cvs-tsk-update-store

Overview

Lambda handler and business logic for the CVS task "Update Store":

1. Receives DynamoDB stream events, containing NoSQL document snapshots ("images")
2. Converts these images to a TypeScript model, then to an SQL-friendly tuple.
3. Upserts (inserts or updates) tuples into RDS Aurora, a relational SQL database.

See full conversion procedure in sections below.

This Lambda currently supports the following conversions:

Source (DynamoDB)	Destination (Aurora)
Technical_Records	technical_record
Test_Results	test_result

See full list of affected Aurora tables in sections below.

Relation to other services

cvs-tsk-update-store was built as part of the VOTT project. See:

• Project home
• Architecture diagram
• The following diagram:

Cloning

This project makes use of Git submodules to import cvs-nop. Instead of the regular git clone, use:

git clone git@github.com:dvsa/cvs-tsk-update-store.git --recurse-submodules

Or, if already cloned:

git submodule update --init --recursive

By default, the submodule will be in a detached HEAD state. If you need a specific branch on cvs-nop, you will need to:

cd cvs-nop
git checkout feature/CVSB-XXXXX
git pull

Debugging

cvs-tsk-update-store is quiet by default. It will log almost nothing to CloudWatch unless an error occurs.

To change this, set the environment variable DEBUG to any non-null value, e.g. DEBUG=1.

This will cause numerous debug logs to fire. Messages will include event information, SQL, template variables, procedure entries and exits and more.

Tests

npm run test

Runs all unit tests

npm run test-all

Runs all the tests (Unit and Integration)

Integration tests

Integration tests depend on:

• a local Docker installation, with docker on the system's path
• a local Liquibase installation, with liquibase or liquibase.bat (on Windows) on the system's path

They work by:

1. Creating a MySQL container
2. Spawning a Liquibase executable
3. Applying a Liquibase changelog to the running container
4. Overriding connection pool configuration to connect to container

Run them using:

npm run test-local-i

On Windows, you will need to manually run:

• SET USE_CONTAINERIZED_DATABASE=1
• Confirm: echo %USE_CONTAINERIZED_DATABASE% should return 1before the above, or run these tests with an IntelliJ configuration which sets the right environment variable for you.

On Tanio Artino's advice, there is a distinction between running integration tests locally, and running them on Jenkins.

• USE_CONTAINERIZED_DATABASE=0 will attempt to talk to 127.0.0.1:3306. This only works if you manually start a DB or, in the case of Jenkins, if there is a pre-existing DB running on port 3306.
• USE_CONTAINERIZED_DATABASE=1 will spin up a TC container as described above.

To run the "Jenkins" version, e.g. USE_CONTAINERIZED_DATABASE=0, use:

npm run test-i

Full conversion procedure

Rough ordering - may not follow code exactly.

1. DynamoDB table emits event on INSERT, MODIFY or REMOVE
2. Event validation: is this really a DynamoDB stream event?
3. Derive correct SQL operation INSERT (supported), UPDATE (supported) or DELETE (not implemented)
4. Parse DynamoDB document snapshot into usable image object
5. Obtain source table name from event source ARN
6. Get conversion procedure by table name
7. Start conversion procedure given image, table name and SQL operation
8. Parse root image: map all applicable fields to equivalent TypeScript object hierarchy
9. Generate INSERT INTO (...) ON DUPLICATE KEY UPDATE (...) for each destination table
10. Transactionally execute all SQL statements, rolling back on error
11. Return upsertion result containing all primary and foreign keys

Technical Record conversion

For the full field-to-column mapping, see tech-record-document-conversion.ts.

• Source (DynamoDB) table: Technical_Records
• Destination (Aurora) tables, in upsertion order:
  • vehicle
  • make_model
  • vehicle_class
  • vehicle_subclass
  • identity
  • contact_details
  • technical_record
  • psv_brakes
  • axle_spacing
  • microfilm
  • plate
  • axle

Test Result conversion

For the full field-to-column mapping, see test-result-record-conversion.ts.

• Source (DynamoDB) table: Test_Results
• Destination (Aurora) tables, in upsertion order:
  • vehicle
  • test_station
  • tester
  • vehicle_class
  • preparer
  • identity
  • fuel_emission
  • test_type
  • test_result
  • defect
  • location
  • test_defect
  • custom_defect