CI	License	Compatibility

python-circuit-breaker-examples

Working examples of using different Python Circuit Breaker packages, with a Flask mock server using http-server-mock

The main purpose is to show how a Cicuit Breaker pattern will work using these packages:

• circuitbreaker
• pybreaker
• python-circuit

The client codes calls against a "REST" API service on an "unreliable" mock server. We have a mock Flask server that we can spin up or down inline using the http-server-mock package to control whether our client responses are successful or not in order to test how the circuit breaker works for an un-responsive service (ie the mocker server).

Installation

Clone repository and then install using pipenv: pipenv install --dev

Usage

After installation, you can run the following circuit breaker examples.

Each have the same scenario:

• Start with a "closed" circuit
• Start with a "down" REST API service (server is OFF)
• Have a maximum of 3 tries to connect till the circuit pops "open"
• Have a 6 second delay till the circuit is tested again in "half-open" state
• Issue 10 API calls on 1 second delays to the endpoint till the server comes back ON
• Issue 10 more API calls with the API service back up to show the change over to a "closed" state

circuitbreaker

Run

pipenv run python python_circuit_breaker_examples/client_circuitbreaker.py

Output

Server is turned OFF...
get_greeting circuit state: closed. Time till open: 5.99578
get_greeting circuit state: closed. Time till open: 4.956267
get_greeting circuit state: open. Time till open: 5.999928
get_greeting circuit state: open. Time till open: 4.998572
get_greeting circuit state: open. Time till open: 3.997259
get_greeting circuit state: open. Time till open: 2.995893
get_greeting circuit state: open. Time till open: 1.994597
get_greeting circuit state: open. Time till open: 0.993119
get_greeting circuit state: open. Time till open: 5.999976
get_greeting circuit state: open. Time till open: 4.998959
Server is turning ON...
 * Serving Flask app "python_circuit_breaker_examples.mock_server" (lazy loading)
 * Environment: production
   WARNING: This is a development server. Do not use it in a production deployment.
   Use a production WSGI server instead.
 * Debug mode: off
 * Running on http://localhost:5000/ (Press CTRL+C to quit)
127.0.0.1 - - [02/Dec/2019 12:35:07] "PUT /0ed229fc-152a-11ea-9309-a08cfd9fd53c/0ed229fd-152a-11ea-9309-a08cfd9fd53c HTTP/1.1" 200 -
get_greeting circuit state: open. Time till open: 3.93516
get_greeting circuit state: open. Time till open: 2.933744
get_greeting circuit state: open. Time till open: 1.932458
get_greeting circuit state: open. Time till open: 0.93114
127.0.0.1 - - [02/Dec/2019 12:35:11] "GET / HTTP/1.1" 200 -
get_greeting circuit state: closed. Time till open: -0.089294
127.0.0.1 - - [02/Dec/2019 12:35:12] "GET / HTTP/1.1" 200 -
get_greeting circuit state: closed. Time till open: -1.093669
127.0.0.1 - - [02/Dec/2019 12:35:13] "GET / HTTP/1.1" 200 -
get_greeting circuit state: closed. Time till open: -2.111054
127.0.0.1 - - [02/Dec/2019 12:35:14] "GET / HTTP/1.1" 200 -
get_greeting circuit state: closed. Time till open: -3.115754
127.0.0.1 - - [02/Dec/2019 12:35:15] "GET / HTTP/1.1" 200 -
get_greeting circuit state: closed. Time till open: -4.122443
127.0.0.1 - - [02/Dec/2019 12:35:16] "GET / HTTP/1.1" 200 -
get_greeting circuit state: closed. Time till open: -5.134389

PyBreaker

Run

pipenv run python python_circuit_breaker_examples/client_pybreaker.py

Output

Server is turned OFF...
get_greeting circuit state: closed. Time till open: 6
get_greeting circuit state: closed. Time till open: 6
get_greeting circuit state: open. Time till open: 5.999963
get_greeting circuit state: open. Time till open: 4.999796
get_greeting circuit state: open. Time till open: 3.998742
get_greeting circuit state: open. Time till open: 2.998512
get_greeting circuit state: open. Time till open: 1.9983659999999999
get_greeting circuit state: open. Time till open: 0.9972519999999996
get_greeting circuit state: open. Time till open: 5.999966
get_greeting circuit state: open. Time till open: 4.999445
Server is turning ON...
 * Serving Flask app "python_circuit_breaker_examples.mock_server" (lazy loading)
 * Environment: production
   WARNING: This is a development server. Do not use it in a production deployment.
   Use a production WSGI server instead.
 * Debug mode: off
 * Running on http://localhost:5000/ (Press CTRL+C to quit)
127.0.0.1 - - [02/Dec/2019 15:53:41] "PUT /cc77db26-1545-11ea-9309-a08cfd9fd53c/cc77db27-1545-11ea-9309-a08cfd9fd53c HTTP/1.1" 200 -
get_greeting circuit state: open. Time till open: 3.986439
get_greeting circuit state: open. Time till open: 2.985255
get_greeting circuit state: open. Time till open: 1.9841490000000004
get_greeting circuit state: open. Time till open: 0.9830350000000001
127.0.0.1 - - [02/Dec/2019 15:53:45] "GET / HTTP/1.1" 200 -
get_greeting circuit state: closed. Time till open: -0.022205999999999726
127.0.0.1 - - [02/Dec/2019 15:53:46] "GET / HTTP/1.1" 200 -
get_greeting circuit state: closed. Time till open: -1.027672
127.0.0.1 - - [02/Dec/2019 15:53:47] "GET / HTTP/1.1" 200 -
get_greeting circuit state: closed. Time till open: -2.0347880000000007
127.0.0.1 - - [02/Dec/2019 15:53:48] "GET / HTTP/1.1" 200 -
get_greeting circuit state: closed. Time till open: -3.039009
127.0.0.1 - - [02/Dec/2019 15:53:49] "GET / HTTP/1.1" 200 -
get_greeting circuit state: closed. Time till open: -4.043248
127.0.0.1 - - [02/Dec/2019 15:53:50] "GET / HTTP/1.1" 200 -
get_greeting circuit state: closed. Time till open: -5.049541

python-circuit

Run

pipenv run python python_circuit_breaker_examples/client_python_circuit.py

Output

Server is turned OFF...
get-greeting circuit state: closed. Time till open: 6
get-greeting circuit state: closed. Time till open: 6
got error ConnectionError(MaxRetryError("HTTPConnectionPool(host='localhost', port=5000): Max retries exceeded with url: / (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7f47d864d518>: Failed to establish a new connection: [Errno 111] Connection refused',))",),) - opening circuit
get-greeting circuit state: open. Time till open: 5.999971866607666
get-greeting circuit state: open. Time till open: 4.99871563911438
get-greeting circuit state: open. Time till open: 3.997462511062622
get-greeting circuit state: open. Time till open: 2.996232032775879
get-greeting circuit state: open. Time till open: 1.995251178741455
get-greeting circuit state: open. Time till open: 0.9939932823181152
got error ConnectionError(MaxRetryError("HTTPConnectionPool(host='localhost', port=5000): Max retries exceeded with url: / (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7f47d864dba8>: Failed to establish a new connection: [Errno 111] Connection refused',))",),) - opening circuit
get-greeting circuit state: open. Time till open: 5.999970436096191
get-greeting circuit state: open. Time till open: 4.998587608337402
Server is turning ON...
 * Serving Flask app "python_circuit_breaker_examples.mock_server" (lazy loading)
 * Environment: production
   WARNING: This is a development server. Do not use it in a production deployment.
   Use a production WSGI server instead.
 * Debug mode: off
 * Running on http://localhost:5000/ (Press CTRL+C to quit)
127.0.0.1 - - [02/Dec/2019 17:18:03] "PUT /95645fa4-1551-11ea-9309-a08cfd9fd53c/95645fa5-1551-11ea-9309-a08cfd9fd53c HTTP/1.1" 200 -
get-greeting circuit state: open. Time till open: 3.941380500793457
get-greeting circuit state: open. Time till open: 2.940016746520996
get-greeting circuit state: open. Time till open: 1.9387359619140625
get-greeting circuit state: open. Time till open: 0.9375171661376953
127.0.0.1 - - [02/Dec/2019 17:18:07] "GET / HTTP/1.1" 200 -
get-greeting circuit state: closed. Time till open: -0.0850987434387207
127.0.0.1 - - [02/Dec/2019 17:18:08] "GET / HTTP/1.1" 200 -
get-greeting circuit state: closed. Time till open: -1.0990118980407715
127.0.0.1 - - [02/Dec/2019 17:18:09] "GET / HTTP/1.1" 200 -
get-greeting circuit state: closed. Time till open: -2.1185436248779297
127.0.0.1 - - [02/Dec/2019 17:18:10] "GET / HTTP/1.1" 200 -
get-greeting circuit state: closed. Time till open: -3.138019561767578
127.0.0.1 - - [02/Dec/2019 17:18:11] "GET / HTTP/1.1" 200 -
get-greeting circuit state: closed. Time till open: -4.158687353134155
127.0.0.1 - - [02/Dec/2019 17:18:12] "GET / HTTP/1.1" 200 -
get-greeting circuit state: closed. Time till open: -5.178531169891357

Authors

python-circuit-breaker-examples was written by Marshall McDonnell