p9 | grep bcache)
    cset.uuid=$(bcache-super-show /dev/nvme1n1p9 | grep cset.uuid | awk -F' ' '{print $2}')
    echo ${cset.uuid} > /sys/block/$bcache_name/bcache/detach
    sleep 1
    echo 1 >/sys/fs/bcache/${cset.uuid}/unregister 
    sleep 1
    echo 1 > /sys/block//dev/sdg/bcache/stop
    bcache_name=$(lsblk -o KNAME /dev/nvme1n1p8 | grep bcache)
    cset.uuid=$(bcache-super-show /dev/nvme1n1p8 | grep cset.uuid | awk -F' ' '{print $2}')
    echo ${cset.uuid} > /sys/block/$bcache_name/bcache/detach
    sleep 1
    echo 1 >/sys/fs/bcache/${cset.uuid}/unregister 
    sleep 1
    echo 1 > /sys/block//dev/sdf/bcache/stop
   

What I want to do is to render this file into three different files located on different nodes. The goal I want to achieve is as follows:

The clean_bcache.sh on the remote ops1 should look like follow. As you can see, it only contains the information related to ops1 in the foregoing Inventory

#!/bin/sh
    bcache_name=$(lsblk -o KNAME /dev/nvme1n1p9 | grep bcache)
    cset.uuid=$(bcache-super-show /dev/nvme1n1p9 | grep cset.uuid | awk -F' ' '{print $2}')
    echo ${cset.uuid} > /sys/block/$bcache_name/bcache/detach
    sleep 1
    echo 1 >/sys/fs/bcache/${cset.uuid}/unregister 
    sleep 1
    echo 1 > /sys/block//dev/sdg/bcache/stop
    
    bcache_name=$(lsblk -o KNAME /dev/nvme1n1p8 | grep bcache)
    cset.uuid=$(bcache-super-show /dev/nvme1n1p8 | grep cset.uuid | awk -F' ' '{print $2}')
    echo ${cset.uuid} > /sys/block/$bcache_name/bcache/detach
    sleep 1
    echo 1 >/sys/fs/bcache/${cset.uuid}/unregister 
    sleep 1
    echo 1 > /sys/block//dev/sdc/bcache/stop

This is the clean_bcache.sh on ops2.

#!/bin/sh
    bcache_name=$(lsblk -o KNAME /dev/nvme1n1p9 | grep bcache)
    cset.uuid=$(bcache-super-show /dev/nvme1n1p9 | grep cset.uuid | awk -F' ' '{print $2}')
    echo ${cset.uuid} > /sys/block/$bcache_name/bcache/detach
    sleep 1
    echo 1 >/sys/fs/bcache/${cset.uuid}/unregister 
    sleep 1
    echo 1 > /sys/block//dev/sdc/bcache/stop
    bcache_name=$(lsblk -o KNAME /dev/nvme1n1p8 | grep bcache)
    cset.uuid=$(bcache-super-show /dev/nvme1n1p8 | grep cset.uuid | awk -F' ' '{print $2}')
    echo ${cset.uuid} > /sys/block/$bcache_name/bcache/detach
    sleep 1
    echo 1 >/sys/fs/bcache/${cset.uuid}/unregister 
    sleep 1
    echo 1 > /sys/block//dev/sdd/bcache/stop

This is the clean_bcache.sh on ops3

#!/bin/sh
    bcache_name=$(lsblk -o KNAME /dev/nvme1n1p9 | grep bcache)
    cset.uuid=$(bcache-super-show /dev/nvme1n1p9 | grep cset.uuid | awk -F' ' '{print $2}')
    echo ${cset.uuid} > /sys/block/$bcache_name/bcache/detach
    sleep 1
    echo 1 >/sys/fs/bcache/${cset.uuid}/unregister 
    sleep 1
    echo 1 > /sys/block//dev/sdg/bcache/stop
    bcache_name=$(lsblk -o KNAME /dev/nvme1n1p8 | grep bcache)
    cset.uuid=$(bcache-super-show /dev/nvme1n1p8 | grep cset.uuid | awk -F' ' '{print $2}')
    echo ${cset.uuid} > /sys/block/$bcache_name/bcache/detach
    sleep 1
    echo 1 >/sys/fs/bcache/${cset.uuid}/unregister 
    sleep 1
    echo 1 > /sys/block//dev/sdf/bcache/stop

I have googled a lot, but none of them worked.

Any ideas? Thanks in advance!!

Answer 1

To solve this problem, you only need to add a if statement if host == inventory_hostname in your template file.

#!/bin/sh

{% for host in groups['ceph_osd'] %}
{% if host == inventory_hostname %}
{% for rule in hostvars[host].rules.values() %}
{% if rule.bcache != 'none' %}
    bcache_name=$(lsblk -o KNAME {{ rule.disks | first }} | grep bcache)
    cset_uuid=$(bcache-super-show {{ rule.bcache }} | grep cset.uuid | awk -F' ' '{print $2}')
    echo $cset_uuid > /sys/block/$bcache_name/bcache/detach
    sleep 1
    echo 1 >/sys/fs/bcache/$cset_uuid/unregister 
    sleep 1
{% for backing_dev in rule.disks %}
    echo 1 > /sys/block/{{backing_dev.split("/") | last}}/bcache/stop
{% endfor %}
{% endif %}
{% endfor %}
{% endif %}
{% endfor %}