Re: [Moosefs-users] changelogs on the metalogger

[Michał B. <mic...@ge...>]

Hello again

Your changelog_ml.0.mfs never got filled? Saving in metalogger takes place
by using write buffer which is flushed by the operating system. This is much
quicker. It also means that in case of metalogger failure it will be missing
some recent changes. But in case of master failure, after shutting down the
metalogger process, system would write all data waiting in the buffer and
metadata file on metalogger machine would be complete.

We've made automatic data flushing every second which won't affect
performance but possilby this behaviour would be more clear to users.


Kind regards
Michał 

-----Original Message-----
From: Bán Miklós [mailto:ba...@vo...] 
Sent: Monday, September 06, 2010 4:16 PM
To: moo...@li...
Subject: Re: [Moosefs-users] changelogs on the metalogger



On Mon, 6 Sep 2010 13:42:30 +0200
Michał Borychowski <mic...@ge...> wrote:

> Hi!
> 
> Metaloggers should continuously receive the current changes from the
> master server and write them into its own text change logs named
> changelog_ml.0.mfs. 
> 
> How do you know that in your system they are save hourly? Don't they
> increment with every change in the filesystem?

Yes, exactly. There is no new lines on metalogger server's
changelog_ml.0.mfs, while the master's changelog.0.mfs updating.
Nevertheless the sessions_ml.mfs is updating continuously.
My server version is 1.6.7 and it is running on Ubuntu Jaunty.

Here is a short log part from a metalogger:
Sep  6 14:02:00 fekete mfsmetalogger[30553]: sessions downloaded
2374B/0.000435s (5.457 MB/s) Sep  6 14:02:02 fekete
mfschunkserver[30562]: testing
chunk: /mnt/mfs_hd1/09/chunk_0000000000000009_00000001.mfs Sep  6
14:02:12 fekete mfschunkserver[30562]: testing
chunk: /mnt/mfs_hd1/0C/chunk_000000000000000C_00000001.mfs Sep  6
14:02:22 fekete mfschunkserver[30562]: testing
chunk: /mnt/mfs_hd1/0E/chunk_000000000000000E_00000001.mfs Sep  6
14:02:32 fekete mfschunkserver[30562]: testing
chunk: /mnt/mfs_hd1/10/chunk_0000000000000010_00000001.mfs Sep  6
14:02:42 fekete mfschunkserver[30562]: testing
chunk: /mnt/mfs_hd1/0A/chunk_000000000000000A_00000001.mfs Sep  6
14:02:52 fekete mfschunkserver[30562]: testing
chunk: /mnt/mfs_hd1/0F/chunk_000000000000000F_00000001.mfs Sep  6
14:03:00 fekete mfsmetalogger[30553]: sessions downloaded
2374B/0.000570s (4.165 MB/s)


> 
> Regarding your second question - yes, this is right. For now,
> metalogger doesn't download the metadata file upon starting. We know
> about this shortcoming and we'll fix the behaviour soon.
> 
> 

Thanx.

&Miklos

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