Document default metadata cache expiration policy

[mmoayyed]

Using version 0.13.0; At the moment, the default cache customizer does the following:

                @Override
		public void customize(javax.cache.CacheManager cacheManager) {
			createMissingCache(cacheManager, "initializr.metadata",
					() -> config().setExpiryPolicyFactory(CreatedExpiryPolicy.factoryOf(Duration.TEN_MINUTES)));
			createMissingCache(cacheManager, "initializr.dependency-metadata", this::config);
			createMissingCache(cacheManager, "initializr.project-resources", this::config);
			createMissingCache(cacheManager, "initializr.templates", this::config);
		}

• Could the expiration policy, that is Duration.TEN_MINUTES, be configurable via application properties? (I am not sure if it's possible to customize this after the fact)
• Could this be documented? Was not able to find it here.

I am happy to help and submit a PR if you find this to be reasonable.

[wilkinsona]

I'm not sure that we want to provide this level of control. The documentation recommends the following approach:

The caches are created with an auto-configured JCacheManagerCustomizer with order 0 and only if they don’t exist already. You can contribute a bean of the same type with a lower @Order to override some of the configuration to suit your specific needs.

Does this not meet your needs?

[mmoayyed]

I am not sure that it does. I don't see how to change the expiration policy duration after the cache is built. This turns into an immutable, complete cache and I don't think any customizer can change those settings without some very ugly hacks. I could of course entirely skip this and supply my own cache, or I could entirely skip the feature altogether and do caching entirely on my own but I don't see how that would be immediately better than having a single-lined setting that says "cache duration is X number of minutes".

[mmoayyed]

I went ahead with:

    @Bean
    @Order(Ordered.HIGHEST_PRECEDENCE)
    public JCacheManagerCustomizer initializrMetadataCacheManagerCustomizer() {
        return cacheManager -> {
            var cacheDuration = Duration.ONE_DAY;
            var config = new MutableConfiguration<>()
                .setStoreByValue(false)
                .setManagementEnabled(true)
                .setStatisticsEnabled(true)
                .setExpiryPolicyFactory(CreatedExpiryPolicy.factoryOf(cacheDuration));
            log.info("Initialize metadata is cached for 1 day");
            cacheManager.createCache("initializr.metadata", config);
        };
    }

You can certainly close this out, if you still feel like this level of control is unwarranted. (I would nonetheless consider documenting this)

Thank you!

[snicoll]

I believe this is already documented.

[mmoayyed]

Certainly, yes; To clarify, I meant that the default duration for the cache should be documented as well. i.e.

The initializr metadata cache by default is configured with an expiration policy that allows entries to remain in the cache for 10 minutes.