nonblocking

What is non-blocking or asynchronous I/O in Node.js?

由 两盒软妹~` 提交于 2019-11-26 19:16:49
In the context of Server Side Javascript engines, what is non-blocking I/O or asynchronous I/O? I see this being mentioned as an advantage over Java server side implementations. Joseph Synchronous vs Asynchronous Synchronous execution usually refers to code executing in sequence. Asynchronous execution refers to execution that doesn't run in the sequence it appears in the code. In the following example, the synchronous operation causes the alerts to fire in sequence. In the async operation, while alert(2) appears to execute second, it doesn't. Synchronous: 1,2,3 alert(1); alert(2); alert(3);

Is asynchronous jdbc call possible?

由 心不动则不痛 提交于 2019-11-26 19:15:36
I wonder if there is a way to make asynchronous calls to a database? For instance, imagine that I've a big request that take a very long time to process, I want to send the request and receive a notification when the request will return a value (by passing a Listener/callback or something). I don't want to block waiting for the database to answer. I don't consider that using a pool of threads is a solution because it doesn't scale, in the case of heavy concurrent requests this will spawn a very large number of threads. We are facing this kind of problem with network servers and we have found

Why does a read-only open of a named pipe block?

由 戏子无情 提交于 2019-11-26 19:05:33
问题 I've noticed a couple of oddities when dealing with named pipes (FIFOs) under various flavors of UNIX (Linux, FreeBSD and MacOS X) using Python. The first, and perhaps most annoying is that attempts to open an empty/idle FIFO read-only will block (unless I use os.O_NONBLOCK with the lower level os.open() call). However, if I open it for read/write then I get no blocking. Examples: f = open('./myfifo', 'r') # Blocks unless data is already in the pipe f = os.open('./myfifo', os.O_RDONLY) #

non-blocking IO vs async IO and implementation in Java

由 ε祈祈猫儿з 提交于 2019-11-26 18:46:09
问题 Trying to summarize for myself the difference between these 2 concepts (because I'm really confused when I see people are using both of them in one sentence, like "non-blocking async IO" which I'm trying to figure out what does it mean). So, in my understanding non-blocking IO is primary the OS mechanism to process the IO if there is any data ready, otherwise just return error/do nothing. In async IO you just provide a callback, and your application will be notified when the data is available

What's the difference between: Asynchronous, Non-Blocking, Event-Base architectures?

由 巧了我就是萌 提交于 2019-11-26 18:42:58
问题 What's the difference between: Asynchronous , Non-Blocking , and Event-base architectures? Can something be both asynchronous and non-blocking (and event-based )? What's most important in programming, to have something: asynchronous, non-blocking and/or event-base (or all 3)? If you could provide examples, that would be great. This question is being asked because I was reading this great StackOverflow article on a similar topic but it doesn't answer my questions above. 回答1: Asynchronous

Node.js server with multiple concurrent requests, how does it work?

由 送分小仙女□ 提交于 2019-11-26 18:13:47
问题 I know node.js is a single threaded, asynchronous, non blocking i/o. I've read a lot about that. e.g PHP uses one thread per request but node uses only one thread for all, like that. Suppose there are three requests a, b, c arriving at same time at node.js server. Three of these requests require large blocking operation e.g they all want to read same big file. Then how are the requests queued, in what sequence will the blocking operation be carried out and in what sequences are the responses

using Flask and Tornado together?

由 倖福魔咒の 提交于 2019-11-26 17:53:30
问题 I am a big fan of Flask - in part because it is simple and in part because has a lot of extensions. However, Flask is meant to be used in a WSGI environment, and WSGI is not a non-blocking, so (I believe) it doesn't scale as well as Tornado for certain kinds of applications. Since each one has an URL dispatcher which will call a function, and both will use Python files (in Django you dont launch the python file but in flask or tornado you do) do does it make sense to have two seperate parts

PySerial non-blocking read loop

由 半腔热情 提交于 2019-11-26 17:40:47
I am reading serial data like this: connected = False port = 'COM4' baud = 9600 ser = serial.Serial(port, baud, timeout=0) while not connected: #serin = ser.read() connected = True while True: print("test") reading = ser.readline().decode() The problem is that it prevents anything else from executing including bottle py web framework. Adding sleep() won't help. Changing "while True"" to "while ser.readline():" doesn't print "test", which is strange since it worked in Python 2.7. Any ideas what could be wrong? Ideally I should be able to read serial data only when it's available. Data is being

How to reset a socket back to blocking mode (after I set it to nonblocking mode)?

由 时光怂恿深爱的人放手 提交于 2019-11-26 17:23:06
问题 I have read this regarding setting a socket to non-blocking mode. http://www.gnu.org/software/libc/manual/html_mono/libc.html#File-Status-Flags Here is what I did: static void setnonblocking(int sock) { int opts; opts = fcntl(sock,F_GETFL); if (opts < 0) { perror("fcntl(F_GETFL)"); exit(EXIT_FAILURE); } opts = (opts | O_NONBLOCK); if (fcntl(sock,F_SETFL,opts) < 0) { perror("fcntl(F_SETFL)"); exit(EXIT_FAILURE); } return; } How can I set the socket back to Blocking mode? I don't see a O_BLOCK

Java serialization, ObjectInputStream.readObject(), check if will block

由 只谈情不闲聊 提交于 2019-11-26 16:56:14
问题 I'm using an ObjectInputStream to call readObject for reading in serialized Objects . I would like to avoid having this method block, so I'm looking to use something like Inputstream.available() . InputStream.available() will tell you there are bytes available and that read() will not block. Is there an equivalent method for seriailzation that will tell you if there are Object s available and readObject will not block? 回答1: No. Although you could use the ObjectInputStream in another thread
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