Add ConfigurationHealthCheck for ensuring required properties are set

Author: nealeu

weblab-common/pom.xml

@@ -18,6 +18,11 @@
             <artifactId>liquibase-core</artifactId>
             <optional>true</optional>
         </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-actuator</artifactId>
+            <optional>true</optional>
+        </dependency>
         <dependency>
             <groupId>org.springframework.data</groupId>
             <artifactId>spring-data-mongodb</artifactId>

weblab-common/src/main/java/ucles/weblab/common/config/ConfigurationHealthCheck.java

@@ -0,0 +1,62 @@
+package ucles.weblab.common.config;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.boot.actuate.health.AbstractHealthIndicator;
+import org.springframework.boot.actuate.health.Health;
+import org.springframework.boot.actuate.health.Health.Builder;
+import org.springframework.core.env.Environment;
+
+import java.util.List;
+
+import static java.util.stream.Collectors.toList;
+import static org.springframework.boot.actuate.health.Status.UP;
+
+/**
+ * Fail health check if configuration is missing.
+ * If the configuration is missing at startup, then an exception will be thrown to prevent startup. If after
+ * startup a configuration variable is removed dynamically (e.g. when using Spring Cloud), then the heath check
+ * will change from UP to DOWN.
+ * To see details, the property management.endpoint.health.show-details must be set to 'when_authorized' or 'always'
+ * */
+public class ConfigurationHealthCheck extends AbstractHealthIndicator {
+
+    private final Logger log = LoggerFactory.getLogger(getClass());
+
+    private final Environment environment;
+
+    /** e.g. ["spring.datasource.hikari.maximum-pool-size", "suppress.errors"] */
+    private final List<String> requiredProperties;
+
+
+    public ConfigurationHealthCheck(Environment environment, List<String> requiredProperties) {
+        this.environment = environment;
+        this.requiredProperties = requiredProperties;
+
+        Builder bldr = new Builder();
+        doHealthCheck(bldr);
+        Health health = bldr.build();
+
+        if (health.getStatus() != UP) {
+            throw new RuntimeException("System failed configuration healthcheck: " + health.toString());
+        }
+    }
+
+
+    @Override
+    protected void doHealthCheck(Builder bldr) {
+
+        List<String> missing = requiredProperties.stream()
+                .filter(key -> !environment.containsProperty(key))
+                .collect(toList());
+
+        if (missing.isEmpty()) {
+            bldr.up();
+        } else {
+            log.error("Environment health check failed. The following properties are not configured: {}", missing);
+            bldr
+                .withDetail("missing-properties", missing)
+                .down();
+        }
+    }
+}