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diff --git a/docs/specs/parallelism_improvement.rst b/docs/specs/parallelism_improvement.rst new file mode 100644 index 0000000..00d66df --- /dev/null +++ b/docs/specs/parallelism_improvement.rst @@ -0,0 +1,199 @@ +.. + This work is licensed under a Creative Commons Attribution 4.0 + International License. + +=============================================== +Parallelism improvement of Multi Cloud Services +=============================================== + + +Problem Description +=================== + +Multi-Cloud runs Django by using Django's built-in webserver currently. +According to Django Document[Django_Document]_, this mode should not be used +in production. This mode has not gone through security audits or performance +tests, and should only be used in development. From test on local computer, +this mode can only handle ONE API request at one time. This can not meet the +performance requirement. + +.. [Django_Document] https://docs.djangoproject.com/en/dev/ref/django-admin/#runserver + +Although security and scalability might be improved as the side effect of +resolving the performance issue, this spec will only focus on how to improve +the parallelism(performance) of current MultiCloud API framework. + +Possible Solutions +================== + +Solution 1 +---------- + +Django is a mature framework. And it has its own way to improve parallelism. +Instead of running Django's build-in webserver, Django APP can be deployed in +some dedicated web server. Django’s primary deployment platform is WSGI[django_deploy]_, +the Python standard for web servers and applications. + +.. [django_deploy] https://docs.djangoproject.com/en/2.0/howto/deployment/wsgi/ + + +But on the other side, Danjgo is very huge. And Django is a black box if one +doesn't have good knowledge of it. Adding feature based on Django may be +time-consuming. For example, the unit test[unit_test]_ of Multi-Cloud can't use +regular python test library because of Django. The unit test has to base on +Django's test framework. When we want to improve the parallelism of Multi-Cloud +services, we need to find out how Django can implement it, instead of using some +common method. + +.. [unit_test] https://gerrit.onap.org/r/#/c/8909/ + +Besides, Django's code pattern is too much like web code. And, most famous use +cases of Django are web UI. Current code of Multi-Cloud puts many logic in +files named `views.py`, but actually there is no view to expose. It is confusing. + +The benefit of this solution is that most current code needs no change. + +Solution 2 +---------- + +Given the fact that Django has shortcomings to move on, this solution propose +to use a alternative framework. Eventlet[Eventlet]_ with Pecan[Pecan]_ will be the +idea web framework in this case, because it is lightweight, lean and widely +used. + +.. [Eventlet] http://eventlet.net/doc/modules/wsgi.html + +.. [Pecan] https://pecan.readthedocs.io/en/latest/ + +For example, most OpenStack projects use such framework. This framework is so +thin that it can provide flexibility for future architecture design. + +However, it needs to change existing code of API exposing. + + +Performance Test Comparison +=========================== + +Test Environment +---------------- + +Apache Benchmark is used as test tool. It is shipped with Ubuntu, if you +don’t find it, just run “sudo apt install -y apache2-utils” + +2 Virtual Machine with Ubuntu1604. Virtual Machines are hosted in a multi-core +hardware server. One VM is for Apache Benchmark. This VM is 1 CPU core, 8G mem. +The other VM is for Multicloud. The VM is 4 CPU core, 6G mem. + +Test Command +~~~~~~~~~~~~ + +`ab -n <num of total requests> -c <concurrency level> http://<IP:port>/api/multicloud/v0/vim_types` + +Test result +----------- + +It should be noted that data may vary in different test run, but overall result is +similar as below. + +100 requests, concurrency level 1 +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Command: `ab -n 100 -c 1 http://<IP:port>/api/multicloud/v0/vim_types` +Result: + Django runserver: total takes 0.512 seconds, all requests success + Django+uwsgi: totally takes 0.671 seconds, all requests success. + Pecan+eventlet: totally takes 0.149 seconds, all requests success. + +10000 requests, concurrency level 100 +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Command: `ab -n 10000 -c 100 http://<IP:port>/api/multicloud/v0/vim_types` +Result: + Django runserver: total takes 85.326 seconds, all requests success + Django+uwsgi: totally takes 3.808 seconds, all requests success. + Pecan+eventlet: totally takes 3.181 seconds, all requests success. + +100000 requests, concurrency level 1000 +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Command: `ab -n 10000 -c 100 http://<IP:port>/api/multicloud/v0/vim_types` +Result: + Django runserver: Apache Benchmark quit because it reports timeout after + running a random portion of all requests. + Django+uwsgi: totally takes 37.316 seconds, about 32% requests fail. I see + some error says that tcp socket open too many. + Pecan+eventlet: totally takes 35.315 seconds, all requests success. + +Proposed Change +=============== + +Given the test result above, this spec proposes to use solution 2. Based on +the consideration of Elastic API exposure[jira_workitem]_, Multi-Cloud will +provide a new way to expose its API. That is to say, existing code of API +exposing needs rewrite in [jira_workitem]_. So the disadvantage of solution +2 doesn't exist. + +.. [jira_workitem] https://jira.onap.org/browse/MULTICLOUD-152 + +To define a clear scope of this spec, VoLTE is the use case that will be used +to perform test to this spec. All functionality that VoLTE needed should be +implemented in this spec and [jira_workitem]_. + +Backward compatibility +---------------------- + +This spec will NOT change current API. This spec will NOT replace the current +API framework in R2, nor will switch to new API framework in R2. Instead, +this spec will provide a configuration option, named `web_framework`, to make +sure use case and functionalities not be broken. Default value of the +configuration will BE `django`, which will still run current Django API +framework. An alternative value is `pecan`, which will run the API framework +proposed in this spec. So users don't care about the change won't be +affected. + +WSGI Server +----------- + +No matter what API framework will be used, a WSGI Server needs to be provided. +This spec will use Eventlet WSGI server. API framework will be run as an +application in WSGI server. + +Multi processes framework +------------------------- + +This spec proposes to run Multi-Cloud API server in multiple processes mode. +Multi-process can provide parallel API handlers. So, when multiple API +requests come to Multi-Cloud, they can be handled simultaneously. On the other +hand, different processes can effectively isolate different API request. So +that, one API request will not affect another. + +Managing multiple processes could be overwhelming difficult and sometimes +dangerous. Some mature library could be used to reduce related work here, for +example oslo.service[oslo_service]_. Since oslo is used by all OpenStack +projects for many releases, and oslo project is actively updated, it can be +seen as a stable library. + +.. [oslo_service] https://github.com/openstack/oslo.service + +Number of processes +~~~~~~~~~~~~~~~~~~~ + +To best utilize multi-core CPU, the number of processes will be set to the +number of CPU cores by default. + +Shared socket file +~~~~~~~~~~~~~~~~~~ + +To make multiple processes work together and provide a unified port number, +multiple processes need to share a socket file. To achieve this, a bootstrap +process will be started and will initialize the socket file. Other processes +can be forked from this bootstrap process. + +Work Items +========== + +#. Add WSGI server. +#. Run Pecan application in WSGI server. +#. Add multiple processes support. +#. Update deploy script to support new API framework. + |