From 40995ae0d7eda351ecc908e46095ab65f42be792 Mon Sep 17 00:00:00 2001
From: Marc Khouzam <marc.khouzam@broadcom.com>
Date: Thu, 3 Oct 2024 22:51:16 -0400
Subject: [PATCH] Avoid writing to the config file if not necessary

Writing to the config file to update the server list has a cost of
about 0.65 seconds on my M1 Mac, making the startup jump from around
0.35 seconds to 1 second. This may be due to writing to a file but also
could be a delay in obtaining the config lock.

Updating the server list does not actually need to be done all the time.
Instead, this commit checks if there is actually any missing servers
by comparing the list of contexts with the list of servers, and only if
there are missing servers will it trigger the update.

This reduces by 65% the execution time for commands that don't access
the backend; this means that shell completion for commands and flags
becomes noticeably more responsive.

Signed-off-by: Marc Khouzam <marc.khouzam@broadcom.com>
---
 pkg/config/context.go | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/pkg/config/context.go b/pkg/config/context.go
index c9555310e..fabf0ec3d 100644
--- a/pkg/config/context.go
+++ b/pkg/config/context.go
@@ -7,6 +7,7 @@ import (
 	"github.com/pkg/errors"
 
 	"github.com/vmware-tanzu/tanzu-plugin-runtime/config"
+	"github.com/vmware-tanzu/tanzu-plugin-runtime/config/types"
 )
 
 // SyncContextsAndServers populate or sync contexts and servers
@@ -16,7 +17,11 @@ func SyncContextsAndServers() error {
 		return errors.Wrap(err, "failed to get client config")
 	}
 
-	config.PopulateContexts(cfg)
+	hasChanged := config.PopulateContexts(cfg)
+	needsSync := doServersNeedUpdate(cfg)
+	if !hasChanged && !needsSync {
+		return nil
+	}
 
 	// Now write the context to the configuration file.  This will also create any missing server for its corresponding context
 	for _, c := range cfg.KnownContexts {
@@ -36,3 +41,22 @@ func SyncContextsAndServers() error {
 	}
 	return nil
 }
+
+func doServersNeedUpdate(cfg *types.ClientConfig) bool {
+	if cfg == nil {
+		return false
+	}
+
+	for _, c := range cfg.KnownContexts {
+		if c.ContextType == types.ContextTypeTanzu || cfg.HasServer(c.Name) {
+			// context of type "tanzu" don't get synched
+			// or context already present in servers; skip
+			continue
+		}
+		// Found a context that is not in the servers.  We need to update
+		// the servers section
+		return true
+	}
+
+	return false
+}