Best practices
Never run blocking code in OnTraffic(), OnOpen() and OnClose()
The above three event handlers (callbacks) are executed in event-loops, therefore, running blocking code in them blocks event-loops, which means that the subsequent tasks will have to wait for the preceding blocking event handlers to complete before they get executed.
To avoid blocking event-loops, asynchronize your blocking code, for example by starting a goroutine with your blocking code and invoking Conn.AsyncWrite() or Conn.AsyncWritev() to send response data to the peer endpoint.
If you're not familiar with how gnet works, go back and read this.
Leverage Conn.Context() to monopolize data instead of sharing it across connections
It's recommended to use Conn.Context() to store necessary resource for each connection, so that each connection can take advantage of its exclusive resource, avoiding the contention of single resource across connections.
Either loop read data in OnTraffic() or invoke c.Wake() regularly
gnet leverages epoll/kqueue with level-triggered mode by default under the hood, you're able to switch to edge-triggered mode since v2.5.0. In LT mode, OnTraffic() might not be invoked constantly given there is data left in the inbound buffer of a gnet.Conn, OnTraffic() will be invoked only when there is data left in the socket recv buffer of the kernel. By contrast, in ET mode, OnTraffic() will be invoked only when new data arrives at the socket recv buffer of the kernel.
Thus, you should loop call c.Read()/c.Peek()/c.Next() on a connection in OnTraffic() to drain the inbound buffer for reading and decoding packets until you reach an incomplete packet, but if you don't, then make sure you call c.Wake() periodically, otherwise you may never get a chance to read the leftover data until the remote sends new data over and there are new arrivals of data on the socket recv buffer.
Enable poll_opt mode to boost performance
By default, gnet utilizes the standard package golang.org/x/sys/unix to implement pollers with epoll or kqueue, where a HASH map of fd->conn is introduced to help retrieve connections by file descriptors returned from pollers, but now you can run go build with build tags poll_opt, like this: go build -tags=poll_opt, and gnet will switch to the optimized implementations of pollers that invoke the system calls of epoll or kqueue directly and add file descriptors to the interest list along with storing the corresponding connection pointers into epoll_data or kevent, in which case gnet can get rid of the HASH MAP of fd->conn and regain each connection pointer by the conversion of void* pointer in the I/O event-looping. In theory, it ought to achieve a higher performance with this optimization.
Visit #230 for code details.
Enable gc_opt mode to reduce GC latency
By default, gnet uses map as the internal storage of connections, but now you can run go build with build tags gc_opt, like this: go build -tags=gc_opt, and gnet will switch to the optimized implementation of connections storage that uses a new data structure matrix for managing connections, in which case gnet eliminates the pointers in map to reduce the GC latency significantly.
Visit Announcing gnet v2.3.0 for more details.