pluggable meter registries

[vladak]

As noted in #3284 Micrometer supports many meter registries. Ideally no source code changes should be needed to make each available.

[vladak]

That should probably be similar to what SpringBoot does (https://micrometer.io/docs/ref/spring/1.5):

Spring Boot auto-configures a composite meter registry and adds a registry to the composite for each of the supported implementations that it finds on the classpath. Having a dependency on micrometer-registry-{system} in your runtime classpath is enough for Spring Boot to configure the registry.

The configuration is then stored as a properties, e.g. for StatsD:

management.metrics.export.statsd.enabled=true # default is true
management.metrics.export.statsd.flavor=etsy # or datadog, telegraf
management.metrics.export.statsd.host=localhost
management.metrics.export.statsd.port=8125

that would obviate the need of those BaseStatsdConfig/BaseGraphiteConfig classes.

So even with similar functionality we would still need to change Maven configuration to include the registry (or ship those most used).

[vladak]

The MeterRegistryConfig interface has

    String prefix();

    @Nullable
    String get(String var1);

and e.g. StatsdConfig is interface that extends MeterRegistryConfig with bunch of default method implementations, e.g.:

    default String host() {
        return (String)PropertyValidator.getString(this, "host").orElse("localhost");
    }

The getString() then eventually calls config.get() with prefixed name of the property.