Automatic flushing of the jnl files

[Eric.BERTHIA...@banque-france.fr]

Hello bind-users,

 

Tried to find the info on my own but couldn’t get accurate understanding of jnl files flushing mechanism.

 

Bind-9.10.0-02.P2

RHEL 5.7

Master DNS server, Chrooted env, receiving updates via nsupdate.

 

Maybe I didn’t catch the memo but I thought the standard way bind handled the dynamic journal (.jnl) files was this way:

 

All changes made to a zone using dynamic update are written to the zone's journal file. The server will periodically flush the complete contents of the updated zone to its zone file this happens approximately every 15 minutes.  NOTE this is from zytrax.com dns documentation so I’m pretty sure this is not from bind 9.10

 

Doesn’t seem to be the case right now and I’m wondering if my server conf is to blame.

 

I’m able to sync to flat files using rndc:

 

rndc sync –clean

 

That I see in my logs:

 

named[3001]: received control channel command 'sync -clean'

named[3001]: dumping all zones, removing journal files: success

 

But the next day I’m seeing tons of jnl files again.  From updates of course.

 

I do have these journal messages in my logs:

 

general: debug 1: zone XX.128.in-addr.arpa/IN: journal rollforward completed successfully: no journal

general: debug 3: no journal file, but that's OK

general: debug 1: zone XX.XX.10.in-addr.arpa/IN: journal rollforward completed successfully: no journal

general: debug 3: no journal file, but that's OK

general: debug 1: zone XX.XX.10.in-addr.arpa/IN: journal rollforward completed successfully: no journal

general: debug 3: no journal file, but that's OK

general: debug 1: zone XX.168.192.in-addr.arpa/IN: journal rollforward completed successfully: no journal

 

So it it does seem to be rolling the changes but jnl files still persist.  It’s not terribly bothering but I would like to know if this is the normal behavior.

 

I do not have dnssec-enable of managed-keys-directory set in named.conf

 

Thanks for your help.

 

E. Berthiaume

 

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[Phil Mayers]

On 21/01/15 15:46, Eric.BERTHIA...@banque-france.fr wrote:

> So it it does seem to be rolling the changes but jnl files still
> persist. It’s not terribly bothering but I would like to know if this
> is the normal behavior.

It's normal. The .jnl files contain the data required to perform
incremental outbound zone transfers.

[Howard, Christopher]

The journal files get flushed to the zone file periodically, but old
transactions don't get removed so the journal file will continue to grow
forever. If you're like me and on virtual machines with limited hard disk
capacity, you can limit the journal file size with the max-journal-size
configuration statement. Just make sure that the size is large enough to
hold all of the transactions between flushes (I believe that's around
every 15 minutes). Otherwise, after a crash you would be missing records.

-Christopher

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[Chris Thompson]

On Jan 21 2015, Howard, Christopher wrote:

>The journal files get flushed to the zone file periodically, but old
>transactions don't get removed so the journal file will continue to grow
>forever. If you're like me and on virtual machines with limited hard disk
>capacity, you can limit the journal file size with the max-journal-size
>configuration statement. Just make sure that the size is large enough to
>hold all of the transactions between flushes (I believe that's around
>every 15 minutes). Otherwise, after a crash you would be missing records.

I am fairly sure you are wrong on that last point. BIND will not flush
journal file entries that have not yet been committed to the master file,
even if they make the journal bigger than max-journal-size. If you specify
"max-journal-size 512;" you will find the journal gets emptied completely,
but only after the master file has been updated. (Of course, as Phil Mayers
points out, this would cause downstream IXFRs to become AXFRs,)

--
Chris Thompson
Email: ce...@cam.ac.uk

[Howard, Christopher]

Oh, well that's good to know. :)

-Christopher

[Tony Finch]

I got annoyed by having to manually tune max-journal-size so I had a hack
at the problem:

https://git.csx.cam.ac.uk/x/ucs/ipreg/bind9.git/commitdiff/c8f083b797f9810f

Tony.
--
f.anthony.n.finch <d...@dotat.at> http://dotat.at/
Viking: Southeast, veering south or southwest later, 4 or 5, increasing 6 at
times. Moderate or rough. Wintry showers. Good, occasionally poor.

[Bob Harold]

I like that solution. 

I assume that "twice the zone file size" is because half of the entries are deletes?  Do deletes get sent in IXFR?  Or is it that typically half of the journal entries are SOA records?

I just took a peek at my journal files and I see one that is 100 times the zone file size.  I wish the entries had dates, even if just as a comment - it would be a good log of changes, and I would be able to see how far back in history the journal went.

--
Bob Harold
hostmaster, UMnet, ITcom
Information and Technology Services (ITS)
rhar...@umich.edu
734-647-6524 desk

[Tony Finch]

Yes, an IXFR is a series of deletes and adds, which both quote whole records. If you re-sign a zone the IXFR can be nearly twice what an AXFR would be! But in fact the factor of two in my patch comes from the journal compaction logic, which halves the size of the journal. So my patch allows the journal to oscillate between the size of the zone and twice that. Smaller journals may mean you have to AXFR when IXFR would be better.

If you use serial-update-method unixtime or date-based serial numbers then you might be able to get the information you want from the journal.

Tony.
--
f.anthony.n.finch <d...@dotat.at> http://dotat.at

[Stuart Browne]

Bob,

Some date and record number details from one of my systems, with 'max-journal-size: 100m'. Yes, I've changed the zone names.. ;)

NOTE: Add/Del numbers show total / non-dnssec-or-soa related update numbers.

'zone1' is a monitoring test zone that has sub-zone delegation changes a few times a minute:
dnssec signed: Yes, NSEC3 with Optout
zone1 size: 127k
one1.jnl size: 63M
date now: Wed Jan 21 22:12:15 UTC 2015
oldest jnl soa: Tue Jan 20 20:42:29 UTC 2015
total records: 1,233
no. SOA del's: 52,964
no. del's: 236,556 / 79,716
no. add's: 236,604 / 79,713

'zone2' is a public delegation zone that changes as customers demand:
dnssec signed: Yes, NSEC3 with Optout
zone2 size: 176M
zone2.jnl size: 100M
date now: Wed Jan 21 22:15:15 UTC 2015
oldest jnl soa: Fri Dec 19 17:22:20 UTC 2014
total records: 5,917,482
no. SOA del's: 138,752
no. del's: 456,870 / 172,427
no. add's: 478,940 / 194,541

'zone3' is a public authoritative zone that rarely changes:
dnssec signed: Yes, NSEC3 with Optout
zone3 size: 1.6M
zone3.jnl size: 69M
date now: Wed Jan 21 22:27:53 UTC 2015
oldest jnl soa: Mon Oct 27 21:19:38 UTC 2014
total records: 6,984
no. SOA del's: 35,144
no. del's: 175,832 / 0
no. add's: 175,832 / 0

So the journal files can live for quite a while ;)

Stuart

[Eric.BERTHIA...@banque-france.fr]

Thanks all for your replies.  Lots of interesting information!

 

I’ll keep a eye out for those jnl files.

 

Thanks again!

 

E. Berthiaume