Hi Thomas,
Thank you for the input – I do recall previously discussing ISP mode and
realising that it was for bigger deployments than ours.
We have three servers. Two handling inbound and one specifically for Office 365
relaying. The two inbound probably do about 50,000 messages per day between
them according to infostats.
CPU Usage on both frontends is 1.62% avg and 1.49% avg respectively. I only
have a single MySQL db (general load average is around 0.1 ) and I’ve been
watching the hypervisor reports on its performance. I did set up a Gluster sync
between the two frontends so they have access to the same corpus without having
to do it over the network – that helped with performance however I’ve never
been able to get the rebuild run to be particularly quick (Last night’s was
total processing time 7,663 seconds, data 486.61 Mbyte). I haven’t brought it
up here because it doesn’t really have much of an effect and it is likely in my
setup rather than an ASSP issue.
So I think I’ll get away with it on my setup, hopefully this information will
be helpful to other people who are trying to figure out if they’ll be impacted.
All the best,
Colin Waring.
From: Thomas Eckardt [mailto:thomas.ecka...@thockar.com]
Sent: 05 January 2018 13:49
To: ASSP development mailing list <assp-test@lists.sourceforge.net>
Subject: Re: [Assp-test] Meltdown/Spectre
I remember an ISP issue, who used 10 assp instances with one enterprise MySQL
backend cluster, sharing all tables for all instances.
In havy workload times (100.000 or even more mails per hour), the MySQL server
was brought to its end - no matter how many physical resouces were made
available. Even holding the complete assp DB in the DB-server RAM has not
solved the problem.
With 100.000 mails per hour and ~50 DB queries per mail (HMMdb and spamDB),
the DB server has to process at least 5 million queries in one hour.
If we exclude HMMdb and spamDB, depending on the configuration, there can be
additionaly 10 to 20 DB queries per mail (for all the other DB-tables). Even
this can lead in to a very high DB workload!
The URIBL-check can also be very resource expensive (read and write !!!).
Assume a mail with 100 different URIs is seen the first time - 100
unsuccessfull cache DB-queries, followed by 100 DNS queries, followed by 100
cache DB-writes.
To prevent this issue, assp V2 has a buildin ISP mode for HMMdb and spamDB.
In short:
- the corpus of all instances is synchronized to a master instance (rsync for
example)
- HMMdb and spamDB are hold in memory in each instance and each worker
- HMMdb and spamDB are build on the master system and are distributed as files
to all other instances using an external script (methode of your choice)
- all other tables are shared traditionaly - but each instance uses a
configurable DB cache to prevent repeated DB-queries for the same results (for
example IP checks, helo ....)
This ISP mode requires at least 16GB RAM per instance, if a maximum of 15 SMTP
workers is used. Using more than 15 workers in an instance, produces a large
overhead without any performance improvement.
Collin, I don't know the workload and configuration of your systems - but the
math is simple.
An possible solution between the standard mode and the ISP mode can be:
- each assp instance has its own DB backend
- all DB-backends are bidirectional synchronized (asynchron) to a
DB-master-server-cluster
Depending on the overall workload, the DB-master-server-cluster must be an
enterprise cluster or something like that.
If we assume 10 assp instances, each record change in one instance will lead in
to one store and nine write sync ops at the master cluster!
If we assume five DB-write ops per mail -> 100 000 mail/h in all instances ->
500 000 store ops/h + 4.5M sync ops/h at the master cluster.
Yes - the workload at the cluster will be very high, but it is no longer time
critical and will balance over all the time.
The disadvantage is, that the tables in all instances are never 100% sychron
and the last instance "winns" in writing the same DB-record. The async state of
the tables in all DB-backends increases with the overall workload.
You may also think about a ring synchronization between the 10 assp
DB-backends. The cluster will not be required and the DB-backends will have a
manageable workload - but the delay of syncing a single record and the data
inconsitency over all instances will be increased.
Thomas
Von: "Colin Waring"
<co...@dolphinict.co.uk<mailto:co...@dolphinict.co.uk>>
An: "ASSP development mailing list"
<assp-test@lists.sourceforge.net<mailto:assp-test@lists.sourceforge.net>>
Datum: 05.01.2018 10:45
Betreff: [Assp-test] Meltdown/Spectre
________________________________
Hi All,
I’m wondering if anyone has updated their ASSP/db backends and monitored the
performance impact yet.
I’m currently working on assessing just how bad this is going to be with how
many systems I’ve got to coordinate hypervisor/OS/microcode updates on so I’m
checking around with everyone to see who’s already got some answers.
All the best,
Colin Waring.
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