Merge pull request #6 from intergral/lazy_eval

feat(evaluator): make evaluators lazy

Author: Umaaz

agent/src/main/java/com/intergral/deep/agent/tracepoint/evaluator/AbstractEvaluator.java renamed to agent-api/src/main/java/com/intergral/deep/agent/api/plugin/AbstractEvaluator.java

@@ -15,11 +15,13 @@
  *     along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-package com.intergral.deep.agent.tracepoint.evaluator;
+package com.intergral.deep.agent.api.plugin;
 
-import com.intergral.deep.agent.api.plugin.IEvaluator;
 import java.util.Map;
 
+/**
+ * This allows for common handling for object to boolean expressions.
+ */
 public abstract class AbstractEvaluator implements IEvaluator {
 
   @Override

agent-api/src/main/java/com/intergral/deep/agent/api/plugin/LazyEvaluator.java

@@ -0,0 +1,62 @@
+/*
+ *     Copyright (C) 2023  Intergral GmbH
+ *
+ *     This program is free software: you can redistribute it and/or modify
+ *     it under the terms of the GNU Affero General Public License as published by
+ *     the Free Software Foundation, either version 3 of the License, or
+ *     (at your option) any later version.
+ *
+ *     This program is distributed in the hope that it will be useful,
+ *     but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *     GNU Affero General Public License for more details.
+ *
+ *     You should have received a copy of the GNU Affero General Public License
+ *     along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.intergral.deep.agent.api.plugin;
+
+import java.util.Map;
+
+/**
+ * This type allows the evaluator to be loaded only if it is needed. ie. if we have no watches or conditions there is no need for an
+ * evaluator.
+ */
+public class LazyEvaluator extends AbstractEvaluator {
+
+  private static final Exception NO_EVALUATOR_EXCEPTION = new RuntimeException(
+      "No evaluator available.");
+  private final IEvaluatorLoader loader;
+  private IEvaluator evaluator;
+
+  public LazyEvaluator(final IEvaluatorLoader loader) {
+    this.loader = loader;
+  }
+
+  private IEvaluator load() {
+    if (this.evaluator == null) {
+      try {
+        this.evaluator = this.loader.load();
+      } catch (Exception e) {
+        this.evaluator = new AbstractEvaluator() {
+          @Override
+          public Object evaluateExpression(final String expression, final Map<String, Object> values) throws Throwable {
+            throw NO_EVALUATOR_EXCEPTION;
+          }
+        };
+      }
+    }
+    return this.evaluator;
+  }
+
+  @Override
+  public Object evaluateExpression(final String expression, final Map<String, Object> values) throws Throwable {
+    return load().evaluateExpression(expression, values);
+  }
+
+  public interface IEvaluatorLoader {
+
+    IEvaluator load();
+  }
+}

agent/src/main/java/com/intergral/deep/agent/tracepoint/cf/CFEvaluator.java

@@ -17,7 +17,7 @@
 
 package com.intergral.deep.agent.tracepoint.cf;
 
-import com.intergral.deep.agent.tracepoint.evaluator.AbstractEvaluator;
+import com.intergral.deep.agent.api.plugin.AbstractEvaluator;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.util.Map;

agent/src/main/java/com/intergral/deep/agent/tracepoint/evaluator/NashornReflectEvaluator.java

@@ -17,6 +17,7 @@
 
 package com.intergral.deep.agent.tracepoint.evaluator;
 
+import com.intergral.deep.agent.api.plugin.AbstractEvaluator;
 import com.intergral.deep.agent.api.plugin.IEvaluator;
 import java.lang.reflect.Method;
 import java.util.HashMap;

agent/src/main/java/com/intergral/deep/agent/tracepoint/handler/Callback.java

@@ -19,6 +19,7 @@
 
 import com.intergral.deep.agent.Utils;
 import com.intergral.deep.agent.api.plugin.IEvaluator;
+import com.intergral.deep.agent.api.plugin.LazyEvaluator;
 import com.intergral.deep.agent.push.PushService;
 import com.intergral.deep.agent.settings.Settings;
 import com.intergral.deep.agent.tracepoint.TracepointConfigService;
@@ -88,7 +89,7 @@ public static void callBackCF(final List<String> bpIds,
       final int lineNo,
       final Map<String, Object> variables) {
     try {
-      final IEvaluator evaluator = CFUtils.findCfEval(variables);
+      final IEvaluator evaluator = new LazyEvaluator(() -> CFUtils.findCfEval(variables));
       commonCallback(bpIds, filename, lineNo, variables, evaluator, CFFrameProcessor::new);
     } catch (Throwable t) {
       LOGGER.debug("Unable to process tracepoint {}:{}", filename, lineNo, t);
@@ -109,7 +110,7 @@ public static void callBack(final List<String> bpIds,
       final int lineNo,
       final Map<String, Object> variables) {
     try {
-      final IEvaluator evaluator = EvaluatorService.createEvaluator();
+      final IEvaluator evaluator = new LazyEvaluator(EvaluatorService::createEvaluator);
       commonCallback(bpIds, filename, lineNo, variables, evaluator, FrameProcessor::new);
     } catch (Throwable t) {
       LOGGER.debug("Unable to process tracepoint {}:{}", filename, lineNo, t);