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* docs: Update README to match new version. * docs: Update events example to use new API. * docs: Correctly print out db query results. * test: Remove concurrent. * test: Remove unimplemented and 3rd party AC tests. * test: Remove unimplemented and 3rd party identity tests. * docs: Move jsdoc config to conf directory. * Point package.json main at index.js to access all exported functions. * docs: Vetted AC docs; these examples should work if implemented in code. Explicitly show orbit-db function imports. * docs: Fix incorrectly declared write objects. * docs: Improved canAppend documentation. Better JS syntax highlighting. * docs: wss and define filters for localhost separately. * docs: Simplified webSockets implementation with filters. * docs: Return manifest json only (no hash). JS highlighting. * docs: Remove operations documentation. * docs: Update heading levels. * docs: Differentiate between db types which expose put/add function. * docs: Correctly import IPFS and pass config. * docs: A simple method for full db replication. * docs: Link to existing examples of db implementation. * docs: Update heading. * docs: JS code formatting. import statements. * docs: Expand on the concepts of identities and identity management. * docs: Describe head sync-ing and full replication. * docs: Comprehensive explanation of setting up a db and sync-ing/replicating data across peers. Examples can be run in node.js. * docs: Syntax highlighting. Correct code implementation for custom/3rd party storage implementations. * docs: Getting started cleanup. * docs: Manifest as an IPLD data strcture.
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Storage
OrbitDB is all about storage, and storage can be configured to best meet the needs of the implementation. Storage is also designed to be hierarchical, allowing for a variety of storage mechanisms to be used together.
Which storage strategy is chosen depends on the requirements of the application. OrbitDB's storage customization allows for trade-offs between memory usage and speed.
Storage types
OrbitDB is bundled with the following storage:
- IPFSBlockStorage: IPFS block level storage,
- LevelStorage: LevelDB-based storage,
- LRUStorage: A Least Recently Used cache,
- MemoryStorage: A memory only array,
- ComposedStorage: Combines two storages, eg. LRUStorage and IPFSBlockStorage.
All storage objects expose two common functions, put for adding a record and get for retrieving a record. This allows for storage to be easily swapped in and out based on the needs of the database solution.
Composed storage
ComposedStorage combines two of the above storage objects. This reduces the need for performance and capability trade-offs because a combination of storage mechanisms can be used for a balance of speed vs memory usage. For example, MemoryStorage plus LevelStorage can be used for fast retrieval plus semi-permanent data storage, or LRU for efficient caching of frequently accessed items plus IPFSBlockStorage for replication.
To use composed storage, create two storage objects and then pass them to an instance of ComposedStorage:
const memoryStorage = await MemoryStorage()
const levelStorage = await LevelStorage()
const composedStorage = await ComposedStorage(memoryStorage, levelStorage)
The order in which primary storage is passed to ComposedStorage is important. When accessed, ComposedStorage will attempt to retrieve the data from the first storage mechanism, so this should be the performance-based storage. If not found, ComposedStorage will attempt to retrieve the data from the second storage; this will likely be some kind of permanent storage mechanism.
Customizing Storage
To override OrbitDB's default storage, alternative storages can be specified when a database is opened:
const entryStorage = await MemoryStorage()
const headsStorage = await MemoryStorage()
const db = await orbitdb.open('my-db', { entryStorage, headsStorage })
Implementing a third party storage solution
Any storage mechanism can be used with OrbitDB provided it implements the OrbitDB storage interface. Once created, simply pass the storage instance to OrbitDB:
// Perhaps some kind of locally developed storage implementation.
import CustomStorage from './custom-storage.js'
const entryStorage = await CustomStorage()
const headsStorage = await CustomStorage()
const indexStorage = await CustomStorage()
const db = await orbitdb.open('my-db', { entryStorage, headsStorage, indexStorage })
See the various storage implementations to see how custom storage should be structured for compatibility with OrbitDB.