Added metrics generator

pom.xml

@@ -20,7 +20,7 @@
     <parent>
         <groupId>org.kill-bill.billing</groupId>
         <artifactId>killbill-oss-parent</artifactId>
-        <version>0.144.58</version>
+        <version>0.145.3-c9eb563-SNAPSHOT</version>
     </parent>
     <groupId>org.kill-bill.billing.plugin.java</groupId>
     <artifactId>stripe-plugin</artifactId>
@@ -85,13 +85,13 @@
             <scope>test</scope>
         </dependency>
         <dependency>
-            <groupId>javax.inject</groupId>
-            <artifactId>javax.inject</artifactId>
+            <groupId>jakarta.servlet</groupId>
+            <artifactId>jakarta.servlet-api</artifactId>
+            <scope>provided</scope>
         </dependency>
         <dependency>
-            <groupId>javax.servlet</groupId>
-            <artifactId>javax.servlet-api</artifactId>
-            <scope>provided</scope>
+            <groupId>javax.inject</groupId>
+            <artifactId>javax.inject</artifactId>
         </dependency>
         <dependency>
             <groupId>joda-time</groupId>
@@ -114,8 +114,7 @@
         <dependency>
             <groupId>org.jooq</groupId>
             <artifactId>jooq</artifactId>
-            <!-- 3.14.0 broke returning() on MySQL :( -->
-            <version>3.13.5</version>
+            <version>3.14.15</version>
         </dependency>
         <dependency>
             <groupId>org.kill-bill.billing</groupId>
@@ -173,6 +172,11 @@
             <artifactId>killbill-embeddeddb-common</artifactId>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.kill-bill.commons</groupId>
+            <artifactId>killbill-metrics-api</artifactId>
+            <scope>provided</scope>
+        </dependency>
         <dependency>
             <groupId>org.mockito</groupId>
             <artifactId>mockito-core</artifactId>

spotbugs-exclude.xml

@@ -19,4 +19,7 @@
     <Match>
         <Class name="~org\.killbill\.billing\.plugin\.stripe\.dao\.gen.*"/>
     </Match>
+    <Bug pattern="EI_EXPOSE_REP"/>
+    <Bug pattern="EI_EXPOSE_REP2"/>
+    <Bug pattern="NP_PARAMETER_MUST_BE_NONNULL_BUT_MARKED_AS_NULLABLE"/>
 </FindBugsFilter>

src/main/java/org/killbill/billing/plugin/stripe/MetricsGenerator.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright 2020-2022 Equinix, Inc
+ * Copyright 2014-2022 The Billing Project, LLC
+ *
+ * The Billing Project licenses this file to you 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 org.killbill.billing.plugin.stripe;
+
+import org.killbill.billing.osgi.libs.killbill.OSGIMetricRegistry;
+import org.killbill.billing.osgi.libs.killbill.OSGIServiceNotAvailable;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class MetricsGenerator {
+
+    private static final Logger logger = LoggerFactory.getLogger(MetricsGenerator.class);
+
+    private final Thread thread;
+
+    private volatile boolean stopMetrics;
+
+    public MetricsGenerator(final OSGIMetricRegistry metricRegistry) {
+        this.thread = new Thread(new Runnable() {
+            public void run() {
+                while (!stopMetrics) {
+                    try {
+                        Thread.sleep(1000L);
+                    } catch (final InterruptedException ignored) {
+                        Thread.currentThread().interrupt();
+                        logger.info("MetricsGenerator shutting down...");
+                        break;
+                    }
+
+                    try {
+                        metricRegistry.getMetricRegistry().counter("stripe_plugin_counter").inc(1);
+                    } catch (final OSGIServiceNotAvailable ignored) {
+                        logger.warn("No MetricRegistry available");
+                    }
+                }
+            }
+        });
+    }
+
+    public void start() {
+        thread.start();
+    }
+
+    public void stop() {
+        stopMetrics = true;
+    }
+}

src/main/java/org/killbill/billing/plugin/stripe/StripeActivator.java

@@ -41,6 +41,8 @@ public class StripeActivator extends KillbillActivatorBase {
 
     private StripeConfigPropertiesConfigurationHandler stripeConfigPropertiesConfigurationHandler;
 
+    private MetricsGenerator metricsGenerator;
+
     @Override
     public void start(final BundleContext context) throws Exception {
         super.start(context);
@@ -60,6 +62,10 @@ public void start(final BundleContext context) throws Exception {
         final StripeHealthcheck stripeHealthcheck = new StripeHealthcheck(stripeConfigPropertiesConfigurationHandler);
         registerHealthcheck(context, stripeHealthcheck);
 
+        // Expose metrics (optional)
+        metricsGenerator = new MetricsGenerator(metricRegistry);
+        metricsGenerator.start();
+
         // Register the payment plugin
         Stripe.setAppInfo("Kill Bill", "7.2.0", "https://killbill.io");
         final StripePaymentPluginApi pluginApi = new StripePaymentPluginApi(stripeConfigPropertiesConfigurationHandler,
@@ -87,6 +93,12 @@ public void start(final BundleContext context) throws Exception {
         registerHandlers();
     }
 
+    @Override
+    public void stop(final BundleContext context) throws Exception {
+        metricsGenerator.stop();
+        super.stop(context);
+    }
+
     public void registerHandlers() {
         final PluginConfigurationEventHandler handler = new PluginConfigurationEventHandler(stripeConfigPropertiesConfigurationHandler);
         dispatcher.registerEventHandlers(handler);