I want to notify my iPhone app of updates using a socket server for real time updates and to prevent the need for polling. My server side language is Coldfusion, and after weeks of searching the web following threads of people attempting to do this the conclusion everyone has come up with is that Coldfusion doesn't support this. Firstly if anyone has any suggestions that no one else has provided as to what is the proper way to do this with Coldfusion then feel free to cut me short and please enlighten me. Anyhow, a solution occurred to me (in my sleep!) and before I invest my time doing this I wanted to ask if it is critically flawed for any reason.
There isn't anything in the adminstrator that supports this, and people rightly point out that you can't instantiate a server socket on the page since it will hang the page waiting for requests, and that then the server will then be destroyed when the page times out.
But what is wrong with the following solution, I create my AppServer.cfc component, which essentially wraps a java ServerSocket. Then to trigger it run this:
<CFSET APPLICATION.servercfm=new AppServer()>
<CFTHREAD timeout="2147483647">
<CFSET APPLICATION.servercfm.start()>
</CFTHREAD>
The server then remains indefinately on the APPLICATION scope, and the page returns instantly. The thread timeout is sets to 60 years, although I'm sure that I'll have more frequent server restarts!
I hope this question isn't flagged as opinionated, my question is: is there ANY means, by which we can provide a service through a socket using Coldfusion whether it be my solution or any suggested by the forum.
Thanks
Related
Before calling a web service from my web app, I set a specific timeout after which if I didnt get any response, the call ends up.
What if I set this timeout to, for instance, 10', is there another timeout after which Chrome does not want to wait for this response?
Thanks
A webservice call is a regular HTTP call, so it's affected by browser settings regarding http.
I suggest you to look these answers :
General purpose answer :
Where can I find the default timeout settings for all browsers?
Chrome focused answer :
https://superuser.com/questions/633648/how-can-i-change-the-default-website-connection-timeout-in-chrome
Unfortunately, AFAIK there is no setting available in Chrome to set the timeout.
Since last answer of the topic, I don't think Google has improved this but you could at least try the registry approach described there :
Create KeepAliveTimeout and ServerInfoTimeout keys in HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\InternetSettings with desired value in ms and check if it helps.
Additionally, very long http calls are not a very good design. If it's an option, it could be interesting to rework the server process and communication method to have some kind of "keep alive ping" on it, for example to display the progress in client browser instead of freezing it for 10 minutes.
I'm working on an online reservation system (the details aren't really relevant to my issue). It's mostly developped in C# with framework 4.0. I have a DB which contains, among other things, the products and the availability of these products. The DB is accessed by a web service, the latter being queried by a web application, which in turn sends the information to be displayed to the browser. Nothing too fancy in term of architecture, but I don't have much experience with that kind of system. This projet is quite old; it's been in development for a few years and I just hopped in six months ago, having no web programming experience before.
I'm currently experiencing concurrency problems. If I open two browsers window (any browser), enter the same query in both windows and post on both pages as fast as humanly possible, I get unhandled exception in my web service. One of the client gets the data, the other receives an error. EDIT : Also, I tested using two different computers simultaneously, and I still could get the unhandled exception.
I was able to trace the problem back to a cache system that was implemented almost a year ago. There's is no locking mecanism, and the cache uses a Dictionary (which is not thread-safe). A few Stack Overflow questions helped me in pinpointing the problem and how I should correct it (this one and that one for example).
That being said, I'm trying to reproduce the problem without having to manually click in two browser windows and hoping to get the right timing to access the same cache simultaneously. The reason I'm trying to do that is that I don't like implementing a solution that should work when I can't reliably prove it actually worked. Also, there's a lot of places where the cache has been (badly) implemented, and I'm not sure I can test all those places by "guessing" the right timing manually.
So, I downloaded Apache JMeter, and using Fiddler2 hooked up to my two browsers, I could find all the HTTP requests I needed to create a Test Plan that sends exactly the same requests.
But to my dismay, JMeter couldn't reproduce the problem, even if I set my Thread Group to create 40 concurrent users! Each one of them receives the data correctly, and none triggers the unhandled exception I am getting by doing it manually. I know it's not a cookie issue, nor a difference in user-agent, as I tested with multiple browsers and with disabled cookies. As the HTTP requests were created directly from Fiddler2, it shouldn't be an issue with hidden fields or URL rewriting, and there's no dynamic field names or content involved. I know Fiddler2 has a "replay" function, but even that couldn't reproduce the problem. This baffles me to no end.
So, my questions are : why can't I reproduce the problem with JMeter? Is there a better tool than JMeter (which is quite complete for a free software) to do that? What are the browsers doing that Jmeter doesn't do (apart from rendering the page, which is really not the issue here)?
Any thought would be much appreciated!
When you say 2 Windows are you sure they use 2 sessions, depending on the browser and the way you open the second window you won't get 2 sessions.
Are you sure you reproduced all the trafic between browser and server ?
If you have more than 1 request then you should Check if it's not 2 parallel Ajax requests from the browser , if so you must know That Without some custom scripting jmeter does not reproduce those 2 parallel request for same session(except for resources download), That might be your issue .
Regards
Philippe M.
http://www.ubik-ingenierie.com
I'm putting together a website that will track user-defined events with time limits. Every user would be free to create events, and when the time limit expired, the server would need to take some action based on the outcome of the event. The specific component I'm struggling with is the time-keeping: think like eBay's auction clock -- it's set to expire at a certain time, clearly runs server-side, and takes some action when the time runs out. Searches for a "server side timer," unfortunately, just bring back results for a timer that gets the time from the server instead of the client. :(
The most obvious solution is to run a script on the server, some program that would watch all the clocks and take action when any of them expired. Tragically, I'll be using free web hosting, and sincerely doubt that I'll be able to find someone who'll let me run arbitrary stuff on their servers.
The solutions that I've looked into:
Major concept option 1: persuade each user's browser to run the necessary timers (trivial javascript), and when the timers expire, take necessary action. The problem with this approach is obvious: there could be hundreds, if not thousands, of simultaneous expiring timers (they'll tend to expire in clusters), and the worst case is that every possible user could be viewing their timer expire. That's a server overload waiting to happen at the worst possible instant.
Major concept option 2: have one really trusted browser, say, a user logged in to the website as "cron" which could run all of the timers at once. The action would all happen in that browser's javascript, and would work great, as long as that browser never crashed, that machine never failed, and that internet connection never went down.
As you can see, I feel like I'm barking up the wrong forest on this problem. Some other ideas that have presented themselves:
AJAX: I'm not seeing anything here that will do quite what I need. It's all browser-run stuff, nothing like a server-side process that could run independent of the user's browser.
PHP: Runs neatly on the server, but only in response to client requests. I'm not seeing any clean way to make PHP fork off a process and run a timer independent of the user's browser.
JS: same problems as PHP, but easier to read. ;)
Ruby: There may be some multi-threading with Ruby, but it isn't readily apparent to me. Would it be possible to have each user's browser check to see if a timer process was running for their event, and spawn a new server-side ruby process if it wasn't?
I'm wide open for ideas -- I've started playing with concepts in JS and PHP, but I'm not tied to any language, particularly. The only constraint, really, is that I won't own the server that I'm running the site on, so I can't just run a neat little local process that does what I need it to do. :(
Any thoughts? Thanks in advance,
Dan
ASP.NET has multi-threading. You can have a static variable to collect the event data, and use a thread to do whatever needed when the time comes. After you can empty the static variable so it's ready for future use.
http://leedale.wordpress.com/2007/07/22/multithreading-with-aspnet-20/
You might want to take a look at the Quartz scheduler for Java which also has a .NET version. With a friendly open source license (Apache 2.0) this is probably a very good starting point.
If you can control cron jobs, which at least I could on HostPapa's shared hosting, you could run a php file every second which checks the timers and takes action based on them.
I would suggest AJAX anyway, what we did on a game server was emulation of "server connects to client" via AJAX request to server without any time-out (asynchronous connection). Basically you create one extra connection for each client that hangs on the server and waits for the server to take self-invoked action. After the action is done you start a new hanging connection immediately so you have one hanging all the time (so the server can talk to your client any time it wants). You can send javascript code from the server that will decide what will happen next. You can check clients to have these hanging connections on the server side to count as valid and of course run your timers on the server.
I'm developing a django-based MMO, and I'm wondering what would be the best way for server-client communication. The solutions I found are:
periodical AJAX calls
keeping a connection alive and sending data through it
Later edit:
This would consist in "you have a message", "user x attacked you", "your transport to x has arrived" and stuff like this. They could grow in number (something like 1/second), but for a typical user they shouldn't reach 1/minute
Not sure if it's applicable to what you're looking for, but there's a pretty good live example of lightweight server-client communication using node.js for a simple chat service:
http://chat.nodejs.org/
You might want to take a look at crossbar
Crossbar.io is an open-source server software that allows developers
to create distributed systems, composed of application components
which are loosely coupled, communicate in (soft) real-time and can be
implemented in different languages
There's also a third technique involving "hanging" queries:
Client requests an updated page (or whatever)
Server doesn't answer right away
Sometime before the request times out, there's a state update in the server, and the server finally answers the client, which can then update.
If there really is nothing new to tell the client within the update period, then the server responds before the timeout with a "no news" message, and the client starts up another "hanging" request.
Advantages:
Client doesn't have to do Ajax. You could even make regular HTML pages "interactive" like this.
Probably not quite as much senseless polling traffic.
Disadvantages:
Server needs to keep more active connections open, and service them at least once per timeout period. Also,
depending on how well the server code supports multi-threading (does PHP provide any help there?), it may be more difficult to code than AJAX response handling.
While building this web service and the app that calls it, we have noticed that the first call to the web service each day is extremely slow. It even will time out on some days. However, every call after that work great. Can anybody shed light on why this might be and how we can get rid of this pain?
Thanks in advance!
If it's an ASP.NET web service, it may be the CLR initializing and loading and verifying the assemblies for the first time. You may want to consider pre-compilation
Agree with the other answers on caching, initialization, etc. As far as a workaround, one possibility may be to set up some sort of daily task (SQL Server job, Windows service, something else?) to simulate a hit to the service each day, so that your users don't experience this first slow request.
If it is an ASP.NET web service, then you might want to check the settings of the application pool the web service is running in, especially the idle timeout which defaults to 20 minutes in IIS7.
Configuring IIS7 idle-timeout
Even if it is not an ASP.NET web service, other web servers will have equivalent configuration settings you have to tweak to keep your web service alive overnight.
Can you duplicate the same behavior on your database? It could just be the db needing to optimise the query for the first run (Maybe the parameter is today's date?).
Are there a lot of static constructors or set up code in the Global.asax class? Because IIS recycles worker processes periodically, the start up code may be running again.
The rule for optimization is: don't guess. Put in profiling to find out exactly what is slow, and then work to make that faster. Everything already posted provides excellent tips on where to start looking for slowness.