In this tutorial we will introduce a new parameter replicate-quantity defining the quantity of nodes that we want for our HTML5AS CDN / replicate system.

This is made possible by making our replicate instance buildout file dynamic through Jinja2 templating. So far we only used the basic templating functionnalities, we will now automatically generate sections according to request parameters.

Here is the commit introducing this functionality to html5as Software release: commit diff.

Edit instance.cfg.in in order to the get the dict of parameters in the configuration key.

[slap-configuration]
...
key = ${slap-connection:key-file}
cert = ${slap-connection:cert-file}

Pass this configuration to the section [instance-replicate] rendering the replicate instance buildout.

[instance-replicate]
...
extensions = jinja2.ext.do
...
default-parameters =
  {
    "download_url": "",
    "replicate-quantity": 1
  }

Edit instance_replicate.cfg.in to add this line at the beginning defining the replicate quantity from the replicate-quantity parameter. We set 1 as a default value for the parameter.

{%- set parameter_dict = dict(default_parameter_dict, **slapparameter_dict) %}
{%- set replicate_quantity = int(parameter_dict['replicate-quantity']) %}

Edit instance_replicate.cfg.in to replace section [instance-1] and [instance-2] by a dynamic rendering.

...
# Set default title and port for each replicate based on requested quantity
{%- for i in range(1, replicate_quantity + 1) %}
{%- do parameter_dict.setdefault("title-%d" % i, "") %}
{%- do parameter_dict.setdefault("port-%d" % i, 8081 + i) %}
{%- do parameter_dict.setdefault("monitor-httpd-port-%d" % i, 8197 + i) %}
{%- endfor %}
...

[instance-request-base]
...
# Remove : 
# config-title = {{ parameter_dict['title'] }} 
...

# Create request section in a loop.
{% for i in range(1, replicate_quantity + 1) %}
# Request a normal html5as instance
[instance-{{ i }}]
<= instance-request-base
# Name of the instance
name = instance-html5as-{{ i }}
config-port = {{ parameter_dict["port-%s" % i] }}
config-title = {{ parameter_dict["title-%s" % i] }}
config-monitor-httpd-port = {{ parameter_dict["monitor-httpd-port-%s" % i] }}
{% endfor %}

Edit instance_replicate.cfg.in to change existing [publish-connection-information] to define default parameters dynamically and publish node parameters dynamically.

# Publish information to connect to the two instances
[publish-connection-information]
recipe = slapos.cookbook:publish
{% for i in range(1, replicate_quantity + 1) %}
instance-{{ i }}-server_url = ${instance-{{ i }}:connection-server_url}
instance-{{ i }}-server-cdn-url = ${instance-{{ i }}:connection-server-cdn-url}
instance-{{ i }}-server-monitor-setup-url = ${instance-{{ i }}:connection-monitor-setup-url}
{% endfor %}

Check you changes in instance_replicate.cfg.in. The final file should be like this:

{%- set parameter_dict = dict(default_parameter_dict, **slapparameter_dict) %}
{%- set replicate_quantity = int(parameter_dict['replicate-quantity']) %}
# Set default title and port for each replicate based on requested quantity
{%- for i in range(1, replicate_quantity + 1) %}
{%- do parameter_dict.setdefault("title-%d" % i, "") %}
{%- do parameter_dict.setdefault("port-%d" % i, 8081 + i) %}
{%- do parameter_dict.setdefault("monitor-httpd-port-%d" % i, 8197 + i) %}
{%- endfor %}

# Standard buildout section
[buildout]
parts =
    publish-connection-information

eggs-directory = {{ buildout['eggs-directory'] }}
develop-eggs-directory = {{ buildout['develop-eggs-directory'] }}
offline = true

################################
# Sections to Request instances
################################

# Macro section sharing request parameters
[instance-request-base]
<= slap-connection
recipe = slapos.cookbook:request
# It is the same software as the current one
software-url = ${slap-connection:software-release-url}
# We want the default behaviour
software-type = default
# What parameter are neede to be retrieved
return = server_url server-cdn-url monitor-setup-url
# Provided parameters
config-download_url = {{ parameter_dict['download_url'] }}

# Create request section in a loop.
{% for i in range(1, replicate_quantity + 1) %}
# Request a normal html5as instance
[instance-{{ i }}]
<= instance-request-base
# Name of the instance
name = instance-html5as-{{ i }}
config-port = {{ parameter_dict["port-%s" % i] }}
config-title = {{ parameter_dict["title-%s" % i] }}
config-monitor-httpd-port = {{ parameter_dict["monitor-httpd-port-%s" % i] }}
{% endfor %}

# Publish information to connect to the two instances
[publish-connection-information]
recipe = slapos.cookbook:publish
{% for i in range(1, replicate_quantity + 1) %}
instance-{{ i }}-server_url = ${instance-{{ i }}:connection-server_url}
instance-{{ i }}-server-cdn-url = ${instance-{{ i }}:connection-server-cdn-url}
instance-{{ i }}-server-monitor-setup-url = ${instance-{{ i }}:connection-monitor-setup-url}
{% endfor %}

Refer How To Move to md5sum automatic update to update md5sum:

$ cd ~/srv/project/slapos/software/html5as-base
$ ../../update-hash

To request a replicate type of sofware, you should define the type in the request script:

slapos request $software_name-1 $software_release_uri --type="replicate" --parameters replicate-quantity=3

Make sure to edit it in your request file instead of the example one. Parameters like replicate-quantity, title, etc. should place after --parameters directly as shown in the screenshot.

Run the request script by

$ cd ~/srv/project/slapos/software/html5as-base
$ bash ../../../request-html5as-base.sh 

Re-compile the software by

$ slapos node software --all

Once it completes, you may re-instantiate it by

$ slapos node instance --all

There is no errors expected. The compiling and instantiation should be completed.

Make sure that the compiling and instantiation is completed. You can now inspect the connection parameters by re-running the request script:

$ cd ~/srv/project/slapos/software/html5as-base
$ bash ../../../request-html5as-base.sh 

As the replicate-quantity is 3, the published connection parameters will be 9 according to [publish-connection-information] defined in instance_replicate.cfg.in.