13. Miscellaneous¶
13.1. The .layerapi2_dependencies file¶
When you create a plugin with the bootstap_plugin command, a .layerapi2_dependencies file is created in the plugin root directory. This file contains the module/package dependencies you need for the plugin.
By default, the .layerapi2_dependencies file contains only minimal dependencies, e.g.:
root@mfserv
python3@mfserv
means the plugin will use the Layer root and Layer python3 supplied in MFSERV.
For more details on layerapi2, check MFEXT layerapi2 and MFEXT layerapi2 syntax documentation.
Let’s assume you need a module or package which is available in the MFEXT ‘scientific’ package, you have to add this dependencies to the .layerapi2_dependencies file:
root@mfserv
python3@mfserv
python3_scientific@mfext
Let’s assume now, you want to build your plugin relies on Python2 instead of Python3, the .layerapi2_dependencies file will look like this:
root@mfserv
python2@mfserv
python2_scientific@mfext
13.2. The .layerapi2_extra_env file¶
The .layerapi2_extra_env file allows you to defined environment variable only in the plugin context. Check layerapi2 MFEXT documentation.
By default, this .layerapi2_extra_env doesn’t exist. If you need to add extra environment variables, create this file in the plugin root directory.
See also
MFEXT layerapi2 syntax documentation.
13.3. Plugins with more than one application¶
Important
A plugin may one or more application.
In most cases, when you create a plugin with bootstrap_plugin.py, only one application called main is created with the corresponding script(s) (i.e. in the main directory).
However, you may create a plugin with more than one application.
For instance, let’s add a second application in the foo_default plugin example.
First, duplicate the main directory of the foo_default plugin directory and name it second
Then duplicate the [app_main] section of the config.ini file of the plugin, rename the duplicated section [app_second] and change its main_arg parameter value as follows:
main_arg = second.wsgi:application
Edit the second/wsgi.py script as follows (just change the response message):
import os
from mflog import get_logger
logger = get_logger("myapp")
def application(environ, start_response):
my_url = os.environ.get("MFSERV_PLUGIN_FOO_DEFAULT_MY_URL", "")
status = '200 OK'
output = '<h1>Hello World from second application!</h1>'
if my_url != "":
output = '{}</br></br><a href="{}">Visit Metwork Framework blog</a>'.format(output, my_url)
logger.info("this is a test message")
response_headers = [('Content-Type', 'text/html; charset=utf-8'),
('Content-Length', str(len(output)))]
start_response(status, response_headers)
return [output.encode('utf-8')]
Let’s now install (as dev build) the plugin by entering the command (from the foo_default plugin directory):
make develop
From a web browser, enter the url of your second application: http://localhost:18868/foo_default/second or http://{remote_host}:18868/foo_default/second. A ‘Hello World from second application!.’ HTML page with a link to my_url should be displayed.
Enter the url of your main application: http://localhost:18868/foo_default/main. A ‘Hello World from second application!.’ HTML page with a link to my_url should be displayed.
Note
13.4. The outside Metwork command¶
The outside is a command utility that allow you execute commands outside the Metwork environment.
For instance, let’s assume the Python version of Metwork is 3.5.6 and the Python version installed on your system is Python 2.7.5.
For instance:
Entering the command from the Metwork environment:
python --version
Output:
Python 3.5.6
Entering the command from the Metwork environment:
outside python --version
Output:
Python 2.7.5
13.5. The crontab support¶
Each plugin has a crontab support to schedule the execution of programs.
In order to enable your plugin crontab, just create a crontab file in the root directory of the plugin and set the tasks you want to schedule. For further details about crontab, check the Linux documentation (man crontab command or http://man7.org/linux/man-pages/man5/crontab.5.html)
In order to (re)load the contab file:
If the crontab file does not exist and you create it, you have to restart MFSERV by entering
mfserv.stopthenmfserv.startcommands (or reinstall the plugin)If the crontab file exists and you just change its content, you have just to wait a few seconds for the changes to be automatically taken into account.
Tip
you may use environment variable in your command surrounded with {{ }} . Environment variables are substituted when cron is installed
you may use the wrapper cronwrap.sh in order to execute the command in the Metwork context.
Warning
Never use crontab -e to edit the crontab file inline.
Never override the crontab file by entering the command crontab [your_crontab_file]
If you need to execute your cron command in the Metwork context, you should use the cron wrapper script ${MFSERV_HOME}/bin/cronwrap.sh, e.g. :
{{MFSERV_HOME}}/bin/cronwrap.sh --lock --low "find {{MFMODULE_RUNTIME_HOME}}/var/archive/ -type f -mtime +5 -exec rm -f {} \;" >/dev/null 2>&1
{{MFSERV_HOME}}/bin/cronwrap.sh -- plugin_wrapper [your_plugin_name] [your_sh_command] >{{MFMODULE_RUNTIME_HOME}}/log/[your_log_filename] 2>&1
Enter cronwrap.sh --help for more details.
13.6. Extra daemon¶
You can add extra daemons which will be launched within your plugin. In order to do this, edit the config.ini plugin configuration file and add an [extra_daemon_xxx] section.
You have to provide a command to daemonize (the command must run in foreground and not daemonize by itself):
[extra_daemon_foo]
cmd_and_args = /your/foreground/command command_arg1 command_arg2
# numprocesses=1
The numprocesses argument is the the number of processes allocated to you daemon command. The default value is 1.
Of course, you can define as many daemon as you want by adding [extra_daemon_*] section:
[extra_daemon_xxx]
cmd_and_args = /your/foreground/command1 command_arg1 command_arg2
[extra_daemon_yyy]
cmd_and_args = /your/foreground/command2 command_arg1
[extra_daemon_zzz]
cmd_and_args = /your/foreground/command3
...
13.7. Extra route¶
You may add redirection of incoming http request, you can set the prefix_based_routing_extra_routes in the config.ini file of the plugin.
For instance, let’s assume you access to your application by invoking the URL http://localhost:18868/foo_nodejs, if you set prefix_based_routing_extra_routes=/hello_from_nodejs, this url will be also redirected to your application.
Warning
Tip
13.8. Access a database¶
A plugin can access a database through Python ORMs, like SQLAlchemy, Records, Django ORM, peewee, and so on.
Metwork supplies PostgreSQL/PostGIS database through the MFBASE storage module. If you want to easily and quickly install a Postgres database, check the MFBASE documentation.
Tip
13.9. Disable request ID to be appeared in the logs¶
By default, for each HTTP request, a unique request ID is added in the X-Request-ID attributes of the HTTP header. This request ID is also added into the log files.
To disable this behaviour, you just have to set to 0 the add_request_id_header parameter in the config/config.ini file configuration of the MFSERV module.
13.10. Disable middleware (asyncio, aiohttp plugins)¶
Thi section applies only for plugin based on aiohttp.
You can disable some (or all) middlewares by changing (omitting) the middlewares parameter in the web.Application() aiohttp API, e.g.:
See also