+1 Pascal From: Tim Donohue [mailto:tdono...@duraspace.org] Sent: Thursday, August 06, 2015 4:48 PM To: Dspace-devel@lists.sourceforge.net Subject: [Dspace-devel] PLEASE VOTE on whether to include "Services API" refactoring in DSpace 6.0
Hi Developers / Committers, As mentioned in yesterday's developers meeting, I'm calling a public VOTE around whether we include the Services API refactoring in the upcoming DSpace 6.0 release. As this change constitutes a major code refactor of the "dspace-api" (DSpace Java API), we'd appreciate feedback from anyone on this direction for 6.0. (If you have not yet read about the Services API refactoring, a brief summary and links to more information is provided at the end of this email) Please VOTE with one of these three options: +1 = "I agree. We should include Services API refactoring in 6.0" 0 = "I'm undecided / unsure" (Please provide a reason) -1 = "I disagree. The Services API refactoring should NOT be included in 6.0" (Please provide a reason why you disagree) Per our Voting Procedures [1], a vote on code modifications requires: "at least three positive (+1) votes, and no negative votes (-1) to pass. In this scenario, a negative vote constitutes a 'veto'." While anyone is welcome to vote, only Committers have "binding" votes (and can cast a veto). Others are free to vote to express your opinion, but those votes are considered advisory in nature. This public vote will be open until 15:00 UTC (11:00am EDT) on Wednesday, August 12 (which is the time of our next Developer Meeting). If there are any questions, feel free to ask them on this thread. Summary of Services API refactoring The Services API refactoring is a major refactoring of the "dspace-api" (DSpace's Java API) to better support "separation of concerns/responsibilities". Simply put, often, in the existing API, there is an intermingling of business logic and database logic which is difficult to maintain, debug and/or build against. One of the most obvious examples is how we deal with database software support (PostgreSQL vs. Oracle), but such intermingling of logic exists in many of our core classes. The DSpace "Services API" attempts to tease apart the database logic from the business logic into separate layers, while also adding support for Hibernate (http://hibernate.org). The goal is to provide an easier to maintain, more modular API, while also enhancing how we deal with database logic in general (via Hibernate). Much more information with documentation, tutorials/examples, and a video presentation at: https://wiki.duraspace.org/display/DSPACE/DSpace+Service+based+api What does adding this refactor to 6.0 mean? * This is essentially a *new* Java API for DSpace. But, it performs a very important refactor (see "Pros" below). * It is not backwards compatible with the existing API. All developers and Committers who work with the Java API will need to learn this new API, as all future development will require using this Java API. * Committers will be expected to learn, use and support this API immediately. @mire will be providing additional training materials / examples to help everyone get up to speed. * We also will need immediate help from Committers (or other volunteers) to refactor and test all other modules within DSpace. Currently, only the XMLUI has been refactored to support this new API. All other modules (JSPUI, OAI, REST, RDF, SWORD, etc) will need similar refactoring as soon as possible. * If this refactor is voted in, Committers will immediately do the following: * The "master" branch will be temporarily frozen. We'll ask for no new changes until this API can be merged (PRs can still be created, but we will refrain from merging them) * We'll start a new (temporary) feature branch (under DSpace/DSpace) based of latest "master" and merge the existing Services API code there. * We'll then rapidly work together to refactor and test all other modules based on the new API. (If we work as a team, the goal would be for this process to only take a few weeks) * Once everything is refactored against this API and passes our Unit Tests, the Services API code will be merged into "master". At this point, "master" will be unfrozen, and we can again merge in PRs for the 6.0 release. PROS to adding to 6.0: * It modularizes our primary API in a way that makes it much easier to achieve future goals on our Roadmap [2] (especially, moving us towards potentially better support of third-party modules) * It cleans up one of the "messiest" areas of our existing API, the Database management / hardcoded Oracle and PostgreSQL queries, in favor of using Hibernate. This allows us the potential to support additional database platforms in the future (e.g. MySQL or similar). It decreases the likelihood of Oracle-specific bugs (which have always been a problem), as the Oracle queries are delegated to Hibernate. It also simplifies the process of testing for database-specific problems in general (as again, all queries are delegated to Hibernate). * It begins teasing apart a true "business logic layer" in the API (see the "service layer" of this new API) * The API itself will not affect the fresh installation or upgrade process of DSpace 6.0, provided that you have not made local changes that rely on the existing Java API (dspace-api). If you have made such local changes, the refactor process should not be difficult, but it will be necessary before you can successfully upgrade to 6.0. CONS: * It is not backwards compatible with the existing Java API. Again, anyone who has made customizations that rely on the Java API (dspace-api) may need to refactor their local customization. But, we believe that vast majority of institutions (likely 90% or more) should not experience any upgrade difficulties, as most only make customizations to the theme / look and feel of either the XMLUI or JSPUI. * As it is not backwards compatible, this does mean that existing PRs (Pull Requests) reliant on the Java API may need refactoring/rebasing. Unfortunately there's no easy way around this, but examples already exist in the documentation (see wiki page linked above) showing how to perform common tasks via the new API. * As this is a major change, it could affect our 6.0 timelines unless we can work together to quickly get this change merged and tested. The quicker the merge process occurs, the more rapidly we can stabilize everything (and refactor existing PRs as needed). [1] https://wiki.duraspace.org/display/DSPACE/Developer+Voting+Procedures [2] https://wiki.duraspace.org/display/DSPACE/RoadMap -- Tim Donohue Technical Lead for DSpace & DSpaceDirect DuraSpace.org | DSpace.org | DSpaceDirect.org
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