JeffLiusGitHub / node_refresh

node_refresh

node_refresh

Node process ->c++ program

use so called single thread (sequence of instructions)

Initialize program (register) -> execute 'top-level' code (no callback) ->require modules -> registger event callbacks -> start event loop (but some task is to heavy, which will block other process)

libuv async io layer link to underlying computer operating system, file system, networking

Thread pool(provide multiple thread 4-128) event loop offloading heavy task to the thread pool eg: file system API, Cryptography, compression, DNS lookups

Event loop

run callback functions (function that called asa other work finished)

event driven architecture

events are emitted event loops picks them up callbacks are called

event loop do orchestration (receive events, call callback functions, offload expensive task to thread pool)

different phase have different queue,

1. take timer callbacks (eg: settimeout) if timer finished, callback function will only be called when Node back to timer phase

2. I/O polling (input output, networking, file access)

3. setimmediate callback

4. close callback (websocket shut down)

5. nexttick()queue

6. other microtasks queue

5/6 will run right after one phase finish

check if any pending timers or I/O tasks. If yes, go through the task again if not exit program HTTP request: IO task

Hints for the performance:

1. Don't use Sync version in fs, crypto, zlib in callback functions
2. Don't perform complex calcuations in event loop
3. Be careful with large JSON
4. Don't use too complex regular expression

what is express?

complex routing, handling requests and responses, middleware, server-side rendering

Mongoose is an Object Data Modeling (ODM) library for mongoDB and Node js, a higher level of abstraction