From 7cebd751abe7258f0b83216fe66ddf418580f8fd Mon Sep 17 00:00:00 2001
From: Cosmin Tupangiu <cosmin@redhat.com>
Date: Thu, 28 Nov 2024 17:16:27 +0100
Subject: [PATCH] agent: Retrieve system-uuid

This commit adds a service to agent image that is retrieving the
system-uuid and write it into `/var/home/core/agent_id`.
Agent reads this file at start up.

Signed-off-by: Cosmin Tupangiu <cosmin@redhat.com>
---
 cmd/planner-agent/main.go | 29 +++++++++++++++++++++++------
 data/ignition.template    | 16 ++++++++++++++++
 2 files changed, 39 insertions(+), 6 deletions(-)

diff --git a/cmd/planner-agent/main.go b/cmd/planner-agent/main.go
index b899d56..c692a8e 100644
--- a/cmd/planner-agent/main.go
+++ b/cmd/planner-agent/main.go
@@ -1,18 +1,21 @@
 package main
 
 import (
+	"bytes"
 	"context"
+	"errors"
 	"flag"
 	"fmt"
 	"os"
+	"path"
 
 	"github.com/google/uuid"
 	"github.com/kubev2v/migration-planner/internal/agent"
 	"github.com/kubev2v/migration-planner/pkg/log"
 )
 
-var (
-	agentID string
+const (
+	agentFilename = "agent_id"
 )
 
 func main() {
@@ -35,7 +38,6 @@ func NewAgentCommand() *agentCmd {
 	}
 
 	flag.StringVar(&a.configFile, "config", agent.DefaultConfigFile, "Path to the agent's configuration file.")
-	flag.StringVar(&agentID, "id", os.Getenv("AGENT_ID"), "ID of the agent")
 
 	flag.Usage = func() {
 		fmt.Fprintf(flag.CommandLine.Output(), "Usage of %s:\n", os.Args[0])
@@ -58,13 +60,28 @@ func NewAgentCommand() *agentCmd {
 }
 
 func (a *agentCmd) Execute() error {
-	// FIXME: !!!
-	if agentID == "" {
-		agentID = uuid.New().String()
+	agentID, err := a.getAgentID()
+	if err != nil {
+		a.log.Fatalf("failed to retreive agent_id: %v", err)
 	}
+
 	agentInstance := agent.New(uuid.MustParse(agentID), a.log, a.config)
 	if err := agentInstance.Run(context.Background()); err != nil {
 		a.log.Fatalf("running device agent: %v", err)
 	}
 	return nil
 }
+
+func (a *agentCmd) getAgentID() (string, error) {
+	// look for it in data dir
+	dataDirPath := path.Join(a.config.DataDir, agentFilename)
+	if _, err := os.Stat(dataDirPath); err == nil {
+		content, err := os.ReadFile(dataDirPath)
+		if err != nil {
+			return "", err
+		}
+		return string(bytes.TrimSpace(content)), nil
+	}
+
+	return "", errors.New("agent_id not found")
+}
diff --git a/data/ignition.template b/data/ignition.template
index a209613..2d9c5bf 100644
--- a/data/ignition.template
+++ b/data/ignition.template
@@ -9,6 +9,21 @@ passwd:
         - {{.SshKey}}
       {{end}}
 
+systemd:
+  units:
+    - name: planner-agent-id.service
+      enabled: true
+      contents: |
+        [Unit]
+        Description=Service to retrieve system uuid
+        [Service]
+        Type=oneshot
+        ExecStart=/bin/bash -c 'cat /sys/class/dmi/id/product_uuid > /var/home/core/.migration-planner/data/agent_id'
+        ExecStartPost=/bin/bash -c 'chown core:core /var/home/core/.migration-planner/data/agent_id'
+        RemainAfterExit=true
+        [Install]
+        WantedBy=multi-user.target
+
 storage:
   links:
     - path: /home/core/.config/systemd/user/timers.target.wants/podman-auto-update.timer
@@ -99,6 +114,7 @@ storage:
           [Service]
           Restart=on-failure
           RestartSec=5
+          ExecStartPre=/bin/bash -c 'until [ -f /var/home/core/.migration-planner/data/agent_id ]; do sleep 1; done'
 
           [Install]
           WantedBy=multi-user.target default.target