Nodejs is popular in recent years, people say it have good performance of high concurrency. Also people say its single thread event loop will make it have problem when a operation block the event loop thread.

I was confused sometimes, if I want to choose java,php,nodjs to implement a service, what should I concern if I prefer nodejs?

After read this How the single threaded non blocking IO model works in Node.js terrific disccussion, I understand:

• Nodejs use libuv implement NIO
• normally we can say the event loop is single thread, the callback is execute in a aysnchronous way, which is powered by the nio(libub) - not multithread.
• sql connection is been abstracted as a nio style, but it is not multithread too. sql query is queued.
• The most important is that, nodejs is good at io operation(network io,filesystem io) - not good at CPU-intensive operation.