The Mongoose Cross Database Transaction library facilitates cross-database transaction rollback and focuses on dependent tree behavior. It is recommended to use a single children dependency to avoid situations where the failure of one child affects only a portion of the operation, leading to potential inconsistencies.
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It is important to set the NODE_ENV environment variable before using the mongoose-cross-db-transaction library. NODE_ENV specifies the execution environment of your application and affects how the library behaves.
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If you are using a database connection that does not support transactions or sessions (particularly when there are no clusters involved), it is recommended to set NODE_ENV to local. This ensures that the library adapts its transaction handling accordingly to work effectively in such scenarios.
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When NODE_ENV is set to local, it's important to note that the queries executed by the library will not provide full ACID (Atomicity, Consistency, Isolation, Durability) properties. This is due to the limitations of the underlying database connection. Therefore, ensure that your application's requirements align with the capabilities provided when using NODE_ENV as local.
To install the mongoose-cross-db-transaction library, follow these steps:
- Ensure you have Node.js and npm (Node Package Manager) installed on your machine.
- Open your terminal or command prompt.
- Navigate to your project directory.
- Run the following command to install the library:
$ npm install mongoose-cross-db-transaction- Once the installation is complete, you can import the library into your project using the following line of code:
const { withTransaction } = require('mongoose-cross-db-transaction');If you are using ES modules or TypeScript, you can import the library as follows:
import { withTransaction } from 'mongoose-cross-db-transaction';- You are now ready to use the mongoose-cross-db-transaction library in your project for managing cross-database transactions.
To gain a clear understanding of the mongoose-cross-db-transaction library's functionality, it is recommended to refer to the test cases available in the repository. These test cases provide comprehensive examples that showcase the library's capabilities. Additionally, here is a sample code snippet that illustrates the configuration:
Consider a scenario where you have two operations originating from different databases, but they are interconnected through a reference in the Order model. These operations enable cross-database updates, meaning that a change made in Database A should reflect in Database B. In the event of a failure, the operations should be rolled back to maintain data consistency.
It is important to note that each model should use a unique connection as they belong to different databases. Assign the appropriate model instance's connection to the action associated with that model. If you have models from different databases, designate one as the parent action and the other as the childrenSession action to establish the dependent relationship. Make sure to pass the respective database connections to the corresponding actions.
By following these guidelines and studying the provided examples, you will be able to effectively configure and utilize the mongoose-cross-db-transaction library for handling cross-database transactions.
In this example, we have a parent action and a single children session. The store variable represents the progressive result passed from one action to another in the specified order. The action function is where you define the logic for each operation within the transaction. The provided code showcases the creation of a new service and the generation of a new key using the serviceModel and keyManagerModel.
Here, only single children for parent and store[0] is the result of action.
import { withTransaction, SessionConfig } from 'mongoose-cross-db-transaction';
let createdService: Service & any;
const transactionConfig: SessionConfig = {
connection: this.serviceConnection,
action: async (store, session) =>
await this.serviceModel.create([newData], { session }),
childrenSessions: [
{
connection: this.keyManagerConnection,
action: async (store, session) => {
createdService = store[0];
const keyPayload: CreateNewKeyType = {
key_type: KeyType.SERVICE,
entity: 'service',
entity_id: createdService._id,
apiCode: serviceCode,
expiryDate,
session,
};
return await (this.keyManagerModel as any).createNewKey(
keyPayload,
);
},
},
],
};
await withTransaction(transactionConfig);This example demonstrates a more complex scenario with nested actions. The transactionConfig object contains the parent action and two levels of children sessions. The code shows the update of a key manager, the generation of a new key, and the update of a tenant record. Each action is defined within its respective action function. The store variable allows you to access the results from previous actions.
The store here is the progressive result from each action function passed to the next action in order at which it is run for dependent parent-children relationship.
Here, we have two parent which are nested and the store result are followed in order of 0,1.
import { withTransaction, SessionConfig } from 'mongoose-cross-db-transaction';
const transactionConfig: SessionConfig = {
connection: this.keyManagerConnection,
action: async (store, session) => {
return this.keyManagerModel.findOneAndUpdate(
{ _id: new Types.ObjectId(keyManager._id.toString()) },
{
$set: {
updatedBy: tenant._id,
status: KeyStatus.REFRESHED,
},
},
{ new: true, lean: true, session },
);
},
childrenSessions: [
{
connection: this.keyManagerConnection,
action: async (store, session) => {
return await generateNewKey(
this.keyManagerModel,
KeyType.TENANT_PRODUCT,
'tenant',
new Types.ObjectId(tenant._id),
expiryDate,
'product',
new Types.ObjectId(keyManager.product),
keyManager.apiCode,
session,
);
},
childrenSessions: [
{
connection: this.tenantConnection,
action: async (store, session) => {
this.tenantModel.updateOne({
_id: store[0].tenant,
type: store[1].manager.type,
}, {name: 'A', data: {sample: 1}}, {session})
},
],
},
],
};
await withTransaction(transactionConfig);This case showcases multiple children sessions at the different levels. The progressive order for this is focus base on parent to children but not the inner children of the first children, in a case of failure, a proper rollback will likewise occur but we need to understand the progressive order of result.
const txnConfig = {
connection,
action,
childrenSessions: [
{
connection,
action: action2,
childrenSessions: [
{ connection, action: action3 },
{ connection, action: action4 },
],
},
{
connection,
action: action5,
childrenSessions: [
{ connection, action: action6 },
{ connection, action: action7 },
],
},
],
}Result of the transaction
You will noticed inner children of first children isn't captured for parent children 2 which is action5 because they are same level and only action, action2 are visible to it and its inner children results.
| SN | Action | Result |
|---|---|---|
| 1 | action | [] |
| 2 | action2 | [1] |
| 3 | action3 | [1, 2] |
| 4 | action4 | [1, 2, 3] |
| 5 | action5 | [1, 2] |
| 6 | action6 | [1, 2, 5] |
| 7 | action7 | [1, 2, 5, 6] |