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Paul B. Henson

2011-Sep-10 02:33 UTC

[Dovecot] mysql auth failover failing

We are running dovecot to provide authentication for postfix, using two 
mysql servers in a multi-master replication set as the password source:

----------------------------------------
# 2.0.13: /etc/dovecot/dovecot.conf
# OS: Linux 2.6.37-gentoo-r4 x86_64 Gentoo Base System release 2.0.2
auth_mechanisms = plain login digest-md5 cram-md5
auth_verbose = yes
passdb {
   args = /etc/dovecot/dovecot-sql.conf
   driver = sql
}
protocols = none
service auth-worker {
   unix_listener auth-worker {
     user = postfix
   }
   user = $default_internal_user
}
service auth {
   unix_listener /var/spool/postfix/private/auth {
     group = postfix
     mode = 0660
     user = postfix
   }
   user = postfix
}
ssl = no
userdb {
   driver = passwd
}
---------------------------------------

With an sql config of:

-------------------------
driver = mysql
connect = host=mysql-1.unx.csupomona.edu host=mysql-2.unx.csupomona.edu 
dbname=idmgmt user=postfix password=XXXXXXX
default_pass_scheme = PLAIN
password_query = XXXXXXXXX
-------------------------

According to the sample SQL configuration file "HA / round-robin 
load-balancing is supported by giving multiple host settings, like: 
host=sql1.host.org host=sql2.host.org".

However, as far as I can tell dovecot only connects to the first listed 
host, and processes all queries through it, there does not appear to be 
any load-balancing going on.

That's not necessarily a dealbreaker; however, high-availability does 
not appear to be working either.

If I shutdown the first mysql server, dovecot starts to log connection 
failures:

Sep  9 15:47:34 tweak dovecot: auth: Error: 
mysql(mysql-1.unx.csupomona.edu): Connect failed to database (idmgmt): 
Can't connect to MySQL server on 'mysql-1.unx.csupomona.edu' (111) -
waiting for 1 seconds before retry

Sep  9 15:47:39 tweak dovecot: auth: Error: 
mysql(mysql-1.unx.csupomona.edu): Connect failed to database (idmgmt): 
Can't connect to MySQL server on 'mysql-1.unx.csupomona.edu' (111) -
waiting for 25 seconds before retry

And postfix starts to fail authentications:

Sep  9 15:47:35 tweak postfix/smtpd[5119]: warning: 
bender.iitsys.csupomona.edu[134.71.250.134]: SASL DIGEST-MD5 
authentication failed: Connection lost to authentication server

Now and again the authentication process dies:

Sep  9 15:47:39 tweak dovecot: auth: Panic: file auth-request-handler.c: 
line 697 (auth_request_handler_flush_failures): assertion failed: 
(auth_request->state == AUTH_REQUEST_STATE_FINISHED)
Sep  9 15:47:39 tweak dovecot: auth: Error: Raw backtrace: 
/usr/lib64/dovecot/libdovecot.so.0(+0x3f71a) [0x7f25822ca71a] -> 
/usr/lib64/dovecot/libdovecot.so.0(+0x3f766) [0x7f25822ca766] -> 
/usr/lib64/dovecot/libdovecot.so.0(+0x198ca) [0x7f25822a48ca] -> 
dovecot/auth() [0x4137f4] -> 
/usr/lib64/dovecot/libdovecot.so.0(io_loop_handle_timeouts+0xd4) 
[0x7f25822d5fe4] -> 
/usr/lib64/dovecot/libdovecot.so.0(io_loop_handler_run+0x5b) 
[0x7f25822d6bcb] -> /usr/lib64/dovecot/libdovecot.so.0(io_loop_run+0x28) 
[0x7f25822d5c48] -> 
/usr/lib64/dovecot/libdovecot.so.0(master_service_run+0x13) 
[0x7f25822c3de3] -> dovecot/auth(main+0x2be) [0x4179de] -> 
/lib64/libc.so.6(__libc_start_main+0xfd) [0x7f2581898bbd] -> 
dovecot/auth() [0x40bdc9]
Sep  9 15:47:39 tweak dovecot: master: Error: service(auth): child 4154 
killed with signal 6 (core dumps disabled)

Requests start to pile up:

Sep  9 15:51:46 tweak dovecot: auth: Warning: auth workers: Auth request 
was queued for 25 seconds, 45 left in queue

Lookups time out:

Sep  9 15:57:22 tweak dovecot: auth: Error: auth worker: Aborted 
request: Lookup timed out

This occasionally pops up:

Sep  9 15:58:38 tweak dovecot: auth: Fatal: 
net_connect_unix(auth-worker) failed: Resource temporarily unavailable

And sometimes the auth process gets temporarily disabled:

Sep  9 15:58:57 tweak dovecot: master: Error: service(auth): command 
startup failed, throttling

Resulting in more postfix authentication failures:

Sep  9 15:58:57 tweak postfix/smtpd[6531]: warning: 
bender.iitsys.csupomona.edu[134.71.250.134]: SASL DIGEST-MD5 
authentication failed:
Sep  9 15:59:08 tweak postfix/smtpd[6551]: fatal: no SASL authentication 
mechanisms

To the point where postfix also temporarily throttles smtpd:

Sep  9 15:59:21 tweak postfix/master[6526]: warning: 
/usr/lib64/postfix/smtpd: bad command startup -- throttling

Resulting in a complete unavailability of smtp service, not just 
unavailability of authenticated services.


I don't think all authentications fail during the scenario, but I think 
the majority do. Based on the network traffic, dovecot is almost 
continuously trying to connect to the first listed server. It sometimes 
connects to the second listed server, but when it does, the connection 
does not persist, it goes away almost immediately.


Ideally, I would like no authentications to fail if one of the MySQL 
servers is unavailable. If a few fail just when the server dies, that 
would be undesirable but acceptable as long as they do not continuously 
fail while the server is down.

Am I doing something wrong? Does the example sql config have incorrect 
information?

We were previously running dovecot 1.2.11, we just recently upgraded to 
2. In the previous version, we actually had two different passdb's 
configured, each one listing only one of the mysql servers. I seem to 
recall that was the recommendation at the time for high-availability. 
When that configuration did not seem to work under version 2, I found an 
updated recommendation to list both servers in the same passdb, which 
also does not appear to work correctly. I actually went back and tested 
the older version, and determined it seemed to work okay in the case 
where the server was up but the service was down, and connections were 
refused, but also failed a large number of authentication attempts when 
the server was completely down and connections were timing out.

Thanks much...

-- 
Paul B. Henson  |  (909) 979-6361  |  http://www.csupomona.edu/~henson/
Operating Systems and Network Analyst  |  henson at csupomona.edu
California State Polytechnic University  |  Pomona CA 91768

Noel Butler

2011-Sep-10 03:02 UTC

head link

[Dovecot] mysql auth failover failing

On Fri, 2011-09-09 at 19:33 -0700, Paul B. Henson wrote:


> default_pass_scheme = PLAIN
Uhg i'll pretend I didnt see that  :)


> 
> According to the sample SQL configuration file "HA / round-robin 
> load-balancing is supported by giving multiple host settings, like: 
> host=sql1.host.org host=sql2.host.org".
> 
> However, as far as I can tell dovecot only connects to the first listed 
> host, and processes all queries through it, there does not appear to be 
> any load-balancing going on.
> 


I suspect the wording here is incorrect, its just a failover AFAIK, it
only hits the first entry failing to second if no response.
HA would be like running a mysql slave on all the front ends failing
over to the master on your CRM server etc, which is what I do and
suggest, having just one master server, after all, dovecot and postfix
just need to read, not alter/update/insert etc.

> That's not necessarily a dealbreaker; however, high-availability does 
> not appear to be working either.
> 
> If I shutdown the first mysql server, dovecot starts to log connection 
> failures:
> 
> Sep  9 15:47:34 tweak dovecot: auth: Error: 
> mysql(mysql-1.unx.csupomona.edu): Connect failed to database (idmgmt): 
> Can't connect to MySQL server on 'mysql-1.unx.csupomona.edu'
(111) -
> waiting for 1 seconds before retry
> 
> Sep  9 15:47:39 tweak dovecot: auth: Error: 
> mysql(mysql-1.unx.csupomona.edu): Connect failed to database (idmgmt): 
> Can't connect to MySQL server on 'mysql-1.unx.csupomona.edu'
(111) -
> waiting for 25 seconds before retry
> 

yep thats correct because it has " gone away" but it still uses the
second host immediately, thats just dovecot trying to re-establish its
link with primary
> And postfix starts to fail authentications:
> 

err postfix is not dovecot, you need to also add failover in postfix's
sql lookup commands
hosts = unix:/var/run/mysql/mysql.sock 10.10.10.2   (assuming .2 is your
master sql server)


> 
> Resulting in a complete unavailability of smtp service, not just 
> unavailability of authenticated services.
> 

You could have a higher sec mx smtp box that uses postfix for virtual
transport for cases of if dovecot is unavailable, this of course means
storing partial paths in your mail db, for use only by that one
non-behind-load-balancer separated sec mx, of course this wont solve
users issue of sending unless you have multiple smtp behind a load
balancer, but allows for inbound still, depends on how big your setup
(and budget) is or can be :)

(note: I talk of load balancer as in real hardware device, not as in
pretend LB's as in software)

> Does the example sql config have incorrect 
> information?
> 

I suspect so.


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Paul B. Henson

2011-Sep-10 03:16 UTC

head link

[Dovecot] mysql auth failover failing

On Fri, Sep 09, 2011 at 08:02:57PM -0700, Noel Butler wrote:
 > Uhg i'll pretend I didnt see that  :)
We only use dovecot to provide sasl authentication to postfix smtp clients,
using a separate password just for that purpose. Storing it in plaintext
is the only way to support all authentication types.
> I suspect the wording here is incorrect, its just a failover AFAIK, it
> only hits the first entry failing to second if no response.
Hmm, that would work for me, if it worked ;).
> suggest, having just one master server, after all, dovecot and postfix
> just need to read, not alter/update/insert etc.
True; but the pieces that are altering/updating/inserting the data that
postfix/dovecot need to read need redundancy as well :).
 > yep thats correct because it has " gone away" but it still uses
the
> second host immediately, thats just dovecot trying to re-establish its
> link with primary
Based on my testing, it doesn't use the second host immediately, but
only sporadically, with most of the authentications failing.
 > err postfix is not dovecot, you need to also add failover in postfix's
> sql lookup commands
postfix relies on dovecot for authentication, this postfix error message
is the result of dovecot not successfully processing an authentication
request. postfix itself handles mysql failure well, it both load
balances queries across both servers and also continues to function when
one isn't available.
> (note: I talk of load balancer as in real hardware device, not as in
> pretend LB's as in software)
We actually have a hardware load balancer, and I've considered just
sticking the mysql servers behind it. But everything else using them
handles failover ok, and initially I'd rather get dovecot doing the same
before changing the current architecture.

Thanks for the reply...


-- 
Paul B. Henson  |  (909) 979-6361  |  http://www.csupomona.edu/~henson/
Operating Systems and Network Analyst  |  henson at csupomona.edu
California State Polytechnic University  |  Pomona CA 91768

Timo Sirainen

2011-Sep-12 12:30 UTC

head link

[Dovecot] mysql auth failover failing

On Fri, 2011-09-09 at 19:33 -0700, Paul B. Henson wrote:
> According to the sample SQL configuration file "HA / round-robin 
> load-balancing is supported by giving multiple host settings, like: 
> host=sql1.host.org host=sql2.host.org".
> 
> However, as far as I can tell dovecot only connects to the first listed 
> host, and processes all queries through it, there does not appear to be 
> any load-balancing going on.
The current code creates connection to the second server only when the
first connection is already busy with an SQL query, or when it's not
working. Once there are more connections, it starts doing round robin
lookups.

This works okay enough with PostgreSQL because it does asynchronous
lookups, so two simultaneous lookups create a second connection. MySQL
does synchronous lookups though, so the second connection is normally
never created.

I suppose the fix to this would be to always connect to all SQL servers
at startup.
> That's not necessarily a dealbreaker; however, high-availability does 
> not appear to be working either.
> 
> If I shutdown the first mysql server, dovecot starts to log connection 
> failures:
> 
> Sep  9 15:47:34 tweak dovecot: auth: Error: 
> mysql(mysql-1.unx.csupomona.edu): Connect failed to database (idmgmt): 
> Can't connect to MySQL server on 'mysql-1.unx.csupomona.edu'
(111) -
> waiting for 1 seconds before retry
> 
> Sep  9 15:47:39 tweak dovecot: auth: Error: 
> mysql(mysql-1.unx.csupomona.edu): Connect failed to database (idmgmt): 
> Can't connect to MySQL server on 'mysql-1.unx.csupomona.edu'
(111) -
> waiting for 25 seconds before retry
Those are intentional.
> And postfix starts to fail authentications:
> 
> Sep  9 15:47:35 tweak postfix/smtpd[5119]: warning: 
> bender.iitsys.csupomona.edu[134.71.250.134]: SASL DIGEST-MD5 
> authentication failed: Connection lost to authentication server
It should have created the second connection here and not fail..
> Now and again the authentication process dies:
> 
> Sep  9 15:47:39 tweak dovecot: auth: Panic: file auth-request-handler.c: 
> line 697 (auth_request_handler_flush_failures): assertion failed: 
> (auth_request->state == AUTH_REQUEST_STATE_FINISHED)
And this of course shouldn't happen either.
> Requests start to pile up:
> 
> Sep  9 15:51:46 tweak dovecot: auth: Warning: auth workers: Auth request 
> was queued for 25 seconds, 45 left in queue
> 
> Lookups time out:
> 
> Sep  9 15:57:22 tweak dovecot: auth: Error: auth worker: Aborted 
> request: Lookup timed out
These are the result of the previous failures.
> This occasionally pops up:
> 
> Sep  9 15:58:38 tweak dovecot: auth: Fatal: 
> net_connect_unix(auth-worker) failed: Resource temporarily unavailable
Probably this too.
> And sometimes the auth process gets temporarily disabled:
> 
> Sep  9 15:58:57 tweak dovecot: master: Error: service(auth): command 
> startup failed, throttling
Most likely related to the crash, although I think this still shouldn't
have happened.
> I don't think all authentications fail during the scenario, but I think
> the majority do. Based on the network traffic, dovecot is almost 
> continuously trying to connect to the first listed server. It sometimes 
> connects to the second listed server, but when it does, the connection 
> does not persist, it goes away almost immediately.
There are multiple auth-worker processes, each one having their own
internal MySQL connections with separate retry counters.

I'll try to debug this soon.

Timo Sirainen

2011-Sep-15 10:53 UTC

head link

[Dovecot] mysql auth failover failing

On Fri, 2011-09-09 at 19:33 -0700, Paul B. Henson wrote:
> Sep  9 15:47:34 tweak dovecot: auth: Error: 
> mysql(mysql-1.unx.csupomona.edu): Connect failed to database (idmgmt): 
> Can't connect to MySQL server on 'mysql-1.unx.csupomona.edu'
(111) -
> waiting for 1 seconds before retry
I did several fixes related to this in v2.0 hg.
> And postfix starts to fail authentications:
> 
> Sep  9 15:47:35 tweak postfix/smtpd[5119]: warning: 
> bender.iitsys.csupomona.edu[134.71.250.134]: SASL DIGEST-MD5 
> authentication failed: Connection lost to authentication server
The reason why it kept failing with Postfix was because Dovecot had 10
second timeout for SQL connecting, and Postfix had 10 second timeout
before failing authentication. So Postfix never waited long enough for
Dovecot to attempt a second connection to the second MySQL server. I
dropped Dovecot's SQL connect timeout to 5 seconds.
> Now and again the authentication process dies:
> 
> Sep  9 15:47:39 tweak dovecot: auth: Panic: file auth-request-handler.c: 
> line 697 (auth_request_handler_flush_failures): assertion failed: 
> (auth_request->state == AUTH_REQUEST_STATE_FINISHED)
This happened only with non-plaintext authentication (e.g. DIGEST-MD5).
Fixed also.

Robert Schetterer

2011-Sep-15 12:11 UTC

head link

[Dovecot] mysql auth failover failing

Am 15.09.2011 13:43, schrieb Timo Sirainen:> On Thu, 2011-09-15 at 13:39 +0200, Robert Schetterer wrote:
>>
>> is there really a native failover mysql in dovecot ?
>> cant remember this , i only remember this as part of dovecot proxiing
> 
> For SQL authentication it can use multiple SQL server hosts (with both
> MySQL and PostgreSQL) and do HA/load balancing.
> 
> ok, i see, but i have nearly all possible parameters
in mysql ( i use  a mysql cluster ), thx anyway for answer

-- 
Best Regards

MfG Robert Schetterer

Germany/Munich/Bavaria

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