Current approach to working with transactions in RMB
To enable the work with a database in FOLIO project there is a custom solution implemented on top of the VERT.X Postgres Client. The main feature of working with RMB and VERT.X is the usage of the asynchronous approach. Sequential execution of operations requires handling the completion of each operation and occurring errors. Each subsequent operation can be executed only if the previous one is succeeded. In order to maintain data consistency there is a need to execute the operations in transaction and be able to rollback the changes in case an error occurred. At the moment, this possibility is implemented as follows:
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The First and the last operations RMB PostgresClient does automatically
Example method with two operation in scope of one transaction
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public Future<Void> example() {
Future future = Future.future();
PostgresClient client = PostgresClient.getInstance(vertx, tenantId);
// start tx
client.startTx(tx -> {
// first operation
client.get(tx, "upload_definition", UploadDefinition.class, new Criterion(), true, false, getHandler -> {
if (getHandler.succeeded()) {
// second operation
client.save(tx, "upload_definition", UUID.randomUUID().toString(), getHandler.result(), saveHandler -> {
if (saveHandler.succeeded()) {
client.endTx(tx, endHandler -> {
if (endHandler.succeeded()) {
future.succeeded();
} else {
client.rollbackTx(tx, rollbackHandler -> {
future.fail(getHandler.cause());
});
}
});
} else {
client.rollbackTx(tx, rollbackHandler -> {
future.fail(getHandler.cause());
});
}
});
} else {
client.rollbackTx(tx, rollbackHandler -> {
future.fail(getHandler.cause());
});
}
});
});
return future;
} |
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- Create Transaction Object
- Select data from database for update (using “SELECT FOR UPDATE”)
- Do some kind of business logic operation
- Update entity in database
- Complete transaction
Such kind of the scenario Such scenario was needed at mod-data-import for file upload functionality.
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