- 1. API with NestJS #1. Controllers, routing and the module structure
- 2. API with NestJS #2. Setting up a PostgreSQL database with TypeORM
- 3. API with NestJS #3. Authenticating users with bcrypt, Passport, JWT, and cookies
- 4. API with NestJS #4. Error handling and data validation
- 5. API with NestJS #5. Serializing the response with interceptors
- 6. API with NestJS #6. Looking into dependency injection and modules
- 7. API with NestJS #7. Creating relationships with Postgres and TypeORM
- 8. API with NestJS #8. Writing unit tests
- 9. API with NestJS #9. Testing services and controllers with integration tests
- 10. API with NestJS #10. Uploading public files to Amazon S3
- 11. API with NestJS #11. Managing private files with Amazon S3
- 12. API with NestJS #12. Introduction to Elasticsearch
- 13. API with NestJS #13. Implementing refresh tokens using JWT
- 14. API with NestJS #14. Improving performance of our Postgres database with indexes
- 15. API with NestJS #15. Defining transactions with PostgreSQL and TypeORM
- 16. API with NestJS #16. Using the array data type with PostgreSQL and TypeORM
- 17. API with NestJS #17. Offset and keyset pagination with PostgreSQL and TypeORM
- 18. API with NestJS #18. Exploring the idea of microservices
- 19. API with NestJS #19. Using RabbitMQ to communicate with microservices
- 20. API with NestJS #20. Communicating with microservices using the gRPC framework
- 21. API with NestJS #21. An introduction to CQRS
- 22. API with NestJS #22. Storing JSON with PostgreSQL and TypeORM
- 23. API with NestJS #23. Implementing in-memory cache to increase the performance
- 24. API with NestJS #24. Cache with Redis. Running the app in a Node.js cluster
- 25. API with NestJS #25. Sending scheduled emails with cron and Nodemailer
- 26. API with NestJS #26. Real-time chat with WebSockets
- 27. API with NestJS #27. Introduction to GraphQL. Queries, mutations, and authentication
- 28. API with NestJS #28. Dealing in the N + 1 problem in GraphQL
- 29. API with NestJS #29. Real-time updates with GraphQL subscriptions
- 30. API with NestJS #30. Scalar types in GraphQL
- 31. API with NestJS #31. Two-factor authentication
- 32. API with NestJS #32. Introduction to Prisma with PostgreSQL
- 33. API with NestJS #33. Managing PostgreSQL relationships with Prisma
- 34. API with NestJS #34. Handling CPU-intensive tasks with queues
- 35. API with NestJS #35. Using server-side sessions instead of JSON Web Tokens
- 36. API with NestJS #36. Introduction to Stripe with React
- 37. API with NestJS #37. Using Stripe to save credit cards for future use
- 38. API with NestJS #38. Setting up recurring payments via subscriptions with Stripe
- 39. API with NestJS #39. Reacting to Stripe events with webhooks
- 40. API with NestJS #40. Confirming the email address
- 41. API with NestJS #41. Verifying phone numbers and sending SMS messages with Twilio
- 42. API with NestJS #42. Authenticating users with Google
- 43. API with NestJS #43. Introduction to MongoDB
- 44. API with NestJS #44. Implementing relationships with MongoDB
- 45. API with NestJS #45. Virtual properties with MongoDB and Mongoose
- 46. API with NestJS #46. Managing transactions with MongoDB and Mongoose
- 47. API with NestJS #47. Implementing pagination with MongoDB and Mongoose
- 48. API with NestJS #48. Definining indexes with MongoDB and Mongoose
- 49. API with NestJS #49. Updating with PUT and PATCH with MongoDB and Mongoose
- 50. API with NestJS #50. Introduction to logging with the built-in logger and TypeORM
- 51. API with NestJS #51. Health checks with Terminus and Datadog
- 52. API with NestJS #52. Generating documentation with Compodoc and JSDoc
- 53. API with NestJS #53. Implementing soft deletes with PostgreSQL and TypeORM
- 54. API with NestJS #54. Storing files inside a PostgreSQL database
- 55. API with NestJS #55. Uploading files to the server
- 56. API with NestJS #56. Authorization with roles and claims
- 57. API with NestJS #57. Composing classes with the mixin pattern
- 58. API with NestJS #58. Using ETag to implement cache and save bandwidth
- 59. API with NestJS #59. Introduction to a monorepo with Lerna and Yarn workspaces
- 60. API with NestJS #60. The OpenAPI specification and Swagger
- 61. API with NestJS #61. Dealing with circular dependencies
- 62. API with NestJS #62. Introduction to MikroORM with PostgreSQL
- 63. API with NestJS #63. Relationships with PostgreSQL and MikroORM
- 64. API with NestJS #64. Transactions with PostgreSQL and MikroORM
- 65. API with NestJS #65. Implementing soft deletes using MikroORM and filters
- 66. API with NestJS #66. Improving PostgreSQL performance with indexes using MikroORM
- 67. API with NestJS #67. Migrating to TypeORM 0.3
- 68. API with NestJS #68. Interacting with the application through REPL
- 69. API with NestJS #69. Database migrations with TypeORM
- 70. API with NestJS #70. Defining dynamic modules
- 71. API with NestJS #71. Introduction to feature flags
- 72. API with NestJS #72. Working with PostgreSQL using raw SQL queries
- 73. API with NestJS #73. One-to-one relationships with raw SQL queries
- 74. API with NestJS #74. Designing many-to-one relationships using raw SQL queries
- 75. API with NestJS #75. Many-to-many relationships using raw SQL queries
- 76. API with NestJS #76. Working with transactions using raw SQL queries
- 77. API with NestJS #77. Offset and keyset pagination with raw SQL queries
- 78. API with NestJS #78. Generating statistics using aggregate functions in raw SQL
- 79. API with NestJS #79. Implementing searching with pattern matching and raw SQL
- 80. API with NestJS #80. Updating entities with PUT and PATCH using raw SQL queries
- 81. API with NestJS #81. Soft deletes with raw SQL queries
- 82. API with NestJS #82. Introduction to indexes with raw SQL queries
- 83. API with NestJS #83. Text search with tsvector and raw SQL
- 84. API with NestJS #84. Implementing filtering using subqueries with raw SQL
- 85. API with NestJS #85. Defining constraints with raw SQL
- 86. API with NestJS #86. Logging with the built-in logger when using raw SQL
- 87. API with NestJS #87. Writing unit tests in a project with raw SQL
- 88. API with NestJS #88. Testing a project with raw SQL using integration tests
- 89. API with NestJS #89. Replacing Express with Fastify
- 90. API with NestJS #90. Using various types of SQL joins
- 91. API with NestJS #91. Dockerizing a NestJS API with Docker Compose
- 92. API with NestJS #92. Increasing the developer experience with Docker Compose
- 93. API with NestJS #93. Deploying a NestJS app with Amazon ECS and RDS
- 94. API with NestJS #94. Deploying multiple instances on AWS with a load balancer
- 95. API with NestJS #95. CI/CD with Amazon ECS and GitHub Actions
- 96. API with NestJS #96. Running unit tests with CI/CD and GitHub Actions
- 97. API with NestJS #97. Introduction to managing logs with Amazon CloudWatch
- 98. API with NestJS #98. Health checks with Terminus and Amazon ECS
- 99. API with NestJS #99. Scaling the number of application instances with Amazon ECS
- 100. API with NestJS #100. The HTTPS protocol with Route 53 and AWS Certificate Manager
- 101. API with NestJS #101. Managing sensitive data using the AWS Secrets Manager
- 102. API with NestJS #102. Writing unit tests with Prisma
- 103. API with NestJS #103. Integration tests with Prisma
- 104. API with NestJS #104. Writing transactions with Prisma
- 105. API with NestJS #105. Implementing soft deletes with Prisma and middleware
- 106. API with NestJS #106. Improving performance through indexes with Prisma
- 107. API with NestJS #107. Offset and keyset pagination with Prisma
- 108. API with NestJS #108. Date and time with Prisma and PostgreSQL
- 109. API with NestJS #109. Arrays with PostgreSQL and Prisma
- 110. API with NestJS #110. Managing JSON data with PostgreSQL and Prisma
- 111. API with NestJS #111. Constraints with PostgreSQL and Prisma
- 112. API with NestJS #112. Serializing the response with Prisma
- 113. API with NestJS #113. Logging with Prisma
- 114. API with NestJS #114. Modifying data using PUT and PATCH methods with Prisma
- 115. API with NestJS #115. Database migrations with Prisma
- 116. API with NestJS #116. REST API versioning
- 117. API with NestJS #117. CORS – Cross-Origin Resource Sharing
- 118. API with NestJS #118. Uploading and streaming videos
- 119. API with NestJS #119. Type-safe SQL queries with Kysely and PostgreSQL
- 120. API with NestJS #120. One-to-one relationships with the Kysely query builder
- 121. API with NestJS #121. Many-to-one relationships with PostgreSQL and Kysely
- 122. API with NestJS #122. Many-to-many relationships with Kysely and PostgreSQL
- 123. API with NestJS #123. SQL transactions with Kysely
- 124. API with NestJS #124. Handling SQL constraints with Kysely
- 125. API with NestJS #125. Offset and keyset pagination with Kysely
- 126. API with NestJS #126. Improving the database performance with indexes and Kysely
- 127. API with NestJS #127. Arrays with PostgreSQL and Kysely
- 128. API with NestJS #128. Managing JSON data with PostgreSQL and Kysely
- 129. API with NestJS #129. Implementing soft deletes with SQL and Kysely
- 130. API with NestJS #130. Avoiding storing sensitive information in API logs
- 131. API with NestJS #131. Unit tests with PostgreSQL and Kysely
- 132. API with NestJS #132. Handling date and time in PostgreSQL with Kysely
- 133. API with NestJS #133. Introducing database normalization with PostgreSQL and Prisma
- 134. API with NestJS #134. Aggregating statistics with PostgreSQL and Prisma
- 135. API with NestJS #135. Referential actions and foreign keys in PostgreSQL with Prisma
- 136. API with NestJS #136. Raw SQL queries with Prisma and PostgreSQL range types
- 137. API with NestJS #137. Recursive relationships with Prisma and PostgreSQL
- 138. API with NestJS #138. Filtering records with Prisma
- 139. API with NestJS #139. Using UUID as primary keys with Prisma and PostgreSQL
- 140. API with NestJS #140. Using multiple PostgreSQL schemas with Prisma
- 141. API with NestJS #141. Getting distinct records with Prisma and PostgreSQL
- 142. API with NestJS #142. A video chat with WebRTC and React
- 143. API with NestJS #143. Optimizing queries with views using PostgreSQL and Kysely
- 144. API with NestJS #144. Creating CLI applications with the Nest Commander
- 145. API with NestJS #145. Securing applications with Helmet
- 146. API with NestJS #146. Polymorphic associations with PostgreSQL and Prisma
- 147. API with NestJS #147. The data types to store money with PostgreSQL and Prisma
- 148. API with NestJS #148. Understanding the injection scopes
- 149. API with NestJS #149. Introduction to the Drizzle ORM with PostgreSQL
- 150. API with NestJS #150. One-to-one relationships with the Drizzle ORM
- 151. API with NestJS #151. Implementing many-to-one relationships with Drizzle ORM
- 152. API with NestJS #152. SQL constraints with the Drizzle ORM
- 153. API with NestJS #153. SQL transactions with the Drizzle ORM
- 154. API with NestJS #154. Many-to-many relationships with Drizzle ORM and PostgreSQL
- 155. API with NestJS #155. Offset and keyset pagination with the Drizzle ORM
- 156. API with NestJS #156. Arrays with PostgreSQL and the Drizzle ORM
- 157. API with NestJS #157. Handling JSON data with PostgreSQL and the Drizzle ORM
- 158. API with NestJS #158. Soft deletes with the Drizzle ORM
- 159. API with NestJS #159. Date and time with PostgreSQL and the Drizzle ORM
- 160. API with NestJS #160. Using views with the Drizzle ORM and PostgreSQL
- 161. API with NestJS #161. Generated columns with the Drizzle ORM and PostgreSQL
- 162. API with NestJS #162. Identity columns with the Drizzle ORM and PostgreSQL
- 163. API with NestJS #163. Full-text search with the Drizzle ORM and PostgreSQL
- 164. API with NestJS #164. Improving the performance with indexes using Drizzle ORM
- 165. API with NestJS #165. Time intervals with the Drizzle ORM and PostgreSQL
- 166. API with NestJS #166. Logging with the Drizzle ORM
- 167. API with NestJS #167. Unit tests with the Drizzle ORM
- 168. API with NestJS #168. Integration tests with the Drizzle ORM
- 169. API with NestJS #169. Unique IDs with UUIDs using Drizzle ORM and PostgreSQL
- 170. API with NestJS #170. Polymorphic associations with PostgreSQL and Drizzle ORM
- 171. API with NestJS #171. Recursive relationships with Drizzle ORM and PostgreSQL
- 172. API with NestJS #172. Database normalization with Drizzle ORM and PostgreSQL
- 173. API with NestJS #173. Storing money with Drizzle ORM and PostgreSQL
- 174. API with NestJS #174. Multiple PostgreSQL schemas with Drizzle ORM
- 175. API with NestJS #175. PUT and PATCH requests with PostgreSQL and Drizzle ORM
- 176. API with NestJS #176. Database migrations with the Drizzle ORM
- 177. API with NestJS #177. Response serialization with the Drizzle ORM
While working with databases, keeping the integrity of the data is crucial. For example, imagine transferring money from one bank account to another. To do that, we need to perform two separate actions. First, we withdraw the amount from the first bank account. Then, we add the same amount to the second account.
If the second operation fails for whatever reason while the first succeeds, we end up with an invalid state of the database. We need the above operations to all succeed or all fail together. We can accomplish that with transactions.
ACID properties
A transaction to be valid needs to have the following properties. Together, they form the ACID acronym:
Atomicity
Operations in the transaction are a single unit. Therefore, it either fully succeeds or fails together.
Consistency
The transaction moves the database from one valid state to the next.
Isolation
The isolation property ensures that multiple transactions can occur concurrently, resulting in a valid database state. To better understand that, let’s continue the example with the banking transaction from above. Another transaction should see the funds in one account or the other, but not in both.
Durability
Once the changes from a transaction are committed, they should survive permanently.
Transactions in MongoDB and Mongoose
Fortunately, MongoDB is equipped with support for multi-document transactions since version 4.0. We can tell the database that we do a transaction, and it keeps track of every update we make. If something fails, then the database rolls back all our updates. The above requires the database to do extra work making notes of our updates and locking the involved resources. Other clients trying to perform operations on the data might be stuck waiting for the transaction to complete. Therefore, this is something to watch out for.
Running a replica set
Transactions with MongoDB only work with a replica set, a group of MongoDB processes that maintain the same data set. In this series, we’ve been using docker-compose to run MongoDB for us. We can either run a replica set locally with docker or use MongoDB atlas. For this article, I’m doing the latter.
If you want to run a replica set, check out this page on Stackoverflow.
Deleting a user
Let’s implement a feature of deleting a user. When we remove users from the database, we also want to delete all posts they wrote.
users.service.ts
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import { Injectable, NotFoundException } from '@nestjs/common'; import { InjectModel } from '@nestjs/mongoose'; import { Model } from 'mongoose'; import { UserDocument, User } from './user.schema'; import PostsService from '../posts/posts.service'; @Injectable() class UsersService { constructor( @InjectModel(User.name) private userModel: Model<UserDocument>, private readonly postsService: PostsService, ) {} async delete(userId: string) { const user = await this.userModel .findByIdAndDelete(userId) .populate('posts'); if (!user) { throw new NotFoundException(); } const posts = user.posts; return this.postsService.deleteMany( posts.map((post) => post._id.toString()), ); } // ... } export default UsersService; |
To do the above, we also need to define the deleteMany in our PostsService.
posts.service.ts
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import { Model } from 'mongoose'; import { Injectable } from '@nestjs/common'; import { InjectModel } from '@nestjs/mongoose'; import { Post, PostDocument } from './post.schema'; @Injectable() class PostsService { constructor(@InjectModel(Post.name) private postModel: Model<PostDocument>) {} async deleteMany(ids: string[]) { return this.postModel.deleteMany({ _id: ids }); } // ... } export default PostsService; |
The shortcoming of the above code is that the delete method might succeed partially. When this happens, we delete the user, but the posts are left in the database without the author. We can deal with the above issue by defining a transaction.
To start a transaction, we need to access the connection we’ve established with MongoDB. To do that, we can use the @InjectConnection decorator:
users.service.ts
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import { Injectable } from '@nestjs/common'; import { InjectModel } from '@nestjs/mongoose'; import { Model } from 'mongoose'; import { UserDocument, User } from './user.schema'; import PostsService from '../posts/posts.service'; import { InjectConnection } from '@nestjs/mongoose'; import * as mongoose from 'mongoose'; @Injectable() class UsersService { constructor( @InjectModel(User.name) private userModel: Model<UserDocument>, private readonly postsService: PostsService, @InjectConnection() private readonly connection: mongoose.Connection, ) {} // ... } export default UsersService; |
Controlling the transaction
There are two ways of working with transactions with Mongoose. To have full control over it, we can call the startTransaction method:
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const session = await this.connection.startSession(); session.startTransaction(); |
When we indicate that everything worked fine, we need to call session.commitTransaction(). This writes our changes to the database.
If we encounter an error, we need to call session.abortTransaction() to indicate that we want to discard the operations we’ve performed so far. Once we’re done with the transaction, we need to call the session.endSession() method.
To indicate that we want to perform an operation within a given session, we need to use the session() method.
users.service.ts
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async delete(userId: string) { const session = await this.connection.startSession(); session.startTransaction(); try { const user = await this.userModel .findByIdAndDelete(userId) .populate('posts') .session(session); if (!user) { throw new NotFoundException(); } const posts = user.posts; await this.postsService.deleteMany( posts.map((post) => post._id.toString()), ); await session.commitTransaction(); } catch (error) { await session.abortTransaction(); throw error; } finally { session.endSession(); } } |
Still, there is an important issue with the above code. Although we’ve deleted the user within a transaction, we didn’t do that when removing posts. To delete posts within a session, we need to modify the postsService.deleteMany function:
posts.service.ts
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import { Model } from 'mongoose'; import { Injectable } from '@nestjs/common'; import { InjectModel } from '@nestjs/mongoose'; import { Post, PostDocument } from './post.schema'; import * as mongoose from 'mongoose'; @Injectable() class PostsService { constructor(@InjectModel(Post.name) private postModel: Model<PostDocument>) {} async deleteMany( ids: string[], session: mongoose.ClientSession | null = null, ) { return this.postModel.deleteMany({ _id: ids }).session(session); } // ... } export default PostsService; |
By adding the optional session argument to the deleteMany method, we can delete posts within a transaction. Let’s use it:
users.service.ts
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async delete(userId: string) { const session = await this.connection.startSession(); session.startTransaction(); try { const user = await this.userModel .findByIdAndDelete(userId) .populate('posts') .session(session); if (!user) { throw new NotFoundException(); } const posts = user.posts; await this.postsService.deleteMany( posts.map((post) => post._id.toString()), session, ); await session.commitTransaction(); } catch (error) { await session.abortTransaction(); throw error; } finally { session.endSession(); } } |
If removing the posts fail for some reason, the user is not deleted from the database either. Thanks to that, the whole operation either succeeds as a whole or fails completely.
A simpler way of using transactions
Instead of controlling every step of the transaction manually, we can use the session.withTransaction() helper.
users.service.ts
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async delete(userId: string) { const session = await this.connection.startSession(); await session.withTransaction(async () => { const user = await this.userModel .findByIdAndDelete(userId) .populate('posts') .session(session); if (!user) { throw new NotFoundException(); } const posts = user.posts; await this.postsService.deleteMany( posts.map((post) => post._id.toString()), session, ); }); session.endSession(); } |
Please notice that we no longer need to call startTransaction(), commitTransaction(), and abortTransaction(). We still are required to end the session with the endSession method, though.
Summary
In this article, we’ve gone through transactions in MongoDB by describing their principles and use-cases. We’ve also implemented them into our application with Mongoose. It is definitely worth it to understand transactions because they can increase the reliability of our application quite a lot.
Thanks for the article, it is very informative as always.
Regarding the transactions, I wonder if it is possible to use a decorator to wrap a function in a transaction? I have tried on my side but could not get it to work.
Actually I found a way, I set the mongoose session inside de request object and use a custom decorator to retrieve it if needed.
Thanks for the article. This is one of the best blogs I have ever seen. Respect.
Hi, I’m following the steps of top comment. I have 4 containers: mongodb1, mongodb2, mongodb3, mongoclient. Now, how to connect to MongoDB? (what uri for MongooseModule?)
Also, I see a error in container: “/deployment_scripts/initiate_replica.sh: line 4: mongo: command not found”. Please help me fix it.