Libguestfs - Sep 2019 - Re: [PATCH nbdkit v3 3/3] retry: Add a test of this filter.

On 9/19/19 10:26 AM, Richard W.M. Jones wrote:
> We use a custom sh plugin to test retries are working.
> ---
>  tests/Makefile.am               |   8 +++
>  tests/test-retry-reopen-fail.sh | 108 ++++++++++++++++++++++++++++++++
>  tests/test-retry.sh             |  97 ++++++++++++++++++++++++++++
>  3 files changed, 213 insertions(+)
> 
> +++ b/tests/test-retry-reopen-fail.sh
> +
> +# Create a custom plugin which will test retrying.
> +nbdkit -v -U - --filter=retry \
> +       sh - \
> +       --run 'qemu-img convert $nbd retry-reopen-fail.img'
<<'EOF'
> +case "$1" in
> +    open)
> +        # Count how many times the connection is (re-)opened.
> +        i=`cat retry-reopen-fail-open-count`
$() is nicer than ``, but even better is just:

read i retry-reopen-fail-open-count
> +        ((i++))
> +        echo $i > retry-reopen-fail-open-count
Potentially racy if more than one thread tries to do this - but sh
plugins don't default to parallel and you aren't requesting parallel
mode, so we are safe due to serialization. But maybe worth a comment?
> +        if [ $i -eq 2 ]; then
> +            echo "EIO open failed" >&2
> +            exit 1
> +        fi
> +        ;;
> +    pread)
> +        # Fail 3 times then succeed, and count how long it takes.
> +        i=`cat retry-reopen-fail-count`
same thing about using 'read'

> +
> +# In this test we should see 4 failures:
> +# pread FAILS
> +# retry and wait 2 seconds
> +# open FAILS
> +# retry and wait 4 seconds
> +# open succeeds
> +# pread FAILS
> +# retry and wait 8 seconds
> +# pread FAILS
> +# retry and wait 16 seconds
> +# pread succeeds
> +
> +# The minimum time for the test should be 2+4+8+16 = 30 seconds.
> +start_t=`stat -c '%Z' retry-reopen-fail-start`
> +end_t=`date +'%s'`
> +if [ $((end_t - start_t)) -lt 30 ]; then
> +    echo "$0: test ran too quickly"
> +    exit 1
> +fi
Slows down 'make check'; is there any way we can scale it to be slightly
faster, such as using a smaller retry interval than just 1 second as our
starting point?
> +
> +# Check the handle was opened 5 times.
> +retry_open_count=`cat retry-reopen-fail-open-count`
Another potential 'read' spot.
> +if [ $retry_open_count -ne 5 ]; then
> +    echo "$0: retry-reopen-fail-open-count ($retry_open_count) !=
5"
> +    exit 1
> +fi
> diff --git a/tests/test-retry.sh b/tests/test-retry.sh
> new file mode 100755
> index 0000000..47d6e23
> --- /dev/null
> +++ b/tests/test-retry.sh
> +touch retry-start
> +
> +# Create a custom plugin which will test retrying.
> +nbdkit -v -U - --filter=retry \
> +       sh - \
> +       --run 'qemu-img convert $nbd retry.img'
<<'EOF'
> +case "$1" in
> +    open)
> +        # Count how many times the connection is (re-)opened.
> +        i=`cat retry-open-count`
and more in this file
> +
> +# The minimum time for the test should be 2+4+8 = 14 seconds.
> +start_t=`stat -c '%Z' retry-start`
> +end_t=`date +'%s'`
I'm not sure how portable this will be to non-Linux, but we'll deal with
that when someone complains.  It may also be an issue if filesystem time
is skewed in relation to system date.

Bash includes $SECONDS which auto-increments at 1-second intervals,
would testing that be more reliable than stat/date?

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

On Thu, Sep 19, 2019 at 11:12:23AM -0500, Eric Blake
wrote:
> > +    open)
> > +        # Count how many times the connection is (re-)opened.
> > +        i=`cat retry-reopen-fail-open-count`
> 
> $() is nicer than ``, but even better is just:
> 
> read i retry-reopen-fail-open-count
Did you mean:

read i < retry-reopen-fail-open-count

Unfortunately it fails when the file does not exist.  (We could
pre-create the files though).

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-p2v converts physical machines to virtual machines.  Boot with a
live CD or over the network (PXE) and turn machines into KVM guests.
http://libguestfs.org/virt-v2v

On 9/19/19 12:04 PM, Richard W.M. Jones wrote:
> On Thu, Sep 19, 2019 at 11:12:23AM -0500, Eric Blake wrote:
>>> +    open)
>>> +        # Count how many times the connection is (re-)opened.
>>> +        i=`cat retry-reopen-fail-open-count`
>>
>> $() is nicer than ``, but even better is just:
>>
>> read i retry-reopen-fail-open-count
> 
> Did you mean:
> 
> read i < retry-reopen-fail-open-count
Yes. Thanks for fixing my typo.
> 
> Unfortunately it fails when the file does not exist.  (We could
> pre-create the files though).
Yes, or even pre-populate it to contain '0' instead of being empty, if
that makes it easier to track what it is doing.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org