Central state cache and update broker
Implements a hierarchal key-value store with publish/watch semanitics at each node of the hierarchy. Plans to support time-stamping, version stamping, real-time playback, security,
The hub holds a collection of dnodes (dictionary nodes). Each dictionary node is a key/value store, where the keys are atoms, and the values are any Erlang term. Sometimes the value is also a dnode, which results in a hierarchy.
Processes publish state on a hub, watch to state changes, request information about the state of the bus, and request changes to the state.
A hub is a process (a gen_server, actually) that holds state for the system, manages changes to state, and and routes notifications of changes of state.
The hub keeps a sequence ID for each change to state, and this is stored as part of the state graph, so that the hub can answer the question: "show me all state that has changed since sequence xxx"
** Limitations and areas for improvement **
Right now the store is only in memory, so a restart removes all data from the store. All persistence must be implemented separately (see HubStorage)
There is currently no change history or playback history feature.
[{key,val},{key,val}...]
if a value at any given path is a proplist (tested as a list whose first term is a tuple, or an empty list).
some special keys that can appear
mgr@ list of dependents in charge of point in graph wch@ list of dependents to be informed about changes
For convenience, you can pass in keys as atoms, but they will be converted to binary keys internally (all keys are stored as binaries). They will be represented as binary keys when returned. This behavior is under review so if you want to be sure, pass binary keys to begin with.
Basic Usage:
# Start the Hub GenServer
iex> Hub.start
{:ok, #PID<0.127.0>}
# Put [status: :online] at path [:some, :point]
iex(2)> Hub.put [:some,:point], [status: :online]
{:changes, {"05142ef7fe86a86D2471CA6869E19648", 1},
[some: [point: [status: :online]]]}
# Fetch all values at path [:some, :point]
Hub.fetch [:some, :point]
{{"05142ef7fe86a86D2471CA6869E19648", 1}, [status: :online]}
# Get particular value :status at [:some, :point]
Hub.get [:some, :point], :status
:onlineWe appreciate any contribution to Cellulose Projects, so check out our CONTRIBUTING.md guide for more information. We usually keep a list of features and bugs [in the issue tracker][2].
Building the documentation requires ex_doc to be installed. Please refer to their README for installation instructions and usage instructions.
The MIT License (MIT)
Copyright (c) 2014 Garth Hitchens
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
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