Make Partition ID non-mandatory during partition creation. (#5016)

* closes #5014, fix, changelog, docs

* documentationf fixes

* checkstyle fix

hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/changelog/6_8_0/5014-auto-generate-partition-id.yaml

@@ -0,0 +1,5 @@
+---
+type: add
+issue: 5014
+title: "It is no longer mandatory to provide a partition ID when executing the `$partition-management-create-partition` operation. If you omit the partition ID, one will be randomly selected 
+from the available pool of values. Note that this may incur a small performance cost when creating partitions."

hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/docs/server_jpa_partitioning/partitioning_management_operations.md

@@ -21,9 +21,9 @@ The `$partition-management-create-partition` operation can be used to create a n
         <tr>
             <td>id</td>
             <td>Integer</td>
-            <td>1..1</td>
+            <td>0..1</td>
             <td>
-                The numeric ID for the partition. This value can be any integer, positive or negative or zero. It must not be a value that has already been used. 
+                The numeric ID for the partition. This value can be any integer, positive or negative or zero. It must not be a value that has already been used. If omitted, a random unused integer will be selected.
             </td>
         </tr>
         <tr>

hapi-fhir-jpaserver-base/src/main/java/ca/uhn/fhir/jpa/partition/IPartitionLookupSvc.java

@@ -46,6 +46,13 @@ public interface IPartitionLookupSvc {
 
 	void clearCaches();
 
+	/**
+	 * Will generate a random unused partition ID. Validates that no partition with that ID exists before returning.
+	 *
+	 * @return an integer, representing a random unused partition ID.
+	 */
+	int generateRandomUnusedPartitionId();
+
 	PartitionEntity createPartition(PartitionEntity thePartition, RequestDetails theRequestDetails);
 
 	PartitionEntity updatePartition(PartitionEntity thePartition);

hapi-fhir-jpaserver-base/src/main/java/ca/uhn/fhir/jpa/partition/PartitionLookupSvcImpl.java

@@ -52,6 +52,7 @@ import javax.annotation.Nonnull;
 import javax.annotation.PostConstruct;
 import java.util.List;
 import java.util.Optional;
+import java.util.concurrent.ThreadLocalRandom;
 import java.util.concurrent.TimeUnit;
 import java.util.regex.Pattern;
 
@@ -120,9 +121,23 @@ public class PartitionLookupSvcImpl implements IPartitionLookupSvc {
 		myIdToPartitionCache.invalidateAll();
 	}
 
+	/**
+	 * Generate a random int which is guaranteed to  be unused by an existing partition.
+	 * @return an integer representing a partition ID that is not currently in use by the system.
+	 */
+	public int generateRandomUnusedPartitionId() {
+		int candidate = ThreadLocalRandom.current().nextInt();
+		Optional<PartitionEntity> partition = myPartitionDao.findById(candidate);
+		while (partition.isPresent()) {
+			candidate = ThreadLocalRandom.current().nextInt();
+			partition = myPartitionDao.findById(candidate);
+		}
+		return candidate;
+	}
 	@Override
 	@Transactional
 	public PartitionEntity createPartition(PartitionEntity thePartition, RequestDetails theRequestDetails) {
+
 		validateNotInUnnamedPartitionMode();
 		validateHaveValidPartitionIdAndName(thePartition);
 		validatePartitionNameDoesntAlreadyExist(thePartition.getName());

hapi-fhir-jpaserver-base/src/main/java/ca/uhn/fhir/jpa/partition/PartitionManagementProvider.java

@@ -21,6 +21,7 @@ package ca.uhn.fhir.jpa.partition;
 
 import ca.uhn.fhir.context.FhirContext;
 import ca.uhn.fhir.jpa.entity.PartitionEntity;
+import ca.uhn.fhir.model.primitive.IntegerDt;
 import ca.uhn.fhir.rest.annotation.Operation;
 import ca.uhn.fhir.rest.annotation.OperationParam;
 import ca.uhn.fhir.rest.annotation.ResourceParam;
@@ -30,6 +31,8 @@ import ca.uhn.fhir.util.ParametersUtil;
 import org.hl7.fhir.instance.model.api.IBase;
 import org.hl7.fhir.instance.model.api.IBaseParameters;
 import org.hl7.fhir.instance.model.api.IPrimitiveType;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Autowired;
 
 import javax.annotation.Nonnull;
@@ -51,6 +54,7 @@ import static org.hl7.fhir.instance.model.api.IPrimitiveType.toValueOrNull;
  * </ul>
  */
 public class PartitionManagementProvider {
+	private static final Logger ourLog = LoggerFactory.getLogger(PartitionLookupSvcImpl.class);
 
 	@Autowired
 	private FhirContext myCtx;
@@ -71,6 +75,11 @@ public class PartitionManagementProvider {
 		@OperationParam(name = ProviderConstants.PARTITION_MANAGEMENT_PARTITION_DESC, min = 0, max = 1, typeName = "string") IPrimitiveType<String> thePartitionDescription,
 		RequestDetails theRequestDetails
 	) {
+
+		if (thePartitionId == null && thePartitionName!= null && thePartitionName.hasValue()) {
+			thePartitionId = requestRandomPartitionId(thePartitionName);
+		}
+
 		validatePartitionIdSupplied(myCtx, toValueOrNull(thePartitionId));
 
 		PartitionEntity input = parseInput(thePartitionId, thePartitionName, thePartitionDescription);
@@ -83,6 +92,13 @@ public class PartitionManagementProvider {
 		return retVal;
 	}
 
+	@Nonnull
+	private IPrimitiveType<Integer> requestRandomPartitionId(IPrimitiveType<String> thePartitionName) {
+		int unusedPartitionId = myPartitionLookupSvc.generateRandomUnusedPartitionId();
+		ourLog.info("Request to create partition came in without a partition ID. Auto-assigning an available ID.[partition_id={}, partition_name={}]", unusedPartitionId, thePartitionName);
+		return new IntegerDt(unusedPartitionId);
+	}
+
 	/**
 	 * Add Partition:
 	 * <code>

hapi-fhir-jpaserver-test-r4/src/test/java/ca/uhn/fhir/jpa/partition/PartitionManagementProviderTest.java

@@ -17,6 +17,8 @@ import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.junit.jupiter.api.extension.RegisterExtension;
+import org.mockito.ArgumentCaptor;
+import org.mockito.Captor;
 import org.mockito.stubbing.Answer;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -33,7 +35,9 @@ import java.util.List;
 import java.util.stream.Collectors;
 
 import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.hasSize;
+import static org.hamcrest.Matchers.instanceOf;
 import static org.hamcrest.Matchers.is;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.fail;
@@ -94,6 +98,34 @@ public class PartitionManagementProviderTest {
 		assertEquals("a description", ((StringType) response.getParameterValue(ProviderConstants.PARTITION_MANAGEMENT_PARTITION_DESC)).getValue());
 	}
 
+	@Test
+	public void testCreatePartitionWithNameOnlyAutogeneratesId() {
+
+		when(myPartitionConfigSvc.createPartition(any(), any())).thenAnswer(createAnswer());
+
+		Parameters input = createInputPartitionWithoutId();;
+		ourLog.debug("Input:\n{}", ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(input));
+
+		Parameters response = myClient
+			.operation()
+			.onServer()
+			.named(ProviderConstants.PARTITION_MANAGEMENT_CREATE_PARTITION)
+			.withParameters(input)
+			.encodedXml()
+			.execute();
+
+		ourLog.debug("Response:\n{}", ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(response));
+		ArgumentCaptor<PartitionEntity> entityCaptor = ArgumentCaptor.forClass(PartitionEntity.class);
+		verify(myPartitionConfigSvc, times(1)).createPartition(entityCaptor.capture(), any());
+		verify(myPartitionConfigSvc, times(1)).generateRandomUnusedPartitionId();
+		verifyNoMoreInteractions(myPartitionConfigSvc);
+		PartitionEntity value = entityCaptor.getValue();
+
+		assertThat(value.getName(), is(equalTo("PARTITION-123")));
+		assertThat(value.getId(), is(instanceOf(Integer.class)));
+		assertThat(value.getDescription(), is(equalTo("a description")));
+	}
+
 	@Nonnull
 	private Parameters createInputPartition() {
 		Parameters input = new Parameters();
@@ -103,6 +135,14 @@ public class PartitionManagementProviderTest {
 		return input;
 	}
 
+	@Nonnull
+	private Parameters createInputPartitionWithoutId() {
+		Parameters input = new Parameters();
+		input.addParameter(ProviderConstants.PARTITION_MANAGEMENT_PARTITION_NAME, new CodeType("PARTITION-123"));
+		input.addParameter(ProviderConstants.PARTITION_MANAGEMENT_PARTITION_DESC, new StringType("a description"));
+		return input;
+	}
+
 	@Test
 	public void testCreatePartition_InvalidInput() {
 		try {