In several cases, developers wanted their uploaded (unreleased) mobile apps to communicate with under-development server-side modules running within company intranet. In absence of a communication channel between Appurify devices and company intranet, developers were forced to either disable such features in their mobile apps or simply ignore testing such features. To facilitate end-to-end testing for such scenarios, I architected a proxy infrastructure; A stripped down version of which was a lightweight HTTP proxy server in Python.
In the last post we saw how Redis can easily be modified to persist the last published message on PubSub channels. Without subscribing to the PubSub channel we were able to get the last published message from Redis db. In this post, I will take that idea one step ahead and add native capabilities within Redis to persist all the unprocessed messages published on PubSub channel in channel specific lists. We’ll also preserve our capability to send the last published message to clients upon subscription.
Redis comes packed with a simple yet powerful PubSub API. It provides low latency and scales well. A message published on a channel is received by subscriber(s) at the other end. However, if no active subscriber is found the message is simply lost. This drawback puts Redis out of the probables list for several use cases where message persistence of unprocessed published messages is desired. It’s also probably a reason why several open source projects that support Redis as a broker are based upon it’s list push / pop API. In this post I will demonstrate how to modify Redis PubSub API to support message persistence, opening possibilities for several interesting use cases.
I started this blog as a way to share my experiments and experiences while learning web development and computer science in general. In the first 2 years (between Apr’08 and Aug’10) I wrote as many as 100 blog posts. Quite a frenzy. Ever since, I only managed to write 5-6 posts in the following 4 years, about nearly 45 drafts which may now never get published. Good thing is that, I am back to blogging, which means a lot to share.
Ever since Jaxl library first introduced support for X-FACEBOOK-PLATFORM XMPP authentication mechanism, it has changed significantly. Also, Google Talk now supports OAuth 2.0 Authorization, an XMPP extension to allow users to log in using OAuth 2.0 credentials. Both these mechanisms are a big win for XMPP developers, since real-time conversation experience can now be provided to their application users without asking them for their passwords. In this blog post, I will demonstrate how to perform X-FACEBOOK-PLATFORM and X-OAUTH2 XMPP authentication mechanism using Jaxl v3.x PHP Library.
Prior to Jaxl v3.x, the most ugliest piece of code inside Jaxl library was handling of XML packets. If you are working with XMPP protocol which is all about sending and receiving XML packets, it can become a nightmare if you don’t have a proper XML manipulation library in your toolkit. For Jaxl v3.x, first thing I decided to write was JAXLXml class, which is a custom XML packet implementation with no external dependencies and is an extension over the ideas from Strophe.Builder class written by Jack Moffitt. JAXLXml is generic enough to find a place inside any PHP application that requires easy and elegant XML packet creation. In this blog post, I will give an exhaustive overview of how to create XML packets using JAXLXml class.
Development of Jaxl library started way back in December’07 while I was working on a self-initiated project called Gtalkbots. The project is now dead, if you are interested in knowing more about it go through Gtalkbots BlogSpot. Jaxl v1.x was first released in Jan’09 and about a year later in Aug’10 Jaxl v2.x was released. First two versions were released as JAbber XMPP Library for writing clients and external server components.
Jaxl v3.x is a successor of v2.x (and is NOT backward compatible), carrying a lot of code from v2.x while throwing away the ugly parts. A lot of components have been re-written keeping in mind the feedback from the developer community over the last 4 years. Also Jaxl shares a few philosophies from my experience with erlang and python languages. Jaxl is an asynchronous, non-blocking I/O, event based PHP library for writing custom TCP/IP client and server implementations. From it’s previous versions, library inherits a full blown stable support for XMPP protocol stack. In v3.0, support for HTTP protocol stack was also added.
Erlang is a beautiful programming language from Ericsson which i first came across while cutomizing authentication flow of ejabberd about 2 years back. Ever since then I have been using erlang for all my application backend needs including custom http server, custom bosh conn. manager, xmpp components and clients, … Recently i have even started churning my application html pages via erlang using erlydtl (an Erlang implementation of the Django Template Language). Years ago, i gave a successful shot at implementing Peter Norvig’s Spell Corrector in PHP. Last weekend i attempted the same “Spell Corrector” algorithm in about 45 lines of Erlang code.
Jaxl 2.x provides an event mechanism using which developers can register callbacks for various xmpp events inside their application code. This blog post will demonstrate how to register callbacks for required xmpp events and go through a list of all available hooks. Finally, we will discuss parameters that are passed to called back methods by Jaxl core.