Reuse buffers in bufio.Scanners

[sinkingpoint]

At the moment, every parser (one of which is constructed for each message), allocates a new buffer (https://github.com/leodido/go-syslog/blob/develop/octetcounting/scanner.go#L42). In high throughput scenarios, this can chew up a huge amount of CPU allocating memory to parse messages. I would like to propose that we create a new sync.Pool that stores bufio.Readers which https://github.com/leodido/go-syslog/blob/develop/octetcounting/scanner.go#L40 can pull from, rather than allocating a new buffer every time.

[sinkingpoint]

As a demonstrative, we were chewing 70 cores using go-syslog through the OpenTelemetry Collector, which reduced to 3 when introducing a sync.Pool to store/reuse bufio.Readers

pprof:

[leodido]

I love the analysis @sinkingpoint (ty!). Also, I like the idea of a pool for buffers.

Would love to get a PR and review it!

[sinkingpoint]

Sure: #18