Re: [Qemu-devel] [PATCH v15 8/9] Implement new driver for block replication

[Changlong Xie <xiecl.fnst@cn.fujitsu.com>]

On 03/05/2016 01:53 AM, Stefan Hajnoczi wrote:
> On Fri, Feb 05, 2016 at 12:18:07PM +0800, Changlong Xie wrote:
>> +static void secondary_do_checkpoint(BDRVReplicationState *s, Error **errp)
>> +{
>> +    Error *local_err = NULL;
>> +    int ret;
>> +
>> +    if (!s->secondary_disk->bs->job) {
>> +        error_setg(errp, "Backup job was cancelled unexpectedly");
>> +        return;
>> +    }
>
> Do you have test cases for the replication driver?
>
> This error code path seems like something that should be exercised to
> make sure it works.
>
> Basic start/checkpoint/stop and checks that the active/secondary/hidden
> disks contain the expected data are also important.
>
> Probably the easiest way to do this would be a file called
> tests/test-replication.c that calls start/checkpoint/stop and read/write
> functions directly instead of running a guest.
>

Hi Stefan

I'm working on the testcase now, and encount some issues.

Replication is different from other block drivers, we just use it for 
COLO live migration what means "primary" and "secondary" *MUST*
co-work with each other.

(1)
There are two test "prototype":
1 "COLO prototype":
     simulate COLO environment, run two guests at the same time and 
setup nbd on both 'primary'/'secondary' side.

2 "Separate prototype"
     test relevant APIs in separate 'primary'/'secondary' mode, so we
don't need run two guests and setup nbd on both side

I prefer *"Separate prototype"*. Which one do you prefer?

(2)
Since we have replication_(start/stop/do_checkpoint/get_error)_all APIs, 
i know how to test start/checkpoint/stop/get_error callbacks.

But I'm confused about how to test read/write of replication, are there 
some ready-made APIs for qemu test system?

I know, for interpreted languages, we can use:
  $QEMU_IO -s -c "read 0 $size" "$TEST_IMG"
  $QEMU_IO -s -c "write -P 0xa 0 $size" "$TEST_IMG"

Also are some APIs to check disks contents(we need check 
active/secondary/hidden disk contents)?

Thanks
	-Xie