Monthly Archives: July 2010

Rockbox

The Rockbox app part II

4 Comments

Hey

In February I wrote about how I think Rockbox’s future involves existing as an app (on Android), and it was also this year accepted as a gsoc project for Rockbox.

In June I got somewhat noticed when Joe Brockmeier wrote about Rockbox on lwn.net and included a lot of references and talk about my post and the app situtation.

Today, Thomas “kugel” Martitz closed the circle by announcing on IRC and mail that he has indeed made Rockbox on Android play its first sounds and he is indeed progressing in a good direction.

While I’m told the current state is rough and there’s no installer or anything yet, I’m sure I share the view of lots of others that this is a great moment in the Rockbox history. A milestone. Thanks Thomas, I hope your work continues equally good and that we get an app to try out at the end of the summer or so.

Thomas’ git repo is here: http://repo.or.cz/w/kugel-rb.git

Rockbox

cURL and libcurl, Network

I’ll talk at FSCONS 2010

Recently I was informed that I got two talks accepted to the FSCONS 2010 conference, to be held in the beginning of November 2010.

My talks will be about the Future and current state of internet transport protocols (TCP, HTTP, SPDY, WebSockets, SCTP and more) and on High performance multi-protocol applications with libcurl, which will educate the audience on how to use libcurl when doing high performance clients with potentially a very large number of simultaneous transfers. A somewhat clueful reader will of course spot that these two talks have a lot in common, and yeah they do reveal a lot of what I do and what I like and what I poke on these days. I hope I’ll be able to put the light on some things not everyone is already perfectly aware of.

The talks will be held in English, and if the past FSCONS conferences tell anything, my talks will be video filmed and become available online afterward for the world to see if you have a funeral or something to attend to that prevents you from actually attending in person.

If you have thoughts, questions or anything on these topics that you would like to get answered in my talk, feel free to bring them up and I’ll see what I can do.

(If those fine guys and gals at FSCONS ever settled for a logo, or had one I could link to, I would’ve shown one of them right here.)

c-ares, cURL and libcurl, Network

C-ares, now and ahead!

3 Comments

The project c-ares started many years ago (March 2004) when I decided to fork the existing ares project to get the changes done that I deemed necessary – and the original project owner didn’t want them.

I did my original work on c-ares back then primarily to get a good asynchronous name resolver for libcurl so that we would get around the limitation of having to do the name resolves totally synchronously as the libc interfaces mandate. Of course, c-ares was and is more than just name resolving and not too surprisingly, there have popped up other projects that are now using c-ares.

I’m maintaining a bunch of open source projects, and c-ares was never one that I felt a lot of love for, it was mostly a project that I needed to get done and when things worked the way I wanted them I found myself having ended up as maintainer for yet another project. I’ve repeatedly mentioned on the c-ares mailing list that I don’t really have time to maintain it and that I’d rather step down and let someone else “take over”.

After having said this for over 4 years, I’ve come to accept that even though c-ares has many users out there, and even seems to be appreciated by companies and open source projects, there just isn’t any particular big desire to help out in our project. I find it very hard to just “give up” a functional project, so I linger and do my best to give it the efforts and love it needs. I very much need and want help to maintain and develop c-ares. I’m not doing a very good job with it right now.

Threaded name resolves competes

I once thought we would be able to make c-ares capable of becoming a true drop-in replacement for the native system name resolver functions, but over the years with c-ares I’ve learned that the dusty corners of name resolving in unix and Linux have so many features and fancy stuff that c-ares is still a long way from that. It has also made me turn around somewhat and I’ve reconsidered that perhaps using a threaded native resolver is the better way for libcurl to do asynchronous name resolves. That way we don’t need any half-baked implementations of the resolver. Of course it comes at the price of a new thread for each name resolve, which turns really nasty of you grow the number of connections just a tad bit, but still most libcurl-using applications today hardly use more than just a few (say less than a hundred) simultaneous transfers.

Future!

I don’t think the future has any radical changes or drastically new stuff in the pipe for c-ares. I think we should keep polishing off bugs and add the small functions and features that we’re missing. I believe we’re not yet parsing all records we could do, to a convenient format.

As usual, a project is not about how much we can add but about how much we can avoid adding and how much we can remain true to our core objectives. I wish the growing popularity will make more people join the project and then not only to through a single patch at us, but to also hand around a while and help us somewhat more.

Hopefully we will one day be able to use c-ares instead of a typical libc-based name resolver and yet resolve the same names.

Join us and help us give c-ares a better future!

c-ares

Development, Network

poll vs select

I’m a person working a lot with networking and development around it. I mostly do this on Linux, often involving drivers or otherwise very close to the operating system and C and the core libraries.

The other day I once again fell over some random inaccuracy about poll compared to select and instead of trying to whine on some IRC channel or complain on their mailing list, I decided I would instead strike back by writing up and presenting a web page of my own. It details as much as possible about poll vs select and related event-based functions. I want it to become a placeholder for everything that is relevant to say about poll and select in a comparison aspect and when comparing them to event-based alternatives like libevent and libev.

So the next time I face someone not quite understanding this whole situation or perhaps when someone reiterates something that isn’t quite true, I have a resource to point to.

Not to mention that I think this new poll vs select page fits in nicely with my other “X vs Y” articles and docs pages I’ve written the last few years.

If you find flaws, or miss details or have questions about this page. Please do not hesitate to comment here, or to mail me about it or tweet me on twitter or whatever method you prefer. I appreciate your feedback!

poll vs select

Network, Web

Webscrapers unite!

The term web scraping has come to stay. It refers to getting stuff off web sites in an automated fashion. Other terms occasionally used for include spidering, web harvesting and more. I’ve used the term HTTP scripting for it.

The art is in many cases to act more or less like a browser with the single purpose of making the server not detect that it is a program in the other end.

This is something I’ve done a lot over the years while developing curl, and I’ve answered countless of questions on the matter. There are several good books (all of them having at least parts of them covering curl).

Today, we’ve setup a little web site over at webscrapers.haxx.se and an associated mailing list, in an attempt to gather people who are working in this field. Whether you do it for fun or profit doesn’t matter and while we can certainly discuss what tools you should or shouldn’t use for scraping, we certainly don’t limit which to discuss on the list as long as the subject is somewhat relevant.

So, if you’re into scraping or you want to learn more on how to automate your web bots, come on over and join the list and let’s see where this might take us!

Open Source, Web

Java apps froze my Iceweasel

I’ve noticed for quite some time that java apps haven’t seemed to work on my computer when I try to use them with my browser. Whenever I’ve started most java apps, my entire browser has just frozen and gone completely unresponsive and I’ve been forced to kill and restart it.

I run Debian Linux on just about all my machines so of course I do that on my primary desktop as well. And Iceweasel is my browser.

I’ve not really bothered much about the problem as java applets are a bit of yesterday’s technology and I rarely face anything in java that I need. Until today, when I had to login to a customer’s site and use an applet for some work related to my job. There was no decent way to avoid it (apart from perhaps logging in using another machine/browser or similar), so I decided to bite the bullet and finally fix my issue.

I searched around and I tried uninstalling all openjdk stuff and more. I restarted Iceweasel countless times to no avail.

Finally I stumbled over this post by user “almatic” and voila, it fixed my problem. As I just wasted like an hour on this, I’ll help out to make the world a little better by providing the answer here as well:

open file /etc/sysctl.d/bindv6only.conf and set net.ipv6.bindv6only=0, then restart the procfs with invoke-rc.d procps restart

here are the corresponding bugs

http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=560238
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=560056