4 ms·
I prefer using tcpdump instead of processlist when dealing with pt-query-digest. You get everything instead of just what happens to show up during the interval
by AaronBBrown 14y ago
I prefer using tcpdump instead of processlist when dealing with pt-query-digest. You get everything instead of just what happens to show up during the interval specified. This is, of course, assuming that you don't allow localhost socket connections.
- falcolas 14y agoVery true - extremely fast queries can slip between the processlist checks. The problem I've encountered with tcpdump is that you can cause packet loss by running it. It's not common, but it happens enough that I've become gun shy about using it on production systems. The pt-query-digest function will cause additional load on the DB, but it won't interrupt communications.
- X-Istence 14y agoWhat OS will drop packets while tcpdump is running?
- falcolas 14y agoLinux. :) If tcpdump can't keep up with the incoming traffic, the kernel will drop the packets in its buffer (or rather overwrite them with new packets). Throw in TCP's flow and congestion control protocols, and dropped packets can have disastrous effects on your database. Google has many references you might find useful on this subject.