docs(examples): Grafana agent java example (#2930)

* move to subfolder

* add java example

examples/grafana-agent/README.md → examples/grafana-agent/golang-pull/README.md

@@ -8,7 +8,7 @@ You'll need to configure the Grafana agent for things like profiling configurati
 
 You can find a list of [arguments](https://grafana.com/docs/agent/latest/flow/reference/components/pyroscope.scrape/#arguments) and [supported blocks](https://grafana.com/docs/agent/latest/flow/reference/components/pyroscope.scrape/#blocks) in the [Grafana Agent documentation for pyroscope](https://grafana.com/docs/agent/latest/flow/reference/components/pyroscope.scrape/)
 
-Refer to [config file](./agent/config/config.river) to see an example of how to configure Grafana Agent to send profiling data to Pyroscope.
+Refer to [config file](agent/config/config.river) to see an example of how to configure Grafana Agent to send profiling data to Pyroscope.
 
 ### 2. Run Grafana agent, Grafana and Pyroscope
 

examples/grafana-agent/java/FastSlow.java

@@ -0,0 +1,21 @@
+import java.util.concurrent.*;
+
+public class FastSlow {
+
+    public static long fib(int n) {
+        if (n < 2) {
+            return n;
+        }
+        return fib(n - 1) + fib(n - 2);
+    }
+
+    public static void main(String[] args) throws ExecutionException, InterruptedException {
+        ExecutorService e = Executors.newSingleThreadExecutor();
+        e.submit(() -> {
+            while (true) {
+                fib(26);
+                fib(24);
+            }
+        });
+    }
+}

examples/grafana-agent/java/config.river

@@ -0,0 +1,56 @@
+logging {
+  level = "debug"
+  format = "logfmt"
+}
+
+discovery.process "all" {
+  // join kuberenetes targets with process targets on container_id to have k8s labels
+  // join = discovery.kubernetes.containers.targets
+}
+
+discovery.relabel "java" {
+    targets = discovery.process.all.targets
+    rule {
+        source_labels = ["__meta_process_exe"]
+        action = "keep"
+        regex = ".*/java$"
+    }
+    rule {
+        source_labels = ["__meta_process_commandline"]
+        regex = "java FastSlow"
+        action = "keep"
+    }
+    rule {
+        action = "replace"
+        target_label = "service_name"
+        replacement = "java-fast-slow-fibonacci"
+    }
+}
+
+pyroscope.java "java" {
+  profiling_config {
+    interval = "15s"
+    alloc = "512k"
+    cpu = true
+    lock = "10ms"
+    sample_rate = 100
+  }
+  forward_to = [pyroscope.write.example.receiver]
+  targets = discovery.relabel.java.output
+}
+
+pyroscope.write "example" {
+  // Send metrics to a locally running Pyroscope instance.
+  endpoint {
+    url = "http://pyroscope:4040"
+
+    // To send data to Grafana Cloud you'll need to provide username and password.
+    // basic_auth {
+    //   username = "myuser"
+    //   password = "mypassword"
+    // }
+  }
+  external_labels = {
+    "env" = "example",
+  }
+}

examples/grafana-agent/java/docker-compose.yml

@@ -0,0 +1,26 @@
+version: '3.9'
+services:
+  java:
+    build:
+      context: .
+      dockerfile: java.Dockerfile
+  pyroscope:
+    image: 'grafana/pyroscope:latest'
+    ports:
+      - 4040:4040
+
+  agent:
+    image: grafana/agent:main
+    volumes:
+      - ./config.river:/etc/agent-config/config.river
+    command:
+      - run
+      - /etc/agent-config/config.river
+      - --server.http.listen-addr=0.0.0.0:12345
+    environment:
+      HOSTNAME: agent
+      AGENT_MODE: flow
+    ports:
+      - "12345:12345"
+    privileged: true
+    pid: host

examples/grafana-agent/java/java.Dockerfile

@@ -0,0 +1,6 @@
+FROM openjdk:17-jdk-slim
+
+ADD ./FastSlow.java /FastSlow.java
+RUN javac FastSlow.java
+
+CMD ["java", "FastSlow"]