Friday, September 3, 2021

[389-users] nsslapd-conntablesize & nsslapd-maxfiledescriptors

Given the current settings on a directory server I'm still seeing the errors below in the logs at peak times.

"ERR - setup_pr_read_pds - Not listening for new connections - too many fds open"

nsslapd-reservedescriptors: 64
nsslapd-maxdescriptors: 65535
nsslapd-conntablesize: 8192

At the OS level the ns-slapd process is set to 65535 as well.

Max open files            65535   

After reading the RHDS documentation it's a bit unclear as to how these parameters work together.

The conntablesize documentation states:

"The default value for nsslapd-conntablesize is the systems maxdescriptors which can be confiured using nsslapd-maxdescriptors"   

Now we look at the documentation for maxdescriptors:

The number of descriptors available for TCP/IP to serve client connections is determined by nsslapd-conntablesize, and is equal to the nsslapd-maxdescriptors attribute minus the number of file descriptors used by the server as specified in the nsslapd-reservedescriptors attribute for non-client connections, such as index management and managing replication. The nsslapd-reservedescriptors attribute is the number of file descriptors available for other uses as described above. 

Based on the numbers currently set does this mean no action needs to be taken as this implies maxdescriptors takes precedence over conntablesize?

Or should I set conntablesize to 65535-64 = 65471? nsslapd-conntablesize

This attribute sets the connection table size, which determines the total number of connections supported by the server.
The server has to be restarted for changes to this attribute to go into effect.
Parameter Description
Entry DN cn=config
Valid Values Operating-system dependent
Default Value The default value is the system's max descriptors, which can be configured using the nsslapd-maxdescriptors attribute as described in Section, "nsslapd-maxdescriptors (Maximum File Descriptors)"
Syntax Integer
Example nsslapd-conntablesize: 4093
Increase the value of this attribute if Directory Server is refusing connections because it is out of connection slots. When this occurs, the Directory Server's error log file records the message Not listening for new connections -- too many fds open.
A server restart is required for the change to take effect.


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