Application does not start anymore with only AbstractRoutingDataSource beans

[tokuhirom]

DataSourceHealthContributorAutoConfiguration loads all DataSources. And monitoring all data sources with an actuator.

It ignores AbstractRoutingDataSource... So it's a good implementation since the destination of AbstractRoutingDataSource may change.

spring-boot/spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/jdbc/DataSourceHealthContributorAutoConfiguration.java

Lines 79 to 96 in b43827d

	@Bean
	@ConditionalOnMissingBean(name = { "dbHealthIndicator", "dbHealthContributor" })
	public HealthContributor dbHealthContributor(Map<String, DataSource> dataSources) {
	return createContributor(filterDataSources(dataSources));
	}
	private Map<String, DataSource> filterDataSources(Map<String, DataSource> candidates) {
	if (candidates == null) {
	return null;
	}
	Map<String, DataSource> dataSources = new LinkedHashMap<>();
	candidates.forEach((name, dataSource) -> {
	if (!(dataSource instanceof AbstractRoutingDataSource)) {
	dataSources.put(name, dataSource);
	}
	});
	return dataSources;
	}

But createContributor throws an exception when the argument is empty.

spring-boot/spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/health/AbstractCompositeHealthContributorConfiguration.java

Lines 51 to 57 in b43827d

	protected final C createContributor(Map<String, B> beans) {
	Assert.notEmpty(beans, "Beans must not be empty");
	if (beans.size() == 1) {
	return createIndicator(beans.values().iterator().next());
	}
	return createComposite(beans);
	}

As a result, if the module have only AbstractRoutingDataSources, boot application can't run.

[snicoll]

Thanks for the report. As far as I can see, we were checking the map isn't null in 2.1.x and the check is a bit more complete in 2.2.x. We need to figure out what to do if the map is empty.

[tokuhirom]

Here's a sample code to reproduce the issue.

https://github.com/tokuhirom/boot22-issue18661

[snicoll]

Thanks for the sample @tokuhirom. Here is the stacktrace:

Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.boot.actuate.health.HealthContributor]: Factory method 'dbHealthContributor' threw exception; nested exception is java.lang.IllegalArgumentException: Beans must not be empty
        at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:185) ~[spring-beans-5.2.0.RELEASE.jar:5.2.0.RELEASE]
        at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:640) ~[spring-beans-5.2.0.RELEASE.jar:5.2.0.RELEASE]
        ... 105 common frames omitted
Caused by: java.lang.IllegalArgumentException: Beans must not be empty
        at org.springframework.util.Assert.notEmpty(Assert.java:549) ~[spring-core-5.2.0.RELEASE.jar:5.2.0.RELEASE]
        at org.springframework.boot.actuate.autoconfigure.health.AbstractCompositeHealthContributorConfiguration.createContributor(AbstractCompositeHealthContributorConfiguration.java:52) ~[spring-boot-actuator-autoconfigure-2.2.0.RELEASE.jar:2.2.0.RELEASE]
        at org.springframework.boot.actuate.autoconfigure.jdbc.DataSourceHealthContributorAutoConfiguration.dbHealthContributor(DataSourceHealthContributorAutoConfiguration.java:82) ~[spring-boot-actuator-autoconfigure-2.2.0.RELEASE.jar:2.2.0.RELEASE]
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_202]
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_202]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_202]
        at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_202]
        at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154) ~[spring-beans-5.2.0.RELEASE.jar:5.2.0.RELEASE]
        ... 106 common frames omitted

[snicoll]

For the time being you can set management.health.db.enabled=false in your application configuration.

[snicoll]

If have a fix for a quite involved condition as I couldn't figure out how to bypass registration. I'd like a review from someone on the team.