django-orchestra-test/docs/create-services.md

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# Creating New Services
1. Think about if the service can fit into one of the existing service models like: SaaS or WebApps, refere to the related documentation if that is the case.
2. Create a new django app using `startapp` management command. For ilustrational purposes we will create a crontab services that will allow orchestra to manage user-based crontabs.
```bash
python3 manage.py startapp crontabs
```
3. Add the new *crontabs* app to the `INSTALLED_APPS` in your project's `settings.py`
3. Create a `models.py` file with the data your service needs to keep in order to be managed by orchestra
```python
from django.db import models
class CrontabSchedule(models.Model):
account = models.ForeignKey('accounts.Account', verbose_name=_("account"))
minute = models.CharField(_("minute"), max_length=64, default='*')
hour = models.CharField(_("hour"), max_length=64, default='*')
day_of_week = models.CharField(_("day of week"), max_length=64, default='*')
day_of_month = models.CharField(_("day of month"), max_length=64, default='*')
month_of_year = models.CharField(_("month of year"), max_length=64, default='*')
class Meta:
ordering = ('month_of_year', 'day_of_month', 'day_of_week', 'hour', 'minute')
def __str__(self):
rfield = lambda f: f and str(f).replace(' ', '') or '*'
return "{0} {1} {2} {3} {4} (m/h/d/dM/MY)".format(
rfield(self.minute), rfield(self.hour), rfield(self.day_of_week),
rfield(self.day_of_month), rfield(self.month_of_year),
)
class Crontab(models.Model):
account = models.ForeignKey('accounts.Account', verbose_name=_("account"))
schedule = models.ForeignKey(CrontabSchedule, verbose_name=_("schedule"))
description = models.CharField(_("description"), max_length=256, blank=True)
command = models.TextField(_("content"))
def __str__(self):
return (self.description or self.command)[:32]
```
4. Create a `admin.py` to enable the admin interface, refere to [Django Admin documentation](https://docs.djangoproject.com/en/1.9/ref/contrib/admin/) for further customization.
```python
from django.contrib import admin
from .models import CrontabSchedule, Crontab
class CrontabScheduleAdmin(admin.ModelAdmin):
pass
class CrontabAdmin(admin.ModelAdmin):
pass
admin.site.register(CrontabSchedule, CrontabScheduleAdmin)
admin.site.register(Crontab, CrontabAdmin)
```
5. Create a `api.py` to enable the REST API.
6. Create a `backends.py` fiel with the needed backends for service orchestration and monitoring.
```python
import os
import textwrap
from django.utils.translation import ugettext_lazy as _
from orchestra.contrib.orchestration import ServiceController, replace
from orchestra.contrib.resources import ServiceMonitor
class UNIXCronBackend(ServiceController):
"""
Basic UNIX cron support.
"""
verbose_name = _("UNIX cron")
model = 'crons.CronTab'
def prepare(self):
super(UNIXCronBackend, self).prepare()
self.accounts = set()
def save(self, crontab):
self.accounts.add(crontab.account)
def delete(self, crontab):
self.accounts.add(crontab.account)
def commit(self):
for account in self.accounts:
crontab = None
self.append("echo '' > %(crontab_path)s" % context)
for crontab in account.crontabs.all():
self.append("
```
7. Configure the routing