swarm

v3.4.0

swarm v3.4.0 Swarm.Distribution.Strategy behaviour

This module implements the interface for custom distribution strategies. The default strategy used by Swarm is a consistent hash ring implemented via the libring library.

Custom strategies are expected to return a datastructure or pid which will be passed along to any functions which need to manipulate the current distribution state. This can be either a plain datastructure (as is the case with the libring-based strategy), or a pid which your strategy module then uses to call a process in your own supervision tree.

For efficiency reasons, it is highly recommended to use plain datastructures rather than a process for storing the distribution state, because it has the potential to become a bottleneck otherwise, however this is really up to the needs of your situation, just know that you can go either way.

Link to this section Summary

Types

key()
nodelist()
reason()
strategy()
t()
weight()

Functions

add_node(strategy, node)

Adds a node to the state of the current distribution strategy

add_node(strategy, node, weight)

Adds a node to the state of the current distribution strategy, and give it a specific weighting relative to other nodes

add_nodes(strategy, nodes)

Adds a list of nodes to the state of the current distribution strategy. The node list can be composed of both node names (atoms) or tuples containing a node name and a weight for that node

create()
create(node)
key_to_node(strategy, node)

Maps a key to a specific node via the current distribution strategy

remove_node(strategy, node)

Removes a node from the state of the current distribution strategy

Callbacks

add_node(strategy, node)
add_node(strategy, node, weight)
add_nodes(strategy, nodelist)
create()
key_to_node(strategy, key)
remove_node(strategy, node)

Link to this section Types

Link to this type key() 
key() :: term()
Link to this type nodelist() 
nodelist() :: [node() | {node(), weight()}]
Link to this type reason() 
reason() :: String.t()
Link to this type strategy() 
strategy() :: term()
Link to this type weight() 
weight() :: pos_integer()

Link to this section Functions

Link to this function add_node(strategy, node)

Adds a node to the state of the current distribution strategy.

Link to this function add_node(strategy, node, weight)

Adds a node to the state of the current distribution strategy, and give it a specific weighting relative to other nodes.

Link to this function add_nodes(strategy, nodes)

Adds a list of nodes to the state of the current distribution strategy. The node list can be composed of both node names (atoms) or tuples containing a node name and a weight for that node.

Link to this function key_to_node(strategy, node)

Maps a key to a specific node via the current distribution strategy.

Link to this function remove_node(strategy, node)

Removes a node from the state of the current distribution strategy.

Link to this section Callbacks

Link to this callback add_node(strategy, node) 
add_node(strategy(), node()) :: strategy() | {:error, reason()}
Link to this callback add_node(strategy, node, weight) 
add_node(strategy(), node(), weight()) :: strategy() | {:error, reason()}
Link to this callback add_nodes(strategy, nodelist) 
add_nodes(strategy(), nodelist()) :: strategy() | {:error, reason()}
Link to this callback create() 
create() :: strategy() | {:error, reason()}
Link to this callback key_to_node(strategy, key) 
key_to_node(strategy(), key()) :: node() | :undefined
Link to this callback remove_node(strategy, node) 
remove_node(strategy(), node()) :: strategy() | {:error, reason()}