I am building a download application which would allow clients to download data( documents + images) from a server, which has exposed download functionality through web services apis. Each client might download anywhere from 1GB-10GB of data. What I am looking for is a possible mechanism to throttle the downloads, so that if too many clients simultaneously start the downloads then the server should not go down because of the load.
What are the standard mechanisms for throttling downloads on the server?
We finally decided to go for a rate of download approach, where the client pings the server for a rate of download and the server sends the rate at which client should download. The rate of download is calculated on the server based on the number of active clients.
Throttling is possible at almost any level: you could add it to your code, but it is also possible on any decent firewall.
Inbetween, you could throttle a VM or (if you're talking Linux) you can throttle applications using cgroups.
Related
I have a web application hosted on iis on windows server. My API uses external APIs as a source for data. There is metrics in my API that show that when there are too many requests to my API, getting response from external APIs takes longer than usual and that elapsed time is usually 3 seconds+time that was really spent by external API to proccess request.
External APIs in fact are soap-services on ESB, if it matters.
Metrics of external APIs and metrics of net channels between my server and ESB and between ESB and external servers don't show these 3 seconds anywhere. It happens not with all external APIs, but with most of them. It seems like it never happens to database requests from my API.
So it seems like there might be a limitation of outbound requests from iis or from app pool or from windows server itself. But I don't know how to check it, where to look. May be perfomance monitor, but there are tons of metrics - what should I choose?
my use case is
I am trying to build an API that takes images as input and does some
image processing operations and return the output JSON back to the
client.
Multiple clients can concurrently request Server and as the server
does take 2 to 3 minutes time to process.
Initially I thought of a normal flask Application, where client
would poll the server for a response on a timely basis
But as Flask-SocketIO can respond back to the client event-based, I
want to use Flask-SocketIO
As the other APIs in my project are hosted on IIS, I wanted to use
the same IIS as the hosting server
my questions are
Can I use Flask-SocketIO for my use case, where API takes 2 to 3
minutes to respond back
If not IIS, how to deploy flask-socketIO on
the windows machine, I have gone through the documentation but I did
not find any deployment strategy for hosting it on windows machine
The best way to achieve concurrency in this case
Thanks in advance
Prasad.
I have a concox GT06 device from which I want to send tracking data to my AWS Server.
The coding protocol manual that comes with it only explains the data structure and protocol.
How does my server receive the GPS data collected by my tracker?
Verify if your server allows you to open sockets, which most low cost solutions do NOT allow for security reasons (i recommend using an Amazon EC2 virtual machine as your platform).
Choose a port on which your application will listen to incoming data, verify if it is open (if not open it) and code your application (i use C++) to listen to that port.
Compile and run your application on the server (and make sure that it stays alive).
Configure your tracker (usually by sending an sms to it) to send data to your server's IP and to the port which your application is listening to.
If you are, as i suspect you are, just beginning, consider that you will invest 2 to 3 weeks to develop this solution from scratch. You might also consider looking for a predeveloped tracking platform, which may or may not be acceptable in terms of data security.
You can find examples and tutorials online. I am usually very open with my coding and would gladly send a copy of the socket server, but, in this case, for security reasons, i cannot do so.
Instead of direct parsing of TCP or UDP packets you may use simplified solution putting in-between middleware backends specialized in data parsing e.g. flespi.
In such approach you may use HTTP REST API to fetch each new portion of data from trackers sent to you dedicated IP:port (called channel) or even send standardized commands with HTTP REST to connected devices.
At the same time it is possible to open MQTT connection using standard libraries and receive converted into JSON messages from devices as MQTT in real time, which is even better then REST due to almost zero latency.
If you are using python you may take a look at open-source flespi_receiver library. In this approach with 10 lines of code you may have on your EC2 whole parsed into JSON messages from Concox GT06.
This is sort of a theoretical question, however, I need to add file sharing capabilities to my web socket powered chat application. I could use a service like Amazon S3 to upload a file to share by posting a link to the file, but that involves the uploading of a file that may already be accessible over the local network (sharing a file between co-workers for example).
So I had the idea that it might be possible to somehow tunnel the upload/download/transfer through the already existing web socket connection. However, I don't know enough about HTTP file transfer to know the next step of how to implement it. Is there a limitation to web sockets that would prevent this from being possible?
I'm using Ruby and EventMachine for my current web socket implementation. If you were able to provide a high level overview to get me started, that would be very much appreciated.
Here's an example of a project that uses only Web Sockets and the javascript File API for transferring files: http://www.github.com/thirtysixthspan/waterunderice
To allow files to be shared without the need to upload it to the server, (i.e Coworkers) you can now use the WebRTC DataChannel API, to create a peer to peer connection.
The Performance Golden Rule from Yahoo's performance best practices is:
80-90% of the end-user response time
is spent downloading all the
components in the page: images,
stylesheets, scripts, Flash, etc.
This means that when I'm developing on my local webserver it's hard to get an accurate idea of what the end user will experience.
How can I simulate latency so that I can understand how my application will perform when I've deployed it on the web?
I develop primarily on Windows, but I would be interested in solutions for other platforms as well.
A laser modem pointed at the mirrors on the moon should give latency that's out of this world.
Fiddler2 can do this very easily. Plus, it does so much more that is useful when doing development.
YSlow might help you out. YSlow analyzes web pages based on Yahoo!'s rules.
Firefox Throttle. This can throttle speed (Windows only).
These are plugins for Firefox.
You can just set up a proxy outside that will tunnel traffic from your web server to it and then back to local browser. It would be quite realistic (of course it depends where you put the proxy).
Otherwise you can find many ways to implement it in software..
Run the web server on a nearby Linux box and configure NetEm to add latency to packets leaving the appropriate interface.
If your web server cannot run under Linux, configure the Linux box as a router between your test client machine and your web server, then use NetEm anyway
While there are many ways to simulate latency, including some very good hardware solutions, one of the easiest for me is to run a TCP proxy in a remote location. The proxy listens and then directs the traffic back to my final destination. On a remote server, I run a unix program called balance. I then point this back to my local server.
If you need to simulate for a just a single server request, a simple way is to simply make the server sleep() for a second before returning.