public class | source

CombinedTransaction

Implements:

ICommittable

This class represents a combined transaction across object stores.

Constructor Summary

Public Constructor
public	constructor(transactions: ...Transaction)

Member Summary

Public Members
public get	backend: JungleDB
public get	dependency: CombinedTransaction
public get	objectStore: ObjectStore Returns the object store this transaction belongs to.
public get	transactions: Array<Transaction>

Protected Members
protected set	_dependency(dependency: CombinedTransaction) Sets a new CombinedTransaction as dependency.

Method Summary

Public Methods
public	abort(): Promise Is used to abort an open transaction.
public	async commit(): Promise<boolean> Is used to commit the state of an open transaction.
public	isConsistent(transactions: Array<Transaction>): boolean Verifies the two most important consistency rules for combined transactions: 1.
public	async onFlushable(tx: Transaction, callback: function(), preprocessing: function(): Promise): Promise<boolean> To be called when a transaction is flushable to the persistent state.
public	snapshot(): Snapshot Creates an in-memory snapshot of the current state.
public	toString(): string
public	transaction(enableWatchdog: boolean): Transaction Creates a new transaction, ensuring read isolation on the most recently successfully committed state.

Protected Methods
protected	async _checkConstraints(): Promise<boolean> Is used to check constraints before committing.
protected	async _commitBackend(): Promise Is used to commit the transaction.
protected	async _commitInternal(tx: Transaction): Promise Unsupported operation for snapshots.
protected	_isCommittable(): boolean Is used to probe whether a transaction can be committed.
protected	_setParent(parent: *) Allows to change the backend of a Transaction when the state has been flushed.

Public Constructors

public constructor(transactions: ...Transaction) source

Params:

Name	Type	Attribute	Description
transactions	...Transaction		The transactions to build the combined transaction from.

Public Members

public get backend: JungleDB source

public get dependency: CombinedTransaction source

public get objectStore: ObjectStore source

Returns the object store this transaction belongs to.

public get transactions: Array<Transaction> source

Protected Members

protected set _dependency(dependency: CombinedTransaction) source

Sets a new CombinedTransaction as dependency.

Public Methods

public abort(): Promise source

Is used to abort an open transaction. A user only needs to call this method on Transactions without arguments. The optional tx argument is only used internally, in order to abort a transaction on the underlying store.

Return:

Promise

The promise resolves after successful abortion of the transaction.

public async commit(): Promise<boolean> source

Is used to commit the state of an open transaction. A user only needs to call this method on Transactions without arguments. The optional tx argument is only used internally, in order to commit a transaction to the underlying store. If the commit was successful, the method returns true, and false otherwise.

Return:

Promise<boolean>

A promise of the success outcome.

public isConsistent(transactions: Array<Transaction>): boolean source

Verifies the two most important consistency rules for combined transactions:

only transactions from different object stores
only open transactions
only transactions from the same JungleDB instance
only non-nested transactions

Params:

Name	Type	Attribute	Description
transactions	Array<Transaction>

Return:

boolean

Whether the given set of transactions is suitable for a combined transaction.

public async onFlushable(tx: Transaction, callback: function(), preprocessing: function(): Promise): Promise<boolean> source

To be called when a transaction is flushable to the persistent state. Triggers combined flush as soon as all transactions are ready.

Params:

Name	Type	Attribute	Description
tx	Transaction		Transaction to be reported flushable.
callback	function()	optional	A callback to be called after the transaction is flushed.
preprocessing	function(): Promise	optional	A callback to be called right before the transaction is flushed.

Return:

Promise<boolean>

Whether the flushing has been triggered.

public snapshot(): Snapshot source

Creates an in-memory snapshot of the current state. This snapshot only maintains the differences between the state at the time of the snapshot and the current state. To stop maintaining the snapshot, it has to be aborted.

Return:

Snapshot

public toString(): string source

Return:

string

public transaction(enableWatchdog: boolean): Transaction source

Creates a new transaction, ensuring read isolation on the most recently successfully committed state.

Params:

Name	Type	Attribute	Description
enableWatchdog	boolean	optional

Return:

Transaction

The transaction object.

Protected Methods

protected async _checkConstraints(): Promise<boolean> source

Is used to check constraints before committing. If a constraint is not satisfied, the commitable is aborted and an exception is thrown.

Return:

Promise<boolean>

Throw:

protected async _commitBackend(): Promise source

Is used to commit the transaction.

Return:

Promise

A promise that resolves upon successful application of the transaction.

protected async _commitInternal(tx: Transaction): Promise source

Unsupported operation for snapshots.

Params:

Name	Type	Attribute	Description
tx	Transaction		The transaction to be applied.

Return:

Promise

A promise that resolves upon successful application of the transaction.

protected _isCommittable(): boolean source

Is used to probe whether a transaction can be committed. This, for example, includes a check whether another transaction has already been committed.

Return:

boolean

Whether a commit will be successful.

protected _setParent(parent: *) source

Allows to change the backend of a Transaction when the state has been flushed.

Params:

Name	Type	Attribute	Description
parent	*