ngadde / mongodb-bookstore

SpringBoot application outlining usage of different MongoDB Data Models for atomic operations / transactions. Referring to and extending the MongoDB Model Data for Atomic Operations example.

Welcome to the

The Fantasy Bookstore is a tiny SpringBoot application outlining usage of different MongoDB Data Models for atomic operations. The Bookstore refers to and extends the Model Data for Atomic Operations example.

Use Application Profiles to activate the different approaches.

Profile	Description
sa	Synchronous Atomic Operations with denormalized Data Model
stxn	Synchronous Multi Document Transactions using just the native MongoClient
stx	Synchronous Spring managed Multi Document Transactions
rtx	Reactive Multi Document Transactions
rcs	Active this profile along with one of the transactional (stx, rtx) ones to subscribe to changes on the order collection.
retry	Activate this profile to retry failed transactions via Spring Retry.
reset	Reset the initial set of collections and pre fill it with test data

Web Endpoints

URL	Sample	Description
GET :8080/books	http :8080/books	List all books.
GET :8080/book/{book}	http :8080/book/bb4e114f	A single Book.
POST :8080/book/{book}/order?customer=	http POST :8080/book/bb4e114f/order?customer=christoph	Place an order for a book.

Synchronous Atomic Operations with denormalized Data Model

The denormalized Data Model keeps all required data in one place, the Document. Hence all updates of the one document are atomic. Each and every Order is tracked by checkout within the Book itself.

{
     "_id" : "bb4e114f",
     "title" : "The Painted Man",
     "author" : [ "Peter V. Brett" ],
     "published_date" : "2009-08-01",
     "pages" : 544,
     "language" : "English",
     "publisher_id" : "Harper Collins Publishers",
     "available" : 3,
     "checkout" : [ { "by": "cstrobl", "date" : "2018-08-27T10:11:59.853Z" } ]
 }

Spring Profile: sa
MongoDB Collections: books
Components: AtomicOrderService, SyncBookstoreHandler

Synchronous Spring Managed Multi Document Transactions

The transactional approach splits data between Book and Order whereas the Order references the Book via a DBRef. Still the number of available copies is kept within the books collection.

{
    "_id" : "bb4e114f",
    "title" : "The Painted Man",
    "author" : [ "Peter V. Brett" ],
    "published_date" : "2009-08-01",
    "pages" : 544,
    "language" : "English",
    "publisher_id" : "Harper Collins Publishers",
    "available" : 3
}

{
    "by" : "cstrobl",
    "date" : "2018-08-27T10:11:59.853Z",
    "books" : [ { "$ref" : "books", "$id" : "bb4e114f" } ]
}

Spring Profile: stx
MongoDB Collections: books, order
Components: TransactionalOrderService, SyncBookstoreHandler

Synchronous Multi Document Transactions with native MongoClient

Just as in the sample above data is split between Book and Order whereas the Order references the Book via a DBRef. However, here we're using the native operations of MongoClient and ClientSession to run the transaction.

Spring Profile: stxn
MongoDB Collections: books, order
Components: NativeMongoTransactionalOrderService, SyncBookstoreHandler

Reactive Multi Document Transactions

Just as the synchronous transactional approach data is split between Book and Order, this time using a reactive API for processing the checkout inside a transaction.

{
    "_id" : "bb4e114f",
    "title" : "The Painted Man",
    "author" : [ "Peter V. Brett" ],
    "published_date" : "2009-08-01",
    "pages" : 544,
    "language" : "English",
    "publisher_id" : "Harper Collins Publishers",
    "available" : 3
}

{
    "by" : "cstrobl",
    "date" : "2018-08-27T10:11:59.853Z",
    "books" : [ { "$ref" : "books", "$id" : "bb4e114f" } ]
}

Spring Profile: rtx
MongoDB Collections: books, order
Components: ReactiveOrderService, ReactiveBookstoreHandler

Retry Transactions

It may happen that multiple transactions try to alter the very same document which leads to write conflicts and therefore the abortion of the transaction.

This scenario can be provoked by:

• Start the application
• Open Mongo Shell and execute

rs0:PRIMARY> session = db.getMongo().startSession({ "mode" : "primary" });
rs0:PRIMARY> session.startTransaction();
rs0:PRIMARY> session.getDatabase("fantasy-bookstore").books.update({ "_id" : "f430cb49", "available" : { "$gt" : 0 } },  { "$inc" : { "available" : -1 } });

• Call the order endpoint

~ $ http POST :8080/book/f430cb49/order?customer=cstrobl

• The Application will retry the operation for 3 times with 5 seconds delay in between.
• Switch to Mongo Shell again and commit the transaction within time to have the other one succeed as well.

rs0:PRIMARY> session.commitTransaction();

Spring Profile: stx,retry
MongoDB Collections: books, order
Components: TransactionalOrderService, SyncBookstoreHandler, RetryTemplate

Requirements

Java

The application requires Java 8 (or better).

MongoDB

The Application requires MongoDB 4.0 or better running as Replica Set.

Project Lombok

Some of the code uses Project Lombok. Make sure to have it.