On Thu, Jul 15, 2021 at 2:25 PM star fan <jfanix@xxxxxxxxx> wrote:
>
> We found some unnormal status of sync status when running multiple
> rgw(15.2.14) multisize sync, then I dig into the codes about rgw sync.
> I think there is a issues of rgw sync concurrency implementation if I
> understand correctly.
> The implementation of the critical process which we want it run once,
> which steps are as below:
> 1. read shared status object
> 2. check status
> 3. lock status
> 4. critical process
> 5. store status
> 6. unlock
>
> It is a problem in concurrent case that the critical process would
> run multiple times because it uses old status, thus it makes no sense.
> The steps should be as below
> 1. read shared status object
> 2. check status
> 3. lock status
> 4. read and check status again
> 5. critical process
> 6. store status
> 7. unlock
>
> one example as below
> do {
> r = run(new RGWReadSyncStatusCoroutine(&sync_env, &sync_status));
> if (r < 0 && r != -ENOENT) {
> tn->log(0, SSTR("ERROR: failed to fetch sync status r=" << r));
> return r;
> }
>
> switch ((rgw_meta_sync_info::SyncState)sync_status.sync_info.state) {
> case rgw_meta_sync_info::StateBuildingFullSyncMaps:
> tn->log(20, "building full sync maps");
> r = run(new RGWFetchAllMetaCR(&sync_env, num_shards,
> sync_status.sync_markers, tn));
>
> And there is no deletion of omapkeys after finishing sync entry in
> full_sync process, thus full_sync would run multiple times in
> concurrent case.
>
> It has no importance impact on data sync because bucket syncing is
> idempotence，but no metadata sync
Moving to dev@xxxxxxx and adding Casey.
Thanks,
Ilya
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