Could repeatably read zeros.

With the handle position caching in, avoiding seeks opened a lovely opportunity for reading zeros. The read handle had read_ahead turned on, so even though the write handle was being sync'd correctly, the next read was reading cached data. Consequently, reading zeros instead of the real message.

This makes a valuable point which is that with read_ahead turned on, the seeks on every read, as was happening previously, were evicting the read_ahead cache, even if the seek was in effect a noop. Thus read_ahead, in combination with the seeks, made no performance gain.

Consequently, turning read_ahead off and only seeking when necessary is a performance gain, over (pointlessly) having read_ahead on and seeking every time. Turning read_ahead off also solves this reading zeros bug.

Finally, corrected some maths so that we now check to see if the sync offset is < the offset we will reach rather than <= the offset we read from. Because the offsets should only ever be on message boundaries, both will work, but the new version is more intuitively correct.

0 files changed, 0 insertions, 0 deletions