Add ruby as a dependency for datadog integration

- Download the ruby binary
- Append the ruby binary path to the PATH env var before the DD startup script

buildpack/telemetry/datadog.py

@@ -389,6 +389,19 @@ def _set_up_environment(model_version, runtime_version):
     e["DD_ENABLE_CHECKS"] = str(bool(_is_checks_enabled())).lower()
     e["LOGS_CONFIG"] = json.dumps(_get_logging_config())
 
+    # Append the ruby binary path
+    ruby_path = os.path.join(ROOT_DIR, "ruby", "bin")
+    e["PATH"] += os.pathsep + ruby_path
+
+    # Add an empty .global_env file as the DD buildpack expects a .global_env
+    # This is in parity with how the DD buildpack sets up the environment before
+    # installing the DD agents. Sourced from bin/supply scripts
+    # https://github.com/DataDog/datadog-cloudfoundry-buildpack/blob/master/bin/supply#L31
+    # Keeping it empty as we're already adding the RUBY path as part of process env
+    global_env_file = os.path.join(_get_agent_dir(), ".global_env")
+    with open(global_env_file, mode='a'):
+        pass
+
     return e
 
 
@@ -492,6 +505,16 @@ def update_config(
 
 
 def _download(buildpack_dir, build_path, cache_dir):
+    # DD for cflinuxfs4 requires ruby to be available, so installing
+    # the ruby dependency first before we proceed
+    # https://github.com/DataDog/datadog-cloudfoundry-buildpack/pull/174
+    util.resolve_dependency(
+        "ruby",
+        os.path.join(build_path, "ruby"),
+        buildpack_dir=buildpack_dir,
+        cache_dir=cache_dir,
+    )
+
     util.resolve_dependency(
         f"{NAMESPACE}.buildpack",
         os.path.join(build_path, NAMESPACE),

dependencies.yml

@@ -90,6 +90,11 @@ dependencies:
     fs: cflinuxfs4
     cpe: cpe:2.3:a:f5:nginx:{{ version }}:*:*:*:*:*:*:*
     version: 1.22.1
+  ruby:
+    artifact: ruby/ruby_{{ version }}_linux_x64_{{ fs }}_{{ commit }}.tgz
+    commit: 5fed98f8
+    fs: cflinuxfs4
+    version: 3.2.2
   telegraf:
     agent:
       artifact: telegraf/telegraf-{{ version }}_linux_amd64.tar.gz