For a SaaS running on Node.JS, is a web-server (ng

For a SaaS running on Node.JS, is a web-server necessary?

If yes, which one and why?

What would be the disadvantages of using just node? It's role is to just handle the CRUD requests and serve JSON back for client to parse the date (like Gmail).

"is a web-server necessary"?

Technically, no. Practically, yes a separate web server is typically used and for good reason.

In this talk by Ryan Dahl in May 2010, at 37'30" he states that he recommends running node.js behind a reverse proxy or web server for "security reasons". To elaborate on that, hardened web servers like nginx or apache have had their TCP stacks evolve for a long time in terms of stability and security. Node.js is not at that same level yet. Thus, since putting node.js behind nginx is easy, doesn't have many negative consequences, and in theory increases the security of your deployment somewhat, it is a good choice. At some point in time, node.js may be deemed officially "ready for live direct Internet connections" but wait for Ryan/Joyent to make some announcement to that effect.

Secondly, binding to sub-1024 ports (like 80 and 443) requires the process to be root. nginx and others automatically handle binding as root and then dropping privileges to a safer user account (www-data or nobody typically). Although node.js has system call wrappers in the process module to drop root privileges with setgid and setuid, AFAIK other than coding this yourself the node community hasn't yet seen a convention emerge for doing this. More on this topic in this discussion.

Thirdly, web servers are good at virtual hosting and in general there are convenient things you can do (URL rewriting and such) that require custom coding in node.js to achieve otherwise.

Fourthly, nginx is great at serving static files. Better than node.js (at least by a little as of right now). Again as time goes forward this point may become less and less relevant, but in my mind a traditional static file web server and a web application server still have distinct roles and purposes.

"If yes, which one and why"?

nginx. Because it has great performance and is simpler to configure than apache.