IConsensusRegisterCollection Interface

A distributed data structure that holds a set of registers with update versions. On concurrent updates, a register internally stores all possible versions of a value by using reference sequence number of the incoming update.

Using all the stored versions, we can then distinguish amongst different read policies. Below are the policies we support:

Atomic: Atomicity requires a linearizable register. A linearizable register behaves as if there is only a single copy of the data, and that every operation appears to take effect atomically at one point in time. This definition implies that operations are executed in an well-defined order. On a concurrent update, we perform a compare-and-set operation, where we compare a register sequence number with the incoming reference sequence number. The earliest operation overwriting prior sequence numbers wins since every client reaches to an agreement on the value. So we can safely return the first value.

LWW: The last write to a key always wins.

This API is provided for existing users, but is not recommended for new users.

To use, import via @fluidframework/register-collection/legacy.

For more information about our API support guarantees, see here.

Signature

export interface IConsensusRegisterCollection<T = any> extends ISharedObject<IConsensusRegisterCollectionEvents>

Extends: ISharedObject<IConsensusRegisterCollectionEvents>

Type Parameters

Parameter	Default	Description
T	any

Methods

Method	Alerts	Return Type	Description
keys()	Beta	string[]	Returns the keys.
read(key, policy)	Beta	T | undefined	Retrieves the agreed upon value for the register based on policy. Returns undefined if not present.
readVersions(key)	Beta	T[] | undefined	Retrives all concurrent versions. Undefined if not present.
write(key, value)	Beta	Promise<boolean>	Attempts to write a register with a value. Returns a promise to indicate the roundtrip completion. For a non existent register, it will attempt to create a new register with the specified value.

Method Details

keys

Returns the keys.

This API is provided for existing users, but is not recommended for new users.

For more information about our API support guarantees, see here.

Signature

keys(): string[];

Returns

Return type: string[]

read

Retrieves the agreed upon value for the register based on policy. Returns undefined if not present.

This API is provided for existing users, but is not recommended for new users.

For more information about our API support guarantees, see here.

Signature

read(key: string, policy?: ReadPolicy): T | undefined;

Parameters

Parameter	Modifiers	Type	Description
key		string
policy	optional	ReadPolicy

Returns

Return type: T | undefined

readVersions

Retrives all concurrent versions. Undefined if not present.

This API is provided for existing users, but is not recommended for new users.

For more information about our API support guarantees, see here.

Signature

readVersions(key: string): T[] | undefined;

Parameters

Parameter	Type	Description
key	string

Returns

Return type: T[] | undefined

write

Attempts to write a register with a value. Returns a promise to indicate the roundtrip completion. For a non existent register, it will attempt to create a new register with the specified value.

This API is provided for existing users, but is not recommended for new users.

For more information about our API support guarantees, see here.

Signature

write(key: string, value: T): Promise<boolean>;

Parameters

Parameter	Type	Description
key	string
value	T

Returns

Promise if write was non-concurrent

Return type: Promise<boolean>