From 8b0907048855d81a338f03d177b827ff31089c18 Mon Sep 17 00:00:00 2001
From: Guillaume Pagnoux <guillaume.pagnoux@datadoghq.com>
Date: Fri, 11 Oct 2024 14:07:10 +0200
Subject: [PATCH 01/18] discovery: add rails service name detector

---
 .../servicediscovery/module/impl_linux.go     |  6 ++
 .../corechecks/servicediscovery/usm/ruby.go   | 90 +++++++++++++++++++
 .../servicediscovery/usm/service.go           |  5 +-
 3 files changed, 100 insertions(+), 1 deletion(-)
 create mode 100644 pkg/collector/corechecks/servicediscovery/usm/ruby.go

diff --git a/pkg/collector/corechecks/servicediscovery/module/impl_linux.go b/pkg/collector/corechecks/servicediscovery/module/impl_linux.go
index 9646bb4d31f28..8f7018a067d94 100644
--- a/pkg/collector/corechecks/servicediscovery/module/impl_linux.go
+++ b/pkg/collector/corechecks/servicediscovery/module/impl_linux.go
@@ -342,12 +342,18 @@ func (s *discovery) getServiceInfo(proc *process.Process) (*serviceInfo, error)
 		return nil, err
 	}
 
+	cwd, err := proc.Cwd()
+	if err != nil {
+		return nil, err
+	}
+
 	createTime, err := proc.CreateTime()
 	if err != nil {
 		return nil, err
 	}
 
 	contextMap := make(usm.DetectorContextMap)
+	contextMap[usm.ServiceCwd] = cwd
 
 	root := kernel.HostProc(strconv.Itoa(int(proc.Pid)), "root")
 	lang := language.FindInArgs(exe, cmdline)
diff --git a/pkg/collector/corechecks/servicediscovery/usm/ruby.go b/pkg/collector/corechecks/servicediscovery/usm/ruby.go
new file mode 100644
index 0000000000000..39c843927598f
--- /dev/null
+++ b/pkg/collector/corechecks/servicediscovery/usm/ruby.go
@@ -0,0 +1,90 @@
+// Unless explicitly stated otherwise all files in this repository are licensed
+// under the Apache License Version 2.0.
+// This product includes software developed at Datadog (https://www.datadoghq.com/).
+// Copyright 2016-present Datadog, Inc.
+
+package usm
+
+import (
+	"io"
+	"io/fs"
+	"regexp"
+	"strings"
+
+	"github.com/DataDog/datadog-agent/pkg/util/log"
+)
+
+var (
+	moduleRegexp  = regexp.MustCompile(`module\s+([A-Z][a-zA-Z0-9_]*)`)
+	matchFirstCap = regexp.MustCompile("(.)([A-Z][a-z]+)")
+	matchAllCap   = regexp.MustCompile("([a-z0-9])([A-Z])")
+)
+
+type railsDetector struct {
+	ctx DetectionContext
+}
+
+func newRailsDetector(ctx DetectionContext) detector {
+	return &railsDetector{ctx}
+}
+
+// detect checks if the service is a Rails application by looking for a
+// `config/application.rb` file generated by `rails new` when a new rails
+// project is created. This file should contain a `module` declaration with the
+// application name.
+func (r railsDetector) detect(_ []string) (ServiceMetadata, bool) {
+	cwd := r.ctx.contextMap[ServiceCwd].(string)
+	absFile := abs("config/application.rb", cwd)
+	if _, err := fs.Stat(r.ctx.fs, absFile); err != nil {
+		log.Debugf("Could not stat (cwd: %v) %v: %v", cwd, absFile, err)
+		return ServiceMetadata{}, false
+	}
+
+	name, ok := r.findRailsApplicationName(absFile)
+	if !ok {
+		return ServiceMetadata{}, false
+	}
+
+	return NewServiceMetadata(railsUnderscore(name)), true
+}
+
+// findRailsApplicationName scans the `config/application.rb` file to find the
+// Rails application name.
+func (r railsDetector) findRailsApplicationName(filename string) (string, bool) {
+	log.Debugf("findRailsApplicationName")
+	file, err := r.ctx.fs.Open(filename)
+	if err != nil {
+		log.Debugf("could not open application.rb")
+		return "", false
+	}
+	defer file.Close()
+
+	reader, err := SizeVerifiedReader(file)
+	if err != nil {
+		log.Debugf("skipping application.rb (%q): %v", filename, err)
+		return "", true // stops here
+	}
+
+	// Scan the file line by line, instead of reading the whole file into memory
+	bytes, err := io.ReadAll(reader)
+	if err != nil {
+		log.Debugf("unable to read application.rb (%q): %v", filename, err)
+		return "", true
+	}
+
+	matches := moduleRegexp.FindSubmatch(bytes)
+	if matches != nil {
+		return string(matches[1]), true
+	}
+
+	// No match found
+	return "", false
+}
+
+// Converts a PascalCasedWord to a snake_cased_word.
+// It keeps uppercase acronyms together when converting (e.g. "HTTPServer" -> "http_server").
+func railsUnderscore(pascalCasedWord string) string {
+	snake := matchFirstCap.ReplaceAllString(pascalCasedWord, "${1}_${2}")
+	snake = matchAllCap.ReplaceAllString(snake, "${1}_${2}")
+	return strings.ToLower(snake)
+}
diff --git a/pkg/collector/corechecks/servicediscovery/usm/service.go b/pkg/collector/corechecks/servicediscovery/usm/service.go
index 36ddc7e804d35..964b07af389f0 100644
--- a/pkg/collector/corechecks/servicediscovery/usm/service.go
+++ b/pkg/collector/corechecks/servicediscovery/usm/service.go
@@ -34,6 +34,8 @@ const (
 	NodePackageJSONPath = iota
 	// The SubdirFS instance package.json path is valid in.
 	ServiceSubFS = iota
+	// The working directory of the service
+	ServiceCwd = iota
 )
 
 const (
@@ -180,8 +182,9 @@ var languageDetectors = map[language.Language]detectorCreatorFn{
 // Map executables that usually have additional process context of what's
 // running, to context detectors
 var executableDetectors = map[string]detectorCreatorFn{
-	"sudo":     newSimpleDetector,
 	"gunicorn": newGunicornDetector,
+	"puma":     newRailsDetector,
+	"sudo":     newSimpleDetector,
 }
 
 func serviceNameInjected(envs map[string]string) bool {

From eb3ca59729b45c0c7b7a4a33d6c9905b99261a7f Mon Sep 17 00:00:00 2001
From: Guillaume Pagnoux <guillaume.pagnoux@datadoghq.com>
Date: Mon, 14 Oct 2024 15:03:41 +0200
Subject: [PATCH 02/18] test: e2e: add check for rails service naming

---
 test/new-e2e/tests/discovery/linux_test.go    | 17 +++-
 .../discovery/testdata/provision/provision.sh | 89 +++++++++++++------
 2 files changed, 76 insertions(+), 30 deletions(-)

diff --git a/test/new-e2e/tests/discovery/linux_test.go b/test/new-e2e/tests/discovery/linux_test.go
index d48cc30962b7c..9238137beed99 100644
--- a/test/new-e2e/tests/discovery/linux_test.go
+++ b/test/new-e2e/tests/discovery/linux_test.go
@@ -33,7 +33,13 @@ type linuxTestSuite struct {
 	e2e.BaseSuite[environments.Host]
 }
 
-var services = []string{"python-svc", "python-instrumented", "node-json-server", "node-instrumented"}
+var services = []string{
+	"python-svc",
+	"python-instrumented",
+	"node-json-server",
+	"node-instrumented",
+	"rails-svc",
+}
 
 func TestLinuxTestSuite(t *testing.T) {
 	agentParams := []func(*agentparams.Params) error{
@@ -125,6 +131,15 @@ func (s *linuxTestSuite) TestServiceDiscoveryCheck() {
 			assert.NotZero(c, found.Payload.RSSMemory)
 		}
 
+		found = foundMap["rails_hello"]
+		if assert.NotNil(c, found) {
+			assert.Equal(c, "rails_hello", found.Payload.ServiceName)
+			assert.Equal(c, "rails_hello", found.Payload.GeneratedServiceName)
+			assert.Empty(c, found.Payload.DDService)
+			assert.Empty(c, found.Payload.ServiceNameSource)
+			assert.NotZero(c, found.Payload.RSSMemory)
+		}
+
 		assert.Contains(c, foundMap, "json-server")
 	}, 3*time.Minute, 10*time.Second)
 }
diff --git a/test/new-e2e/tests/discovery/testdata/provision/provision.sh b/test/new-e2e/tests/discovery/testdata/provision/provision.sh
index 93bb7a0deeec1..852a21e3ca789 100755
--- a/test/new-e2e/tests/discovery/testdata/provision/provision.sh
+++ b/test/new-e2e/tests/discovery/testdata/provision/provision.sh
@@ -2,6 +2,47 @@
 
 set -e
 
+install_systemd_unit() {
+  while [[ $# -ge 2 ]]; do
+    case $1 in
+      --workdir)
+        shift
+        workdir="WorkingDirectory=$1"
+        shift
+        ;;
+    *)
+      break
+      ;;
+    esac
+  done
+
+  name=$1
+  command=$2
+  port=$3
+  extraenv=$4
+
+  cat > "/etc/systemd/system/${name}.service" <<- EOM
+[Unit]
+Description=${name}
+After=network.target
+StartLimitIntervalSec=0
+
+[Service]
+Type=simple
+Restart=always
+RestartSec=1
+User=root
+ExecStart=${command}
+Environment="PORT=${port}"
+Environment="NODE_VERSION=20"
+Environment="${extraenv}"
+${workdir}
+
+[Install]
+WantedBy=multi-user.target
+EOM
+}
+
 apt-get update
 apt-get install -y \
         ca-certificates \
@@ -28,43 +69,33 @@ nvm install 20 || nvm install 20 || nvm install 20
 npm install json-server || npm install json-server
 npm install /home/ubuntu/e2e-test/node/instrumented
 
-# Install our own services
-install_systemd_unit () {
-  name=$1
-  command=$2
-  port=$3
-  extraenv=$4
-
-  cat > "/etc/systemd/system/${name}.service" <<- EOM
-[Unit]
-Description=${name}
-After=network.target
-StartLimitIntervalSec=0
-
-[Service]
-Type=simple
-Restart=always
-RestartSec=1
-User=root
-ExecStart=${command}
-Environment="PORT=${port}"
-Environment="NODE_VERSION=20"
-Environment="${extraenv}"
+# Install Ruby
+## Packages
+apt-get install -y \
+        ruby \
+        ruby-dev \
+        ruby-rails \
+        sqlite3 \
 
-[Install]
-WantedBy=multi-user.target
-EOM
-}
+## Create new Rails project
+pushd /home/ubuntu
+rails new rails-hello --minimal
+bundle install --gemfile=/home/ubuntu/rails-hello/Gemfile
+popd
 
-# Node
+# Install our own services
+## Node
 install_systemd_unit "node-json-server" "$NVM_DIR/nvm-exec npx json-server --port 8084 /home/ubuntu/e2e-test/node/json-server/db.json" "8084" ""
 install_systemd_unit "node-instrumented" "$NVM_DIR/nvm-exec node /home/ubuntu/e2e-test/node/instrumented/server.js" "8085" ""
 
-# Python
+## Python
 install_systemd_unit "python-svc" "/usr/bin/python3 /home/ubuntu/e2e-test/python/server.py" "8082" "DD_SERVICE=python-svc-dd"
 install_systemd_unit "python-instrumented" "/usr/bin/python3 /home/ubuntu/e2e-test/python/instrumented.py" "8083" ""
 
+## Ruby
+install_systemd_unit --workdir "/home/ubuntu/rails-hello" "rails-svc" "rails server" "7777" ""
+
 systemctl daemon-reload
 
-# leave them stopped
+## leave them stopped
 systemctl stop python-svc

From fbaf76d2270d1b92ed52009ea24591f143b3a0e4 Mon Sep 17 00:00:00 2001
From: Guillaume Pagnoux <guillaume.pagnoux@datadoghq.com>
Date: Fri, 18 Oct 2024 13:06:55 +0200
Subject: [PATCH 03/18] CR: remove debug log

---
 pkg/collector/corechecks/servicediscovery/usm/ruby.go | 1 -
 1 file changed, 1 deletion(-)

diff --git a/pkg/collector/corechecks/servicediscovery/usm/ruby.go b/pkg/collector/corechecks/servicediscovery/usm/ruby.go
index 39c843927598f..18e17b7d71522 100644
--- a/pkg/collector/corechecks/servicediscovery/usm/ruby.go
+++ b/pkg/collector/corechecks/servicediscovery/usm/ruby.go
@@ -36,7 +36,6 @@ func (r railsDetector) detect(_ []string) (ServiceMetadata, bool) {
 	cwd := r.ctx.contextMap[ServiceCwd].(string)
 	absFile := abs("config/application.rb", cwd)
 	if _, err := fs.Stat(r.ctx.fs, absFile); err != nil {
-		log.Debugf("Could not stat (cwd: %v) %v: %v", cwd, absFile, err)
 		return ServiceMetadata{}, false
 	}
 

From e838cefce0d3c2d60e47da6cba3161d2a1468f17 Mon Sep 17 00:00:00 2001
From: Guillaume Pagnoux <guillaume.pagnoux@datadoghq.com>
Date: Fri, 18 Oct 2024 13:07:50 +0200
Subject: [PATCH 04/18] CR: remove outdated comments

---
 pkg/collector/corechecks/servicediscovery/usm/ruby.go | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/pkg/collector/corechecks/servicediscovery/usm/ruby.go b/pkg/collector/corechecks/servicediscovery/usm/ruby.go
index 18e17b7d71522..ee833ad456110 100644
--- a/pkg/collector/corechecks/servicediscovery/usm/ruby.go
+++ b/pkg/collector/corechecks/servicediscovery/usm/ruby.go
@@ -61,10 +61,9 @@ func (r railsDetector) findRailsApplicationName(filename string) (string, bool)
 	reader, err := SizeVerifiedReader(file)
 	if err != nil {
 		log.Debugf("skipping application.rb (%q): %v", filename, err)
-		return "", true // stops here
+		return "", true
 	}
 
-	// Scan the file line by line, instead of reading the whole file into memory
 	bytes, err := io.ReadAll(reader)
 	if err != nil {
 		log.Debugf("unable to read application.rb (%q): %v", filename, err)

From d6d1609de4462cb8c1b80e95cd76e37169bbdc50 Mon Sep 17 00:00:00 2001
From: Guillaume Pagnoux <guillaume.pagnoux@datadoghq.com>
Date: Fri, 18 Oct 2024 13:37:55 +0200
Subject: [PATCH 05/18] CR: store Process pointer in contextMap

---
 .../corechecks/servicediscovery/module/impl_linux.go   |  7 +------
 pkg/collector/corechecks/servicediscovery/usm/ruby.go  | 10 +++++++++-
 .../corechecks/servicediscovery/usm/service.go         |  4 ++--
 3 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/pkg/collector/corechecks/servicediscovery/module/impl_linux.go b/pkg/collector/corechecks/servicediscovery/module/impl_linux.go
index 8f7018a067d94..70935ff79092b 100644
--- a/pkg/collector/corechecks/servicediscovery/module/impl_linux.go
+++ b/pkg/collector/corechecks/servicediscovery/module/impl_linux.go
@@ -342,18 +342,13 @@ func (s *discovery) getServiceInfo(proc *process.Process) (*serviceInfo, error)
 		return nil, err
 	}
 
-	cwd, err := proc.Cwd()
-	if err != nil {
-		return nil, err
-	}
-
 	createTime, err := proc.CreateTime()
 	if err != nil {
 		return nil, err
 	}
 
 	contextMap := make(usm.DetectorContextMap)
-	contextMap[usm.ServiceCwd] = cwd
+	contextMap[usm.ServiceProc] = proc
 
 	root := kernel.HostProc(strconv.Itoa(int(proc.Pid)), "root")
 	lang := language.FindInArgs(exe, cmdline)
diff --git a/pkg/collector/corechecks/servicediscovery/usm/ruby.go b/pkg/collector/corechecks/servicediscovery/usm/ruby.go
index ee833ad456110..27b0a91e4ed42 100644
--- a/pkg/collector/corechecks/servicediscovery/usm/ruby.go
+++ b/pkg/collector/corechecks/servicediscovery/usm/ruby.go
@@ -11,6 +11,8 @@ import (
 	"regexp"
 	"strings"
 
+	"github.com/shirou/gopsutil/v3/process"
+
 	"github.com/DataDog/datadog-agent/pkg/util/log"
 )
 
@@ -33,7 +35,13 @@ func newRailsDetector(ctx DetectionContext) detector {
 // project is created. This file should contain a `module` declaration with the
 // application name.
 func (r railsDetector) detect(_ []string) (ServiceMetadata, bool) {
-	cwd := r.ctx.contextMap[ServiceCwd].(string)
+	proc := r.ctx.contextMap[ServiceProc].(*process.Process)
+	cwd, err := proc.Cwd()
+	if err != nil {
+		log.Debugf("could not get cwd of process: %s", err)
+		return ServiceMetadata{}, false
+	}
+
 	absFile := abs("config/application.rb", cwd)
 	if _, err := fs.Stat(r.ctx.fs, absFile); err != nil {
 		return ServiceMetadata{}, false
diff --git a/pkg/collector/corechecks/servicediscovery/usm/service.go b/pkg/collector/corechecks/servicediscovery/usm/service.go
index 964b07af389f0..d34603b284292 100644
--- a/pkg/collector/corechecks/servicediscovery/usm/service.go
+++ b/pkg/collector/corechecks/servicediscovery/usm/service.go
@@ -34,8 +34,8 @@ const (
 	NodePackageJSONPath = iota
 	// The SubdirFS instance package.json path is valid in.
 	ServiceSubFS = iota
-	// The working directory of the service
-	ServiceCwd = iota
+	// The pointer to the Process instance of the service
+	ServiceProc = iota
 )
 
 const (

From 6b7022872212d29f8f0b72cd6a6834d03bc26b7e Mon Sep 17 00:00:00 2001
From: Guillaume Pagnoux <guillaume.pagnoux@datadoghq.com>
Date: Fri, 18 Oct 2024 15:10:46 +0200
Subject: [PATCH 06/18] CR: add unit tests

---
 .../servicediscovery/usm/ruby_test.go         | 48 +++++++++++++++++++
 .../usm/testdata/root/testdata/application.rb | 38 +++++++++++++++
 .../root/testdata/application_invalid.rb      |  2 +
 3 files changed, 88 insertions(+)
 create mode 100644 pkg/collector/corechecks/servicediscovery/usm/ruby_test.go
 create mode 100644 pkg/collector/corechecks/servicediscovery/usm/testdata/root/testdata/application.rb
 create mode 100644 pkg/collector/corechecks/servicediscovery/usm/testdata/root/testdata/application_invalid.rb

diff --git a/pkg/collector/corechecks/servicediscovery/usm/ruby_test.go b/pkg/collector/corechecks/servicediscovery/usm/ruby_test.go
new file mode 100644
index 0000000000000..c7cc732cf1ac8
--- /dev/null
+++ b/pkg/collector/corechecks/servicediscovery/usm/ruby_test.go
@@ -0,0 +1,48 @@
+// Unless explicitly stated otherwise all files in this repository are licensed
+// under the Apache License Version 2.0.
+// This product includes software developed at Datadog (https://www.datadoghq.com/).
+// Copyright 2016-present Datadog, Inc.
+
+//go:build !windows
+
+package usm
+
+import (
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestGenerateNameFromRailsApplicationRb(t *testing.T) {
+	tests := []struct {
+		name     string
+		path     string
+		expected string
+	}{
+		{
+			name:     "name is found",
+			path:     "./testdata/application.rb",
+			expected: "rails_hello",
+		},
+		{
+			name:     "name not found",
+			path:     "./testdata/application_invalid.rb",
+			expected: "",
+		},
+	}
+	full, err := filepath.Abs("testdata/root")
+	require.NoError(t, err)
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			instance := &railsDetector{ctx: DetectionContext{
+				fs:         NewSubDirFS(full),
+				contextMap: make(DetectorContextMap),
+			}}
+			value, ok := instance.findRailsApplicationName(tt.path)
+			assert.Equal(t, len(tt.expected) > 0, ok)
+			assert.Equal(t, tt.expected, railsUnderscore(value))
+		})
+	}
+}
diff --git a/pkg/collector/corechecks/servicediscovery/usm/testdata/root/testdata/application.rb b/pkg/collector/corechecks/servicediscovery/usm/testdata/root/testdata/application.rb
new file mode 100644
index 0000000000000..6af9567680208
--- /dev/null
+++ b/pkg/collector/corechecks/servicediscovery/usm/testdata/root/testdata/application.rb
@@ -0,0 +1,38 @@
+require_relative "boot"
+
+require "rails"
+# Pick the frameworks you want:
+require "active_model/railtie"
+# require "active_job/railtie"
+require "active_record/railtie"
+# require "active_storage/engine"
+require "action_controller/railtie"
+# require "action_mailer/railtie"
+# require "action_mailbox/engine"
+# require "action_text/engine"
+require "action_view/railtie"
+# require "action_cable/engine"
+require "sprockets/railtie"
+require "rails/test_unit/railtie"
+
+# Require the gems listed in Gemfile, including any gems
+# you've limited to :test, :development, or :production.
+Bundler.require(*Rails.groups)
+
+module RailsHello
+  class Application < Rails::Application
+    # Initialize configuration defaults for originally generated Rails version.
+    config.load_defaults 6.1
+
+    # Configuration for the application, engines, and railties goes here.
+    #
+    # These settings can be overridden in specific environments using the files
+    # in config/environments, which are processed later.
+    #
+    # config.time_zone = "Central Time (US & Canada)"
+    # config.eager_load_paths << Rails.root.join("extras")
+
+    # Don't generate system test files.
+    config.generators.system_tests = nil
+  end
+end
diff --git a/pkg/collector/corechecks/servicediscovery/usm/testdata/root/testdata/application_invalid.rb b/pkg/collector/corechecks/servicediscovery/usm/testdata/root/testdata/application_invalid.rb
new file mode 100644
index 0000000000000..5120fe0be00a0
--- /dev/null
+++ b/pkg/collector/corechecks/servicediscovery/usm/testdata/root/testdata/application_invalid.rb
@@ -0,0 +1,2 @@
+class SomeRubyClass
+end

From 5d0c6d050d7d10c5beb827c422da627d8f5e6860 Mon Sep 17 00:00:00 2001
From: Guillaume Pagnoux <guillaume.pagnoux@datadoghq.com>
Date: Tue, 22 Oct 2024 10:13:50 +0200
Subject: [PATCH 07/18] CR: fix copyright

---
 pkg/collector/corechecks/servicediscovery/usm/ruby_test.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pkg/collector/corechecks/servicediscovery/usm/ruby_test.go b/pkg/collector/corechecks/servicediscovery/usm/ruby_test.go
index c7cc732cf1ac8..1edc3991be0bc 100644
--- a/pkg/collector/corechecks/servicediscovery/usm/ruby_test.go
+++ b/pkg/collector/corechecks/servicediscovery/usm/ruby_test.go
@@ -1,7 +1,7 @@
 // Unless explicitly stated otherwise all files in this repository are licensed
 // under the Apache License Version 2.0.
 // This product includes software developed at Datadog (https://www.datadoghq.com/).
-// Copyright 2016-present Datadog, Inc.
+// Copyright 2024-present Datadog, Inc.
 
 //go:build !windows
 

From c1425faa2f701171d7d82a6fcacc298e1f27b877 Mon Sep 17 00:00:00 2001
From: Guillaume Pagnoux <guillaume.pagnoux@datadoghq.com>
Date: Tue, 22 Oct 2024 10:14:15 +0200
Subject: [PATCH 08/18] CR: fix documentation format

---
 pkg/collector/corechecks/servicediscovery/usm/ruby.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pkg/collector/corechecks/servicediscovery/usm/ruby.go b/pkg/collector/corechecks/servicediscovery/usm/ruby.go
index 27b0a91e4ed42..5aa33fe117c54 100644
--- a/pkg/collector/corechecks/servicediscovery/usm/ruby.go
+++ b/pkg/collector/corechecks/servicediscovery/usm/ruby.go
@@ -87,7 +87,7 @@ func (r railsDetector) findRailsApplicationName(filename string) (string, bool)
 	return "", false
 }
 
-// Converts a PascalCasedWord to a snake_cased_word.
+// railsUnderscore converts a PascalCasedWord to a snake_cased_word.
 // It keeps uppercase acronyms together when converting (e.g. "HTTPServer" -> "http_server").
 func railsUnderscore(pascalCasedWord string) string {
 	snake := matchFirstCap.ReplaceAllString(pascalCasedWord, "${1}_${2}")

From c87d97ed0e4d942655ffc1fe3082a2df22339c69 Mon Sep 17 00:00:00 2001
From: Guillaume Pagnoux <guillaume.pagnoux@datadoghq.com>
Date: Tue, 22 Oct 2024 10:14:26 +0200
Subject: [PATCH 09/18] CR: remove extraneous log

---
 pkg/collector/corechecks/servicediscovery/usm/ruby.go | 1 -
 1 file changed, 1 deletion(-)

diff --git a/pkg/collector/corechecks/servicediscovery/usm/ruby.go b/pkg/collector/corechecks/servicediscovery/usm/ruby.go
index 5aa33fe117c54..53fa2e4d1f3ec 100644
--- a/pkg/collector/corechecks/servicediscovery/usm/ruby.go
+++ b/pkg/collector/corechecks/servicediscovery/usm/ruby.go
@@ -58,7 +58,6 @@ func (r railsDetector) detect(_ []string) (ServiceMetadata, bool) {
 // findRailsApplicationName scans the `config/application.rb` file to find the
 // Rails application name.
 func (r railsDetector) findRailsApplicationName(filename string) (string, bool) {
-	log.Debugf("findRailsApplicationName")
 	file, err := r.ctx.fs.Open(filename)
 	if err != nil {
 		log.Debugf("could not open application.rb")

From d18d420f46904d438f889760bedcbc56af0a9f57 Mon Sep 17 00:00:00 2001
From: Guillaume Pagnoux <guillaume.pagnoux@datadoghq.com>
Date: Tue, 22 Oct 2024 10:14:44 +0200
Subject: [PATCH 10/18] CR: make map access and cast safe in rails detector

---
 pkg/collector/corechecks/servicediscovery/usm/ruby.go | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/pkg/collector/corechecks/servicediscovery/usm/ruby.go b/pkg/collector/corechecks/servicediscovery/usm/ruby.go
index 53fa2e4d1f3ec..82a0220641328 100644
--- a/pkg/collector/corechecks/servicediscovery/usm/ruby.go
+++ b/pkg/collector/corechecks/servicediscovery/usm/ruby.go
@@ -35,7 +35,16 @@ func newRailsDetector(ctx DetectionContext) detector {
 // project is created. This file should contain a `module` declaration with the
 // application name.
 func (r railsDetector) detect(_ []string) (ServiceMetadata, bool) {
-	proc := r.ctx.contextMap[ServiceProc].(*process.Process)
+	var proc *process.Process
+
+	if procEntry, ok := r.ctx.ContextMap[ServiceProc]; ok {
+		if p, ok := procEntry.(*process.Process); ok {
+			proc = p
+		} else {
+			log.Error("could not get process object in rails detector")
+		}
+	}
+
 	cwd, err := proc.Cwd()
 	if err != nil {
 		log.Debugf("could not get cwd of process: %s", err)

From 3f545e3ba6ff93231c86a3379a4feab6bd8d3299 Mon Sep 17 00:00:00 2001
From: Guillaume Pagnoux <guillaume.pagnoux@datadoghq.com>
Date: Tue, 22 Oct 2024 10:22:36 +0200
Subject: [PATCH 11/18] CR: improve error handling in ruby detector

---
 .../corechecks/servicediscovery/usm/ruby.go   | 21 +++++++++----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/pkg/collector/corechecks/servicediscovery/usm/ruby.go b/pkg/collector/corechecks/servicediscovery/usm/ruby.go
index 82a0220641328..3b305a8471b59 100644
--- a/pkg/collector/corechecks/servicediscovery/usm/ruby.go
+++ b/pkg/collector/corechecks/servicediscovery/usm/ruby.go
@@ -6,6 +6,7 @@
 package usm
 
 import (
+	"fmt"
 	"io"
 	"io/fs"
 	"regexp"
@@ -56,8 +57,9 @@ func (r railsDetector) detect(_ []string) (ServiceMetadata, bool) {
 		return ServiceMetadata{}, false
 	}
 
-	name, ok := r.findRailsApplicationName(absFile)
-	if !ok {
+	name, err := r.findRailsApplicationName(absFile)
+	if err != nil {
+		log.Debugf("could not find ruby application name: %s", err)
 		return ServiceMetadata{}, false
 	}
 
@@ -66,33 +68,30 @@ func (r railsDetector) detect(_ []string) (ServiceMetadata, bool) {
 
 // findRailsApplicationName scans the `config/application.rb` file to find the
 // Rails application name.
-func (r railsDetector) findRailsApplicationName(filename string) (string, bool) {
+func (r railsDetector) findRailsApplicationName(filename string) (string, error) {
 	file, err := r.ctx.fs.Open(filename)
 	if err != nil {
-		log.Debugf("could not open application.rb")
-		return "", false
+		return "", fmt.Errorf("could not open application.rb: %w", err)
 	}
 	defer file.Close()
 
 	reader, err := SizeVerifiedReader(file)
 	if err != nil {
-		log.Debugf("skipping application.rb (%q): %v", filename, err)
-		return "", true
+		return "", fmt.Errorf("skipping application.rb (%q): %w", filename, err)
 	}
 
 	bytes, err := io.ReadAll(reader)
 	if err != nil {
-		log.Debugf("unable to read application.rb (%q): %v", filename, err)
-		return "", true
+		return "", fmt.Errorf("unable to read application.rb (%q): %w", filename, err)
 	}
 
 	matches := moduleRegexp.FindSubmatch(bytes)
 	if matches != nil {
-		return string(matches[1]), true
+		return string(matches[1]), nil
 	}
 
 	// No match found
-	return "", false
+	return "", fmt.Errorf("could not find Ruby module name")
 }
 
 // railsUnderscore converts a PascalCasedWord to a snake_cased_word.

From 3d19532c236d9b5b6bfc295eaa949c8767286597 Mon Sep 17 00:00:00 2001
From: Guillaume Pagnoux <guillaume.pagnoux@datadoghq.com>
Date: Tue, 22 Oct 2024 10:23:17 +0200
Subject: [PATCH 12/18] CR: fix copyright in ruby.go

---
 pkg/collector/corechecks/servicediscovery/usm/ruby.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pkg/collector/corechecks/servicediscovery/usm/ruby.go b/pkg/collector/corechecks/servicediscovery/usm/ruby.go
index 3b305a8471b59..f831914ed0e64 100644
--- a/pkg/collector/corechecks/servicediscovery/usm/ruby.go
+++ b/pkg/collector/corechecks/servicediscovery/usm/ruby.go
@@ -1,7 +1,7 @@
 // Unless explicitly stated otherwise all files in this repository are licensed
 // under the Apache License Version 2.0.
 // This product includes software developed at Datadog (https://www.datadoghq.com/).
-// Copyright 2016-present Datadog, Inc.
+// Copyright 2024-present Datadog, Inc.
 
 package usm
 

From 414f1bea020d361a618901f3f4981cb82dddd9d0 Mon Sep 17 00:00:00 2001
From: Guillaume Pagnoux <guillaume.pagnoux@datadoghq.com>
Date: Tue, 22 Oct 2024 10:26:02 +0200
Subject: [PATCH 13/18] CR: fix Submatch call

---
 pkg/collector/corechecks/servicediscovery/usm/ruby.go | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/pkg/collector/corechecks/servicediscovery/usm/ruby.go b/pkg/collector/corechecks/servicediscovery/usm/ruby.go
index f831914ed0e64..65686e7c70a37 100644
--- a/pkg/collector/corechecks/servicediscovery/usm/ruby.go
+++ b/pkg/collector/corechecks/servicediscovery/usm/ruby.go
@@ -86,12 +86,12 @@ func (r railsDetector) findRailsApplicationName(filename string) (string, error)
 	}
 
 	matches := moduleRegexp.FindSubmatch(bytes)
-	if matches != nil {
-		return string(matches[1]), nil
+	if len(matches) < 2 {
+		// No match found
+		return "", fmt.Errorf("could not find Ruby module name")
 	}
 
-	// No match found
-	return "", fmt.Errorf("could not find Ruby module name")
+	return string(matches[1]), nil
 }
 
 // railsUnderscore converts a PascalCasedWord to a snake_cased_word.

From 0bf6cc5e5ea23b3c6424dd6543b2c33cf604906a Mon Sep 17 00:00:00 2001
From: Guillaume Pagnoux <guillaume.pagnoux@datadoghq.com>
Date: Tue, 22 Oct 2024 10:27:31 +0200
Subject: [PATCH 14/18] CR: test: run test on Linux only

---
 pkg/collector/corechecks/servicediscovery/usm/ruby_test.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pkg/collector/corechecks/servicediscovery/usm/ruby_test.go b/pkg/collector/corechecks/servicediscovery/usm/ruby_test.go
index 1edc3991be0bc..eac7d4ec2bfc0 100644
--- a/pkg/collector/corechecks/servicediscovery/usm/ruby_test.go
+++ b/pkg/collector/corechecks/servicediscovery/usm/ruby_test.go
@@ -3,7 +3,7 @@
 // This product includes software developed at Datadog (https://www.datadoghq.com/).
 // Copyright 2024-present Datadog, Inc.
 
-//go:build !windows
+//go:build linux
 
 package usm
 

From 23e9270135a35ce6a36ef15cfa4c8990d0f0654c Mon Sep 17 00:00:00 2001
From: Guillaume Pagnoux <guillaume.pagnoux@datadoghq.com>
Date: Tue, 22 Oct 2024 10:45:02 +0200
Subject: [PATCH 15/18] CR: detector: log type in case of case error

---
 pkg/collector/corechecks/servicediscovery/usm/ruby.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pkg/collector/corechecks/servicediscovery/usm/ruby.go b/pkg/collector/corechecks/servicediscovery/usm/ruby.go
index 65686e7c70a37..6617cb12c6545 100644
--- a/pkg/collector/corechecks/servicediscovery/usm/ruby.go
+++ b/pkg/collector/corechecks/servicediscovery/usm/ruby.go
@@ -42,7 +42,7 @@ func (r railsDetector) detect(_ []string) (ServiceMetadata, bool) {
 		if p, ok := procEntry.(*process.Process); ok {
 			proc = p
 		} else {
-			log.Error("could not get process object in rails detector")
+			log.Errorf("could not get process object in rails detector: got type %T", procEntry)
 		}
 	}
 

From f5c967517a47bb3e2abd6d7deb42ced81551f728 Mon Sep 17 00:00:00 2001
From: Guillaume Pagnoux <guillaume.pagnoux@datadoghq.com>
Date: Tue, 22 Oct 2024 10:45:44 +0200
Subject: [PATCH 16/18] CR: use errors.New instead of fmt.Errorf when regex
 does not match

---
 pkg/collector/corechecks/servicediscovery/usm/ruby.go | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/pkg/collector/corechecks/servicediscovery/usm/ruby.go b/pkg/collector/corechecks/servicediscovery/usm/ruby.go
index 6617cb12c6545..69122052ec277 100644
--- a/pkg/collector/corechecks/servicediscovery/usm/ruby.go
+++ b/pkg/collector/corechecks/servicediscovery/usm/ruby.go
@@ -6,6 +6,7 @@
 package usm
 
 import (
+	"errors"
 	"fmt"
 	"io"
 	"io/fs"
@@ -88,7 +89,7 @@ func (r railsDetector) findRailsApplicationName(filename string) (string, error)
 	matches := moduleRegexp.FindSubmatch(bytes)
 	if len(matches) < 2 {
 		// No match found
-		return "", fmt.Errorf("could not find Ruby module name")
+		return "", errors.New("could not find Ruby module name")
 	}
 
 	return string(matches[1]), nil

From 548757c5b2c7c950af5d58ebd09633130fccc9a3 Mon Sep 17 00:00:00 2001
From: Guillaume Pagnoux <guillaume.pagnoux@datadoghq.com>
Date: Tue, 22 Oct 2024 17:23:08 +0200
Subject: [PATCH 17/18] CR: add additional test cases

---
 .../servicediscovery/usm/ruby_test.go         | 21 ++++++++++++++-----
 .../root/testdata/{ => ruby}/application.rb   |  0
 .../testdata/ruby/application_accronym.rb     |  1 +
 .../{ => ruby}/application_invalid.rb         |  0
 4 files changed, 17 insertions(+), 5 deletions(-)
 rename pkg/collector/corechecks/servicediscovery/usm/testdata/root/testdata/{ => ruby}/application.rb (100%)
 create mode 100644 pkg/collector/corechecks/servicediscovery/usm/testdata/root/testdata/ruby/application_accronym.rb
 rename pkg/collector/corechecks/servicediscovery/usm/testdata/root/testdata/{ => ruby}/application_invalid.rb (100%)

diff --git a/pkg/collector/corechecks/servicediscovery/usm/ruby_test.go b/pkg/collector/corechecks/servicediscovery/usm/ruby_test.go
index eac7d4ec2bfc0..40f6323027a80 100644
--- a/pkg/collector/corechecks/servicediscovery/usm/ruby_test.go
+++ b/pkg/collector/corechecks/servicediscovery/usm/ruby_test.go
@@ -23,12 +23,22 @@ func TestGenerateNameFromRailsApplicationRb(t *testing.T) {
 	}{
 		{
 			name:     "name is found",
-			path:     "./testdata/application.rb",
+			path:     "./testdata/ruby/application.rb",
 			expected: "rails_hello",
 		},
 		{
 			name:     "name not found",
-			path:     "./testdata/application_invalid.rb",
+			path:     "./testdata/ruby/application_invalid.rb",
+			expected: "",
+		},
+		{
+			name:     "accronym in module name",
+			path:     "./testdata/ruby/application_accronym.rb",
+			expected: "http_server",
+		},
+		{
+			name:     "file does not exists",
+			path:     "./testdata/ruby/application_does_not_exist.rb",
 			expected: "",
 		},
 	}
@@ -38,10 +48,11 @@ func TestGenerateNameFromRailsApplicationRb(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			instance := &railsDetector{ctx: DetectionContext{
 				fs:         NewSubDirFS(full),
-				contextMap: make(DetectorContextMap),
+				ContextMap: make(DetectorContextMap),
 			}}
-			value, ok := instance.findRailsApplicationName(tt.path)
-			assert.Equal(t, len(tt.expected) > 0, ok)
+			value, err := instance.findRailsApplicationName(tt.path)
+			t.Log(err)
+			assert.Equal(t, len(tt.expected) > 0, err == nil)
 			assert.Equal(t, tt.expected, railsUnderscore(value))
 		})
 	}
diff --git a/pkg/collector/corechecks/servicediscovery/usm/testdata/root/testdata/application.rb b/pkg/collector/corechecks/servicediscovery/usm/testdata/root/testdata/ruby/application.rb
similarity index 100%
rename from pkg/collector/corechecks/servicediscovery/usm/testdata/root/testdata/application.rb
rename to pkg/collector/corechecks/servicediscovery/usm/testdata/root/testdata/ruby/application.rb
diff --git a/pkg/collector/corechecks/servicediscovery/usm/testdata/root/testdata/ruby/application_accronym.rb b/pkg/collector/corechecks/servicediscovery/usm/testdata/root/testdata/ruby/application_accronym.rb
new file mode 100644
index 0000000000000..5e33caace3fc1
--- /dev/null
+++ b/pkg/collector/corechecks/servicediscovery/usm/testdata/root/testdata/ruby/application_accronym.rb
@@ -0,0 +1 @@
+module HTTPServer
diff --git a/pkg/collector/corechecks/servicediscovery/usm/testdata/root/testdata/application_invalid.rb b/pkg/collector/corechecks/servicediscovery/usm/testdata/root/testdata/ruby/application_invalid.rb
similarity index 100%
rename from pkg/collector/corechecks/servicediscovery/usm/testdata/root/testdata/application_invalid.rb
rename to pkg/collector/corechecks/servicediscovery/usm/testdata/root/testdata/ruby/application_invalid.rb

From bf02b556d21f971da801449a9d678c59921fba1c Mon Sep 17 00:00:00 2001
From: Guillaume Pagnoux <guillaume.pagnoux@datadoghq.com>
Date: Tue, 22 Oct 2024 17:24:46 +0200
Subject: [PATCH 18/18] CR: use path.Join instead of abs

---
 pkg/collector/corechecks/servicediscovery/usm/ruby.go | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/pkg/collector/corechecks/servicediscovery/usm/ruby.go b/pkg/collector/corechecks/servicediscovery/usm/ruby.go
index 69122052ec277..8df8b59991e8d 100644
--- a/pkg/collector/corechecks/servicediscovery/usm/ruby.go
+++ b/pkg/collector/corechecks/servicediscovery/usm/ruby.go
@@ -10,6 +10,7 @@ import (
 	"fmt"
 	"io"
 	"io/fs"
+	"path"
 	"regexp"
 	"strings"
 
@@ -53,7 +54,7 @@ func (r railsDetector) detect(_ []string) (ServiceMetadata, bool) {
 		return ServiceMetadata{}, false
 	}
 
-	absFile := abs("config/application.rb", cwd)
+	absFile := path.Join(cwd, "config/application.rb")
 	if _, err := fs.Stat(r.ctx.fs, absFile); err != nil {
 		return ServiceMetadata{}, false
 	}