要child_process分叉还是不分叉I / O任务？

Question

Does it make sense to use child_process fork for long running (15 - 30 seconds) I/O tasks such as fetching a feed and saving it to a db?

The context for this question is for an express route, and I need to mention that a status response is sent to the browser early when the feed url has been validated. After the status response has been sent the fetching and saving of the feed items continues and can obviously take a bit of time (10-30 sec). Should this second part be forked with a child process?

I have read contradictory posts (not on SO) about the I/O efficiency of node with/out forking the job to a background process, so I wanted to have a clear response to this. Does it make sense to fork I/O tasks (not CPU intensive tasks per se which I reckon is a separate question)

Answer 1

In general cases, Node is great for handling I/O. Due to the Event driven architecture, as soon as an I/O intensive action leaves Node (or any I/O action, really), Node forgets about that action until said action is finished (or has an error). The returning Event then goes back into the single-threaded Node process.

Take for example a remote DB and an intensive query. Even if the DB server takes seconds to query and return the results, the Node process was only responsible for building the query (a string?), and putting said query on TCP socket. The transferring of data on the socket doesn't even take up the Node process! Then, Node cares nothing about the request until the returning data has finished coming across the socket. (There could be some processing you don't see in your DB package, like when a RDBMS result is converted into JSON).

There might be corner cases to this and those you will have to look out for . . . if they ever come up. A huge majority of the time, Node will handle I/O very well. (Post some links to said articles, in your question or as comments under this answer.)

Forking child processes is typically reserved for high CPU tasks that would slow down the main event loop. There could be other reasons, but "in general."