Querying the Configuration File

This section details the utilities used to query the configuration file.

The tafc_properties Utility

tafc_properties displays the contents of the local configuration file. This is useful when determining if the file has been found and if it is correctly formatted.

tafc_properties displays sections and meta-section from the file but, unlike confchk, it does not display environment variables.

The confchk Utility

confchk compares parameters from the local configuration file with their equivalents on remote servers. Equality or inequality is checked for individual parameters or all parameters in a section.

Broadcast Mechanism

confchk discovers remote servers using a broadcast mechanism (actually UDP multicast). When a remote TAFC instance (see below) receives the broadcast it returns a reply containing the requested parameters.

ClosedTTL value

When a broadcast message is sent it contains a time to live (TTL) value. A detailed description of is beyond the scope of this document. Essentially this tells the network how many routers to pass the message through, before it is discarded. If all your servers are on the same subnet, then a TTL of 0 is sufficient.

TTL can be specified via the confchk command line.

NOTE: The higher TTL is set the more hops across the network multicast packets will be made, that is, the more machines will potentially try to become part of your named cluster. Therefore, keep TTL as low as possible. Whatever value TTL is set to broadcasts are not generally forwarded onto a WAN. It is not envisaged that clusters will span more that one site. If this is to be done, then some form of tunnelling will be required such that both sites are effectively part of the same LAN.
ClosedHow long to wait for replies?

Following a broadcast there is the question of how long to wait for replies. Have all the remote servers replied or are the requests or replies just travelling slowly across the network, hung up in router queues, being processed by the remote system, etc.?

By default, confchk waits for 5 seconds and then assumes all replies have arrived. This value is configurable through the command line.

ClosedFirewalls

A likely cause of confchk failure is the presence of a firewall on either the client or server. If this is suspected, then enable the multicast ports (currently 20003 and 20007) for UDP traffic.


Bookmark Name Actions
BACK

In this topic

Feedback
x

Are you sure you want to log-off?