From 4b8f5598f0eb97a8656f1d5fa73806ecc9bd1e82 Mon Sep 17 00:00:00 2001
From: Vladimir Dementyev <palkan@hey.com>
Date: Thu, 2 Nov 2023 10:23:12 -0700
Subject: [PATCH] fix: infer nats server name FLY_ALLOC_ID

---
 cli/options.go         | 7 +++++++
 config/presets.go      | 6 ++++++
 config/presets_test.go | 1 +
 3 files changed, 14 insertions(+)

diff --git a/cli/options.go b/cli/options.go
index 7979bc58..2bbf0f4f 100644
--- a/cli/options.go
+++ b/cli/options.go
@@ -508,6 +508,13 @@ func embeddedNatsCLIFlags(c *config.Config, routes *string, gateways *string) []
 			Destination: &c.EmbeddedNats.StoreDir,
 		},
 
+		&cli.StringFlag{
+			Name:        "enats_server_name",
+			Usage:       "Embedded NATS unique server name (required for JetStream), auto-generated by default",
+			Value:       c.EmbeddedNats.Name,
+			Destination: &c.EmbeddedNats.Name,
+		},
+
 		&cli.BoolFlag{
 			Name:        "enats_debug",
 			Usage:       "Enable NATS server logs",
diff --git a/config/presets.go b/config/presets.go
index bf906484..db78b51e 100644
--- a/config/presets.go
+++ b/config/presets.go
@@ -66,6 +66,8 @@ func (c *Config) loadFlyPreset(defaults *Config) error {
 		return errors.New("FLY_APP_NAME env is missing")
 	}
 
+	appId, _ := os.LookupEnv("FLY_ALLOC_ID")
+
 	redisEnabled := (c.Redis.URL != defaults.Redis.URL)
 
 	// Use the same port for HTTP broadcasts by default
@@ -73,6 +75,10 @@ func (c *Config) loadFlyPreset(defaults *Config) error {
 		c.HTTPBroadcast.Port = c.Port
 	}
 
+	if c.EmbeddedNats.Name == defaults.EmbeddedNats.Name && appId != "" {
+		c.EmbeddedNats.Name = fmt.Sprintf("fly-%s-%s", region, appId)
+	}
+
 	if c.EmbeddedNats.ServiceAddr == defaults.EmbeddedNats.ServiceAddr {
 		c.EmbeddedNats.ServiceAddr = "nats://0.0.0.0:4222"
 	}
diff --git a/config/presets_test.go b/config/presets_test.go
index bf69e57c..d7717b5a 100644
--- a/config/presets_test.go
+++ b/config/presets_test.go
@@ -43,6 +43,7 @@ func TestFlyPresets(t *testing.T) {
 	assert.Equal(t, true, config.EmbedNats)
 	assert.Equal(t, "nats", config.PubSubAdapter)
 	assert.Equal(t, "", config.BrokerAdapter)
+	assert.Equal(t, "fly-mag-1234", config.EmbeddedNats.Name)
 	assert.Equal(t, "nats://0.0.0.0:4222", config.EmbeddedNats.ServiceAddr)
 	assert.Equal(t, "nats://0.0.0.0:5222", config.EmbeddedNats.ClusterAddr)
 	assert.Equal(t, "any-test-mag-cluster", config.EmbeddedNats.ClusterName)