Add logging MDC

README.md

@@ -22,6 +22,7 @@ public class TaxiApplication {
 
 1. [Worker ID](#worker-id)
 1. [Workflow modules](#workflow-modules)
+2. [Logging](#logging)
 1. [Spring boot profiles](#spring-boot-profiles)
 1. [Migrating from one BPM system to another](#migrating-from-one-bpm-system-to-another)
 1. [Noteworthy & Contributors](#noteworthy--contributors)
@@ -129,6 +130,28 @@ Therefore, on migrating workflows from one engine to another, the BPMN files hav
 according to new engine used. Having this in mind one should also define a resources location specific to the current engine used,
 even if there are no plans to migrate to any other engine yet (see sample above).
 
+## Logging
+
+All VanillaBP adapter implementations use `Slf4J` as a logging-framework wrapper. According to the current
+action (running a method annotated by `@WorkflowTask` or a method of `ProcessService` called) MDCs are setting
+using the keys defined in class `io.vanillabp.springboot.adapter.LoggingContext`:
+
+* The current workflow module's ID.
+* The current VanillaBP adapter's ID.
+* The current aggregate's ID - may be null if not yet filled by the database for auto-increments.
+* The current workflow's BPMN process ID ("id" attribute of BPMN "process" tag)
+  regardless whether the current action belongs to a call-activity's BPMN task. Secondary BPMN process IDs
+  are not available for logging (see [Call-activities](https://github.com/vanillabp/spi-for-java#call-activities))</a>.
+* The current workflow's ID, specific to underlying BPM system (aka process instance ID) - if already known by the adapter.
+* The current workflow task's ID.
+* The current workflow task's BPMN node ("id" attribute of the BPMN XML tag in combination with the BPMN process ID the task belongs to - e.g. "MyProcess#MyTask").
+* The current workflow task's BPMN node ID (aka flow node instance ID).
+
+However, if those values
+are needed without using `Slf4J` then you can use the `LoggingContext`'s static class methods to retrieve them. 
+
+*Hint:* Adapters may add additional logging context. Checkout their README.md for details.
+
 ## Spring boot profiles
 
 Typically, profiles are used to set environment specific properties (e.g. stages):

src/main/java/io/vanillabp/springboot/adapter/LoggingContext.java

@@ -0,0 +1,129 @@
+package io.vanillabp.springboot.adapter;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public abstract class LoggingContext {
+
+    /**
+     * The current workflow module's ID.
+     */
+    public static final String WORKFLOW_MODULE_ID = "workflowModuleId";
+
+    /**
+     * The current VanillaBP adapter's ID.
+     */
+    public static final String WORKFLOW_ADAPTER_ID = "workflowAdapterId";
+
+    /**
+     * The current aggregate's ID - may be null if not yet filled by the database for auto-increments.
+     */
+    public static final String WORKFLOW_AGGREGATE_ID = "workflowAggregateId";
+
+    /**
+     * The current workflow's BPMN process ID ("id" attribute of BPMN "process" tag)
+     * regardless whether the current action belongs to a call-activity's BPMN task. Secondary BPMN process IDs
+     * are not available for logging.
+     *
+     * #see <a href="https://github.com/vanillabp/spi-for-java#call-activities">Call-activities</a>
+     */
+    public static final String WORKFLOW_BPMN_ID = "workflowBpmnId";
+
+    /**
+     * The current workflow's ID, specific to underlying BPM system (aka process instance ID)
+     * - if already known by the adapter.
+     */
+    public static final String WORKFLOW_BPM_ID = "workflowBpmId";
+
+    /**
+     * The current workflow task's ID.
+     */
+    public static final String WORKFLOW_TASK_ID = "workflowTaskId";
+
+    /**
+     * The current workflow task's BPMN node (&quot;id&quot; attribute of the BPMN XML tag in combination with
+     * the BPMN process ID the task belongs to - e.g. &quot;MyProcess#MyTask&quot;).
+     */
+    public static final String WORKFLOW_TASK_NODE = "workflowTaskNode";
+
+    /**
+     * The current workflow task's BPMN node ID (aka flow node instance ID).
+     */
+    public static final String WORKFLOW_TASK_NODE_ID = "workflowTaskNodeId";
+
+
+    private static ThreadLocal<Map<String, Object>> context = ThreadLocal.withInitial(HashMap::new);
+
+    /**
+     * @return Immutable context
+     */
+    public static Map<String, Object> getContext() {
+        return Map.copyOf(context.get());
+    }
+
+    protected static void clearContext() {
+        context.get().clear();
+    }
+
+    protected static Map<String, Object> getWriteableContext() {
+        return context.get();
+    }
+
+    /**
+     * @see LoggingContext#WORKFLOW_AGGREGATE_ID
+     */
+    public static String getWorkflowAggregateId() {
+        return (String) context.get().get(WORKFLOW_AGGREGATE_ID);
+    }
+
+    /**
+     * @see LoggingContext#WORKFLOW_BPMN_ID
+     */
+    public static String getWorkflowBpmnId() {
+        return (String) context.get().get(WORKFLOW_BPMN_ID);
+    }
+
+    /**
+     * @see LoggingContext#WORKFLOW_BPM_ID
+     */
+    public static String getWorkflowBpmId() {
+        return (String) context.get().get(WORKFLOW_BPM_ID);
+    }
+
+    /**
+     * @see LoggingContext#WORKFLOW_MODULE_ID
+     */
+    public static String getWorkflowModuleId() {
+        return (String) context.get().get(WORKFLOW_MODULE_ID);
+    }
+
+    /**
+     * @see LoggingContext#WORKFLOW_ADAPTER_ID
+     */
+    public static String getWorkflowAdapterId() {
+        return (String) context.get().get(WORKFLOW_ADAPTER_ID);
+    }
+
+    /**
+     * @see LoggingContext#WORKFLOW_TASK_ID
+     */
+    public static String getWorkflowTaskId() {
+        return (String) context.get().get(WORKFLOW_TASK_ID);
+    }
+
+    /**
+     * @see LoggingContext#WORKFLOW_TASK_NODE
+     */
+    public static String getWorkflowTaskNode() {
+        return (String) context.get().get(WORKFLOW_TASK_NODE);
+    }
+
+    /**
+     * @see LoggingContext#WORKFLOW_TASK_NODE_ID
+     */
+    public static String getWorkflowTaskNodeId() {
+        return (String) context.get().get(WORKFLOW_TASK_NODE_ID);
+    }
+
+
+}

src/main/java/io/vanillabp/springboot/adapter/ProcessServiceImplementation.java

@@ -11,4 +11,6 @@ public interface ProcessServiceImplementation<DE> extends ProcessService<DE> {
 
     void setParent(AdapterAwareProcessService<DE> parent);
 
+    String getPrimaryBpmnProcessId();
+
 }