The site: http://fraze.it
The issue: when connecting to the site via my PC I see 251 likes but when connecting
via my IPAD I see 229.
Both use the same connection.
How comes the count value is different?
I will appreciate your thoughts.
thank you.
There is something called a CAP Theorem in the database world. I suspect facebook to be a eventually consistent system. Thus even though the client connection is the same, its probable the servers serving the content are not the same. Thus you see the mismatch. Wait is all I can say, that is the only guarantee of an eventual consistent system.
Related
I have two windows computers, both using the Microsoft Edge browser. When I'm typing on the Overleaf website, the connection gets lost every 2-5 minutes. What's worse, some unsynced sentences are gone when the connection resumes. I'm not sure whether this is a network problem since all other websites look good, including Twitter and Gmail. I wondered if this is about the framework of what Overleaf cloud service used. Could anyone give some tips about the issue here?
At 9am this morning I found that my server was unresponsive I was unable to connection into via either ssh or http/s.
When I finally logged in, everything was fine other then a high cpu (averaging 70-80%). Via the console I see that the disk IO was high and also there was a peak in the amount of API requests per second.
Can anyone point me in the right direction so I can find out what happened ?
Thanks,
What you experienced was most likely the result of the networking issue described here. Also, in general, this forum is a good source to stay updated.
Beyond this, if the time window does not line up with your observations (there's no time zone specified in the question), one would need logs (i.e. Apache's, syslog, etc) in order to determine a possible cause, albeit it can turn into an exercise in speculation after the fact.
I have an Apache2 and Django (mod_wsgi) setup that provides a RESTful API. I have a set of automated tests for this, that executes ~1000 API requests (pure http GET/POST/PUT/DELETE) in sequential order.
The problem is, for every 80 requests or so, I get a strange lag/timeout for exactly 5s or 10s. See timestamp examples here:
Request 1: 2013-08-30T03:49:20.915
Response 1: 2013-08-30T03:49:30.940
Request 2: 2013-08-30T03:50:32.559
Response 2: 2013-08-30T03:50:37.597
I can't figure out why this happens. I have an apache config with KeepAlive Off (recommended setup setting for Django) but otherwise standard install for Ubuntu 12.04 LTS.
I'm running the tests from the same server where the webserver is, I first thought this was some kind of DNS cache thing, but I've added the hostname I'm requesting to /etc/hosts but the problem persists.
The system is idle and have lots of cpu and mem when this lag/timeouts happens.
The lag is not specific to a certain request (URL), it seems kinda random.
Considering that it's always exactly to the millisecond 5s or 10s, it feels like this is some specific setting somewhere causing this.
In case it provides some insight, watch my talk from PyCon US.
http://lanyrd.com/2013/pycon/scdyzk/
The talk deals with things like process churn and startup costs. One thing you shouldn't do is set maximum requests if you don't really need it.
Also consider trying New Relic to help diagnose where the issue is. That will save a lot of guessing if it is a web application of backend service infrastructure issue.
As far as seeing how such monitoring can help, watch another one of my PyCon talks.
http://lanyrd.com/2012/pycon/spcdg/
This was a DNS issue, adding the domainname I used locally to /etc/hosts actually solved the problem. I just hadn't reboot the server for the changes to take effect, thought restarting networking would take care of that, but apparently not.
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 have a winsock IOCP server written in c++ using TCP IP connections. I have tested this server locally, using the loopback address with a client simulator. I have been able to get upwards of 60,000 clients no sweat. The issue I am having, is when I run the server at my house and the client simulator at a friends house. Everything works fine up until we hit around 3700 connections, after that every call to connect() fails from the client side with a return of 10060 (this is the winsock timed out error). Last night this number was 3700, but it has been around 300 before, and we also saw it near 1000. But whatever the number is, every time we try to simulate it, it will fail right around that number (within 10 or so).
Both computers are using Windows 7 Ultimate. We have also both modified the TCPIP registry setting MaxTcpConnections to around 16 million. We also changed the MaxUserPort setting from its 5000 default to 65k. No useful information is showing up in the event viewer. We also both watched our resource monitor, and we havent even gotten to 1% network utilization, the CPU is also close to 0% usage as well.
We just got off the phone with our ISP, and they are saying that they are not limiting us in any way but the guy was kinda unsure and ended up hanging up on us anyway after a 30 minute hold time...
We are trying everything to figure this issue out, but cannot come up with the solution. I would be very greatful if someone out there could give us a hand with this issue.
P.S. Both computers are on Verizon FIOS with the same verizon router. Another thing to note, the server is using WSAAccept and NOT AcceptEx. The client simulator is attempting to connect over many seconds though, so I am pretty sure the connects are not getting backlogged. We have tried to change the speed at which the client simulator connects, and no matter what speed it is set to it fails right around the same number each time.
UPDATE
We simulated 2 separate clients (on 2 separate machines) on network A. The server was running on network B. Each client was only able to connect half (about 1600) connections to the server. We were initially using a port below 1,000, this has been changed to above 50,000. The router log on both machines showed nothing. We are both using the Actiontec MI424WR verizon FIOS router. This leads me to believe the problem is not with the client code. The server throws no errors and has no unexpected behavior. Could this be an ISP/Router issue?
UPDATE
The solution has been found. The verizon router we were using (MI424WR revision C) is unable to handle any more than 3700 connections, we tested this with a separate set of networks. Thanks for the help guys!
Thanks
- Rick
I would have guessed that this was a MaxUserPort issue, but you say you've changed that. Did you reboot after changing it?
Run the test on the exact same computers on your local network (this will take the computers out of the equation).
The issue could be one of your routers not being up to the job?