pool(3erl) Erlang Module Definition pool(3erl)
NAME
pool - Load distribution facility.
DESCRIPTION
This module can be used to run a set of Erlang nodes as a pool of com-
putational processors. It is organized as a master and a set of slave
nodes and includes the following features:
* The slave nodes send regular reports to the master about their cur-
rent load.
* Queries can be sent to the master to determine which node will have
the least load.
The BIF statistics(run_queue) is used for estimating future loads. It
returns the length of the queue of ready to run processes in the Erlang
runtime system.
The slave nodes are started with the slave(3erl) module. This effects
terminal I/O, file I/O, and code loading.
If the master node fails, the entire pool exits.
EXPORTS
attach(Node) -> already_attached | attached
Types:
Node = node()
Ensures that a pool master is running and includes Node in the
pool master's pool of nodes.
get_node() -> node()
Returns the node with the expected lowest future load.
get_nodes() -> [node()]
Returns a list of the current member nodes of the pool.
pspawn(Mod, Fun, Args) -> pid()
Types:
Mod = module()
Fun = atom()
Args = [term()]
Spawns a process on the pool node that is expected to have the
lowest future load.
pspawn_link(Mod, Fun, Args) -> pid()
Types:
Mod = module()
Fun = atom()
Args = [term()]
Spawns and links to a process on the pool node that is expected
to have the lowest future load.
start(Name) -> Nodes
start(Name, Args) -> Nodes
Types:
Name = atom()
Args = string()
Nodes = [node()]
Starts a new pool. The file .hosts.erlang is read to find host
names where the pool nodes can be started; see section Files.
The startup procedure fails if the file is not found.
The slave nodes are started with slave:start/2,3, passing along
Name and, if provided, Args. Name is used as the first part of
the node names, Args is used to specify command-line arguments.
Access rights must be set so that all nodes in the pool have the
authority to access each other.
The function is synchronous and all the nodes, and all the sys-
tem servers, are running when it returns a value.
stop() -> stopped
Stops the pool and kills all the slave nodes.
FILES
.hosts.erlang is used to pick hosts where nodes can be started. For in-
formation about format and location of this file, see
net_adm:host_file/0.
$HOME/.erlang.slave.out.HOST is used for all extra I/O that can come
from the slave nodes on standard I/O. If the startup procedure does not
work, this file can indicate the reason.
Ericsson AB stdlib 3.13 pool(3erl)