Tag Archives: libspdy

The first month of Spindly

Let me entertain you with some info and updates from the Spindly project. (Unfortunately we don't have any logo yet so I don't get to show it off here.)

Since I announced my intention to proceed and write the SPDY library on my own instead of waiting for libspdy to get back to life, I have worked on a number of infrastructure details.

I converted the build to use autotools and libtool to help us really make it a portable library. I made all test cases run without memory leaks and this took some amount of changes of libspdy since it was clearly not written with carefully checking memory and there were also a lot of unnecessarily small mallocs(). Anyone who does malloc() of 8 bytes should reconsider what they're doing.

Since I've had to bugfix the libspdy so much, change structs and APIs and add new functions that were missing I decided that there's no point in us trying to keep the original libspdy code or code style intact anymore so I've re-indented the whole code base to a style I like better than the original style.

I've started to write the fundamentals of a client and server demo application that is meant to use the Spindly API to implement both sides. They don't really do much yet but the basics are in place. I've worked more on my idea of what the spindly API should look like. I've written the code for a few functions from that API and I've also added a few tests for them.

Most of this work has been made by me and me alone with no particular feedback or help by others. I continue to push my changes to github without delay and I occasionally announce stuff on the mailing list to keep interested people up to date. Hopefully this will lead to someone else joining in sooner or later.

The progress has not been very fast, not only because I've had to do a lot of thinking about how the API should ideally work to be really useful, but also because I have quite a lot of commitments in other open source projects (primarily curl and libssh2) that require their amount of time, not to mention that my day job of course needs proper attention.

We offer a daily snapshot of the code if you can't use or don't want to use git.

Upcoming

I intend to add more functions from the API document, one by one and test cases for each as I go along. In parallel I hope to get the demo client and server to run so that the API proves to actually work properly.

I want the demo client and server also to allow them to run interop tests against other implementations and I want them to be able to speak SPDY with SSL switched off - for debugging reasons. Later on, I hope to be able to use the demo server in the curl test suite so that I can test that the curl SPDY integration works correctly.

We need to either fix "check" (the unit test suite) to work C89 compatible or replace it with something else.

Want to help?

If you want to help, please subscribe to the mailing list, get familiar with the code base, study the API doc and see if it makes sense to you and then help me get that API turned into code...

libspdy

SPDY is a neat new protocol and possible contender to replace HTTP - at least in some areas and for some use cases. SPDY has been invented and developed mostly by Google engineers.

SPDY allows better usage of fewer TCP connections (since it sends multiple logical streams over a single physical TCP connection) and it helps clients overcome problems with TCP (like how a new connection starts slowly) while at the same time reducing latency and bandwidth requirements. Very similar to how channels are handled over an SSH connection.SPDY

Chrome of course already supports SPDY and Firefox has some early experimental support being worked on.

Of course there are also legitimate criticisms against SPDY as well, including subjects like how it makes caching proxies impossible (because everything goes over SSL), how it makes debugging a lot harder by using compressed headers, how it is impossible to extract just a single header from the stream due to its compression approach and how the compression state buffers make each individual stream use more memory than plain old HTTP (plain TCP) ones.

We can expect SPDY<=>HTTP gateways to appear so that nobody gets locked into either side of these protocols.

SPDY will provide faster transfers. libcurl is currently used for speed reasons in many cases. To me, it makes perfect sense to have libcurl use and try to use SPDY instead of HTTP exactly like how the browsers are starting to do it, so that the libcurl using applications will get their contents transferred faster.

My thinking is that we introduce some new magic option(s) that makes libcurl use SPDY, and for normal easy interface transfers it will remain to use a single connection for each new SPDY transfer, but if you use the multi interface and you enable pipelining you'll instead make libcurl do multiple transfers over the same single SPDY connection (as long as you speak with the same server and port etc). From an application's stand-point it shouldn't make any difference, apart from being faster than otherwise. Just like we want it!

Implementation wise, I would like to use a reliable and efficient third-party library for the actual SPDY implementation. If there doesn't exist any, we make one and run that one independently. I found libspdy, but I found some concerns about it (no mailing list, looks like one-man project, not C89 compliant, no API docs etc). I mailed the libspdy author, I hoping we'd sort out my doubts and then I'd base my continued work on that library.

After some time Thomas Roth, primary libspdy author, responded and during our subsequent email exchange I've gotten a restored faith and belief in this library and its direction. Not only did he fix the C89 compliance pretty quickly, he is also promising rather big changes that are pending to get committed within a week or so.

Comforted by what I've learned from Thomas, I'll wait for his upcoming changes and I'll join the soon to be created mailing list for the libspdy project and I'll contribute some ideas and efforts to help shape it into the fine SPDY library we all want. I can only encourage other fellow SPDY library interested persons to do the same!

Updated: Join the SPDY library development