Hey, Recently, our site has been experiencing slowdowns off and on. It seems to be due to PHP-FPM processes using a high amount of CPU (greater than 50%). So I’ve been trying to track down the cause by searching log files and for possible culprits on the web. And one issue that I have found which I can’t find any documentation on is an http2 warning that is now frequently appearing in our Apache error log. The warning messages look something like the following:
[date] [http2:warn] [pid number:tid longer-number] [cient ip-address:port] h2_stream(22742-138-1,CLEANUP): started=1, scheduled=1, ready=0, out_buffer=0 Whether these messages are related to the slowdowns, I am not sure; but they never used to appear, and now they show up in groups (every 5 seconds for 1 minute) usually multiple times an hour. The variables at the end of each warning (started=1, scheduled=1, etc.) always have the same values (1, 1, 0, 0). As I don’t know what the message is telling me, I thought it could be a worker issue, so I tried adjusting the H2MaxWorkers directive to different values (20, 50, 100) but it makes no difference. Once Apache is restarted, the messages start showing up again within an hour or two. The site is running Apache2.4 on CentOS7, using CPanel. We’ve had HTTP2 active for quite some time (a couple of years at least), but I don’t think I’ve seen these warning messages before. So my question is: does anyone know what these http2 warning messages mean, and what causes them (or what could cause them)?
