Initial commit of log method weaving hook

.gitignore

@@ -0,0 +1,6 @@
+.classpath
+.project
+.settings/
+target/
+.DS_Store
+.idea/

README.md

@@ -0,0 +1,27 @@
+# Sling Observability Weaving Hooks
+
+Library of weaving hooks to ease the process of observability in out-of-the-box code
+
+## Log Method Weaving Hook
+
+When all else fails, and you have no logs available because there are no log statements in the out-of-the-box classes, use this Log Method Weaving Hook to add a dynamic log statements
+
+### Usage
+
+Install the bundle in start level 1 and add an OSGi config for every method log you would like to add.
+
+Example, search for your classname, method name and amount of parameters you want to log and add an OSGi config `be.orbinson.sling.observability.weavinghooks.logmethod.LogMethodWeavingHookConfiguration~MyClass-doGet.cfg.json`
+
+```json
+{
+  "className": "my.package.MyClass",
+  "methodName": "doGet",
+  "amountOfParameters": 2
+}
+```
+
+To make the weaving hook work, either a framework restart of an entire java process restart is required.
+
+## Future
+
+- Add weaving hooks to create custom spans and metrics using OpenTelemetry

pom.xml

@@ -0,0 +1,138 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project
+        xmlns="http://maven.apache.org/POM/4.0.0"
+        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+        xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
+
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>be.orbinson.sling</groupId>
+    <artifactId>sling-observability-weavinghooks</artifactId>
+    <packaging>bundle</packaging>
+    <version>0.0.1-SNAPSHOT</version>
+
+    <name>Sling Observability Weaving Hooks</name>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.felix</groupId>
+                <artifactId>maven-bundle-plugin</artifactId>
+                <version>5.1.9</version>
+                <extensions>true</extensions>
+                <configuration>
+                    <outputDirectory>${basedir}/target/classes</outputDirectory>
+                    <instructions>
+                        <Bundle-SymbolicName>${project.artifactId}</Bundle-SymbolicName>
+                        <Bundle-Version>${project.version}</Bundle-Version>
+                        <Embed-Dependency>asm,asm-util,asm-tree,asm-analysis</Embed-Dependency>
+                    </instructions>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>1.8</source>
+                    <target>1.8</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <properties>
+        <sling.host>localhost</sling.host>
+        <sling.port>8080</sling.port>
+        <sling.user>admin</sling.user>
+        <sling.password>admin</sling.password>
+    </properties>
+
+    <profiles>
+        <profile>
+            <id>auto-deploy</id>
+            <build>
+                <plugins>
+                    <plugin>
+                        <groupId>org.apache.sling</groupId>
+                        <artifactId>sling-maven-plugin</artifactId>
+                        <version>2.4.0</version>
+                        <configuration>
+                            <slingUrl>
+                                http://${sling.host}:${sling.port}/apps/sling-observability-weaving-hooks/install/1
+                            </slingUrl>
+                            <deploymentMethod>SlingPostServlet</deploymentMethod>
+                            <user>${sling.user}</user>
+                            <password>${sling.password}</password>
+                        </configuration>
+                        <executions>
+                            <execution>
+                                <id>install-bundle</id>
+                                <goals>
+                                    <goal>install</goal>
+                                </goals>
+                            </execution>
+                        </executions>
+                    </plugin>
+                </plugins>
+            </build>
+        </profile>
+    </profiles>
+
+    <dependencies>
+        <!-- OSGi -->
+        <dependency>
+            <groupId>org.osgi</groupId>
+            <artifactId>osgi.core</artifactId>
+            <version>7.0.0</version>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.osgi</groupId>
+            <artifactId>osgi.cmpn</artifactId>
+            <version>7.0.0</version>
+            <scope>provided</scope>
+        </dependency>
+
+        <!-- Bytecode transformation -->
+        <dependency>
+            <groupId>org.ow2.asm</groupId>
+            <artifactId>asm</artifactId>
+            <version>9.7</version>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.ow2.asm</groupId>
+            <artifactId>asm-util</artifactId>
+            <version>9.7</version>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.ow2.asm</groupId>
+            <artifactId>asm-tree</artifactId>
+            <version>9.7</version>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.ow2.asm</groupId>
+            <artifactId>asm-analysis</artifactId>
+            <version>9.7</version>
+            <scope>provided</scope>
+        </dependency>
+
+        <!-- Logging -->
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>slf4j-api</artifactId>
+            <version>1.7.36</version>
+            <scope>provided</scope>
+        </dependency>
+
+        <!-- Testing -->
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>5.10.2</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+</project>

src/main/java/be/orbinson/sling/observability/weavinghooks/logmethod/LogMethodAdapter.java

@@ -0,0 +1,48 @@
+package be.orbinson.sling.observability.weavinghooks.logmethod;
+
+import org.objectweb.asm.MethodVisitor;
+import org.objectweb.asm.Type;
+
+import static org.objectweb.asm.Opcodes.*;
+
+/**
+ * Method visitor that will add a LoggerFactory log statement call of all parameters when entering a method
+ */
+public class LogMethodAdapter extends MethodVisitor {
+
+    private final String classDescriptor;
+    private final String methodName;
+    private final String methodDescriptor;
+    private final String logLevel;
+
+    public LogMethodAdapter(MethodVisitor mv, String classDescriptor, String methodName, String methodDescriptor, String logLevel) {
+        super(ASM9, mv);
+        this.classDescriptor = classDescriptor;
+        this.methodName = methodName;
+        this.methodDescriptor = methodDescriptor;
+        this.logLevel = logLevel;
+    }
+
+
+    @Override
+    public void visitCode() {
+        mv.visitVarInsn(ALOAD, 0);
+        mv.visitLdcInsn(Type.getType(classDescriptor));
+        mv.visitMethodInsn(INVOKESTATIC, "org/slf4j/LoggerFactory", "getLogger", "(Ljava/lang/Class;)Lorg/slf4j/Logger;", false);
+        StringBuilder logString = new StringBuilder(methodName);
+        Type[] types = Type.getArgumentTypes(methodDescriptor);
+        for (int i = 0; i < types.length; i++) {
+            logString.append(String.format(", param_%s: <{}>", i + 1));
+        }
+        mv.visitLdcInsn(logString.toString());
+        mv.visitInsn(ICONST_0 + types.length);
+        mv.visitTypeInsn(ANEWARRAY, "java/lang/Object");
+        for (int i = 0; i < types.length; i++) {
+            mv.visitInsn(DUP);
+            mv.visitInsn(ICONST_0 + i);
+            mv.visitVarInsn(ALOAD, i + 1);
+            mv.visitInsn(AASTORE);
+        }
+        mv.visitMethodInsn(INVOKEINTERFACE, "org/slf4j/Logger", logLevel.toLowerCase(), "(Ljava/lang/String;[Ljava/lang/Object;)V", true);
+    }
+}

src/main/java/be/orbinson/sling/observability/weavinghooks/logmethod/LogMethodClassVisitor.java

@@ -0,0 +1,54 @@
+package be.orbinson.sling.observability.weavinghooks.logmethod;
+
+import org.objectweb.asm.ClassVisitor;
+import org.objectweb.asm.MethodVisitor;
+import org.objectweb.asm.Opcodes;
+import org.objectweb.asm.Type;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * ClassVisitor that will add the {@link LogMethodAdapter} when the method name matches with the requested method name
+ */
+public class LogMethodClassVisitor extends ClassVisitor {
+
+    private final Logger log = LoggerFactory.getLogger(getClass());
+
+    private final String methodName;
+    private final String className;
+    private final String logLevel;
+    private String classDescriptor;
+
+    public LogMethodClassVisitor(ClassVisitor cv, String className, String methodName, String logLevel) {
+        super(Opcodes.ASM9, cv);
+        this.cv = cv;
+        this.className = className;
+        this.methodName = methodName;
+        this.logLevel = logLevel;
+    }
+
+    @Override
+    public void visit(int version, int access, String name, String signature, String superName, String[] interfaces) {
+        cv.visit(version, access, name, signature, superName, interfaces);
+        this.classDescriptor = Type.getObjectType(name).getDescriptor();
+    }
+
+    @Override
+    public MethodVisitor visitMethod(
+            int access,
+            String name,
+            String desc,
+            String signature,
+            String[] exceptions) {
+
+        MethodVisitor mv;
+        mv = cv.visitMethod(access, name, desc, signature, exceptions);
+        if (mv != null) {
+            if (name.equals(methodName)) {
+                log.debug("Adding dynamic log method to class {} and method {}", className, methodName);
+                mv = new LogMethodAdapter(mv, classDescriptor, methodName, desc, logLevel);
+            }
+        }
+        return mv;
+    }
+}

src/main/java/be/orbinson/sling/observability/weavinghooks/logmethod/LogMethodWeavingHook.java

@@ -0,0 +1,62 @@
+package be.orbinson.sling.observability.weavinghooks.logmethod;
+
+import org.objectweb.asm.ClassReader;
+import org.objectweb.asm.ClassVisitor;
+import org.objectweb.asm.ClassWriter;
+import org.objectweb.asm.util.TraceClassVisitor;
+import org.osgi.framework.hooks.weaving.WeavingHook;
+import org.osgi.framework.hooks.weaving.WovenClass;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.PrintWriter;
+
+public class LogMethodWeavingHook implements WeavingHook {
+
+    private final Logger log = LoggerFactory.getLogger(getClass());
+
+    private final PrintWriter printWriter = new PrintWriter(System.out);
+
+    private final String className;
+    private final String methodName;
+    private final String logLevel;
+    private final boolean enableTraceVisitor;
+
+    public LogMethodWeavingHook(LogMethodWeavingHookConfiguration config) {
+        this.className = config.getClassName();
+        this.methodName = config.getMethodName();
+        this.logLevel = config.getLogLevel();
+        this.enableTraceVisitor = config.isEnableTraceVisitor();
+    }
+
+    @Override
+    public void weave(WovenClass wovenClass) {
+        if (wovenClass.getClassName().equals(className)) {
+            log.debug("Adding dynamic log methods to class  {}", wovenClass.getClassName());
+            addLogMethodToClass(wovenClass);
+            addDynamicImports(wovenClass);
+        }
+    }
+
+    private void addLogMethodToClass(WovenClass wovenClass) {
+        final ClassReader cr = new ClassReader(wovenClass.getBytes());
+        final ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS | ClassWriter.COMPUTE_FRAMES);
+        ClassVisitor logMethodClassVisitor;
+        if (enableTraceVisitor) {
+            final TraceClassVisitor tcv = new TraceClassVisitor(cw, printWriter);
+            logMethodClassVisitor = new LogMethodClassVisitor(tcv, className, methodName, logLevel);
+        } else {
+            logMethodClassVisitor = new LogMethodClassVisitor(cw, className, methodName, logLevel);
+        }
+        cr.accept(logMethodClassVisitor, 0);
+        wovenClass.setBytes(cw.toByteArray());
+    }
+
+    /**
+     * Required to add sl4fj as dynamic import if it would not be used in the bundle
+     */
+    private void addDynamicImports(WovenClass wovenClass) {
+        wovenClass.getDynamicImports().add("org.slf4j");
+    }
+
+}