IConsensusRegisterCollection Interface
Consensus Register Collection.
A consensus register collection is a distributed data structure, which 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.
Signature
export interface IConsensusRegisterCollection<T = any> extends ISharedObject<IConsensusRegisterCollectionEvents>
Extends: ISharedObject<IConsensusRegisterCollectionEvents
Type Parameters
| Parameter | Default | Description |
|---|---|---|
| T | any |
Methods
| Method | Return Type | Description |
|---|---|---|
| keys() | string[] | Returns the keys. |
| read(key, policy) | T | undefined | Retrieves the agreed upon value for the register based on policy. Returns undefined if not present. |
| readVersions(key) | T[] | undefined | Retrives all concurrent versions. Undefined if not present. |
| write(key, value) | 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.
Signature
keys(): string[];
Returns
Return type: string[]
read
Retrieves the agreed upon value for the register based on policy. Returns undefined if not present.
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.
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.
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>