fix(arangodb): register metrics and return not-connected errors when Connect fails

docs/datasources/arangodb/page.md

@@ -18,6 +18,8 @@ To connect to `ArangoDB`, you need to provide the following environment variable
 - `PASSWORD`: The password for the specified user.
 - `PORT`: The port number
 
+If any of these values is missing, GoFr logs the error, the ArangoDB health check reports `DOWN` with the reason in `details.error`, and ArangoDB calls return a "not connected to ArangoDB" error instead of panicking. If the server is unreachable at startup, GoFr logs the error and keeps the client; the health check reports `DOWN` (with the connection error in `details.error`) until the server becomes reachable, after which queries and the `app_arango_stats` metric work without a restart.
+
 ## Setup
 
 GoFr supports injecting `ArangoDB` that implements the following interface. Any driver that implements the interface can be

pkg/gofr/datasource/arangodb/arango.go

@@ -17,6 +17,7 @@ import (
 const (
 	defaultTimeout           = 5 * time.Second
 	arangoEdgeCollectionType = 3
+	statusDown               = "DOWN"
 )
 
 // Client represents an ArangoDB client.
@@ -56,6 +57,7 @@ var (
 	ErrDatabaseExists         = errors.New("database already exists")
 	ErrCollectionExists       = errors.New("collection already exists")
 	ErrGraphExists            = errors.New("graph already exists")
+	errNotConnected           = errors.New("not connected to ArangoDB, check the Connect error logs")
 )
 
 // New creates a new ArangoDB client with the provided configuration.
@@ -94,6 +96,14 @@ func (c *Client) UseTracer(tracer any) {
 
 // Connect establishes a connection to the ArangoDB server.
 func (c *Client) Connect() {
+	// Register the histogram before any step that can fail, so operations record latency even when
+	// the server is unreachable at startup and becomes available later.
+	arangoBuckets := []float64{
+		50, 75, 100, 125, 150, 200, 300, 500, 750, 1000, 2000, 3000, 5000, 7500, 10000, // 50µs-10ms
+		25000, 50000, 100000, 250000, 500000, 1000000, 5000000, 10000000, 30000000, 60000000, 120000000, 180000000, // 25ms-3min
+	}
+	c.metrics.NewHistogram("app_arango_stats", "Response time of ArangoDB operations in microseconds.", arangoBuckets...)
+
 	if err := c.validateConfig(); err != nil {
 		c.logger.Errorf("config validation error: %v", err)
 		return
@@ -127,14 +137,16 @@ func (c *Client) Connect() {
 		return
 	}
 
-	// Initialize metrics
-	arangoBuckets := []float64{
-		50, 75, 100, 125, 150, 200, 300, 500, 750, 1000, 2000, 3000, 5000, 7500, 10000, // 50µs-10ms
-		25000, 50000, 100000, 250000, 500000, 1000000, 5000000, 10000000, 30000000, 60000000, 120000000, 180000000, // 25ms-3min
+	c.logger.Logf("Connected to ArangoDB successfully at %s", c.endpoint)
+}
+
+// arangoClient returns the underlying driver client, or errNotConnected when Connect failed before creating it.
+func (c *Client) arangoClient() (arangodb.Client, error) {
+	if c.client == nil {
+		return nil, errNotConnected
 	}
-	c.metrics.NewHistogram("app_arango_stats", "Response time of ArangoDB operations in microseconds.", arangoBuckets...)
 
-	c.logger.Logf("Connected to ArangoDB successfully at %s", c.endpoint)
+	return c.client, nil
 }
 
 func (c *Client) validateConfig() error {
@@ -239,7 +251,7 @@ func (c *Client) Query(ctx context.Context, dbName, query string, bindVars map[s
 	ctx, done := c.instrumentOp(ctx, &QueryLog{Operation: "query", Database: dbName, Query: query})
 	defer done()
 
-	db, err := c.client.GetDatabase(ctx, dbName, nil)
+	db, err := c.database(ctx, dbName)
 	if err != nil {
 		return err
 	}
@@ -363,9 +375,18 @@ func (c *Client) HealthCheck(ctx context.Context) (any, error) {
 		},
 	}
 
+	if c.client == nil {
+		h.Status = statusDown
+		h.Details["error"] = errNotConnected.Error()
+
+		return &h, errNotConnected
+	}
+
 	version, err := c.client.Version(ctx)
 	if err != nil {
-		h.Status = "DOWN"
+		h.Status = statusDown
+		h.Details["error"] = err.Error()
+
 		return &h, errStatusDown
 	}
 

pkg/gofr/datasource/arangodb/arango_db.go

@@ -17,8 +17,13 @@ func (d *DB) CreateDB(ctx context.Context, database string) error {
 	ctx, done := d.client.instrumentOp(ctx, &QueryLog{Operation: "createDB", Database: database})
 	defer done()
 
+	client, err := d.client.arangoClient()
+	if err != nil {
+		return err
+	}
+
 	// Check if the database already exists
-	exists, err := d.client.client.DatabaseExists(ctx, database)
+	exists, err := client.DatabaseExists(ctx, database)
 	if err != nil {
 		return err
 	}
@@ -28,7 +33,7 @@ func (d *DB) CreateDB(ctx context.Context, database string) error {
 		return ErrDatabaseExists
 	}
 
-	_, err = d.client.client.CreateDatabase(ctx, database, nil)
+	_, err = client.CreateDatabase(ctx, database, nil)
 
 	return err
 }
@@ -41,7 +46,12 @@ func (d *DB) DropDB(ctx context.Context, database string) error {
 	ctx, done := d.client.instrumentOp(ctx, &QueryLog{Operation: opDropDB, Database: database})
 	defer done()
 
-	db, err := d.client.client.GetDatabase(ctx, database, &arangodb.GetDatabaseOptions{})
+	client, err := d.client.arangoClient()
+	if err != nil {
+		return err
+	}
+
+	db, err := client.GetDatabase(ctx, database, &arangodb.GetDatabaseOptions{})
 	if err != nil {
 		return err
 	}
@@ -62,7 +72,7 @@ func (d *DB) CreateCollection(ctx context.Context, database, collection string,
 		Collection: collection, Filter: isEdge})
 	defer done()
 
-	db, err := d.client.client.GetDatabase(ctx, database, nil)
+	db, err := d.client.database(ctx, database)
 	if err != nil {
 		return err
 	}
@@ -105,7 +115,7 @@ func (d *DB) DropCollection(ctx context.Context, database, collectionName string
 }
 
 func (d *DB) getCollection(ctx context.Context, dbName, collectionName string) (arangodb.Collection, error) {
-	db, err := d.client.client.GetDatabase(ctx, dbName, nil)
+	db, err := d.client.database(ctx, dbName)
 	if err != nil {
 		return nil, err
 	}

pkg/gofr/datasource/arangodb/arango_graph.go

@@ -36,7 +36,7 @@ func (g *Graph) CreateGraph(ctx context.Context, database, graph string, edgeDef
 		Database: database, Graph: graph})
 	defer done()
 
-	db, err := g.client.client.GetDatabase(ctx, database, nil)
+	db, err := g.client.database(ctx, database)
 	if err != nil {
 		return err
 	}
@@ -91,7 +91,7 @@ func (g *Graph) DropGraph(ctx context.Context, database, graphName string) error
 		Database: database, Graph: graphName})
 	defer done()
 
-	db, err := g.client.client.GetDatabase(ctx, database, nil)
+	db, err := g.client.database(ctx, database)
 	if err != nil {
 		return err
 	}
@@ -140,7 +140,7 @@ func (c *Client) GetEdges(ctx context.Context, dbName, graphName, edgeCollection
 	})
 	defer done()
 
-	db, err := c.client.GetDatabase(ctx, dbName, nil)
+	db, err := c.database(ctx, dbName)
 	if err != nil {
 		return err
 	}

pkg/gofr/datasource/arangodb/arango_helper.go

@@ -8,11 +8,21 @@ import (
 )
 
 func (c *Client) user(ctx context.Context, username string) (arangodb.User, error) {
-	return c.client.User(ctx, username)
+	client, err := c.arangoClient()
+	if err != nil {
+		return nil, err
+	}
+
+	return client.User(ctx, username)
 }
 
 func (c *Client) database(ctx context.Context, name string) (arangodb.Database, error) {
-	return c.client.GetDatabase(ctx, name, nil)
+	client, err := c.arangoClient()
+	if err != nil {
+		return nil, err
+	}
+
+	return client.GetDatabase(ctx, name, nil)
 }
 
 // createUser creates a new user in ArangoDB.
@@ -25,7 +35,12 @@ func (c *Client) createUser(ctx context.Context, username string, options any) e
 		return fmt.Errorf("%w", errInvalidUserOptionsType)
 	}
 
-	_, err := c.client.CreateUser(ctx, username, userOptions.toArangoUserOptions())
+	client, err := c.arangoClient()
+	if err != nil {
+		return err
+	}
+
+	_, err = client.CreateUser(ctx, username, userOptions.toArangoUserOptions())
 	if err != nil {
 		return err
 	}
@@ -38,7 +53,12 @@ func (c *Client) dropUser(ctx context.Context, username string) error {
 	ctx, done := c.instrumentOp(ctx, &QueryLog{Operation: "dropUser", ID: username})
 	defer done()
 
-	err := c.client.RemoveUser(ctx, username)
+	client, err := c.arangoClient()
+	if err != nil {
+		return err
+	}
+
+	err = client.RemoveUser(ctx, username)
 	if err != nil {
 		return err
 	}
@@ -51,7 +71,7 @@ func (c *Client) grantDB(ctx context.Context, database, username, permission str
 	ctx, done := c.instrumentOp(ctx, &QueryLog{Operation: "grantDB", Database: database, ID: username})
 	defer done()
 
-	user, err := c.client.User(ctx, username)
+	user, err := c.user(ctx, username)
 	if err != nil {
 		return err
 	}
@@ -67,7 +87,7 @@ func (c *Client) grantCollection(ctx context.Context, database, collection, user
 		Database: database, Collection: collection, ID: username})
 	defer done()
 
-	user, err := c.client.User(ctx, username)
+	user, err := c.user(ctx, username)
 	if err != nil {
 		return err
 	}