JarCasting
mongoTrek is a Java library inspired by Liquibase for managing collection and document migrations within your application's database.
This library is a "roll-forward" migration tool, meaning to rollback changes, new migrations are required to undertake this task.
Note: As of version 5.0.0 mongoTrek has switched it's backing driver to the org.mongodb:mongodb-driver-sync library. Support for org.mongodb:mongodb-driver-legacy and org.mongodb:mongo-java-driver will be maintained under version 4.x of the library until such time as Mongo stops releasing legacy library versions.
Java Mongo Migrations Upgrade
mongoTrek is a fork from the Java Mongo Migrations project. As such, projects that have previously managed migrations using this project can upgrade to mongoTrek and it will understand the previous migrations schema version collection documents.
Dependency
Maven
<dependency>
<groupId>net.ozwolf</groupId>
<artifactId>mongo-trek</artifactId>
<version>5.0.0</version>
</dependency>
Gradle
compile 'net.ozwolf:mongo-trek:5.0.0'
Provided Dependencies
As part of your own project, you will need to include the following dependencies:
Mongo Java Driver
This library was tested against the 4.0.4 MongoDB sync driver library version. If you require support for the mongodb-driver-legacy or mongo-java-driver libraries, refer to the 4.x versions of the library.
Build Version: 4.0.4
<dependency>
<groupId>org.mongodb</groupId>
<artifactId>mongodb-driver-sync</artifactId>
<version>[4.0.4,5)</version>
</dependency>
Slf4j Implementation
This library is tested against the Logback Classic library at version 1.2.3
MongoDB Database Commands
mongoTrek uses the MongoDB database commands framework to execute commands.
Refer to the MongoDB Database Commands documentation.
Usage
Define Your Migrations File
The migrations file for mongoTrek is a YAML or JSON file that is either a resource in your classpath or a file on your file system. The library will first scan the classpath before the file system.
The file can define the schemaVersionCollection here. If the schema version collection is also defined via the MongoTrek.setSchemaVersionCollection(<string>) command, the value in the file will be ignored.
Each migration entry consists of:
version[REQUIRED] - A unique version identifier. Migrations will be played in schemantic version order, regardless of their order in the migrations file (eg. version2.0.0will always be played ahead of2.0.0.1)description[REQUIRED] - A short description of the migrations purposeauthor[OPTIONAL] - The author of the migration. If not supplied, the author will be recorded astrekBotcommand[REQUIRED] - The database command to run. Because mongoTrek uses YAML, this can be in the form of a direct JSON or YAML structure, as long as it meets the MongoDB Database Command requirements.
Example Migrations File
schemaVersionCollection: my_schema_version
migrations:
- version: 1.0.0
description: populate people base data
author: John Trek
command: {
insert: "people",
documents: [
{ name: "Homer Simpson", age: 37 },
{ name: "Marge Simpson", age: 36 }
]
}
- version: 1.0.1
description: populate town base data
command: {
insert: "town",
documents: [
{ name: "Springfield", country: "USA" },
{ name: "Shelbyville", country: "USA" }
]
}
Map-Reduce Forced Collection Creation
If mongoTrek encouters a mapReduce command, it will ensure the collection being reduced exists. If it doesn't, it will run a simple createCollection call. It will use the default collection settings defined here in the MongoDB documentation.
Embedded Functions
For commands such as the MapReduce Command, functions should be enclosed as strings. For example:
migrations:
- version: 1.0.0
description: run a map-reduce
command: {
mapReduce: "towns",
map: "function() { emit(this.country, 1); }",
reduce: "function(country, towns) { return Array.sum(towns); }",
out: "town_counts"
}
Dates & Times
This library is designed to handle the $date strict JSON operator. Internally, it will convert the value into a valid Java Date object for the Java driver to interpret correctly.
The library currently supports date, time and date-time strings in the formats compatible with following DateTimeFormatter predefined formatters.
Running Your Migrations
To run your migrations, provide either a MongoDB Connection String URI or a MongoDatabase instance on initialization.
You can then either migrate your database (MongoTrek.migrate(<file>)) or request a status update (MongoTrek.status(<file>)). Both methods will return a MongoTrekState, allowing you to query applied, pending and current migration versions.
Example Usage
public class MyApplication {
private final static Logger LOGGER = LoggerFactory.getLogger(MyApplication.class);
public void start() {
try {
MongoTrek trek = new MongoTrek("mongodb/trek.yml", "mongodb://localhost:27017/my_app_schema");
trek.setSchemaVersionCollection("_my_custom_schema_version");
MongoTrekState state = trek.migrate();
LOGGER.info("Successfully migrated schema to version: " + state.getCurrentVersion());
} catch (MongoTrekFailureException e) {
LOGGER.error("Failed to migrate database", e);
System.exit(-1);
}
}
}
Migration Results
As of version 3.0.0 of this library, the Migration class now contains the migration result as a Map<String, Object>.
With a MongoTrekState you can get the list of applied transactions and review the migration command result.
Logging Configuration
mongoTrek uses the LOGBack project log outputs.
The logger in question is the MongoTrek class logger (ie. Logger migrationsLogger = LoggerFactory.getLogger(MongoTrek.class);)
You can configure the output of migrations logger using this class.
Messages are logged via the following levels:
INFO- All migration information (ie. configuration, versions, migration information)ERROR- If an error occurs (ie. invalid migration command definition or general connection/execution errors)
