From e8aa9c64292efcf9d05d49ea4dd26e5f523cd7f4 Mon Sep 17 00:00:00 2001
From: Violet Hynes <violet.hynes@hashicorp.com>
Date: Fri, 13 Jan 2023 09:49:36 -0500
Subject: [PATCH] VAULT-12542 Add info encouraging users to upgrade if agent
 version is different to server (#18684)

* VAULT-12542 Add info encouraging users to upgrade if agent version is different to server

* VAULT-12542 Changelog

* VAULT-12542 Language update
---
 changelog/18684.txt |  3 +++
 command/agent.go    | 13 ++++++++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)
 create mode 100644 changelog/18684.txt

diff --git a/changelog/18684.txt b/changelog/18684.txt
new file mode 100644
index 000000000..803c7cc57
--- /dev/null
+++ b/changelog/18684.txt
@@ -0,0 +1,3 @@
+```release-note:improvement
+agent: Add note in logs when starting Vault Agent indicating if the version differs to the Vault Server.
+```
diff --git a/command/agent.go b/command/agent.go
index 75ae5acdc..4fbcd6ba2 100644
--- a/command/agent.go
+++ b/command/agent.go
@@ -250,7 +250,7 @@ func (c *AgentCommand) Run(args []string) int {
 		return 0
 	}
 
-	// Ignore any setting of agent's address. This client is used by the agent
+	// Ignore any setting of Agent's address. This client is used by the Agent
 	// to reach out to Vault. This should never loop back to agent.
 	c.flagAgentAddress = ""
 	client, err := c.Client()
@@ -261,6 +261,17 @@ func (c *AgentCommand) Run(args []string) int {
 		return 1
 	}
 
+	serverHealth, err := client.Sys().Health()
+	if err == nil {
+		// We don't exit on error here, as this is not worth stopping Agent over
+		serverVersion := serverHealth.Version
+		agentVersion := version.GetVersion().VersionNumber()
+		if serverVersion != agentVersion {
+			c.UI.Info("==> Note: Vault Agent version does not match Vault server version. " +
+				fmt.Sprintf("Vault Agent version: %s, Vault server version: %s", agentVersion, serverVersion))
+		}
+	}
+
 	// ctx and cancelFunc are passed to the AuthHandler, SinkServer, and
 	// TemplateServer that periodically listen for ctx.Done() to fire and shut
 	// down accordingly.