This section describes the purpose and goals of the iPOPO project, as well as some background history.
What is iPOPO ?¶
iPOPO is a Python-based Service-Oriented Component Model (SOCM). It is split into two parts:
- Pelix, a dynamic service platform
- iPOPO, the SOCM framework, hence the name.
iPOPO allows to conceive long-running and modular IT services in Python.
About the name, iPOPO is inspired from iPOJO, which stands for injected Plain Old Java Object. Java being replaced by Python, the name became iPOPO. The logo comes from the similarity of pronunciation with the french word for the hippo: hippopotame.
By the way, I pronounce the name iPOPO the french way, i.e. /i.pɔ.pɔ/ (International Phonetic Alphabet). The english way, i.e. /aɪ.pɔ.pɔ/, is the most commonly used by the users I had the chance to talk to.
A bit of history¶
During my PhD thesis, I had to monitor applications built as multiple instances of OSGi frameworks and based on iPOJO components. This required to access some OS-specific low-level methods and was initially done in Java with JNA.
To ease the development of probes, the monitoring code has been translated to Python. At first, it was only a set of scripts without any relations, but as the project grown, it was necessary to develop a framework to handle those various parts and to link them together. In order to be consistent, I decided to develop a component model similar to what was used used in Java, i.e. iPOJO, and keeping the concepts of OSGi.
A first draft, called
python.injections was developed in
It was a proof of concept which was good enough for my employer,
(now Cohorte Technologies), to allow the development of what would
The first public release was version 0.3 in April 2012, under the GPLv3 license. In November 2013, iPOPO adopts the Apache Software License 2.0 with release 0.5.5.
On March 2015, release 0.6 dropped support for Python 2.6. Since then, the development slowed down as the core framework is considered stable.
As of 2018, the development of iPOPO is still active. iPOPO 1.0 will come out when some features, existing or currently in development, will have been completed, tested and polished.
SOA and SOCM in Python¶
The Service-Oriented Architecture (SOA) consists in linking objects through provided contracts (services) registered in a service registry.
A service is an object associated to properties describing it, including the names of the contracts it implements. It is stored in the service registry of the framework by the service provider. The provider or the service itself (they are often the same) must handle the requirements, i.e. looking for the services required to work and handling their late un/registration.
A component is an object instantiated and handled by an instance manager created by iPOPO. The manager handles the life cycle of the component, looking for its dependencies and handling their late registration, unregistration and replacement. It eases the development and allows a lot of dynamism in an application.
The conclusion is that the parts of an application which only provide a feature can be written as a simple service, whereas parts using other elements of the application should be written as components.