Re: [Libguestfs] [nbdkit PATCH] retry: Tweak error message

On 4/1/20 5:12 AM, Richard W.M. Jones wrote: >On Tue, Mar 31, 2020 at 04:00:22PM -0500, Eric Blake wrote: >>The retry filter defaults to 5 retries, but when run with verbose >>details produces some confusing output: >> >>$ rm -f /tmp/inject; (sleep 5s; touch /tmp/inject)& ./nbdkit -f -v -U - \ >> null 1G --filter=retry --filter=noextents --filter=error error-rate=100% \ >> error-file=/tmp/inject --filter=delay rdelay=1 \ >> --run 'qemu-img convert $nbd out.img' >>... >>nbdkit: null[1]: debug: noextents: pread count=2097152 offset=14680064 >>nbdkit: null[1]: debug: error: pread count=2097152 offset=14680064 >>nbdkit: null[1]: error: injecting EIO error into pread >>nbdkit: null[1]: debug: retry 6: original errno = 5 >>nbdkit: null[1]: debug: could not recover after 5 retries >> >> again: >> /* Log the original errno since it will be lost when we retry. */ >>- nbdkit_debug ("retry %d: original errno = %d", data->retry+1, *err); >>+ nbdkit_debug ("retry attempt %d: original errno = %d", data->retry, *err); >> >> if (data->retry >= retries) { >> nbdkit_debug ("could not recover after %d retries", retries); > >I think adding 1 was correct, so that the retries count from 1. But the problem is the timing of when the messages are printed. And remember, this code is only reached after a failed attempt, not on success. Pre-patch, we have: initial try succeeds - no message or (here, with retries limited to 2): initial try fails: retry 1: original error delay retry 1 fails: retry 2: original error delay retry 2 fails: retry 3: original error could not recover after 2 retries > >How about moving the message to make it conditional instead, >like this? > >again: > /* Log the original errno since it will be lost when we retry. */ > if (data->retry < retries) > nbdkit_debug ("retry %d: original errno = %d", data->retry+1, *err); > else { > nbdkit_debug ("could not recover after %d retries", retries); > ... with your suggestion, we'd have: initial try fails: retry 1: original error delay retry 1 fails: retry 2: original error delay retry 2 fails: could not recover after 2 retries where we lost the log of the errno of retry 2.