# Module lb_psv_simple

- Description
- Data Types
- Function Index
- Function Details

Simple passive load balancing sampling k nodes and choosing the one that reduces the standard deviation the most.

Copyright © 2010-2011 Zuse Institute Berlin

Version: $Id$

Behaviours: `lb_psv_beh`.

Authors: Nico Kruber (`kruber@zib.de`).

## Description

Simple passive load balancing sampling k nodes and choosing the one that reduces the standard deviation the most. Uses randomly sampled IDs.

## Data Types

### custom_message()

    custom_message() = none()

## Function Index

check_config/0 | Checks whether config parameters of the passive load balancing algorithm exist and are valid.
create_join/4 | Creates a join operation if a node would join at my node with the given key.
get_number_of_samples/1 | Gets the number of IDs to sample during join.
get_number_of_samples_remote/2 | Sends the number of IDs to sample during join to the joining node.
process_join_msg/3 |
sort_candidates/1 | Sorts all provided operations so that the one with the biggest change of the standard deviation is at the front.

## Function Details

### get_number_of_samples/1

    get_number_of_samples(Conn :: dht_node_join:connection()) -> ok

Gets the number of IDs to sample during join. Note: this is executed at the joining node.

### get_number_of_samples_remote/2

    get_number_of_samples_remote(SourcePid :: comm:mypid(),
                                 Conn :: dht_node_join:connection()) ->
                                    ok

Sends the number of IDs to sample during join to the joining node. Note: this is executed at the existing node.

### create_join/4

    create_join(DhtNodeState :: dht_node_state:state(),
                SelectedKey :: rt_chord:key(),
                SourcePid :: comm:mypid(),
                Conn :: dht_node_join:connection()) ->
                   dht_node_state:state()

Creates a join operation if a node would join at my node with the given key. This will simulate the join operation and return a lb_op() with all the data needed in sort_candidates/1. Note: this is executed at an existing node.

### sort_candidates/1

    sort_candidates(Ops :: [lb_op:lb_op()]) -> [lb_op:lb_op()]

Sorts all provided operations so that the one with the biggest change of the standard deviation is at the front. Note: this is executed at the joining node.

### process_join_msg/3

    process_join_msg(Msg :: comm:message(),
                     State :: any(),
                     DhtNodeState :: dht_node_state:state()) ->
                        unknown_event

### check_config/0

    check_config() -> boolean()

Checks whether config parameters of the passive load balancing algorithm exist and are valid.

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