Full Answer
What is the difference between blocking and Non-Blocking IO?
Non-blocking IO means an IO request is queued straight away and the function returns. The actual IO is then processed at some later point by the kernel. For blocking IO you either need to accept that you are going to wait for every IO request or you are going to need to fire off a thread per request (Which will get very complicated very quickly).
What is non-blocking I/O in sockets?
Non-blocking I/O means that the request is immediately queued and the function is returned. The actual I/O is then processed at some later point. By setting a socket to a non-blocking mode, you can effectively interrogate it.
What is Nio (nonblocking I/O)?
Non-blocking I/O (Java) java.nio (NIO stands for Non-blocking I/O) is a collection of Java programming language APIs that offer features for intensive I/O operations.
How does Non-Blocking IO work under the hood?
To understand how non-blocking IO works under the hood we first need some understanding of how IO works at low level. A common use case for non-blocking IO is network IO, so it is best explained in this context. At kernel level a socket is used as an abstraction to communicate with a NIC.
What mean non blocking IO?
A blocking IO means: a given thread cannot do anything more until the IO is fully received (in the case of sockets this wait could be a long time). Non-blocking IO means: an IO request is queued straight away and. the function returns.
What is non blocking IO in C?
Sometimes it's convenient to have I/O that doesn't block i.e we don't want a read call to block on one in case of input from the other. Solution for this is the given function: To specify non-blocking option: #include
What are non-blocking servers?
A Non-Blocking server means that it is able to have multiple requests in progress at the same time by the same process or thread because it uses Non-Blocking I/O.
What is the difference between blocking and non blocking I O model?
Blocking IO waits for data to be read or written before returning. You can guarantee you always have some data. Non blocking IO doesn't block, and always returns ASAP even if this means you get no data.
How does non-blocking IO work in Java?
The primary features of Java NIO are: Java NIO is an asynchronous IO or non-blocking IO. For instance, a thread needs some data from the buffer. While the channel reads data into the buffer, the thread can do something else. Once data is read into the buffer, the thread can then continue processing it.
What is non-blocking IO in Linux?
Non-blocking I/O means that the request is immediately queued and the function is returned. The actual I/O is then processed at some later point. By setting a socket to a non-blocking mode, you can effectively interrogate it.
What is a non-blocking thread?
A task (thread) is non-blocking when it doesn't cause other tasks (threads) to wait until the task is finished.
What is blocking and non-blocking server?
a blocking web-server is similar to a phone call. you need to wait on-line to get a response and continue; where as a non-blocking web-server is like a sms service. you sms your request,do your things and react when you receive an sms back!
Does blocking IO use CPU?
Some I/O requests are blocked, which means control does not return to the application until the I/O task is over. In such cases, the CPU has to run multiple threads/processes to complete other tasks.
What is non blocking I O operations in node JS?
Non-Blocking: It refers to the program that does not block the execution of further operations. Non-Blocking methods are executed asynchronously. Asynchronously means that the program may not necessarily execute line by line.
What is non-blocking system call?
The alternative is non-blocking system calls. In this case the system call returns (almost) immediately. For lengthy system calls the result of the system call is either sent to the caller later (e.g. as some sort of event or message or signal) or polled by the caller later.
What is an IO block?
The input/output block (IOB) is used for communication between the problem program and the system. It provides the addresses of other control blocks, and maintains information about the channel program, such as the type of chaining and the progress of I/O operations.
What is blocking function in C?
A block definition produces an opaque value which contains both a reference to the code within the block and a snapshot of the current state of local stack variables at the time of its definition. The block may be later invoked in the same manner as a function pointer.
What is the difference between asynchronous and non-blocking?
Non-Blocking: It refers to the program that does not block the execution of further operations. Non-Blocking methods are executed asynchronously. Asynchronously means that the program may not necessarily execute line by line.
What is a non-blocking file descriptor?
By default, read() waits until at least one byte is available to return to the application; this default is called “blocking” mode. Alternatively, individual file descriptors can be switched to “non-blocking” mode, which means that a read() on a slow file will return immediately, even if no bytes are available.
What is blocking and non-blocking threads?
In a blocking thread model, when the program carries out a blocking action such as IO, the OS level thread also blocks. In contrast, a non-blocking system does not block an OS thread when the thread needs to block on a blocking operation (e.g. I/O) rather it frees up the OS thread.
What does NIO stand for in Java?
java.nio (NIO stands for Non-blocking I/O) is a collection of Java programming language APIs that offer features for intensive I/O operations. It was introduced with the J2SE 1.4 release of Java by Sun Microsystems to complement an existing standard I/O. NIO was developed under the Java Community Process as JSR 51. An extension to NIO that offers a new file system API, called NIO.2, was released with Java SE 7 ("Dolphin").
Why is NIO limited?
The NIO buffer is intentionally limited in features in order to support these goals. There are buffer classes for all of Java's primitive types except boolean, which can share memory with byte buffers and allow arbitrary interpretation of the underlying bytes.
What is NIO buffer?
NIO data transfer is based on buffers ( java.nio.Buffer and related classes). These classes represent a contiguous extent of memory, together with a small number of data transfer operations. Although theoretically these are general-purpose data structures, the implementation may select memory for alignment or paging characteristics, which are not otherwise accessible in Java. Typically, this would be used to allow the buffer contents to occupy the same physical memory used by the underlying operating system for its native I/O operations, thus allowing the most direct transfer mechanism, and eliminating the need for any additional copying. In most operating systems, provided the particular area of memory has the right properties, transfer can take place without using the CPU at all. The NIO buffer is intentionally limited in features in order to support these goals.
Where are Java NIO APIs provided?
The Java NIO APIs are provided in the java.nio package and its subpackages. The documentation by Oracle identifies these features.
How many get methods are there in NIO?
Three get () methods are supplied for transferring data out of a NIO buffer. The bulk implementation, rather than performing a "get" in the traditional sense, "puts" the data into a specified array. The "offset" argument supplied to this method refers not to the offset from within the buffer from which to read, nor an offset from the position pointer, but rather the offset from 0 within the target array.
Does clear buffer ensure zeroing?
The clear () method does not ensure zero-ing of the buffer, but does return the limit pointer to the upper boundary of the underlying array, and the position pointer to zero.
Can you map a Java.nio channel?
You can only map () a java.nio.MappedByteBuffer from a java.nio.channels.FileChannel up to Integer.MAX_VALUE in size (2GiB); regions beyond this limit can be accessed using an offset greater than zero.
Why non-blocking IO?
The main benefit of non-blocking IO is that we need less threads to handle the same amount of IO requests. When multiple calls to IO are done using blocking IO, for each call a new thread is created. A thread costs around 1MB, and there are some costs due to context switching. If you have a web server that handles 50k connections per second, a thread per connection can be quite expensive.
How does non-blocking IO work?
At kernel level a socket is used as an abstraction to communicate with a NIC. This socket takes care of reading and writing data to/from the NIC, which in turn sends the data over the UTP cable on its way to the internet. For example, if you go to a URL in your browser; at low level the data in your HTTP request is written to a socket using the send (2) system call. When a response is returned, the response data can be read from that socket using the recv (2) system call. The important thing to understand here is that when data has returned from network IO, it is ready to be read from the socket.
What happens when a thread is blocked in Linux?
When a thread is blocked in Linux, it will be put in a Sleep state by the kernel until data has returned to the caller. Threads in sleep state immediately give up its access to the CPU, so to not waste CPU time. After IO is ready, the thread is taken out of the Sleep state and put in Runnable state.
How many types of thread blocking are there?
There are actually two types of thread blocking:
What happens when you call an API that is not blocking?
This means the thread can immediately continue executing the code that comes after calling the API.
What is IO in a CPU?
Generally anything that is not happening in the CPU is called IO . When you call an API that requests data from IO, you will not get a response instantly, but with some delay. This delay can be very small for requesting a file on a hard drive, and much longer when requesting data from a network.
What is the only listener that is natively available in most computers?
The only “listener” that is natively available in most computers is the hardware interrupt processor. But hardware interrupts do not scale well and lack flexibility. And what happens when there are 100k events per second, will there be 100k hardware interrupts per second? This also seems unlikely.
What does it mean when a function is blocking?
So if a function is blocking (for whatever reasons), it is capable of delaying execution of other tasks. And the overall progress of the entire system may get suffered. If the function is blocking because it is doing some CPU task, well then we cannot do much. But if it is blocking because of I/O, we know that the CPU is idle and can be used for starting another task that needs CPU.
How do tasks work in a block?
In our main block, we maintain a list of functions that we want to call in a list called tasks. To be precise, both our functions use yield and hence return generators when we call them. So tasks actually maintains a list of generators returned by the functions we want to co-operatively execute. We run a loop as long as our tasks don’t complete their execution. On every iteration of the loop, we run each task one-by-one using the next () function. The function resumes its execution and yields whenever it can.
How does while loop work?
The while loop runs as long as tasks list is not empty or we have any fds or socket objects to watch. We run every task one-by-one. When we call send_data_task, it yields a tuple with the operation (reading or writing) we were performing on the socket and the socket object itself. We keep the socket object in a dictionary called fds where we maintain two different dictionaries of objects - one for those which we are writing to and another for those we are reading from. Then we run the other_task () and it yields nothing.
What is I/O in computing?
Note: I/O refers to Input/Output in computing world to denote how the communication happen between systems.
What does OP_ACCEPT mean?
Now we need to register this server socket channel with the selector and the “ SelectionKey.OP_ACCEPT ” parameter tells the “ selector ” to listen to only incoming connections. Basically the second parameter tells what events we are interested in listening for in the monitored channel. In our case, “ OP_ACCEPT” tells that the server socket channel is ready to accept a new connection from a client.
Can non-blocking I/O handle multiple concurrent connections?
With non-blocking I/O, we can use a single thread to handle multiple concurrent connections. Before we go into details there are few terms that we need to understand first.
Can you use Java NIO to build a client server?
So, this is basically how you can create a simple client-server using Java NIO, but instead of directly building your applications using Java NIO, you can use a reliable, high performing networking framework like netty for your application needs. This post is written merely to help you understand basic theories around blocking and non-blocking IO.
What is non-blocking I/O?
Non-blocking I/O means that the request is immediately queued and the function is returned. The actual I/O is then processed at some later point.
What happens when a client blocks I/O?
With the blocking I/O, when the client makes a connection request to the server, the socket processing that connection and the corresponding thread that reads from it is blocked until some read data appears. This data is placed in the network buffer until it is all read and ready for processing. Until the operation is complete, the server can do nothing more but wait.
What happens if you set a socket to non-blocking?
By setting a socket to a non-blocking mode, you can effectively interrogate it. If you try to read from a non-blocking socket and there is no data, it will return an error code ( EAGAIN or EWOULDBLOCK ).
How to get rid of inefficient loop?
To get rid of this inefficient loop, we need polling readiness mechanism. In this mechanism, we could interrogate the readiness of all sockets, and they would tell us which one is ready for the new I/O operation and which one is not without being explicitly asked. When any of the sockets is ready, we will perform operations in the queue and then be able to return to the blocking state, waiting for the sockets to be ready for the next I/O operation.
Why does a thread have a deadlock?
A deadlock occurs when a process or thread enters a waiting state because the requested system resource is held by another waiting process which in turn is waiting for another resource held by another waiting process. For example, the following situation will cause a deadlock between two processes: Process 1 requests resource B from process 2. Resource B is locked while process 2 is running. Process 2 requires resource A from process 1 to finish running. Resource A is locked while process 1 is running.
What are the two types of I/O?
Also, there are two types of I/O operations: synchronous and asynchronous.
Can you map I/O to other inputs?
In this post, we will be talking about networking but you can easily map it to other input/output (I/O) operations, for example, change sockets to file descriptors. Also, this explanation is not focusing on any specific programming language although the examples will be given in Python (what can I say – I love Python!).
