scalability

问题 We have server APIs to support clients running on ten millions devices. Normally clients call server once a day. That is about 116 clients seen per second. For each client (each with unique ID), it may make several APIs calls concurrently. Server then need to sequence those API calls from the same client. Because, those API calls will update the same document in the Mongodb database. For example: last seen time and other embedded documents. Therefore, I need to create a synchronization

问题 I am trying to figure out how to aggregate data from a dataset and then add the result to the original dataset using Apache Spark. I have tried 2 solutions that I'm not satisfied with, and I wonder if there's a more scalable and efficient solution that I'm not seeing. Here are very simplified samples of input and expected output data: Input : A list of customers, and for each customer, a list of purchased items. (John, [toast, butter]) (Jane, [toast, jelly]) Output : A list of customers, and

问题 I have a huge JSON file (1GB) which is basically an array of objects in the below format [{"x":"y", "p":"q"}, {"x1":"y1", "p1":"q1"},....] I want to parse this file such the all the data is not loaded in memory. Basically I want to get for eg: first 1000 objects in the array to memory process it and then get the next 1000 objects into the memory process it and so on util all data is read. Is there any JSON library that supports this use case? I currently use Gson . However it loads all the

问题 Everybody tells me that polling server for new data is stupid if the server is yours and you should implement push with GCM instead. Well, I agree and have done so but, I was wondering, how often can or should you perform push? I have a simple app where people post stuff to the server and have a feed of everyone else's posts. The method on the server that does the saving to the database also triggers the GCM Push at the end, so Google sends out the push notifications to everybody and

问题 I'm wondering if there is a way to use media queries to scale a divs contents (not the entire browser's contents). I have a fluid width site in which, when the window resizes past a certain point, some of the content gets buried behind some other content, and I'd like to be able to scale it. I have two issues - one is that I'm using ems for the fonts, but the fonts don't scale as the browser resizes. Are they supposed to? Second, some of the contents of the div I'd like to resize are images -

问题 I am new to NoSQL and trying to understand it's meaning. I have seen many articles in many different websites that repeat the fact that "SQL DataBases are scaled vertically (by adding CPU/memory) whereas NoSQL DataBases are scaled horizontally (by adding more machines that can perform distributed calculations)". For example these articles: http://dataconomy.com/sql-vs-nosql-need-know/ http://www.thegeekstuff.com/2014/01/sql-vs-nosql-db/ The thing is that I can't understand why. As far as I am

问题 Are there in the literature some standard scalability measures for distributed systems ? I'm searching in google (and also google scholar) but I came up with only few papers (e.g., https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=862209). In particular, I was wondering if there are some scalability measures for the three axes of the AKF cube or cube of the scalability (http://microservices.io/articles/scalecube.html), which is described in the book The Art of Scalability, by Abbott

问题 So I've read some articles about scaling Socket.IO. For various reasons I don't want to use built-in Socket.IO scaling mechanism (mostly it seems to be inefficient, since it publishes a lot more stuff to Redis then required from my point of view). So I've came up with this simple idea: Each Socket.IO server creates Redis pub/sub/store clients, connects to Redis and subscribes to a channel. Now, when I want to broadcast data I just publish it to Redis and all other Socket.IO servers get it and

问题 I am learning to design scalable system, for now using Windows machine. I created two servers that will listen to port 27016 and 27015, all they do is return "HelloWorld!" response. I had set listen(ListenSocket, SOMAXCONN) for both the servers when creating them in Visual studio following Winsock tutorial. Using jmter performed load test on each of them individually (1000 request per sec) and got everything OK. Now when I introduced nginx which is listening to port 80 and load balancing the

问题 Is there a maximum number of views you can create for a list in SharePoint? I mean views like the ones which are listed in the top right corner o the AllItems.aspx page: (source: microsoft.com) Are there performance issues which arise when you add a lot of views to one list, like 50-100? 回答1: Apparently there is limit of 50 views per list, though no citations in any of the pages which suggest this. http://www.eggheadcafe.com/software/aspnet/31692572/limit-on--of-views-in-se.aspx http://www