Using goroutines for Performance
This lesson focuses on handling multiple clients at the same time through goroutines.
We'll cover the following...
There is still a performance problem with the 2nd version if too many clients attempt to add URLs simultaneously. Our map is safely updated for concurrent access thanks to the locking mechanism, but the immediate writing of each new record to disk is a bottleneck. The disk writes may happen simultaneously, and depending on the characteristics of your OS, this may cause corruption. Even if the writes do not collide, each client must wait for their data to be written to disk before their Put function will return. Therefore, on a heavily I/O-loaded system, clients will wait longer than necessary for their Add requests to go through. To remedy these issues, we must decouple the Put and save processes; we do this by using Go’s concurrency mechanism. Instead of saving records directly to disk, we send them to a channel, which is a kind of buffer, so the sending function doesn’t have to wait for it.
The save process, writes to disk reads from that channel and is started on a separate thread by launching it as a goroutine called saveloop. The main program and saveloop are now executed concurrently, so there is no more blocking.
We replace the file field in URLStore by a channel of ...