What is a parallel processing unit?
Web hosting packages have a limit on the number of parallel units that can be used to ensure the stable operation of the shared environment, so that no action taken by one host affects the others.
The parallel unit shows how many concurrent requests can be made against your web server. Additional information in our blog (in Estonian).
The limit of parallel units depends on the web hosting package, which is listed on our website under the detailed comparison of packages.
In the logs, the entries of the parallel processing units can be found under the Zunami name. You can also check the limit of the package in use at the end of the log line, for example (115/100).
ZunamiSoftRequestLimit
The number of connections allowed, above which activity is logged to the Apache log, but requests are not yet rejected and the next log entry remains:
[2024-01-01 00:00:00.000000] [vhost: domain.ee] [zunami:error] [pid: 12345] mod_zunami.c(341): [client: 123.123.123.123:12345] ZunamiSoftRequestLimit exceeded for 123456 (115/100)
ZunamiHardRequestLimit
Number of connections allowed before they are rejected. When the given limit is reached, an error message “503 – Service Temporarily Unavailable” is returned for the request and the following entry is left in the log:
[2024-01-01 00:00:00.000000] [vhost: domain.ee] [zunami:error] [pid: 12345] [client: 123.123.123.123:12345] ZunamiHardRequestLimit exceeded for 123456 (170/150)
There is no limit on the number of parallel units on the Managed CloudServer and Managed Dedicated Server.
ZunamiIpConnVHostsLimit
In addition to parallel processing units, the logs also contain entries for ZunamiIpConn and ZunamiIpConnVHostsLimit. Their purpose is to limit aggressive web scanner requests that simultaneously overload many different virtual hosts (main and subdomains located on the web server) with requests:
- A ZunamiIpConn message means that more than the allowed 100 simultaneous connections came from one IP address.
- The ZunamiIpConnVHostsLimit message means that more than the allowed 10 different hosts were connected from one IP address.
Requests that exceed the limit will receive a “429 – Too many requests” error message and the following entry will be left in the log:
[2024-01-01 00:00:00.000000] [vhost: domeen.ee] [zunami:error] [pid: 12345] [client: 123.123.123.123:12345] ZunamiIpConn exceeded for 123.123.123.123 (120/100)
[2024-01-01 00:00:00.000000] [vhost: domeen.ee] [zunami:error] [pid: 12345] [client: 123.123.123.123:12345] ZunamiIpConnVHostsLimit exceeded for 123.123.123.123 (11/10)
This example shows that an attempt was made to establish 120 connections (120/100) to 11 different web servers located on the virtual host (11/10).
ZunamiIpConn limits are the same regardless of the web hosting package.