A serverless application on AWS Lambda to provide an API for Alma, using data cached in DynamoDB
This service is built on the serverless framework.
The service is intended to respond to HTTP API calls through the AWS API Gateway. It is intended to read data from a cache of Alma in DynamoDB, and default to using the existing Alma API where no data is available in the cache.
The service consists of seven AWS Lambda functions, get-user, get-user-loan, get-user-loans, get-user-request, get-user-requests, get-user-fee and get-user-fees. All Lambdas are invoked through the Lambda proxy API gateway integration for a specific endpoint on the API. All Lambdas will also pass the user ID of a requested item to the users Queue if the specified user is not available in the cache.
This handles the endpoint GET /users/<userID>. It will return a complete list of all of the user's loans, requests and fees. It will attempt to resolve the list of these IDs from the cache, and default to Alma where the cache returns no user record. It will then attempt to resolve all individual loans, requests and fees from the cache, again defaulting to Alma where this data is not available in the cache.
Handles the endpoint GET /users/<userID>/loans. It will return a complete list of all of the user's loans, following the same process as get-user to resolve this data.
Handles the endpoint GET /users/<userID>/loans/<loanID>. It will return a complete single loan record, either from cached data if available, or Alma if not.
Handles the endpoint GET /users/<userID>/requests. It will return a complete list of all of the user's requests, following the same process as get-user to resolve this data.
Handles the endpoint GET /users/<userID>/requests/<requestID>. It will return a complete single requests record, either from cached data if available, or Alma if not.
Handles the endpoint GET /users/<userID>/fees. It will return a complete list of all of the user's fees, following the same process as get-user to resolve this data.
Handles the endpoint GET /users/<userID>/fees/<feeID>. It will return a complete single fees record, either from cached data if available, or Alma if not.
The service can be deployed using the command
sls deploy --stage <STAGE> --region <REGION>
There are two valid stages defined in the serverless.yml configuration file. These are stg and prod. Environment variables for the SQS Users queue URL and ARN, and the User, Loan, Request and Fee DynamoDB table names should be set for the chosen stage. The name of the Alma API key SSM parameter should also be provided. The full set of environment variable names is:
| Resource | Staging | Production |
|---|---|---|
| User Queue URL | USER_QUEUE_URL_STG |
USER_QUEUE_URL_PROD |
| User Queue ARN | USER_QUEUE_ARN_STG |
USER_QUEUE_ARN_PROD |
| User Table Name | USER_CACHE_TABLE_NAME_STG |
USER_CACHE_TABLE_NAME_PROD |
| Loan Table Name | LOAN_CACHE_TABLE_NAME_STG |
LOAN_CACHE_TABLE_NAME_PROD |
| Request Table Name | REQUEST_CACHE_TABLE_NAME_STG |
REQUEST_CACHE_TABLE_NAME_PROD |
| Request Table Name | FEE_CACHE_TABLE_NAME_STG |
FEE_CACHE_TABLE_NAME_PROD |
| Alma API Key Name | ALMA_API_KEY_NAME |
ALMA_API_KEY_NAME |
Deploying the service will create the seven Lambdas. This service creates no other resources.
There are four services that make up the Alma caching stack. These are:
- alma-webhook-handler - passes Alma webhook data to SNS topics :
- LAG-sns-update-cache - writes webhook data from SNS topics to DynanoDB
- LAG-bulk-update-cache - updates DynamoDB with data from Alma API for queued records
- LAG-api-gateway - provides a REST API for cached Alma data with fallback to Alma API
There are also 3 custom packages on which these depend. These are:
- LAG-Utils - utility library for AWS services
- LAG-Alma-Utils - utility library for DynamoDB cache schemas
- node-alma-api-wrapper - utility library for querying Alma API
Contributions to this service or any of the associated services and packages are welcome.