Add beat/process config to elastic agent diagnostics collect (#29902)

* Add beat/process config to elastic agent diagnostics collect

Add the configs that are output from elastic-agent inspect output to the
bundle generated by elastic-agent diagnostics collect. Files are named
as ProcID_RouteKey.

* Apply suggestions from code review

Co-authored-by: Anderson Queiroz <contato@andersonq.eti.br>

Co-authored-by: Anderson Queiroz <contato@andersonq.eti.br>

x-pack/elastic-agent/CHANGELOG.next.asciidoc

@@ -157,3 +157,4 @@
 - Allow pprof endpoints for elastic-agent or beats if enabled. {pull}28983[28983] {pull}29155[29155]
 - Add --fleet-server-es-ca-trusted-fingerprint flag to allow agent/fleet-server to work with elasticsearch clusters using self signed certs. {pull}29128[29128]
 - Discover changes in Kubernetes nodes metadata as soon as they happen. {pull}23139[23139]
+- Add results of inspect output command into archive produced by diagnostics collect. {pull}29902[29902]

x-pack/elastic-agent/pkg/agent/cmd/diagnostics.go

@@ -22,6 +22,7 @@ import (
 	"github.com/spf13/cobra"
 	"gopkg.in/yaml.v2"
 
+	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/agent/application/info"
 	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/agent/application/paths"
 	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/agent/configuration"
 	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/agent/control/client"
@@ -47,6 +48,7 @@ type DiagnosticsInfo struct {
 type AgentConfig struct {
 	ConfigLocal    *configuration.Configuration
 	ConfigRendered map[string]interface{}
+	AppConfig      map[string]interface{} // map of processName_rk:config
 }
 
 func newDiagnosticsCommand(s []string, streams *cli.IOStreams) *cobra.Command {
@@ -361,6 +363,35 @@ func gatherConfig() (AgentConfig, error) {
 	}
 	cfg.ConfigRendered = mapCFG
 
+	// Gather vars to render process config
+	isStandalone, err := isStandalone(renderedCFG)
+	if err != nil {
+		return AgentConfig{}, err
+	}
+
+	agentInfo, err := info.NewAgentInfo(false)
+	if err != nil {
+		return AgentConfig{}, err
+	}
+
+	log, err := newErrorLogger()
+	if err != nil {
+		return AgentConfig{}, err
+	}
+
+	// Get process config - uses same approach as inspect output command.
+	// Does not contact server process to request configs.
+	pMap, err := getProgramsFromConfig(log, agentInfo, renderedCFG, isStandalone)
+	if err != nil {
+		return AgentConfig{}, err
+	}
+	cfg.AppConfig = make(map[string]interface{}, 0)
+	for rk, programs := range pMap {
+		for _, p := range programs {
+			cfg.AppConfig[p.Identifier()+"_"+rk] = p.Configuration()
+		}
+	}
+
 	return cfg, nil
 }
 
@@ -419,6 +450,15 @@ func createZip(fileName, outputFormat string, diag DiagnosticsInfo, cfg AgentCon
 	if err := writeFile(zf, outputFormat, cfg.ConfigRendered); err != nil {
 		return closeHandlers(err, zw, f)
 	}
+	for name, appCfg := range cfg.AppConfig {
+		zf, err := zw.Create("config/" + name + "." + outputFormat)
+		if err != nil {
+			return closeHandlers(err, zw, f)
+		}
+		if err := writeFile(zf, outputFormat, appCfg); err != nil {
+			return closeHandlers(err, zw, f)
+		}
+	}
 
 	if err := zipLogs(zw); err != nil {
 		return closeHandlers(err, zw, f)