Tag Archives: client

MySQL Connector/Arduino

Chuck Bell, one of my former colleague from MySQL AB, has created a connector for Arduino to MySQL. So this allows Arduino code to be a direct client of a MySQL or MariaDB server, with Ethernet and WiFi shields supported.

With Arduino boards being used more and more, this can come in really handy – not only for retrieving (for instance) centralised configuration data, but also for logging. Useful stuff. Thanks Chuck!

Links

 Introducing MySQL Connector/Arduino 1.0.0 beta

MariaDB C client libraries and the end of dual-licensing

Finally there is an LGPL C client library for MariaDB, and thus also for MySQL. Monty Program and SkySQL have been working on this for some time. Admittedly there was already the BSD licensed Drizzle client library which was also able to talk to a MySQL/MariaDB server, however its API is different. The C client library for MariaDB has exactly the same API existing applications are used to, so you can just re-link and keep going! There is also a new LGPL Java client library for MariaDB.

In case you don’t quite realise: this is actually a major thing.

At MySQL AB, the client library was made GPL and this flowed through to Sun Microsystems and then Oracle Corp. This licensing choice for the client library was the basis of the infamous “dual licensing” model: if you developed a proprietary application to distribute (not just internal or used in a website), you could obviously not just link against the GPL client library was its license explicitly states that whomever receives that code is entitled to ask for the source code. Some describe that as the “viral nature” of GPL – if you want to use such licensed code it prescribes what kind of license you can use for the rest of the code it’s linked to – but in any case that’s how the license operates, following the objective of GPL to promote free as in freedom (for recipients of the programs).

So the way this worked in practice is that MySQL Sales could sell you a non-GPL license for this code, thus enabling proprietary use. It’s legal leverage and not intrinsically bad, but IMHO the way the sales people played this was. Using FUD (fear-uncertainty-doubt) and sometimes misdirection they coaxed clients in to costly licensing arrangements, including in cases where really the GPL license would have sufficed. While this behaviour was by no means corporate policy, the sales people got a lot of leeway – and being paid on commission, these were the consequences.

When the MySQL Network subscription offering (now called MySQL Enterprise) for support was introduced around 2004, the intent was that this new revenue stream would make the dual licensing irrelevant. But that’s not what happened (hindsight gives insight). Since selling non-GPL licenses was a major revenue stream for the sales people, they kept on pushing it. Clayton Christensen and others at Harvard Business School observed years ago that you can’t disrupt yourself, and this might be an interesting example. While the subscription model did take off nicely, the licensing sales were still making lots of money, and thus it did not diminish in importance. Note that this sales model exists until today, see Commercial License for OEMs, ISVs and VARs (Oracle Corp) .

The MySQL Enterprise subscription (which is still sold by Oracle Corp) has had other consequences also. The tools that clients get via that subscription are nice, they provide information on how the server is running and how queries are handled. But it does so at a cost: for some tasks it needs a proxy (sits inbetween app and db server) which of course adds overhead. One simple example is the case where you want to know whether a particular query uses a tmp table or a sort operation, and whether those operations happened in memory or on disk. But the server already knows, so why is a proxy required? Because if the code were in the server, everybody would have it and not just the subscribers. That’s a valid business decision of course, but as you see it has significant technical consequences and someone’s business model should not concern us. In the MySQL 5.0 OurDelta enhanced builds we already applied a patch (an amalgamation of work by several people) to enhance the slow query log, Monty ported it for 5.1 and it’s now a standard part of MariaDB.

For everybody’s sake it would have been great if the dual licensing model had gone the way of the dodo. It had its time (until around 2004-2005, arguably), after which it became a hindrance, actually hurting the MySQL ecosystem – and that situation pretty much persisted until now. That’s why this replacement library is so important, it makes that whole case obsolete. I say horay, and I hope distributions will soon use this library (as apart from anything else, the licensing for it is clear rather than messy).

To summarise, as talks about licensing often confuse (particularly with the amount of FUD and old info around on the net):

  1. GPL v2 only “kicks in” when software is distributed (beyond the boundary of your organisation).
  2. Internal use (which includes the code on running a website) is not distribution.
  3. Whether or not you sell something is irrelevant for GPL: it’s purely about distribution of code, not whether money is involved.
  4. Using MySQL or MariaDB Server is almost always fine under GPL, since you’re not linking against anything else.
  5. The old MySQL client library is GPL, so if you link your app against it you’re subject to GPL, that is, the rest of the app would need to be licensed under something compatible with GPL (typically, GPL itself). Again, this is only relevant if you distribute that app.
  6. The new MariaDB client library is LGPL v2.1, so you are allowed to link it with proprietary application code and then distribute. The recipients must be able to re-link the proprietary code with another version (modified or not) of the client library (easily satisfied if you link dynamically rather than statically).
  7. If someone tells you that use of a wire protocol constitutes linking and that therefore a proprietary app is in essence linked to MySQL/MariaDB Server (which are GPL licensed), this can easily be disputed using the following example (there are many): Microsoft Internet Explorer often talks to an Apache web server using the HTTP protocol, but noone would suggest that these two codebases are in any way linked or co-dependent in a way that would be relevant to their licensing.
  8. While I was one of the people at MySQL AB who dealt with licensing questions and I strongly encourage you to reject FUD (the above info given is no different from what I used to tell while employed by MySQL), I am not a lawyer. Get legal advice if/when you need it, and get it from someone with a serious clue about GPL. Check their public credentials, not just advertising claims.

Also see:

On a side-note, perhaps someone can now link the LibreOffice Base code and the native MySQL SDBC driver (written by Georg Richter years ago) with the MariaDB client library, as they’re all LGPL. This would resolve a long-standing issue that Sun Microsystems (when they owned both OpenOffice and MySQL) sadly did not fix. See OpenOffice.org, MySQL… aren’t they both owned by Sun? And there may be other software projects that can now be “fixed up” in a similar way. If you know of any, please let me know!