Fix lookup issues with inputs.d fragment yml (#840)

* Fix lookup issues with inputs.d fragment yml

The Elastic Agent was looking next to the binary for the `inputs.d`
folder instead it should look up into the `Home` folder where
the Elastic Agent symlink is located.

Fixes: #663

* Changelog

* Fix input.d path, tie to the agent Config() directory

* Update CHANGELOG to reflect that the agent configuration directory is used to locate the inputs.d directory

Co-authored-by: Aleksandr Maus <aleksandr.maus@elastic.co>

CHANGELOG.next.asciidoc

@@ -112,6 +112,7 @@
 - Allow the / char in variable names in eql and transpiler. {issue}715[715] {pull}718[718]
 - Fix data duplication for standalone agent on Kubernetes using the default manifest {issue-beats}31512[31512] {pull}742[742]
 - Agent updates will clean up unneeded artifacts. {issue}693[693] {issue}694[694] {pull}752[752]
+- Use the Elastic Agent configuration directory as the root of the `inputs.d` folder. {issues}663[663]
 - Fix a panic caused by a race condition when installing the Elastic Agent. {issues}806[806]
 
 ==== New features

internal/pkg/agent/application/local_mode.go

@@ -173,7 +173,7 @@ func newLocal(
 }
 
 func externalConfigsGlob() string {
-	return filepath.Join(paths.Config(), configuration.ExternalInputsPattern)
+	return filepath.Join(paths.AgentInputsDPath(), "*.yml")
 }
 
 // Routes returns a list of routes handled by agent.

internal/pkg/agent/application/paths/files.go

@@ -32,6 +32,9 @@ const defaultAgentStateStoreYmlFile = "state.yml"
 // defaultAgentStateStoreFile is the file that will contain the action that can be replayed after restart encrypted.
 const defaultAgentStateStoreFile = "state.enc"
 
+// defaultInputDPath return the location of the inputs.d.
+const defaultInputsDPath = "inputs.d"
+
 // AgentConfigYmlFile is a name of file used to store agent information
 func AgentConfigYmlFile() string {
 	return filepath.Join(Config(), defaultAgentFleetYmlFile)
@@ -82,3 +85,8 @@ func AgentStateStoreYmlFile() string {
 func AgentStateStoreFile() string {
 	return filepath.Join(Home(), defaultAgentStateStoreFile)
 }
+
+// AgentInputsDPath is directory that contains the fragment of inputs yaml for K8s deployment.
+func AgentInputsDPath() string {
+	return filepath.Join(Config(), defaultInputsDPath)
+}

internal/pkg/agent/configuration/settings.go

@@ -5,8 +5,6 @@
 package configuration
 
 import (
-	"path/filepath"
-
 	"github.com/elastic/elastic-agent/internal/pkg/artifact"
 	monitoringCfg "github.com/elastic/elastic-agent/internal/pkg/core/monitoring/config"
 	"github.com/elastic/elastic-agent/internal/pkg/core/process"
@@ -15,9 +13,6 @@ import (
 	"github.com/elastic/elastic-agent/pkg/core/server"
 )
 
-// ExternalInputsPattern is a glob that matches the paths of external configuration files.
-var ExternalInputsPattern = filepath.Join("inputs.d", "*.yml")
-
 // SettingsConfig is an collection of agent settings configuration.
 type SettingsConfig struct {
 	DownloadConfig   *artifact.Config                `yaml:"download" config:"download" json:"download"`