arangojs
Version:
The official ArangoDB JavaScript driver.
329 lines • 11.5 kB
JavaScript
import { isArangoError } from "./error.js";
import { TRANSACTION_NOT_FOUND } from "./lib/codes.js";
/**
* Indicates whether the given value represents a {@link Transaction}.
*
* @param transaction - A value that might be a transaction.
*/
export function isArangoTransaction(transaction) {
return Boolean(transaction && transaction.isArangoTransaction);
}
/**
* Represents a streaming transaction in a {@link database.Database}.
*/
export class Transaction {
_db;
_id;
/**
* @internal
*/
constructor(db, id) {
this._db = db;
this._id = id;
}
/**
* @internal
*
* Indicates that this object represents an ArangoDB transaction.
*/
get isArangoTransaction() {
return true;
}
/**
* Unique identifier of this transaction.
*
* See {@link database.Database#transaction}.
*/
get id() {
return this._id;
}
/**
* Checks whether the transaction exists.
*
* @example
* ```js
* const db = new Database();
* const trx = db.transaction("some-transaction");
* const result = await trx.exists();
* // result indicates whether the transaction exists
* ```
*/
async exists() {
try {
await this.get();
return true;
}
catch (err) {
if (isArangoError(err) && err.errorNum === TRANSACTION_NOT_FOUND) {
return false;
}
throw err;
}
}
/**
* Retrieves general information about the transaction.
*
* @example
* ```js
* const db = new Database();
* const col = db.collection("some-collection");
* const trx = db.beginTransaction(col);
* await trx.step(() => col.save({ hello: "world" }));
* const info = await trx.get();
* // the transaction exists
* ```
*/
get() {
return this._db.request({
path: `/_api/transaction/${encodeURIComponent(this.id)}`,
}, (res) => res.parsedBody.result);
}
/**
* Attempts to commit the transaction to the databases.
*
* @param options - Options for comitting the transaction.
*
* @example
* ```js
* const db = new Database();
* const col = db.collection("some-collection");
* const trx = db.beginTransaction(col);
* await trx.step(() => col.save({ hello: "world" }));
* const result = await trx.commit();
* // result indicates the updated transaction status
* ```
*/
commit(options = {}) {
const { allowDirtyRead = undefined } = options;
return this._db.request({
method: "PUT",
path: `/_api/transaction/${encodeURIComponent(this.id)}`,
allowDirtyRead,
}, (res) => res.parsedBody.result);
}
/**
* Attempts to abort the transaction to the databases.
*
* @param options - Options for aborting the transaction.
*
* @example
* ```js
* const db = new Database();
* const col = db.collection("some-collection");
* const trx = db.beginTransaction(col);
* await trx.step(() => col.save({ hello: "world" }));
* const result = await trx.abort();
* // result indicates the updated transaction status
* ```
*/
abort(options = {}) {
const { allowDirtyRead = undefined } = options;
return this._db.request({
method: "DELETE",
path: `/_api/transaction/${encodeURIComponent(this.id)}`,
allowDirtyRead,
}, (res) => res.parsedBody.result);
}
/**
* Executes the given function locally as a single step of the transaction.
*
* @param T - Type of the callback's returned promise.
* @param callback - Callback function returning a promise.
*
* **Warning**: The callback function should wrap a single call of an async
* arangojs method (e.g. a method on a `Collection` object of a collection
* that is involved in the transaction or the `db.query` method).
* If the callback function is async, only the first promise-returning (or
* async) method call will be executed as part of the transaction. See the
* examples below for how to avoid common mistakes when using this method.
*
* **Note**: Avoid defining the callback as an async function if possible
* as arangojs will throw an error if the callback did not return a promise.
* Async functions will return an empty promise by default, making it harder
* to notice if you forgot to return something from the callback.
*
* **Note**: Although almost anything can be wrapped in a callback and passed
* to this method, that does not guarantee ArangoDB can actually do it in a
* transaction. Refer to the ArangoDB documentation if you are unsure whether
* a given operation can be executed as part of a transaction. Generally any
* modification or retrieval of data is eligible but modifications of
* collections or databases are not.
*
* @example
* ```js
* const db = new Database();
* const vertices = db.collection("vertices");
* const edges = db.collection("edges");
* const trx = await db.beginTransaction({ write: [vertices, edges] });
*
* // The following code will be part of the transaction
* const left = await trx.step(() => vertices.save({ label: "left" }));
* const right = await trx.step(() => vertices.save({ label: "right" }));
*
* // Results from preceding actions can be used normally
* await trx.step(() => edges.save({
* _from: left._id,
* _to: right._id,
* data: "potato"
* }));
*
* // Transaction must be committed for changes to take effected
* // Always call either trx.commit or trx.abort to end a transaction
* await trx.commit();
* ```
*
* @example
* ```js
* // BAD! If the callback is an async function it must only use await once!
* await trx.step(async () => {
* await collection.save(data);
* await collection.save(moreData); // WRONG
* });
*
* // BAD! Callback function must use only one arangojs call!
* await trx.step(() => {
* return collection.save(data)
* .then(() => collection.save(moreData)); // WRONG
* });
*
* // BETTER: Wrap every arangojs method call that should be part of the
* // transaction in a separate `trx.step` call
* await trx.step(() => collection.save(data));
* await trx.step(() => collection.save(moreData));
* ```
*
* @example
* ```js
* // BAD! If the callback is an async function it must not await before
* // calling an arangojs method!
* await trx.step(async () => {
* await doSomethingElse();
* return collection.save(data); // WRONG
* });
*
* // BAD! Any arangojs inside the callback must not happen inside a promise
* // method!
* await trx.step(() => {
* return doSomethingElse()
* .then(() => collection.save(data)); // WRONG
* });
*
* // BETTER: Perform any async logic needed outside the `trx.step` call
* await doSomethingElse();
* await trx.step(() => collection.save(data));
*
* // OKAY: You can perform async logic in the callback after the arangojs
* // method call as long as it does not involve additional arangojs method
* // calls, but this makes it easy to make mistakes later
* await trx.step(async () => {
* await collection.save(data);
* await doSomethingDifferent(); // no arangojs method calls allowed
* });
* ```
*
* @example
* ```js
* // BAD! The callback should not use any functions that themselves use any
* // arangojs methods!
* async function saveSomeData() {
* await collection.save(data);
* await collection.save(moreData);
* }
* await trx.step(() => saveSomeData()); // WRONG
*
* // BETTER: Pass the transaction to functions that need to call arangojs
* // methods inside a transaction
* async function saveSomeData(trx) {
* await trx.step(() => collection.save(data));
* await trx.step(() => collection.save(moreData));
* }
* await saveSomeData(); // no `trx.step` call needed
* ```
*
* @example
* ```js
* // BAD! You must wait for the promise to resolve (or await on the
* // `trx.step` call) before calling `trx.step` again!
* trx.step(() => collection.save(data)); // WRONG
* await trx.step(() => collection.save(moreData));
*
* // BAD! The trx.step callback can not make multiple calls to async arangojs
* // methods, not even using Promise.all!
* await trx.step(() => Promise.all([ // WRONG
* collection.save(data),
* collection.save(moreData),
* ]));
*
* // BAD! Multiple `trx.step` calls can not run in parallel!
* await Promise.all([ // WRONG
* trx.step(() => collection.save(data)),
* trx.step(() => collection.save(moreData)),
* ]));
*
* // BETTER: Always call `trx.step` sequentially, one after the other
* await trx.step(() => collection.save(data));
* await trx.step(() => collection.save(moreData));
*
* // OKAY: The then callback can be used if async/await is not available
* trx.step(() => collection.save(data))
* .then(() => trx.step(() => collection.save(moreData)));
* ```
*
* @example
* ```js
* // BAD! The callback will return an empty promise that resolves before
* // the inner arangojs method call has even talked to ArangoDB!
* await trx.step(async () => {
* collection.save(data); // WRONG
* });
*
* // BETTER: Use an arrow function so you don't forget to return
* await trx.step(() => collection.save(data));
*
* // OKAY: Remember to always return when using a function body
* await trx.step(() => {
* return collection.save(data); // easy to forget!
* });
*
* // OKAY: You do not have to use arrow functions but it helps
* await trx.step(function () {
* return collection.save(data);
* });
* ```
*
* @example
* ```js
* // BAD! You can not pass promises instead of a callback!
* await trx.step(collection.save(data)); // WRONG
*
* // BETTER: Wrap the code in a function and pass the function instead
* await trx.step(() => collection.save(data));
* ```
*
* @example
* ```js
* // WORSE: Calls to non-async arangojs methods don't need to be performed
* // as part of a transaction
* const collection = await trx.step(() => db.collection("my-documents"));
*
* // BETTER: If an arangojs method is not async and doesn't return promises,
* // call it without `trx.step`
* const collection = db.collection("my-documents");
* ```
*/
step(callback) {
const conn = this._db._connection;
conn.setTransactionId(this.id);
try {
const promise = callback();
if (!promise) {
throw new Error("Transaction callback was not an async function or did not return a promise!");
}
return Promise.resolve(promise);
}
finally {
conn.clearTransactionId();
}
}
}
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