[go-migration] add cf-metrics-exporter framework

docs/framework-cf_metrics_exporter.md

@@ -0,0 +1,40 @@
+# cf-metrics-exporter (Agent Mode)
+
+This framework integrates the [cf-metrics-exporter](https://github.com/rabobank/cf-metrics-exporter) as a Java agent in the Java buildpack.
+
+## Enabling the Exporter
+
+Set the following environment variable in the cloud foundry env to enable the agent (via manifest.yml or `cf set-env`):
+
+```
+CF_METRICS_EXPORTER_ENABLED=true
+```
+
+## Configuration
+
+- **CF_METRICS_EXPORTER_ENABLED**: Set to `true` to enable the agent (default: disabled).
+- **CF_METRICS_EXPORTER_PROPS**: (Optional) Properties string to pass to the agent, e.g. `enableLogEmitter,rpsType=tomcat-bean`.
+
+## How it Works
+
+- The agent JAR is downloaded during the buildpack supply phase.
+- The agent is injected into the JVM at runtime using the `-javaagent` option.
+- If `CF_METRICS_EXPORTER_PROPS` is set, its value is appended to the `-javaagent` option.
+
+## Example
+
+```
+CF_METRICS_EXPORTER_ENABLED=true
+CF_METRICS_EXPORTER_PROPS="enableLogEmitter,rpsType=tomcat-bean"
+```
+
+## Version
+
+- Default version: 0.7.1
+- Default download URI: https://github.com/rabobank/cf-metrics-exporter/releases/download/0.7.1/cf-metrics-exporter-0.7.1.jar
+
+## Notes
+
+- The agent is injected with priority 43 in JAVA_OPTS (after other APM agents).
+
+

manifest.yml

@@ -80,6 +80,8 @@ default_versions:
   version: 7.x
 - name: newrelic
   version: 8.x
+- name: cf-metrics-exporter
+  version: 0.7.x
 
 url_to_dependency_map:
 - match: openjdk-jre-(\d+\.\d+\.\d+)
@@ -544,6 +546,14 @@ dependencies:
   cf_stacks:
   - cflinuxfs4
 
+# cf-metrics-exporter Agent
+- name: cf-metrics-exporter
+  version: 0.7.1
+  uri: https://repo1.maven.org/maven2/io/github/rabobank/cf-metrics-exporter/0.7.1/cf-metrics-exporter-0.7.1.jar
+  sha256: 7ebabd3ffd812082cf92a513c8d2ac52906f5b42cd952cbe740bd5d5b086e79b
+  cf_stacks:
+  - cflinuxfs4
+
 # Container Security Provider
 # Note: Always enabled by default, provides container-specific security context
 - name: container-security-provider

src/java/finalize/finalize.go

@@ -2,9 +2,11 @@ package finalize
 
 import (
 	"fmt"
-	"github.com/cloudfoundry/java-buildpack/src/java/common"
 	"os"
 	"path/filepath"
+	"strings"
+
+	"github.com/cloudfoundry/java-buildpack/src/java/common"
 
 	"github.com/cloudfoundry/java-buildpack/src/java/containers"
 	"github.com/cloudfoundry/java-buildpack/src/java/frameworks"
@@ -157,7 +159,7 @@ func (f *Finalizer) finalizeFrameworks() error {
 		return nil
 	}
 
-	f.Log.Info("Finalizing frameworks: %v", frameworkNames)
+	f.Log.Info("Finalizing frameworks: %v", strings.Join(frameworkNames, ","))
 
 	// Finalize all detected frameworks
 	for i, framework := range detectedFrameworks {

src/java/frameworks/cf_metrics_exporter.go

@@ -0,0 +1,126 @@
+package frameworks
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/cloudfoundry/java-buildpack/src/java/common"
+	"github.com/cloudfoundry/libbuildpack"
+)
+
+const cfMetricsExporterDependencyName = "cf-metrics-exporter"
+const cfMetricsExporterDirName = "cf_metrics_exporter"
+
+// Installer interface for dependency installation
+// Allows for mocking in tests
+// Only the InstallDependency method is needed for this framework
+// (matches the signature of libbuildpack.Installer)
+type Installer interface {
+	InstallDependency(dep libbuildpack.Dependency, outputDir string) error
+}
+
+type CfMetricsExporterFramework struct {
+	context   *common.Context
+	installer Installer
+}
+
+func NewCfMetricsExporterFramework(ctx *common.Context) *CfMetricsExporterFramework {
+	installer := ctx.Installer
+	if installer == nil {
+		installer = libbuildpack.NewInstaller(ctx.Manifest)
+	}
+	return &CfMetricsExporterFramework{context: ctx, installer: installer}
+}
+
+func (f *CfMetricsExporterFramework) Detect() (string, error) {
+	enabled := os.Getenv("CF_METRICS_EXPORTER_ENABLED")
+	if enabled == "true" || enabled == "TRUE" {
+		_, err := f.context.Manifest.DefaultVersion(cfMetricsExporterDependencyName)
+		if err != nil {
+			return "", fmt.Errorf("cf-metrics-exporter version not found in manifest: %w", err)
+		}
+		return "CF Metrics Exporter", nil
+	}
+	return "", nil
+}
+
+func (f *CfMetricsExporterFramework) getManifestDependency() (libbuildpack.Dependency, *libbuildpack.ManifestEntry, error) {
+	dep, err := f.context.Manifest.DefaultVersion(cfMetricsExporterDependencyName)
+	if err != nil {
+		return libbuildpack.Dependency{}, nil, fmt.Errorf("cf-metrics-exporter version not found in manifest: %w", err)
+	}
+	entry, err := f.context.Manifest.GetEntry(dep)
+	if err != nil {
+		return dep, nil, fmt.Errorf("cf-metrics-exporter manifest entry not found: %w", err)
+	}
+	return dep, entry, nil
+}
+
+func (f *CfMetricsExporterFramework) Supply() error {
+	enabled := os.Getenv("CF_METRICS_EXPORTER_ENABLED")
+	if enabled != "true" && enabled != "TRUE" {
+		return nil
+	}
+
+	dep, _, err := f.getManifestDependency()
+	if err != nil {
+		return err
+	}
+
+	agentDir := filepath.Join(f.context.Stager.DepDir(), cfMetricsExporterDirName)
+	jarName := fmt.Sprintf("cf-metrics-exporter-%s.jar", dep.Version)
+	jarPath := filepath.Join(agentDir, jarName)
+
+	// Ensure agent directory exists
+	if err := os.MkdirAll(agentDir, 0755); err != nil {
+		return fmt.Errorf("failed to create agent dir: %w", err)
+	}
+
+	// Download the JAR if not present
+	if _, err := os.Stat(jarPath); os.IsNotExist(err) {
+		if err := f.installer.InstallDependency(dep, agentDir); err != nil {
+			return fmt.Errorf("failed to download cf-metrics-exporter: %w", err)
+		}
+		if _, err := os.Stat(jarPath); err != nil {
+			return fmt.Errorf("expected jar file not found after download: %w", err)
+		}
+	}
+
+	// Log activation, including properties if set
+	props := os.Getenv("CF_METRICS_EXPORTER_PROPS")
+	if props != "" {
+		f.context.Log.Info("CF Metrics Exporter v%s enabled, with properties: %s", dep.Version, props)
+	} else {
+		f.context.Log.Info("CF Metrics Exporter v%s enabled", dep.Version)
+	}
+
+	return nil
+}
+
+func (f *CfMetricsExporterFramework) Finalize() error {
+	enabled := os.Getenv("CF_METRICS_EXPORTER_ENABLED")
+	if enabled != "true" && enabled != "TRUE" {
+		return nil
+	}
+
+	dep, _, err := f.getManifestDependency()
+	if err != nil {
+		return err
+	}
+
+	jarName := fmt.Sprintf("cf-metrics-exporter-%s.jar", dep.Version)
+	depsIdx := f.context.Stager.DepsIdx()
+	agentPath := fmt.Sprintf("$DEPS_DIR/%s/cf_metrics_exporter/%s", depsIdx, jarName)
+
+	props := os.Getenv("CF_METRICS_EXPORTER_PROPS")
+	var javaOpt string
+	if props != "" {
+		javaOpt = fmt.Sprintf("-javaagent:%s=%s", agentPath, props)
+	} else {
+		javaOpt = fmt.Sprintf("-javaagent:%s", agentPath)
+	}
+
+	// Priority 43: after SkyWalking (41), Splunk OTEL (42)
+	return writeJavaOptsFile(f.context, 43, cfMetricsExporterDirName, javaOpt)
+}