Unable to create conf file using Jinja - Expected Variables for Nginx - nginx

Question

I am learning to use Jinja today to template a config file that I manually created and tested for Nginx. So far the template works as expected and it pulls the dynamic variables as expected. However, I have one line in my conf that needs to be on two separate lines and for some reason, it puts the two host on the same line.
This seems really simple, but I can't seem to spot what is causing it. I've gotten this far so!
My nginx.yml file
---
test_url: abc.{{ nginx_domain }}
nginx_ssl_port: 443
nginx_proxy_conf_dir: /etc/some/place
nginx_ssl_key_dir: /etc/somekey/place
nginx_ssl_cert_dir: /etc/somecert/place
nginx_proxy_log_dir: /etc/some/proxy/place
##Env depends on ansible inventory
test_nginx_proxy_sites:
- name: test
params:
- 'listen {{ nginx_ssl_port }} ssl'
- 'server_name {{test_url}}'
- 'include {{ nginx_proxy_conf_dir }}/conf.d/ssl.conf'
- 'ssl_certificate {{ nginx_ssl_cert_dir }}/{{ nginx_domain }}.crt'
- 'ssl_certificate_key {{ nginx_ssl_key_dir }}/{{ nginx_domain }}.key'
- 'access_log {{ nginx_proxy_log_dir }}/management_access.log'
- 'error_log {{ nginx_proxy_log_dir }}/management_error.log'
locations:
- path: /
location_params:
- 'proxy_pass http://stream_{{ Env }}/'
- 'include {{ nginx_proxy_conf_dir }}/conf.d/proxy.conf'
upstreams:
- name: stream_{{ Env }}
params:
- '{% for host in groups.tag_Class_host %}
server {{ hostvars[host].ipv4_local }}:{{ management_port }};
{% endfor %}
'
My sites.conf.j2
{{ remotely_managed }}
server {
{% if item.blocks is defined and item.blocks|length > 0 %}
{% for block in item.blocks %}
{{ block }}
{% endfor %}
{% endif %}
{% for param in item.params %}
{{ param }};
{% endfor %}
{% if item.locations is defined and item.locations|length > 0 %}
{% for location in item.locations %}
location {% if location.match is defined %}{{ location.match }} {% endif %}{{ location.path }} {
{% if location.root is defined %}
root {{ location.root }};
{% endif %}
{% if location.location_params is defined and location.location_params|length > 0 %}
{% for param in location.location_params %}
{{ param }};
{% endfor %}
{% endif %}
}
{% endfor %}
{% endif %}
{% if item.errors is defined and item.errors|length > 0 %}
{% for error in item.errors %}
{{ error.directive }};
location {{ error.location }} {
{% for param in error.error_params %}
{{ param }};
{% endfor %}
}
{% endfor %}
{% endif %}
}
{% if item.upstreams is defined %}
{% for u in item.upstreams %}
upstream {{ u.name }} {
{% if u.params is defined %}
{% for param in u.params %}
{{ param }}
{% endfor %}
{% endif %}
}
{% endfor %}
{% endif %}
My output
server {
server_name abc.mytest.com;
include /etc/nginx/conf.d/ssl.conf;
ssl_certificate /etc/somecert/place/certs/abc.mytest.com.crt;
ssl_certificate_key /etc/somekey/place/private/abc.mytest.com.key;
access_log /var/log/nginx/management_access.log;
error_log /var/log/nginx/management_error.log;
location / {
proxy_pass http://stream_qa/;
include /etc/nginx/conf.d/proxy.conf;
}
}
upstream stream_qa {
server 1.1.1.09:11111; server 1.1.1.10:11111;
}
The upstream should print out like below:
upstream stream_qa {
server 1.1.1.09:11111;
server 1.1.1.10:11111;
}

Answer 1

Okay - so.
To understand this issue, it's important to know how jinja templating works.
For the solution: Simply put a new line in, like this
{% if item.upstreams is defined %}
{% for u in item.upstreams %}
upstream {{ u.name }} {
{% if u.params is defined %}
{% for param in u.params %}
{{ param }}
{% endfor %}
{% endif %}
The reason for this is due to how jinja templating works.
When rendering jinja, it does not know to put things on a new line, it just knows to put a copy of whatever is in your loop. So if your loop is missing provision for a new line, it will not put things on a new line.
so when you have a loop like yours, or more simply an array of [a, b, c, d, e, f]
{% for i in items %}
{{ i }}
{% endfor %}
it will print as abcdef because the {{i}} literrally means render i here.
By placing a new line in your loop.
{% for i in items %}
{{ i }}
{% endfor %}
it will render i at the end of the last item in the loop, ie on a new line.
In really simple terms, what you want to do is have i also include provision for a new line in your loop so that when jinja renders whats in the loop, its also rendering a new line.
If you look at it like this, the first loop I mentioned renders like this
abcde but the second loop renders like this: a\nb\nc\nd\ne, As you can see, the value for each item in this loop has provision for a new line.
ps: This was really difficult to explain :(

Answer 2

I was able to resolve this issue by editing my nginx.yml file:
upstreams:
- name: stream_{{ Env }}
params:
-
{% for host in groups.tag_Class_host %}
server {{ hostvars[host].ipv4_local }}:{{ management_port }};
{% endfor %}
Rather than looking at Jinja, I should have reviewed YAML. A new pipe in YAML will make my string a multi-string line.
The output matches the output above.