SmartUp Handyman

What does it do?

This project is meant to solve the simple problem of activating, inactivating and interrogating the status of a maintenance mode flag in a Java web application.

Modules

• handyman-core - core models and interfaces
• handyman-parent - maven parent pom for easy dependency management
• handyman-s3 - implementation that stores and retrieves the maintenance mode settings from S3
• handyman-zuul - Zuul filter to check maintenance mode and short-circuit requests if it is enabled
• handyman-sample - Sample code to show you how to use it

Core classes

MaintenanceStatusManager

Interface to set the maintenance status.

    void setMaintenanceStatus(MaintenanceStatus status);

MaintenanceStatusProvider

Interface for retrieving the maintenance status.

    MaintenanceStatus getStatus();

InMemoryMaintenanceStatusService

Solely for testing purposes, or for really simple, single instance deployments. It is purely in-memory and does not persist maintenance status anywhere.

CachingMaintenanceStatusProvider

Provided a delegate MaintenanceStatusProvider called origin it is going to cache and periodically refresh the maintenance status.

You can provide the refresh interval, which defaults to 10 000 milliseconds.

Backends

S3 backend

To use the S3 backend you'll have to build an S3MaintenanceStatusService. You can use the nested builder to do so.

Example:

public S3MaintenanceStatusService s3Service() {
        return S3MaintenanceStatusService.builder()
                .withAmazonS3(
                        AmazonS3ClientBuilder.standard()
                                .build()
                )
                .withBucketName(BUCKET_NAME)
                .withFileName(S3_FILE_NAME)
                .build();
    }

Filters

Filters allow you to short circuit the incoming request-response flow and quickly return HTTP 503 (Service Unavailable).

IMPORTANT In servlet context each request is going to hit your filters, no matter your choice of tech(Java Servlet Filter, Spring Once-Per-Request, Zuul, etc), you most probably want to use the CachingMaintenanceStatusProvider to avoid making too many round trips to the flag providing backend.

Zuul Filter

Contains MaintenanceZuulFilter which is a "pre" filter in Zuul terms. It's going to stop the filter chain and respond to the incoming request without routing to origin.