Quorum Class

The Quorum distributed data structure provides key/value storage with a cautious conflict resolution strategy. This strategy optimizes for all clients being aware of the change prior to considering the value as accepted.

It is still experimental and under development. Please do try it out, but expect breaking changes in the future.

Signature

export declare class Quorum extends SharedObject<IQuorumEvents> implements IQuorum

Extends: SharedObject<IQuorumEvents

Implements: IQuorum

Remarks

### Creation

To create a Quorum, call the static create method:

const quorum = Quorum.create(this.runtime, id);

### Usage

Setting and reading values is somewhat similar to a SharedMap. However, because the acceptance strategy cannot be resolved until other clients have witnessed the set, the new value will only be reflected in the data after the consensus is reached.

quorum.on("pending", (key: string) => {
    console.log(quorum.getPending(key));
});
quorum.on("accepted", (key: string) => {
    console.log(quorum.get(key));
});
quorum.set("myKey", "myValue");

// Reading from the quorum prior to the async operation's completion will still return the old value.
console.log(quorum.get("myKey"));

The acceptance process has two stages. When an op indicating a client's attempt to set a value is sequenced, we first verify that it was set with knowledge of the most recently accepted value (consensus-like FWW). If it meets this bar, then the value is "pending". During this time, clients may observe the pending value and act upon it, but should be aware that not all other clients may have witnessed the value yet. Once all clients that were connected at the time of the value being set have explicitly acknowledged the new value, the value becomes "accepted". Once the value is accepted, it once again becomes possible to set the value, again with consensus-like FWW resolution.

### Eventing

Quorum is an EventEmitter, and will emit events when a new value is accepted for a key.

quorum.on("accept", (key: string) => {
    console.log(`New value was accepted for key: ${ key }, value: ${ quorum.get(key) }`);
});

Constructors

Constructor	Description
(constructor)(id, runtime, attributes)	Constructs a new quorum. If the object is non-local an id and service interfaces will be provided

Static Methods

Method	Return Type	Description
create(runtime, id)	Quorum	Create a new Quorum
getFactory()	IChannelFactory	Get a factory for Quorum to register with the data store.

Methods

Method	Return Type	Description
applyStashedOp()	void
delete(key)	void	Deletes the key/value pair at the given key. After issuing the delete, the delete is in "pending" state until all connected clients have ack'd the delete. The accepted value remains unchanged until that time.
get(key)	any	Gets the accepted value for the given key.
getPending(key)	any	Gets the pending value for the given key.
has(key)	boolean	Checks if the quorum has an accepted value for the given key.
set(key, value)	void	Sets the value for the given key. After setting the value, it will be in "pending" state until all connected clients have ack'd the set. The accepted value remains unchanged until that time.

Constructor Details

(constructor)

Constructs a new quorum. If the object is non-local an id and service interfaces will be provided

Signature

constructor(id: string, runtime: IFluidDataStoreRuntime, attributes: IChannelAttributes);

Parameters

Parameter	Type	Description
id	string	optional name of the quorum
runtime	IFluidDataStoreRuntime	data store runtime the quorum belongs to
attributes	IChannelAttributes

Method Details

applyStashedOp

Signature

applyStashedOp(): void;

create

Create a new Quorum

Signature

static create(runtime: IFluidDataStoreRuntime, id?: string): Quorum;

Parameters

Parameter	Modifiers	Type	Description
runtime		IFluidDataStoreRuntime	data store runtime the new quorum belongs to
id	optional	string	optional name of the quorum

Returns

newly created quorum (but not attached yet)

Return type: Quorum

delete

Deletes the key/value pair at the given key. After issuing the delete, the delete is in "pending" state until all connected clients have ack'd the delete. The accepted value remains unchanged until that time.

Signature

delete(key: string): void;

Parameters

Parameter	Type	Description
key	string	the key to delete

get

Gets the accepted value for the given key.

Signature

get(key: string): any;

Parameters

Parameter	Type	Description
key	string	The key to retrieve from

Returns

Return type: any

getFactory

Get a factory for Quorum to register with the data store.

Signature

static getFactory(): IChannelFactory;

Returns

a factory that creates and load Quorum

Return type: IChannelFactory

getPending

Gets the pending value for the given key.

Signature

getPending(key: string): any;

Parameters

Parameter	Type	Description
key	string	The key to retrieve from

Returns

Return type: any

has

Checks if the quorum has an accepted value for the given key.

Signature

has(key: string): boolean;

Parameters

Parameter	Type	Description
key	string	The key to check

Returns

Return type: boolean

set

Sets the value for the given key. After setting the value, it will be in "pending" state until all connected clients have ack'd the set. The accepted value remains unchanged until that time.

Signature

set(key: string, value: unknown): void;

Parameters

Parameter	Type	Description
key	string	The key to set
value	unknown	The value to store