peerleader.markdown

layout	title	categories	published	alias	tags
default	peerleader	Reference Functions peerleader	true	reference-functions-peerleader.html	reference communication functions functions peerleader

Prototype: peerleader(filename, regex, groupsize)

Return type: string

Description: Returns the assigned peer-leader of the partition to which the current host belongs.

This function returns the name of a host that may be considered the leader of a group of peers of the current host. Peers are defined according to a list of hosts, provided as a file in filename. This file should contain a list (one per line), possibly with comments matching regex, of fully qualified host names. CFEngine breaks up this list into non-overlapping groups of up to groupsize, each of which has a leader that is the first host in the group.

The current host should belong to this file if it is expected to interact with the others. The function returns nothing if the host does not belong to the list.

Arguments:

• filename : File name of host list, in the range "?(/.*)

A path to a file containing the list of hosts.

• regex : Comment regex pattern, in the range .*

A pattern that matches a legal comment in the file. The regex is [unanchored][unanchored], meaning it may match a partial line. Comments are stripped as the file is read.

• arg3 : Peer group size, in the range 0,99999999999

A number between 2 and 64 which represents the number of peers in a peer-group. An arbitrary limit of 64 is set on groups to avoid nonsensical promises.

Example:

Example file:

     one
     two
     three # this is a comment
     four
     five
     six
     seven
     eight
     nine
     ten
     eleven
     twelve
     etc

    bundle agent peers
    {
    vars:

      "mygroup" slist => peers("/tmp/hostlist","#.*",4);

      "myleader" string => peerleader("/tmp/hostlist","#.*",4);

      "all_leaders" slist => peerleaders("/tmp/hostlist","#.*",4);

    reports:

       "mypeer $(mygroup)";
       "myleader $(myleader)";
       "another leader $(all_leaders)";
    }