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>
An: "ASSP development mailing list" <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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