Re: WebDAV folders internally have hundreds of copies of the same few files

[Ken Murchison <murch@xxxxxxxxxxxx>]

What are you using as the mailbox name? 

On 11/20/18 1:01 AM, Anatoli wrote:

> Enable the imapmagicplus option in imapd.conf

With this option I could login with imtest specifying "+DAV" for the user, both as the admin and as a regular user, but then when trying to select a folder, I got "NO Permission denied" for the admin and "NO Mailbox does not exist" for a common user. This looks like undocumented magic and mbexamine actually provides all needed information, so I will get file details with it.

Thanks for you help, Ken.

From: Ken Murchison
Sent: Friday, November 16, 2018 13:17
To: Info-cyrus
Subject: Re: WebDAV folders internally have hundreds of copies of the same few files

On 11/16/18 1:19 AM, Anatoli wrote:

Ken,

> If you login as an admin, you should be able to SELECT the mailbox and use normal IMAP commands.  Alternatively, if you add "+DAV" to a regular userid, this will also allow SELECTing of DAV collection mailboxes.

When I do imtest -a mailadmin and then issue a002 select #drive/folder, I get:

a002 NO Invalid mailbox type

It appears that just logging in as an admin won't do the trick.

When I do imtest -a mailadmin+DAV, I get (XX replaces the real auth value):

C: A01 AUTHENTICATE PLAIN XXXXXXXXXXXXXXXXXXX
S: A01 NO authentication failure
Authentication failed. generic failure

I've also tried these combinations with the same result: "user@xxxxxxxxxx+DAV" and "user+DAV@xxxxxxxxxx". Am I doing it wrong?

Enable the imapmagicplus option in imapd.conf

Independently of this, is there a way to obtain the details about the flags for each message in a folder directly from the db files? My idea is to rsync the Cyrus store where the WebDAV is located to some other folder (probably on another server), purge there the files marked as deleted and backup the remaining files, all this without altering the Cyrus store. Is it possible?


> If the append of the resource into the mailbox, or updating the DAV db entry fails, the operation should be reverted, with partial saving done.  Which version of Cyrus are you using?

Currently it is 3.0.5, but I can upgrade if there were any related changes in the later versions. What I was observing is that if a PC (LibreOffice Calc on Ubuntu 16.04, the folder mounted with davfs2) crashes in the middle of saving a file on the server, the result was a damaged file: some 400 bytes instead of 3-4Mb of a real file.

I was thinking that maybe when the TCP stream hangs in the middle, Cyrus would interpret it as an end of data and write a file, but I've just tried to make some tests killing mount.davfs2 process and/or blocking the stream with iptables in the middle of file transmission and Cyrus responded correctly. For killing mount.davfs2 it showed in the corresponding log file the bytestream followed by:

HTTP/1.1 400 Bad Request

Unable to read body data

And for blocking the stream with iptables it was showing the bytestream ending where the transmission stopped, without the 400 Bad Request, but in both cases the original file was not modified by the partial upload. So it appears the problem is elsewhere.


Regards,
Anatoli

From: Ken Murchison
Sent: Thursday, November 15, 2018 14:09
To: Info-cyrus
Subject: Re: WebDAV folders internally have hundreds of copies of the same few files

On 11/15/18 1:48 AM, Anatoli wrote:

Hi Ken,

Thanks a lot for the clarification, everything makes sense now. How can I list the files marked for deletion and those that are not marked? unexpunge can provide the list of files marked for deletion, is there any better way to list them, directly reading the DB? How to list those that are not marked?

If you login as an admin, you should be able to SELECT the mailbox and use normal IMAP commands.  Alternatively, if you add "+DAV" to a regular userid, this will also allow SELECTing of DAV collection mailboxes.

One more question, related: we got a client who's PC was crashing exactly during the modify operation (some issue with the PC hardware triggered by Excel save operation, probably a RAM spike touching some bad blocks). As a result, the file in Cyrus was becoming damaged, i.e. partially saved. Is it expected?

Shouldn't Cyrus update the db with the pointer to the new file (a new message in the store) only if the operation completes successfully (e.g. the WebDAV messages exchange completes and the connection is closed at the right time or something similar)?

If the append of the resource into the mailbox, or updating the DAV db entry fails, the operation should be reverted, with partial saving done.  Which version of Cyrus are you using?

From: Ken Murchison
Sent: Wednesday, November 14, 2018 10:54
To: Info-cyrus
Subject: Re: WebDAV folders internally have hundreds of copies of the same few files

On 11/13/18 10:15 PM, Anatoli wrote:

Hi,

I'm not sure this is due to some configuration option, bug or feature, but I'm observing some folders on Cyrus HTTP WebDAV server having hundreds (995 at this moment to be precise) internal files in the format "NNN." that correspond to the same file but different versions in time.

There are 2-3 files (xls) in the folder that are edited constantly during the day and it looks like each save operation creates a new file. The files are of some 3-5Mb each. In the explorer/web view there are only a couple of files with a total size of 17.5Mb, but the reported disk usage for the folder is of 1.6Gb.

Could someone please shed some light on what's going on and how to make each file visible to the users to be stored in only one internal file?

Thanks,
Anatoli

Because *DAV is layered on top of an IMAP store, we have to abide by IMAP semantics in which messages (in this case DAV resources) are immutable.  Therefore, we can NOT overwrite an existing message in the mailbox.  Each change MUST result in a new message.  However, the server does mark the previous version(s) as deleted and expunged, which means that they will eventually be removed by cyr_expire.  If you aren't running cyr_expire, you should consider adding an event to cyrus.conf to remove expunged messages (see -X option).

-- 
Ken Murchison
Cyrus Development Team
FastMail US LLC

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FastMail US LLC

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FastMail US LLC

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