rqbit spends significant disk I/O to save DHT cache

[izderadicka]

I'm running rqbit on linux "server" as service (using latest Docker image] and I see significant disk I/O related to rqbit, even if nothing is "happening" - no active torrents.

Command is simple/default: /bin/rqbit server start /home/rqbit/downloads
rqbit is far most active process for disk IO - disk writes - see iotop - accumulated over 10 secs:

    PID  PRIO  USER     DISK READ DISK WRITE>    COMMAND                                                                                            
2528676 be/4 root          0.00 B   2021.00 K rqbit server start /home/rqbit/downloads
    371 be/3 root          0.00 B    356.00 K systemd-journald
   3261 be/4 999           0.00 B     46.00 K postgres: stats collector process

with iostat it looks like ongoing write is about 200 KB/s continuously

Looking with strace what's going on:

$ sudo strace -p 2528676 -f -e trace=file,write 
strace: Process 2528676 attached with 6 threads
[pid 2528698] open("/home/rqbit/cache/com.rqbit.dht/dht.json.tmp.1", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE|O_CLOEXEC, 0666) = 19
[pid 2528698] write(19, "{\"addr\":\"0.0.0.0:55022\",\"table\":"..., 8163) = 8163
[pid 2528698] write(19, "3caad6911d8e95475da6a6dc498ab3d8"..., 8191) = 8191
...
[pid 2528698] rename("/home/rqbit/cache/com.rqbit.dht/dht.json.tmp.1", "/home/rqbit/cache/com.rqbit.dht/dht.json") = 0
[pid 2528698] write(19, "2d721ae6fa4a2a24f2bd3e1886e91371"..., 315) = 315
...

File /home/rqbit/cache/com.rqbit.dht/dht.json is rewritten every ~ 3 second. Size of file is ~ 200 KB.

And this generates notable load to disks.

I have not looked for CLI options, if it can be disabled - will look, but as default option it seem to me bit aggressive from disk IO perspective.

[izderadicka]

indeed this option solves problem:

 --disable-dht-persistence
          Set this to disable DHT reading and storing it's state. For now this is a useful workaround if you want to launch multiple rqbit instances, otherwise DHT port will conflict

          [env: RQBIT_DHT_PERSISTENCE_DISABLE=]

However I would line DHT persistance - with some much more "reasonable" storage period - ideally store on program exit on SIGTERM, or with some much longer, configurable period - like 1h

[ikatson]

Thanks for reporting definitely smth worth optimizing