lovely-ws-status 1.0.0

Service Status Utilities for Pyramid Apps

This package provides service status utilities for Pyramid applications. Register your own status handlers and see the service status of all registered handlers in the svc_status Pyramid view.

Status Handler

A status handler can be any method or class that checks any part of your application stack. This can be for example a check that your database connection is still working, or checking some external service. The status handler must return a dict with a state property which can have the value OK, YELLOW or RED. Additional properties like detail can be optionally added, but will only be displayed in the JSON SVC status view.

As Callable

Create a status handler as a python function:

>>> from lovely.ws.status import OK
>>> def statusHandler():
...     # Do whatever you need to do to check the status
...     return {
...         'state': OK
...     }

Register the status handler:

>>> from lovely.ws.status import addStatusHandler
>>> addStatusHandler('DatabaseConnection', statusHandler)

Status handlers can also be classes, just provide a __call__ method:

>>> from lovely.ws.status import RED
>>> class StatusHandler(object):
...     def __call__(self):
...         # Do whatever you need to do to check the status
...         return {
...             'state': RED,
...             'detail': 'Service not available',
...         }
>>> statusHandler2 = StatusHandler()
>>> addStatusHandler('UserService', statusHandler2)

Mixin Class

To simplify the implementation of status providers there is a mixin class which handles the state and provides logging on status changes:

>>> from lovely.ws.status import YELLOW, GREEN
>>> from lovely.ws.status.statehandler import StateHandlerMixin
>>> class MyHandler(StateHandlerMixin):
...     def __init__(self):
...         self.setState(YELLOW)
>>> myHandler = MyHandler()
>>> addStatusHandler('myHandler', myHandler)

Now just use setState to change the state. setState allows to set any additional property on the state:

>>> myHandler.setState(GREEN, detail='running')

SVC Status View

There’s a Pyramid view that can be added to your project which creates an endpoint to see the live service status provided by all registered status handlers.

For the view to get registered, you need to configure this module in your application by adding these two lines in your app factory:

config.include('lovely.ws.status.svcstatus')
config.scan('lovely.ws.status.svcstatus')

Calling the /svc_status endpoint will return a CSV response with an output like this:

DatabaseConnection OK
UserService RED

It’s also possible to receive the response in JSON format by calling the svc_status endpoint with accept header application/json or by calling the svc_status.json endpoint. Additional properties like the detail will only be shown in the JSON formatted output. The output will look like this:

{
    "DatabaseConnection": {
        "state": "OK"
    },
    "UserService":{
        "state": "OK",
        "detail": "Service not available"
    }
}

Calling the svc_status.prometheus endpoint returns the service status as a prometheus template. The output will look like this:

# HELP svc_status Status 0->OK, 1->YELLOW, 2->RED
# TYPE svc_status untyped
svc_status{name="DatabaseConnection"} 0
# HELP svc_status Status 0->OK, 1->YELLOW, 2->RED
# TYPE svc_status untyped
svc_status{name="UserService"} 2

More information can be found in the SVC status test suite.

Probe Status View

This view allows to check if the service is available and to decommission the service. The view returns status 200 and the body OK by default.

The probe status view can be included into a Pyramid project in the server.py file by adding these two lines in your app factory:

config.include('lovely.ws.status.probestatus')
config.scan('lovely.ws.status.probestatus')

Decommissioning can be used to make the service unavailable for load balancers before the service is shut down.

More information can be found in the probe status test suite.

Development

Information on how to contribute can be found in the DEVELOPMENT.rst file.