feat(diagnostics): Add API handler for invoking GC (#492)

Co-authored-by: Andrew Azores <me@andrewazor.es>

README.md

@@ -159,6 +159,18 @@ stopped or the host JVM shuts down.
 
 ## Configuration
 
+### Logging
+
+`cryostat-agent` uses [SLF4J](https://www.slf4j.org/) for its logging. Currently it ships with `slf4j-simple` as the
+log implementation, but this should change in the future to hook in to any existing SLF4J providers found on the
+classpath at runtime, or fallback to `slf4j-simple` if nothing is found.
+
+The Agent's log levels can be controlled by setting a JVM system property on the target JVM:
+`-Dio.cryostat.agent.shaded.org.slf4j.simpleLogger.defaultLogLevel=trace`, or replace `trace` with whatever level you
+prefer. This can also be passed as a dynamic attachment argument when starting the Agent after the target JVM.
+
+### Agent Properties
+
 `cryostat-agent` uses [smallrye-config](https://github.com/smallrye/smallrye-config) for configuration.
 Below is a list of configuration properties that can be used to influence how `cryostat-agent` runs
 and how it advertises itself to a Cryostat server instance. Properties that require configuration are indicated with a checked box.

pom.xml

@@ -94,7 +94,7 @@
   <com.github.spotbugs.plugin.version>4.8.6.4</com.github.spotbugs.plugin.version>
   <org.junit.jupiter.version>5.11.1</org.junit.jupiter.version>
   <org.hamcrest.version>3.0</org.hamcrest.version>
-  <org.mockito.version>5.2.0</org.mockito.version>
+  <org.mockito.version>5.14.1</org.mockito.version>
   <org.jacoco.maven.plugin.version>0.8.12</org.jacoco.maven.plugin.version>
   <com.diffplug.spotless.maven.plugin.version>2.43.0</com.diffplug.spotless.maven.plugin.version>
   <com.google.googlejavaformat.version>1.17.0</com.google.googlejavaformat.version>
@@ -256,7 +256,7 @@
   </dependency>
   <dependency>
     <groupId>org.mockito</groupId>
-    <artifactId>mockito-inline</artifactId>
+    <artifactId>mockito-core</artifactId>
     <version>${org.mockito.version}</version>
     <scope>test</scope>
   </dependency>

src/main/java/io/cryostat/agent/remote/InvokeContext.java

@@ -0,0 +1,117 @@
+/*
+ * Copyright The Cryostat Authors.
+ *
+ * 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.cryostat.agent.remote;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.lang.management.ManagementFactory;
+import java.util.Objects;
+
+import javax.inject.Inject;
+import javax.management.MBeanServer;
+import javax.management.ObjectName;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.sun.net.httpserver.HttpExchange;
+import org.apache.http.HttpStatus;
+import org.eclipse.microprofile.config.Config;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+class InvokeContext extends MutatingRemoteContext {
+
+    private final Logger log = LoggerFactory.getLogger(getClass());
+    private final ObjectMapper mapper;
+
+    @Inject
+    InvokeContext(ObjectMapper mapper, Config config) {
+        super(config);
+        this.mapper = mapper;
+    }
+
+    @Override
+    public String path() {
+        return "/mbean-invoke/";
+    }
+
+    @Override
+    public void handle(HttpExchange exchange) throws IOException {
+        try {
+            String mtd = exchange.getRequestMethod();
+            switch (mtd) {
+                case "POST":
+                    try (InputStream body = exchange.getRequestBody()) {
+                        MBeanInvocationRequest req =
+                                mapper.readValue(body, MBeanInvocationRequest.class);
+                        if (!req.isValid()) {
+                            exchange.sendResponseHeaders(
+                                    HttpStatus.SC_BAD_REQUEST, BODY_LENGTH_NONE);
+                        }
+                        MBeanServer server = ManagementFactory.getPlatformMBeanServer();
+                        Object response =
+                                server.invoke(
+                                        ObjectName.getInstance(req.beanName),
+                                        req.operation,
+                                        req.parameters,
+                                        req.signature);
+                        if (Objects.nonNull(response)) {
+                            exchange.sendResponseHeaders(HttpStatus.SC_OK, BODY_LENGTH_UNKNOWN);
+                            try (OutputStream responseStream = exchange.getResponseBody()) {
+                                mapper.writeValue(responseStream, response);
+                            }
+                        } else {
+                            exchange.sendResponseHeaders(HttpStatus.SC_ACCEPTED, BODY_LENGTH_NONE);
+                        }
+                    } catch (Exception e) {
+                        log.error("mbean serialization failure", e);
+                        exchange.sendResponseHeaders(HttpStatus.SC_BAD_GATEWAY, BODY_LENGTH_NONE);
+                    }
+                    break;
+                default:
+                    log.warn("Unknown request method {}", mtd);
+                    exchange.sendResponseHeaders(
+                            HttpStatus.SC_METHOD_NOT_ALLOWED, BODY_LENGTH_NONE);
+                    break;
+            }
+        } finally {
+            exchange.close();
+        }
+    }
+
+    static class MBeanInvocationRequest<T> {
+
+        public String beanName;
+        public String operation;
+        public Object[] parameters;
+        public String[] signature;
+
+        public boolean isValid() {
+            if (this.beanName.equals(ManagementFactory.MEMORY_MXBEAN_NAME)) {
+                return true;
+            }
+            return false;
+        }
+
+        public String getBeanName() {
+            return beanName;
+        }
+
+        public void setBeanName(String beanName) {
+            this.beanName = beanName;
+        }
+    }
+}

src/main/java/io/cryostat/agent/remote/RemoteModule.java

@@ -22,6 +22,10 @@
 @Module
 public abstract class RemoteModule {
 
+    @Binds
+    @IntoSet
+    abstract RemoteContext bindInvokeContext(InvokeContext ctx);
+
     @Binds
     @IntoSet
     abstract RemoteContext bindMBeanContext(MBeanContext ctx);