diff options
Diffstat (limited to 'lib/stdlib/doc/src/pool.xml')
| -rw-r--r-- | lib/stdlib/doc/src/pool.xml | 148 |
1 files changed, 148 insertions, 0 deletions
diff --git a/lib/stdlib/doc/src/pool.xml b/lib/stdlib/doc/src/pool.xml new file mode 100644 index 0000000000..2b890352eb --- /dev/null +++ b/lib/stdlib/doc/src/pool.xml @@ -0,0 +1,148 @@ +<?xml version="1.0" encoding="latin1" ?> +<!DOCTYPE erlref SYSTEM "erlref.dtd"> + +<erlref> + <header> + <copyright> + <year>1996</year><year>2009</year> + <holder>Ericsson AB. All Rights Reserved.</holder> + </copyright> + <legalnotice> + The contents of this file are subject to the Erlang Public License, + Version 1.1, (the "License"); you may not use this file except in + compliance with the License. You should have received a copy of the + Erlang Public License along with this software. If not, it can be + retrieved online at http://www.erlang.org/. + + Software distributed under the License is distributed on an "AS IS" + basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See + the License for the specific language governing rights and limitations + under the License. + + </legalnotice> + + <title>pool</title> + <prepared></prepared> + <docno></docno> + <date></date> + <rev></rev> + </header> + <module>pool</module> + <modulesummary>Load Distribution Facility</modulesummary> + <description> + <p><c>pool</c> can be used to run a set of Erlang nodes as a pool + of computational processors. It is organized as a master and a + set of slave nodes and includes the following features:</p> + <list type="bulleted"> + <item>The slave nodes send regular reports to the master about + their current load.</item> + <item>Queries can be sent to the master to determine which node + will have the least load.</item> + </list> + <p>The BIF <c>statistics(run_queue)</c> is used for estimating + future loads. It returns the length of the queue of ready to run + processes in the Erlang runtime system.</p> + <p>The slave nodes are started with the <c>slave</c> module. This + effects, tty IO, file IO, and code loading.</p> + <p>If the master node fails, the entire pool will exit.</p> + </description> + <funcs> + <func> + <name>start(Name) -></name> + <name>start(Name, Args) -> Nodes</name> + <fsummary>>Start a new pool</fsummary> + <type> + <v>Name = atom()</v> + <v>Args = string()</v> + <v>Nodes = [node()]</v> + </type> + <desc> + <p>Starts a new pool. The file <c>.hosts.erlang</c> is read to + find host names where the pool nodes can be started. See + section <seealso marker="#files">Files</seealso> below. The + start-up procedure fails if the file is not found.</p> + <p>The slave nodes are started with <c>slave:start/2,3</c>, + passing along <c>Name</c> and, if provided, <c>Args</c>. + <c>Name</c> is used as the first part of the node names, + <c>Args</c> is used to specify command line arguments. See + <seealso marker="slave#start/2">slave(3)</seealso>.</p> + <p>Access rights must be set so that all nodes in the pool have + the authority to access each other.</p> + <p>The function is synchronous and all the nodes, as well as + all the system servers, are running when it returns a value.</p> + </desc> + </func> + <func> + <name>attach(Node) -> already_attached | attached</name> + <fsummary>Ensure that a pool master is running</fsummary> + <type> + <v>Node = node()</v> + </type> + <desc> + <p>This function ensures that a pool master is running and + includes <c>Node</c> in the pool master's pool of nodes.</p> + </desc> + </func> + <func> + <name>stop() -> stopped</name> + <fsummary>Stop the pool and kill all the slave nodes</fsummary> + <desc> + <p>Stops the pool and kills all the slave nodes.</p> + </desc> + </func> + <func> + <name>get_nodes() -> Nodes</name> + <fsummary>Return a list of the current member nodes of the pool</fsummary> + <type> + <v>Nodes = [node()]</v> + </type> + <desc> + <p>Returns a list of the current member nodes of the pool.</p> + </desc> + </func> + <func> + <name>pspawn(Mod, Fun, Args) -> pid()</name> + <fsummary>Spawn a process on the pool node with expected lowest future load</fsummary> + <type> + <v>Mod = Fun = atom()</v> + <v>Args = [term()]</v> + </type> + <desc> + <p>Spawns a process on the pool node which is expected to have + the lowest future load.</p> + </desc> + </func> + <func> + <name>pspawn_link(Mod, Fun, Args) -> pid()</name> + <fsummary>Spawn and link to a process on the pool node with expected lowest future load</fsummary> + <type> + <v>Mod = Fun = atom()</v> + <v>Args = [term()]</v> + </type> + <desc> + <p>Spawn links a process on the pool node which is expected to + have the lowest future load.</p> + </desc> + </func> + <func> + <name>get_node() -> node()</name> + <fsummary>Return the node with the expected lowest future load</fsummary> + <desc> + <p>Returns the node with the expected lowest future load.</p> + </desc> + </func> + </funcs> + + <section> + <marker id="files"></marker> + <title>Files</title> + <p><c>.hosts.erlang</c> is used to pick hosts where nodes can + be started. See + <seealso marker="kernel:net_adm#host_file/0">net_adm(3)</seealso> + for information about format and location of this file.</p> + <p><c>$HOME/.erlang.slave.out.HOST</c> is used for all additional IO + that may come from the slave nodes on standard IO. If the start-up + procedure does not work, this file may indicate the reason.</p> + </section> +</erlref> + |