Merge branch 'jshook/heartbeat'

engine-cli/src/main/java/io/nosqlbench/engine/cli/NBCLI.java

@@ -401,25 +401,28 @@ public class NBCLI implements Function<String[], Integer>, NBLabeledElement {
         // intentionally not shown for warn-only
         NBCLI.logger.info(() -> "console logging level is " + options.getConsoleLogLevel());
 
+        Map<String, String> props = Map.of(
+                "summary", options.getReportSummaryTo(),
+                "logsdir", options.getLogsDirectory().toString(),
+                "progress", options.getProgressSpec(),
+                "prompush_cache", "prompush_cache.txt",
+                "heartbeat", String.valueOf(options.wantsHeartbeatIntervalMs())
+        );
         /**
          * At this point, the command stream from the CLI should be handed into the session, and the session should
          * marshal and transform it for any scenario invocations directly.
          */
+
+        try (
                 NBSession session = new NBSession(
                         new NBBaseComponent(null,
                                 options.getLabelMap()
                                         .andDefault("jobname", "nosqlbench")
                                         .andDefault("instance", "default")
                         ),
-            sessionName
+                        sessionName,
-        );
+                        props
-        // TODO: Decide whether this should be part of ctor consistency
+                )) {
-        Map.of(
-            "summary", options.getReportSummaryTo(),
-            "logsdir", options.getLogsDirectory().toString(),
-            "progress", options.getProgressSpec(),
-            "prompush_cache", "prompush_cache.txt"
-        ).forEach(session::setComponentProp);
 
             options.wantsReportCsvTo().ifPresent(cfg -> {
                 MetricInstanceFilter filter = new MetricInstanceFilter();
@@ -446,9 +449,10 @@ public class NBCLI implements Function<String[], Integer>, NBLabeledElement {
 
 
             ExecutionResult sessionResult = session.apply(options.getCommands());
-//        sessionResult.printSummary(System.out);
             logger.info(sessionResult);
             return sessionResult.getStatus().code;
+        }
+//        sessionResult.printSummary(System.out);
 
     }
 
@@ -465,10 +469,8 @@ public class NBCLI implements Function<String[], Integer>, NBLabeledElement {
         }
         basicHelp = basicHelp.replaceAll("PROG", this.commandName);
         return basicHelp;
-
     }
 
-
     @Override
     public NBLabels getLabels() {
         return labels;

engine-cli/src/main/java/io/nosqlbench/engine/cli/NBCLIOptions.java

@@ -63,6 +63,8 @@ public class NBCLIOptions {
     private static final String LABELSPEC = "--labelspec";
     private static final String ANNOTATORS_CONFIG = "--annotators";
 
+    private static final String HEARTBEAT_MILLIS = "--heartbeat-millis";
+
     // Enabled if the TERM env var is provided
     private static final String ANSI = "--ansi";
 
@@ -202,6 +204,7 @@ public class NBCLIOptions {
     private String annotateLabelSpec = "";
     private String metricsLabelSpec = "";
     private String wantsToCatResource ="";
+    private long heartbeatIntervalMs;
 
     public boolean wantsLoggedMetrics() {
         return this.wantsConsoleMetrics;
@@ -642,6 +645,11 @@ public class NBCLIOptions {
                     arglist.removeFirst();
                     this.wantsToCatResource = this.readWordOrThrow(arglist, "workload to cat");
                     break;
+                case HEARTBEAT_MILLIS:
+                    arglist.removeFirst();
+                    this.heartbeatIntervalMs =
+                            Long.parseLong(this.readWordOrThrow(arglist, "heartbeat interval in ms"));
+                    break;
                 default:
                     nonincludes.addLast(arglist.removeFirst());
             }
@@ -739,6 +747,10 @@ public class NBCLIOptions {
         return this.wantsActivityTypes;
     }
 
+    public long wantsHeartbeatIntervalMs() {
+        return this.heartbeatIntervalMs;
+    }
+
     public boolean wantsTopicalHelp() {
         return this.wantsActivityHelp;
     }

engine-core/src/main/java/io/nosqlbench/engine/core/lifecycle/session/NBSession.java

@@ -16,6 +16,8 @@
 
 package io.nosqlbench.engine.core.lifecycle.session;
 
+import io.nosqlbench.engine.core.lifecycle.scenario.execution.NBInvokableCommand;
+import io.nosqlbench.nb.api.components.status.NBLiveComponent;
 import io.nosqlbench.nb.api.engine.activityimpl.ActivityDef;
 import io.nosqlbench.nb.api.engine.metrics.instruments.MetricCategory;
 import io.nosqlbench.nb.api.engine.metrics.instruments.NBFunctionGauge;
@@ -43,7 +45,7 @@ import java.util.function.Function;
  * on.
  * All NBScenarios are run within an NBSession.
  */
-public class NBSession extends NBBaseComponent implements Function<List<Cmd>, ExecutionResult>, NBTokenWords {
+public class NBSession extends NBLiveComponent implements Function<List<Cmd>, ExecutionResult>, NBTokenWords {
     private final static Logger logger = LogManager.getLogger(NBSession.class);
 //    private final ClientSystemMetricChecker clientMetricChecker;
 
@@ -57,12 +59,15 @@ public class NBSession extends NBBaseComponent implements Function<List<Cmd>, Ex
 
     public NBSession(
         NBLabeledElement labelContext,
-        String sessionName
+        String sessionName,
+        Map<String, String> props
     ) {
         super(
             null,
             labelContext.getLabels()
-                .and("session", sessionName)
+                .and("session", sessionName),
+            props,
+            "session"
         );
 
         new NBSessionSafetyMetrics(this);
@@ -86,13 +91,16 @@ public class NBSession extends NBBaseComponent implements Function<List<Cmd>, Ex
         ResultCollector collector = new ResultCollector();
         try (ResultContext results = new ResultContext(collector).ok()) {
             for (NBCommandAssembly.CommandInvocation invocation : invocationCalls) {
-                try {
                 String targetContext = invocation.containerName();
+                String explanation = "in context '" + targetContext + "'";
+                try (NBInvokableCommand command = invocation.command()) {
+                    explanation += " command '" + command.toString() + "'";
                     NBBufferedContainer container = getContext(targetContext);
-                    NBCommandResult cmdResult = container.apply(invocation.command(), invocation.params());
+                    NBCommandResult cmdResult = container.apply(command, invocation.params());
                     results.apply(cmdResult);
                 } catch (Exception e) {
-                    String msg = "While running command '" + invocation.command() + "' in container '" + invocation.containerName() + "', an error occurred: " + e.toString();
+                    String msg = "While running " + explanation + "', an error occurred: " + e.toString();
+                    onError(e);
                     logger.error(msg);
                     results.error(e);
                     break;

engine-core/src/main/java/io/nosqlbench/engine/core/logging/LoggerConfig.java

@@ -391,7 +391,7 @@ public class LoggerConfig extends ConfigurationFactory {
 
     private void attachAuxLogger(ConfigurationBuilder<BuiltConfiguration> builder, String loggerName, Level fileLevel) {
         String appenderName = loggerName+(("_APPENDER").toUpperCase());
-        String fileName = loggerDir.resolve(getFileBase() + "_"+loggerName+".log").toString().toLowerCase();
+        String fileName = loggerDir.resolve(getFileBase() + "_"+loggerName.toLowerCase()+".log").toString();
         var appender = builder
             .newAppender(appenderName, FileAppender.PLUGIN_NAME)
             .addAttribute("append", false)

nb-api/src/main/java/io/nosqlbench/nb/api/components/core/NBBaseComponent.java

@@ -21,7 +21,6 @@ import io.nosqlbench.nb.api.components.events.ComponentOutOfScope;
 import io.nosqlbench.nb.api.components.events.DownEvent;
 import io.nosqlbench.nb.api.components.events.NBEvent;
 import io.nosqlbench.nb.api.components.events.UpEvent;
-import io.nosqlbench.nb.api.config.params.ElementData;
 import io.nosqlbench.nb.api.engine.metrics.instruments.NBMetric;
 import io.nosqlbench.nb.api.labels.NBLabels;
 import org.apache.logging.log4j.LogManager;
@@ -30,30 +29,37 @@ import org.apache.logging.log4j.Logger;
 import java.util.*;
 import java.util.concurrent.ConcurrentHashMap;
 
-public class NBBaseComponent extends NBBaseComponentMetrics implements NBComponent, NBTokenWords {
+public class NBBaseComponent extends NBBaseComponentMetrics implements NBComponent, NBTokenWords, NBComponentTimeline {
     private final static Logger logger = LogManager.getLogger("RUNTIME");
     protected final NBComponent parent;
     protected final NBLabels labels;
     private final List<NBComponent> children = new ArrayList<>();
-    private long endAt=0L;
-    private final long startAt;
     protected NBMetricsBuffer metricsBuffer = new NBMetricsBuffer();
     protected boolean bufferOrphanedMetrics = false;
     private ConcurrentHashMap<String,String> props = new ConcurrentHashMap<>();
+    protected Exception error;
+    protected long started_ns, teardown_ns, closed_ns, errored_ns;
+    protected NBInvokableState state = NBInvokableState.STARTING;
 
     public NBBaseComponent(NBComponent parentComponent) {
         this(parentComponent, NBLabels.forKV());
     }
 
     public NBBaseComponent(NBComponent parentComponent, NBLabels componentSpecificLabelsOnly) {
+        this.started_ns = System.nanoTime();
         this.labels = componentSpecificLabelsOnly;
-        this.startAt = System.nanoTime();
         if (parentComponent != null) {
             parent = parentComponent;
             parent.attachChild(this);
         } else {
             parent = null;
         }
+        state = (state==NBInvokableState.ERRORED) ? state : NBInvokableState.RUNNING;
+    }
+
+    public NBBaseComponent(NBComponent parentComponent, NBLabels componentSpecificLabelsOnly, Map<String, String> props) {
+        this(parentComponent,componentSpecificLabelsOnly);
+        props.forEach(this::setComponentProp);
     }
 
     @Override
@@ -117,30 +123,40 @@ public class NBBaseComponent extends NBBaseComponentMetrics implements NBCompone
 
     @Override
     public final void close() throws RuntimeException {
+        state = (state==NBInvokableState.ERRORED) ? state : NBInvokableState.CLOSING;
+        closed_ns = System.nanoTime();
+
         try {
             logger.debug("cleaning up");
             ArrayList<NBComponent> children = new ArrayList<>(getChildren());
             for (NBComponent child : children) {
                 child.close();
             }
-            teardown();
         } catch (Exception e) {
-            logger.error(e);
+            onError(e);
         } finally {
             logger.debug("detaching " + description());
             if (parent != null) {
                 parent.detachChild(this);
             }
+            teardown();
         }
     }
 
+    public void onError(Exception e) {
+        RuntimeException wrapped = new RuntimeException("While in state " + this.state + ", an error occured: " + e, e);
+        logger.error(wrapped);
+        this.error = wrapped;
+        state=NBInvokableState.ERRORED;
+    }
     /**
      * Override this method in your component implementations when you need to do something
      * to close out your component.
      */
     protected void teardown() {
         logger.debug("tearing down " + description());
-        this.endAt = System.nanoTime();
+        this.teardown_ns = System.nanoTime();
+        this.state=(state==NBInvokableState.ERRORED) ? state : NBInvokableState.STOPPED;
     }
 
     @Override
@@ -229,10 +245,10 @@ public class NBBaseComponent extends NBBaseComponentMetrics implements NBCompone
 
     @Override
     public long getNanosSinceStart() {
-        if (endAt==0) {
+        if (teardown_ns ==0) {
-            return System.nanoTime()-startAt;
+            return System.nanoTime()- started_ns;
         } else {
-            return endAt-startAt;
+            return teardown_ns - started_ns;
         }
     }
 
@@ -255,4 +271,29 @@ public class NBBaseComponent extends NBBaseComponentMetrics implements NBCompone
         props.put(name, value);
         return this;
     }
+
+    @Override
+    public NBInvokableState getComponentState() {
+        return state;
+    }
+
+    @Override
+    public long nanosof_start() {
+        return this.started_ns;
+    }
+
+    @Override
+    public long nanosof_close() {
+        return this.closed_ns;
+    }
+
+    @Override
+    public long nanosof_teardown() {
+        return this.teardown_ns;
+    }
+
+    @Override
+    public long nanosof_error() {
+        return this.errored_ns;
+    }
 }

nb-api/src/main/java/io/nosqlbench/nb/api/components/core/NBComponentTimeline.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) 2024 nosqlbench
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.nosqlbench.nb.api.components.core;
+
+public interface NBComponentTimeline {
+
+    NBInvokableState getComponentState();
+    /**
+     * This will be 0L if the component hasn't fully started, else it will be
+     * the {@link System#nanoTime()} of when the component entered its constructor
+     * @return nanosecond time of component construction
+     */
+    long nanosof_start();
+
+    /**
+     * This will be 0L if the component hasn't began the process of closing down.
+     * @return nanosecond time of invoking {@link NBBaseComponent#close()}
+     */
+    long nanosof_close();
+
+    /**
+     * This will be 0L if the component hasn't completed teardown. Otherwise it will be
+     * the {@link System#nanoTime()} when the base teardown logic in the component has completed.
+     * For this reason, it is imperative that any overrides to {@link NBBaseComponent#teardown()}
+     * are called, and called last in the overridden teardown method.
+     * @return nanosecond time of teardown completion
+     */
+    long nanosof_teardown();
+
+    /**
+     * This will be 0L if the component hasn't logged an error. Otherwise it will be
+     * the {@link System#nanoTime()} of when the error was reported.
+     * @return nanosecond time of the error
+     */
+    long nanosof_error();
+}

nb-api/src/main/java/io/nosqlbench/nb/api/components/core/NBInvokableState.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2024 nosqlbench
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.nosqlbench.nb.api.components.core;
+
+/**
+ * <PRE>{@code
+ * errored_at > 0   -> ERROR
+ * started_at == 0   -> STARTING
+ * <p>
+ * <p>
+ * <p>
+ * started_at > closed_at
+ * STARTING
+ * closed_at > started_at
+ * RUNNING
+ * teardown_at > closed_at
+ * STOPPING
+ * teardown_at
+ * STOPPED
+ * stopped_at
+ * }</pre>
+ */
+public enum NBInvokableState {
+    /**
+     * The component exists in some state but has not completed initialization / construction
+     */
+    STARTING,
+    /**
+     * The component has completed initialization and is presumed to be running
+     */
+    RUNNING,
+    /**
+     * The component has begun closing down, which means unwinding/closing any child components
+     */
+    CLOSING,
+    /**
+     * The component has completed closing down, including its teardown logic
+     */
+    STOPPED,
+    /**
+     * There was an error
+     */
+    ERRORED;
+
+}

nb-api/src/main/java/io/nosqlbench/nb/api/components/core/PeriodicTaskComponent.java

@@ -25,90 +25,10 @@ import java.util.concurrent.locks.Condition;
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
 
-public abstract class PeriodicTaskComponent extends NBBaseComponent implements Runnable {
+public abstract class PeriodicTaskComponent extends UnstartedPeriodicTaskComponent {
 
-    private static final Logger logger = LogManager.getLogger(PeriodicTaskComponent.class);
+    public PeriodicTaskComponent(NBComponent node, NBLabels extraLabels, long millis, String threadName, FirstReport firstReport, LastReport lastReport) {
-    private final long intervalmillis;
+        super(node, extraLabels, millis, threadName, firstReport, lastReport);
-    private final Lock lock = new ReentrantLock();
+        start();
-    private final Condition shutdownSignal = lock.newCondition();
-    private final boolean oneLastTime;
-
-    Thread thread;
-    private boolean running = true;
-
-    public PeriodicTaskComponent(
-        NBComponent node,
-        NBLabels extraLabels,
-        long millis,
-        boolean oneLastTime,
-        String threadName
-    ) {
-        super(node, extraLabels);
-        this.intervalmillis = millis;
-        thread = Thread.ofVirtual().name(threadName).start(this);
-        this.oneLastTime = oneLastTime;
-    }
-
-    protected abstract void task();
-
-    @Override
-    public void run() {
-        long now = System.currentTimeMillis();
-        long reportAt = now + intervalmillis;
-        long waitfor = reportAt - now;
-
-        while (running) {
-            while (running && waitfor > 0) {
-                boolean signalReceived = false;
-                try {
-                    lock.lock();
-                    signalReceived = shutdownSignal.await(waitfor, TimeUnit.MILLISECONDS);
-                } catch (InterruptedException ignored) {
-                } finally {
-                    lock.unlock();
-                }
-                if (signalReceived) {
-                    logger.debug("signal shutting down " + this);
-                    return;
-                }
-                now = System.currentTimeMillis();
-                waitfor = reportAt - now;
-            }
-//            logger.info("summarizing metrics to console");
-            try {
-                task();
-            } catch (Exception e) {
-                logger.error(e);
-                throw new RuntimeException(e);
-            } finally {
-                reportAt = reportAt + (intervalmillis);
-                now = System.currentTimeMillis();
-                waitfor = reportAt - now;
     }
 }
-        logger.info("shutting down periodic runnable component: " + description());
-    }
-
-    public void teardown() {
-        logger.debug("shutting down " + this);
-
-        lock.lock();
-        running = false;
-        shutdownSignal.signalAll();
-        lock.unlock();
-        logger.debug("signaled reporter thread to shut down " + description());
-
-        try {
-            thread.join();
-        } catch (InterruptedException e) {
-            logger.warn("interrupted while joining thread");
-        }
-
-        if (oneLastTime) {
-            logger.debug("running " + this + " one last time.");
-            task();
-        }
-
-    }
-
-}

nb-api/src/main/java/io/nosqlbench/nb/api/components/core/UnstartedPeriodicTaskComponent.java

@@ -0,0 +1,167 @@
+/*
+ * Copyright (c) 2023 nosqlbench
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.nosqlbench.nb.api.components.core;
+
+import io.nosqlbench.nb.api.labels.NBLabels;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
+
+
+/**
+ * <P>Because of ctor super calling order requirements, the task thread can't always be started
+ * automatically in super(...). If that is the case, then use this class directly and call
+ * start() at the end of your subtype ctor.</P>
+ *
+ * <P>Otherwise, it is safe to use {@link PeriodicTaskComponent} directly.</P>
+ */
+public abstract class UnstartedPeriodicTaskComponent extends NBBaseComponent implements Runnable {
+
+    private static final Logger logger = LogManager.getLogger(UnstartedPeriodicTaskComponent.class);
+    protected final long intervalmillis;
+    private final Lock lock = new ReentrantLock();
+    private final Condition shutdownSignal = lock.newCondition();
+    private final FirstReport firstReport;
+    private final LastReport lastReport;
+    private final String threadName;
+    Thread thread;
+    private boolean running = true;
+
+    public enum FirstReport {
+        Immediately,
+        OnInterval
+    }
+    public enum LastReport {
+        None,
+        onClose,
+        /**
+         * OnInterrupt is a stronger version of OnClose, including scenarios where the process is interrupted with a signal
+         */
+        OnInterrupt
+    }
+
+    public UnstartedPeriodicTaskComponent(
+        NBComponent node,
+        NBLabels extraLabels,
+        long millis,
+        String threadName,
+        FirstReport firstReport,
+        LastReport lastReport
+    ) {
+        super(node, extraLabels);
+        this.threadName = threadName;
+        this.intervalmillis = millis;
+        this.firstReport = firstReport;
+        this.lastReport = lastReport;
+        if(lastReport== LastReport.OnInterrupt) {
+            Thread hook=new Thread(this::task,"shutdownhook-"+threadName);
+            Runtime.getRuntime().addShutdownHook(hook);
+        }
+        // TODO: There is a potential race condition between init and invoke here, if millis is low enough and post-super() state is needed
+    }
+
+    public void start() {
+        if (firstReport==FirstReport.Immediately) task();
+        thread = Thread.ofVirtual().name(threadName).start(this);
+    }
+    /**
+     * This task should only do what is needed once each period.
+     * If it throws any exceptions, then these exceptions will cause the period task
+     * to exit. Thus, if you need to allow failures in some cases while keeping
+     * the caller (scheduler) active, all errors should be caught and handled
+     * internally.
+     */
+    protected abstract void task();
+
+    @Override
+    public void run() {
+        long now = System.currentTimeMillis();
+        long reportAt = now + intervalmillis;
+        long waitfor = reportAt - now;
+
+        while (running) {
+            while (running && waitfor > 0) {
+                boolean signalReceived = false;
+                try {
+                    lock.lock();
+                    signalReceived = shutdownSignal.await(waitfor, TimeUnit.MILLISECONDS);
+                } catch (InterruptedException ignored) {
+                } finally {
+                    lock.unlock();
+                }
+                if (signalReceived) {
+                    logger.debug("signal shutting down " + this);
+                    return;
+                }
+                now = System.currentTimeMillis();
+                waitfor = reportAt - now;
+            }
+//            logger.info("summarizing metrics to console");
+            try {
+                lock.lock();
+                task();
+            } catch (Exception e) {
+                logger.error(e);
+                throw new RuntimeException(e);
+            } finally {
+                reportAt = reportAt + (intervalmillis);
+                now = System.currentTimeMillis();
+                waitfor = reportAt - now;
+                lock.unlock();
+            }
+        }
+        logger.info("shutting down periodic runnable component: " + description());
+    }
+
+    public void teardown() {
+
+        logger.debug("shutting down " + this);
+
+        lock.lock();
+        running = false;
+        shutdownSignal.signalAll();
+        lock.unlock();
+
+//        if (lastReport==LastReport.onClose || lastReport==LastReport.OnInterrupt) {
+//            logger.debug("final task() call for period component " + description());
+//            task();
+//        }
+
+        logger.debug("signaled reporter thread to shut down " + description());
+
+        try {
+            thread.join();
+        } catch (InterruptedException e) {
+            logger.warn("interrupted while joining thread");
+        }
+
+        if (this.lastReport== LastReport.onClose) {
+            logger.debug("running " + this + " one last time on close().");
+            task();
+        }
+
+        super.teardown();
+
+    }
+
+
+
+}

nb-api/src/main/java/io/nosqlbench/nb/api/components/status/ComponentPulse.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2024 nosqlbench
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.nosqlbench.nb.api.components.status;
+
+import io.nosqlbench.nb.api.components.core.UnstartedPeriodicTaskComponent;
+import io.nosqlbench.nb.api.labels.NBLabels;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.StandardOpenOption;
+
+public class ComponentPulse extends UnstartedPeriodicTaskComponent {
+    private final static Logger logger = LogManager.getLogger(ComponentPulse.class);
+    private final Path hbpath;
+    private final NBLiveComponent pulseOf;
+
+    public ComponentPulse(NBLiveComponent pulseOf, NBLabels extraLabels, String fileNameLabel, long millis) {
+        super(
+            pulseOf,
+            extraLabels,
+            millis,
+            "PULSE-" + pulseOf.description(),
+            FirstReport.Immediately,
+            LastReport.OnInterrupt
+        );
+        this.pulseOf = pulseOf;
+        String logsdir = getComponentProp("logsdir").orElseThrow();
+        this.hbpath = Path.of(logsdir).resolve(pulseOf.getLabels().valueOf(fileNameLabel)+"_status.yaml");
+        start();
+    }
+
+    @Override
+    protected void task() {
+        logger.debug("emitting pulse for :" + this.pulseOf.description());
+        Heartbeat heartbeat = pulseOf.heartbeat().withHeartbeatDetails(intervalmillis,System.currentTimeMillis());
+        try {
+            Files.writeString(hbpath, heartbeat.toYaml(), StandardOpenOption.WRITE, StandardOpenOption.CREATE, StandardOpenOption.TRUNCATE_EXISTING);
+        } catch (IOException e) {
+            logger.error("Unable to write heartbeat data to " + hbpath.toString() + ": " + e);
+        }
+    }
+}

nb-api/src/main/java/io/nosqlbench/nb/api/components/status/Heartbeat.java

@@ -0,0 +1,73 @@
+/*
+ * Copyright (c) 2024 nosqlbench
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.nosqlbench.nb.api.components.status;
+
+import io.nosqlbench.nb.api.components.core.NBInvokableState;
+import io.nosqlbench.nb.api.labels.NBLabels;
+import org.snakeyaml.engine.v2.api.Dump;
+import org.snakeyaml.engine.v2.api.DumpSettings;
+import org.snakeyaml.engine.v2.common.FlowStyle;
+
+import java.util.Map;
+
+public record Heartbeat(
+        NBLabels labels,
+        NBInvokableState state,
+        long started_at,
+        long session_time_ns,
+        long heartbeat_interval_ms,
+        long heartbeat_epoch_ms
+) {
+    public final static Dump dump = createDump();
+
+    private static Dump createDump() {
+
+        DumpSettings settings = DumpSettings.builder().setDefaultFlowStyle(FlowStyle.BLOCK).build();
+        return new Dump(settings, new HeartbeatRepresenter(settings));
+    }
+
+    public Heartbeat withHeartbeatDetails(long new_heartbeat_interval_ms, long new_heartbeat_ms_epoch) {
+        return new Heartbeat(
+                labels,
+                state,
+                started_at,
+                session_time_ns,
+                new_heartbeat_interval_ms,
+                new_heartbeat_ms_epoch
+        );
+    }
+
+    public String toYaml() {
+        return toString();
+    }
+
+    public Map<String, Object> toMap() {
+        return Map.of(
+                "labels", labels.asMap(),
+                "state", state,
+                "started_at_epochms", started_at,
+                "session_time_ns", session_time_ns,
+                "heartbeat_interval_ms", heartbeat_interval_ms,
+                "heartbeat_epoch_ms", heartbeat_epoch_ms
+        );
+    }
+
+    @Override
+    public String toString() {
+        return dump.dumpToString(toMap());
+    }
+}

nb-api/src/main/java/io/nosqlbench/nb/api/components/status/HeartbeatRepresenter.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2024 nosqlbench
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.nosqlbench.nb.api.components.status;
+
+import io.nosqlbench.nb.api.components.core.NBInvokableState;
+import org.snakeyaml.engine.v2.api.DumpSettings;
+import org.snakeyaml.engine.v2.api.RepresentToNode;
+import org.snakeyaml.engine.v2.nodes.Node;
+import org.snakeyaml.engine.v2.representer.StandardRepresenter;
+
+public class HeartbeatRepresenter extends StandardRepresenter {
+    public HeartbeatRepresenter(DumpSettings settings) {
+        super(settings);
+        this.representers.put(NBInvokableState.class, new RepresentEnumToString());
+    }
+
+    public class RepresentEnumToString implements RepresentToNode {
+
+        @Override
+        public Node representData(Object o) {
+            if (o instanceof Enum<?> e) {
+                String name = e.name();
+                return HeartbeatRepresenter.this.represent(name);
+            } else {
+                throw new RuntimeException("Unable to represent as enum: " + o.toString() + " (class " + o.getClass().getSimpleName() + "'");
+            }
+        }
+    }
+}

nb-api/src/main/java/io/nosqlbench/nb/api/components/status/NBLiveComponent.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright (c) 2024 nosqlbench
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.nosqlbench.nb.api.components.status;
+
+import io.nosqlbench.nb.api.components.core.NBBaseComponent;
+import io.nosqlbench.nb.api.components.core.NBComponent;
+import io.nosqlbench.nb.api.components.core.NBInvokableState;
+import io.nosqlbench.nb.api.labels.NBLabels;
+
+import java.util.Map;
+
+/**
+ * A <EM>live</EM> component is one which provides evidence that it is either
+ * in a healthy state or that it is not, via a heartbeat mechanism.
+ */
+public class NBLiveComponent extends NBBaseComponent {
+
+    public NBLiveComponent(NBComponent parentComponent) {
+        super(parentComponent);
+    }
+
+    public NBLiveComponent(NBComponent parentComponent, NBLabels componentSpecificLabelsOnly, Map<String, String> props, String liveLabel) {
+        super(parentComponent, componentSpecificLabelsOnly, props);
+        // attaches, no further reference needed
+        new ComponentPulse(this, NBLabels.forKV(), liveLabel, Long.parseLong(getComponentProp("heartbeat").orElse("60000")));
+    }
+
+    public Heartbeat heartbeat() {
+        return new Heartbeat(
+            getLabels(),
+            this.getComponentState(),
+            started_ns,
+            sessionTimeMs(),
+            0L,
+            0L
+        );
+    }
+
+    private long sessionTimeMs() {
+        NBInvokableState state = getComponentState();
+        long nanos = switch (state) {
+            case ERRORED -> (nanosof_error() - nanosof_start());
+            case STARTING, RUNNING -> (System.nanoTime() - nanosof_start());
+            case CLOSING -> (nanosof_close() - nanosof_start());
+            case STOPPED -> (nanosof_teardown() - nanosof_start());
+        };
+        return nanos / 1_000_000L;
+    }
+}

nb-api/src/main/java/io/nosqlbench/nb/api/engine/metrics/reporters/ConsoleReporter.java

@@ -44,7 +44,7 @@ public class ConsoleReporter extends PeriodicTaskComponent {
 
     public ConsoleReporter(NBComponent node, NBLabels extraLabels, long millis, boolean oneLastTime,
                            PrintStream output, Set<MetricAttribute> disabledMetricAttributes) {
-        super(node, extraLabels, millis, oneLastTime, "REPORT-CONSOLE");
+        super(node, extraLabels, millis, "REPORT-CONSOLE", FirstReport.OnInterval, LastReport.OnInterrupt);
         this.output = output;
         this.dateFormat = DateFormat.getDateTimeInstance(DateFormat.SHORT,
             DateFormat.MEDIUM,

nb-api/src/main/java/io/nosqlbench/nb/api/engine/metrics/reporters/CsvReporter.java

@@ -59,7 +59,7 @@ public class CsvReporter extends PeriodicTaskComponent {
 
     public CsvReporter(NBComponent node, Path reportTo, long intervalMs, MetricInstanceFilter filter,
                        NBLabels extraLabels) {
-        super(node, extraLabels, intervalMs, false,"REPORT-CSV");
+        super(node, extraLabels, intervalMs, "REPORT-CSV", FirstReport.OnInterval, LastReport.OnInterrupt);
         this.component = node;
         this.reportTo = reportTo;
         this.filter = filter;

nb-api/src/main/java/io/nosqlbench/nb/api/engine/metrics/reporters/Log4JMetricsReporter.java

@@ -51,7 +51,7 @@ public class Log4JMetricsReporter extends PeriodicTaskComponent {
                                 final NBLabels extraLabels,
                                 final long millis,
                                 final boolean oneLastTime) {
-        super(component, extraLabels, millis, oneLastTime,"REPORT-LOG4J");
+        super(component, extraLabels, millis, "REPORT-LOG4J", FirstReport.OnInterval, LastReport.OnInterrupt);
         this.loggerProxy = loggerProxy;
         this.marker = marker;
     }

nb-api/src/main/java/io/nosqlbench/nb/api/engine/metrics/reporters/PromPushReporterComponent.java

@@ -51,7 +51,7 @@ public class PromPushReporterComponent extends PeriodicTaskComponent {
     private String bearerToken;
 
     public PromPushReporterComponent(NBComponent parent, String endpoint, long intervalMs, NBLabels nbLabels) {
-        super(parent, nbLabels.and("_type", "prom-push"), intervalMs, true, "REPORT-PROMPUSH");
+        super(parent, nbLabels.and("_type", "prom-push"), intervalMs,  "REPORT-PROMPUSH",FirstReport.OnInterval, LastReport.OnInterrupt);
         String jobname = getLabels().valueOfOptional("jobname").orElse("default");
         String instance = getLabels().valueOfOptional("instance").orElse("default");
         if (jobname.equals("default") || instance.equals("default")) {

nbr-examples/src/test/java/io/nosqlbench/nbr/examples/injavascript/ScenarioExampleTests.java

@@ -30,6 +30,7 @@ import org.junit.jupiter.api.parallel.Execution;
 import org.junit.jupiter.api.parallel.ExecutionMode;
 
 import java.util.List;
+import java.util.Map;
 
 @Disabled
 @Execution(ExecutionMode.SAME_THREAD)
@@ -44,7 +45,7 @@ public class ScenarioExampleTests {
         NBCLIOptions parser = new NBCLIOptions(params);
         List<Cmd> commands = parser.getCommands();
         var myroot = new TestComponent("test_"+params[0]);
-        NBSession session = new NBSession(myroot,"session_"+params[0]);
+        NBSession session = new NBSession(myroot,"session_"+params[0], Map.of());
         System.out.println("=".repeat(29) + " Running scenario test for example scenario: " + params[0]);
         ExecutionResult result = session.apply(commands);
         return result;