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Date: Mon, 23 Nov 2015 12:00:35 -0800
From: Konstantin Boudnik <cos@apache.org>
To: dev@ignite.apache.org
Subject: Re: Igfs PURGE events: do we need them?
Message-ID: <20151123200035.GR4878@tpx>
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Let me ask a different question: what's the point of having the concept of
TRASH?

Here's an example why I think the 'soft' delete would only complicate thing.
Suppose IGFS is sitting on top of HDFS and both have 'Trash' enabled. Now,
the file is getting soft-deleted from IGFS and is moved to TRASH folder. But
in HDFS it is also a move to a place which doesn't have any special meaning
for HDFS.=20

Even worst, if IFGS TRASH is linked to HDFS .Trash. HDFS has it's own policy
on how to clean that up, which is likely to be different from that on IGFS.
Often enough, HDFS .Trash is simply disabled. This discrepancy is going to
create a situation when a file should still be in TRASH, but the secondary =
FS
has already purged it.

And what if yet another secondary file system like S3 has yet another policy
around their own trash, which they don't even have, I believe?

Where I am going with this is pretty straight forward: let's drop the
soft-delete support and let the secondary FS to deal with it. If there's no
secondary FS configured - the content of deleted file will have to retrieved
by other means.

Thoughts?
  Cos

On Fri, Nov 20, 2015 at 07:15PM, Ivan V. wrote:
> Hi, dev,
> need opinions on the question discussed in
> https://issues.apache.org/jira/browse/IGNITE-1679  (IGFS: Purge event is
> inconsistent).
> In short: in Igfs we have "soft" delete that moves the deleted file or
> folder to special "TRASH" folder.
> Special async worker walks inside TRASH and removes the items permanently.
> When an item is completely removed, an event of type
> org.apache.ignite.events.EventType#EVT_IGFS_FILE_PURGED  is fired.
> But such events are now fired only for files, and only in case if such fi=
le
> was deleted itself, but not a part of a folder sub-tree. It's quite obvio=
us
> that such behavior is not quite consistent, so we should either get rid of
> PURGE events at all, or make them consistent.
> In the latter case it would be good to have answer to the question: what
> are real  use cases when we may need the purge events ? (Now they seem to
> be used in tests only).
> If we don't have such real use cases, are there any objections to get rid
> of the purge events at all?
> Thanks in advance.

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