Add Micrometer counter for job launches

Resolves #4226

spring-batch-core/src/main/java/org/springframework/batch/core/launch/support/SimpleJobLauncher.java

@@ -17,6 +17,9 @@ package org.springframework.batch.core.launch.support;
 
 import java.time.Duration;
 
+import io.micrometer.core.instrument.Counter;
+import io.micrometer.core.instrument.MeterRegistry;
+import io.micrometer.core.instrument.Metrics;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
@@ -73,6 +76,10 @@ public class SimpleJobLauncher implements JobLauncher, InitializingBean {
 
 	private TaskExecutor taskExecutor;
 
+	private MeterRegistry meterRegistry = Metrics.globalRegistry;
+
+	private Counter jobLaunchCount; // NoopCounter is still incubating
+
 	/**
 	 * Run the provided job with the given {@link JobParameters}. The
 	 * {@link JobParameters} will be used to determine if this is an execution of an
@@ -96,6 +103,9 @@ public class SimpleJobLauncher implements JobLauncher, InitializingBean {
 
 		Assert.notNull(job, "The Job must not be null.");
 		Assert.notNull(jobParameters, "The JobParameters must not be null.");
+		if (this.jobLaunchCount != null) {
+			this.jobLaunchCount.increment();
+		}
 
 		final JobExecution jobExecution;
 		JobExecution lastExecution = jobRepository.getLastJobExecution(job.getName(), jobParameters);
@@ -202,6 +212,16 @@ public class SimpleJobLauncher implements JobLauncher, InitializingBean {
 		this.taskExecutor = taskExecutor;
 	}
 
+	/**
+	 * Set the meter registry to use for metrics. Defaults to
+	 * {@link Metrics#globalRegistry}.
+	 * @param meterRegistry the meter registry
+	 * @since 5.0
+	 */
+	public void setMeterRegistry(MeterRegistry meterRegistry) {
+		this.meterRegistry = meterRegistry;
+	}
+
 	/**
 	 * Ensure the required dependencies of a {@link JobRepository} have been set.
 	 */
@@ -212,6 +232,7 @@ public class SimpleJobLauncher implements JobLauncher, InitializingBean {
 			logger.info("No TaskExecutor has been set, defaulting to synchronous executor.");
 			taskExecutor = new SyncTaskExecutor();
 		}
+		this.jobLaunchCount = BatchMetrics.createCounter(this.meterRegistry, "job.launch.count", "Job launch count");
 	}
 
 }

spring-batch-core/src/main/java/org/springframework/batch/core/observability/BatchMetrics.java

@@ -20,6 +20,7 @@ import java.time.LocalDateTime;
 import java.util.Arrays;
 import java.util.concurrent.TimeUnit;
 
+import io.micrometer.core.instrument.Counter;
 import io.micrometer.core.instrument.LongTaskTimer;
 import io.micrometer.core.instrument.MeterRegistry;
 import io.micrometer.core.instrument.Tag;
@@ -71,6 +72,20 @@ public final class BatchMetrics {
 				.register(meterRegistry);
 	}
 
+	/**
+	 * Create a {@link Counter}.
+	 * @param meterRegistry the meter registry to use
+	 * @param name of the counter. Will be prefixed with
+	 * {@link BatchMetrics#METRICS_PREFIX}.
+	 * @param description of the counter
+	 * @param tags of the counter
+	 * @return a new timer instance
+	 */
+	public static Counter createCounter(MeterRegistry meterRegistry, String name, String description, Tag... tags) {
+		return Counter.builder(METRICS_PREFIX + name).description(description).tags(Arrays.asList(tags))
+				.register(meterRegistry);
+	}
+
 	/**
 	 * Create a new {@link Observation}. It's not started, you must explicitly call
 	 * {@link Observation#start()} to start it.

spring-batch-core/src/test/java/org/springframework/batch/core/observability/BatchMetricsTests.java

@@ -45,7 +45,6 @@ import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
-import org.springframework.context.annotation.Import;
 import org.springframework.jdbc.datasource.embedded.EmbeddedDatabaseBuilder;
 import org.springframework.jdbc.support.JdbcTransactionManager;
 import org.springframework.transaction.PlatformTransactionManager;
@@ -60,7 +59,7 @@ import static org.junit.jupiter.api.Assertions.assertTrue;
  */
 class BatchMetricsTests {
 
-	private static final int EXPECTED_SPRING_BATCH_METRICS = 10;
+	private static final int EXPECTED_SPRING_BATCH_METRICS = 11;
 
 	@Test
 	void testCalculateDuration() {
@@ -149,6 +148,9 @@ class BatchMetricsTests {
 
 		// Job metrics
 
+		assertDoesNotThrow(() -> Metrics.globalRegistry.get("spring.batch.job.launch.count").counter(),
+				"There should be a meter of type COUNTER named spring.batch.job.launch.count registered in the global registry");
+
 		assertDoesNotThrow(
 				() -> Metrics.globalRegistry.get("spring.batch.job").tag("spring.batch.job.name", "job")
 						.tag("spring.batch.job.status", "COMPLETED").timer(),