From ffe9aa74b36ef7d6e7972d9098b9611a45417148 Mon Sep 17 00:00:00 2001
From: Ken Hibino <ken.hibino7@gmail.com>
Date: Sun, 9 May 2021 07:15:09 -0700
Subject: [PATCH] Add errors.RedisCommandError type

---
 internal/errors/errors.go | 18 ++++++++++++++++++
 internal/rdb/inspect.go   |  6 +++---
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/internal/errors/errors.go b/internal/errors/errors.go
index 7e6da13..4736095 100644
--- a/internal/errors/errors.go
+++ b/internal/errors/errors.go
@@ -213,6 +213,24 @@ func IsTaskAlreadyArchived(err error) bool {
 	return As(err, &target)
 }
 
+// RedisCommandError indicates that the given redis command returned error.
+type RedisCommandError struct {
+	Command string // redis command (e.g. LRANGE, ZADD, etc)
+	Err     error  // underlying error
+}
+
+func (e *RedisCommandError) Error() string {
+	return fmt.Sprintf("redis command error: %s failed: %v", strings.ToUpper(e.Command), e.Err)
+}
+
+func (e *RedisCommandError) Unwrap() error { return e.Err }
+
+// IsRedisCommandError reports whether any error in err's chain is of type RedisCommandError.
+func IsRedisCommandError(err error) bool {
+	var target *RedisCommandError
+	return As(err, &target)
+}
+
 /*************************************************
     Standard Library errors package functions
 *************************************************/
diff --git a/internal/rdb/inspect.go b/internal/rdb/inspect.go
index 26bef61..6430f1a 100644
--- a/internal/rdb/inspect.go
+++ b/internal/rdb/inspect.go
@@ -183,7 +183,7 @@ func (r *RDB) memoryUsage(qname string) (int64, error) {
 	for {
 		data, cursor, err = r.client.Scan(cursor, fmt.Sprintf("asynq:{%s}*", qname), 100).Result()
 		if err != nil {
-			return 0, errors.E(op, errors.Unknown, fmt.Sprintf("redis command error: SCAN failed: %v", err))
+			return 0, errors.E(op, errors.Unknown, &errors.RedisCommandError{Command: "scan", Err: err})
 		}
 		keys = append(keys, data...)
 		if cursor == 0 {
@@ -194,7 +194,7 @@ func (r *RDB) memoryUsage(qname string) (int64, error) {
 	for _, k := range keys {
 		n, err := r.client.MemoryUsage(k).Result()
 		if err != nil {
-			return 0, errors.E(op, errors.Unknown, fmt.Sprintf("redis command error: MEMORY USAGE failed: %v", err))
+			return 0, errors.E(op, errors.Unknown, &errors.RedisCommandError{Command: "memory usage", Err: err})
 		}
 		usg += n
 	}
@@ -220,7 +220,7 @@ func (r *RDB) HistoricalStats(qname string, n int) ([]*DailyStats, error) {
 	}
 	exists, err := r.client.SIsMember(base.AllQueues, qname).Result()
 	if err != nil {
-		return nil, errors.E(op, errors.Unknown, fmt.Sprintf("redis command error: SISMEMBER failed: %v", err))
+		return nil, errors.E(op, errors.Unknown, &errors.RedisCommandError{Command: "sismember", Err: err})
 	}
 	if !exists {
 		return nil, errors.E(op, errors.NotFound, &errors.QueueNotFoundError{Queue: qname})