Node js for backend server development.
- 1. Ramanujan College, University of Delhi New Delhi-110019, India. Topic: Full Stack Web Development-2
- 2. Introduction • Learning about the Internals of Node.js • Describes the inner workings of Node.js • Its principles, and basic ideas
- 3. Introduction
- 4. Introduction • Node.js was first released in 2009 by Ryan Dahl as a reaction to how slow web servers were at the time • Most web servers would block for any I/O task, such as reading from the file system or accessing the network, and this would dramatically lower their throughput. • Node.js changed this model by making all I/O tasks non-blocking and asynchronous. This allowed web servers written in Node.js to serve thousands of requests concurrently.
- 5. Introduction
- 6. Introduction • Illustrates the threaded model processing two requests, GetFile and GetData. • The GetFile request first opens the file, reads the contents, and then sends the data back in a response. • All this occurs in order on the same thread. • The GetData request connects to the DB, queries the necessary data, and then sends the data in the response.
- 7. Introduction The Node.js event model does things differently. • Instead of executing all the work for each request on individual threads, • work is added to an event queue and then picked up by a single thread running an event loop. • The event loop grabs the top item in the event queue, executes it, and then grabs the next item. • When executing code that is no longer live or has blocking I/O, instead of calling the function directly, the function is added to the event queue along with a callback that is executed after the function completes. • When all events on the Node.js event queue have been executed, the Node application terminates.
- 8. Introduction
- 9. Introduction • illustrates the way Node.js handles the GetFile and GetData requests. • The GetFile and GetData requests are added to the event queue. • Node.js first picks up the GetFile request, executes it, and then completes by adding the Open() callback function to the event queue. • Next, it picks up the GetData request, executes it, and completes by adding the Connect() callback function to the event queue. • This continues until there are no callback functions to be executed. • Notice that the events for each thread do not necessarily follow a direct interleaved order. • For example, the Connect request takes longer to complete than the Read request, so Send(file) is called before Query(db).
- 10. Blocking I/O in Node.js • Blocking I/O stops the execution of the current thread and waits for a response before continuing. • Some examples of blocking I/O are • Reading a file • Querying a database • Socket request • Accessing a remote service • Therefore, any requests that perform blocking I/O are performed on a different thread in the background. Node.js implements a thread pool in the background. When an event that requires blocking I/O is retrieved from the event queue, Node.js retrieves a thread from the thread pool and executes the function there instead of on the main event loop thread. This prevents the blocking I/O from holding up the rest of the events in the event queue
- 11. Introduction
- 12. Introduction •In the Node.js event model, •work is added as a function with a callback to the event queue, •and then picked up on the event loop thread. • The function is then executed on the event loop thread in the case of non-blocking, or on a separate thread in the case of blocking
- 13. Introduction
- 14. Internal composition of Node.js
- 15. Libuv
- 16. Libuv
- 17. Libuv
- 19. EventLoop