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Description:

pythonrangertn 1.8.4

Python Ranger

Before you start, you might wanna check Ranger for more details. You'll need it
to follow some jargon being used in this readme.
There are 3 sections in here.

Ranger Service Finder
Ranger Service Provider
Ranger Daemon

Ranger Service Finder
A service finder in Ranger is something can be used to discover individual host:port pairs of a distributed service
which allows clients to connect and request for services (make http calls). This finding is done using zookeeper. The
following python class helps you do the same for any python based service/tool. It follows the same data models as
present in the main ranger java library. (which is paramount for this to work across languages).
Similar details can be found at PyPi
Installation
python3.9 -m pip install python-ranger-tn

Usage
import requests
from rangermodels import *
from servicefinder import RangerServiceFinder, RoundRobinNodeSelector

## Create the ranger service provider
ranger = RangerServiceFinder(cluster_details=ClusterDetails(zk_string='localhost:2181', update_interval_in_secs=1),
namespace="org",
services=["serviceA", "serviceB"],
selector=RoundRobinNodeSelector()) # optional
# or in one line
ranger = RangerServiceFinder(ClusterDetails('localhost:2181'), "org", ["serviceA", "serviceB"])

## Start the updates in background (this is important)
ranger.start()

## Get one of the healthy nodes to make requests
node = ranger.get_node("serviceA")
response = requests.get(node.get_endpoint() + "/my/api")
node = ranger.get_node("serviceA")
response_again = requests.get(node.get_endpoint(secure=True) + "/my/secure/api")

## to get the full list of healthy nodes
nodes = ranger.get_all_nodes("serviceB")

## When you wish to clean up
ranger.stop()

Details
The above sample shows how to set up a service finder for 2 services. You get the node and then fetch the relevant
details from the node. There would be one background thread created, that continuously refreshes updates from zookeeper.
There is support for being able to apply a custom criteria based filter just like in the java lib(check criteria_filter)
The only difference you might see from the java implementation, is the registration of services before the start (In the
java lib, the expectation is to create one service finder per service, here we create one finder for all services that
may be required for by your python app)

Ranger Service Provider
A service provider in Ranger does the opposite. It can a way to broadcast that a service is available at some host:
port, where clients can connect and request services (make http calls). This broadcast is essentially done using
zookeeper. The following python class helps you do the same for any python based service/tool. Again, it follows the
same data models as present in the main ranger java library.
Usage
from rangermodels import *
from serviceprovider import RangerServiceProvider, HealthCheck

# Create the ranger service provider
ranger = RangerServiceProvider(cluster_details=ClusterDetails(zk_string='localhost:2181', update_interval_in_secs=1),
service_details=ServiceDetails(host='localhost', port=12211, environment='stage',
namespace='myorg',
service_name='python-test'),
health_check=HealthCheck(url='localhost:12211/health', scheme=UrlScheme.GET))

## Or in 2 lines
ranger = RangerServiceProvider(ClusterDetails('localhost:2181'),
ServiceDetails('localhost', 12211, 'stage', 'myorg', 'python-test'))

## Start the updates in background (this will update zookeeper at regular intervals)
ranger.start()

## You may also start the updates and block your current thread (until we hit an interrupt)
ranger.start(block=True)

## When you wish to stop updates
ranger.stop()

Details
The above sample shows how to set up a background thread, that does the job of publishing regular updates to zk. You can
optionally provide a healthcheck url, which will receive a ping at regular intervals. A HEALTHY broadcast will only be
done if the ping check was successful. You can check HealthCheck to customize the URL to your needs.

Ranger Daemon setup
This section deals with using the code as a simple light daemon that can run alongside your software (but outside it) to
provide regular service discovery updates to zookeeper. As usual, check Ranger
for more details.
Intent
Ideally, you would directly use the standard Ranger java client to deeply integrate the service's health updates with
ranger.
In scenarios where you can't do the above, you can rely on this daemon. Say you need discovery updates to be published
for a service written in a langauge other than java, or you are unable to add the ranger dependency directly, in your
java application.
The intent of this daemon is to run along-side your software and publish updates, as long as your software is up and
healthy. Currently, support has been added for a dockerized setup, as well as an import based custom setup. Currently,
Support has been provided for the following:

Simple usage
Import based usage
Docker multi-container setup

1. Simple usage
If you just wish to invoke the script directly, clone the project and follow along the helper. Your command would look
something like this
python3.9 serviceprovider/ranger_daemon.py -zk localhost:2181 -s myapp -host localhost -p 12211 -n org -e stage -hcu 'http://localhost:12211/healthcheck?pretty=true'

2. Import Based Usage
You can also choose to run the daemon from within another python file, by forwarding the command line arguments. Install
the package first, as shown below
python3.9 -m pip install python-ranger-tn

import sys
from serviceprovider.ranger_daemon import ranger_daemon_trigger

ranger_daemon_trigger(sys.argv[1:])

3. Docker Based
Imagine a scenario where you already have a docker application, but you want to run this daemon alongside the container,
to make the existing container discoverable, without having to code up an integration with ranger. The following is a
solution to this problem. You can use docker compose to run your service and this daemon as a multi container docker
application.
After this, your existing container should be ready for service discovery.
Docker containers are available on
the DockerHub.
The following docker command can be used to start the daemon, using environment variables. The table below explains the
various environment variables required to run the script

Env Variable
Description

HOST
Hostname

PORT
Port

RANGER_ZK
Zookeeper connection string

SERVICE_NAME
Name of service

ENV
Environment (stage/prod)

NAMESPACE
Namespace in zookeeper

HEALTH_CHECK
[optional] GET healthcheck URL to be used for pings

REGION
[optional] Region value

TAGS
[optional] Comma separated tags

docker run --rm -d -e RANGER_ZK=<zookeeper_info> -e SERVICE_NAME=<name_of_service> -e HOST=<host_of_machine> -e PORT=<port> -e ENV=<environment> -e NAMESPACE=<namespace> -e HEALTH_CHECK=<health_check_url> --name python-ranger-daemon tusharknaik/python-ranger-daemon:1.8.4

Here is an example for running it on a Mac machine, assuming your zookeeper is already running on localhost:2181 (
notice the network being set to host and zookeeper being sent as host.docker.internal for connecting to localhost
from within docker)
docker run --rm -d --network host -e RANGER_ZK=host.docker.internal:2181 -e SERVICE_NAME=python-test -e HOST=localhost -e PORT=12211 -e ENV=stage -e NAMESPACE=myorg -e HEALTH_CHECK="localhost:12211/health" --name python-ranger-daemon tusharknaik/python-ranger-daemon:1.8.4

Under the hood
The daemon/thread will write data to zookeeper in the following format (datamodel from ranger):
{
"host": "localhost",
"port": 12211,
"nodeData": {
"environment": "stage",
"tags": [
"identity",
"auth"
],
"region": "IN-nm"
},
"healthcheckStatus": "healthy",
"lastUpdatedTimeStamp": 1639044989841
}

Updates will be published in the path: /NAMESPACE/SERVICE_NAME at a periodic intervals of --interval (default: 1
second)
The following will be taken care of:

Infinite retry and connection reattempts in case of zk connection issues
Proper cleanup of zk connections to get rid of ephemeral nodes
Proper logging
Does continuous health check pings on a particular health check url if required [optional]