docs: Add comprehensive documentation for blocking Redis operations (XReadGroup, Blpop) (#5221)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: kevwan <1918356+kevwan@users.noreply.github.com>
Co-authored-by: Kevin Wan <wanjunfeng@gmail.com>

core/stores/redis/redis.go

@@ -259,12 +259,34 @@ func (s *Redis) BitPosCtx(ctx context.Context, key string, bit, start, end int64
 }
 
 // Blpop uses passed in redis connection to execute blocking queries.
+//
+// For blocking operations, you must create a dedicated RedisNode using CreateBlockingNode to avoid
+// exhausting the connection pool. Blocking commands hold connections for extended periods and should
+// not share the regular connection pool.
+//
+// Example usage:
+//
+//	node, err := redis.CreateBlockingNode(rds)
+//	if err != nil {
+//	    // handle error
+//	}
+//	defer node.Close()
+//
+//	value, err := rds.Blpop(node, "mylist")
+//	if err != nil {
+//	    // handle error
+//	}
+//
 // Doesn't benefit from pooling redis connections of blocking queries
 func (s *Redis) Blpop(node RedisNode, key string) (string, error) {
 	return s.BlpopCtx(context.Background(), node, key)
 }
 
 // BlpopCtx uses passed in redis connection to execute blocking queries.
+//
+// For blocking operations, you must create a dedicated RedisNode using CreateBlockingNode.
+// See Blpop for usage examples.
+//
 // Doesn't benefit from pooling redis connections of blocking queries
 func (s *Redis) BlpopCtx(ctx context.Context, node RedisNode, key string) (string, error) {
 	return s.BlpopWithTimeoutCtx(ctx, node, blockingQueryTimeout, key)
@@ -272,12 +294,18 @@ func (s *Redis) BlpopCtx(ctx context.Context, node RedisNode, key string) (strin
 
 // BlpopEx uses passed in redis connection to execute blpop command.
 // The difference against Blpop is that this method returns a bool to indicate success.
+//
+// For blocking operations, you must create a dedicated RedisNode using CreateBlockingNode.
+// See Blpop for usage examples.
 func (s *Redis) BlpopEx(node RedisNode, key string) (string, bool, error) {
 	return s.BlpopExCtx(context.Background(), node, key)
 }
 
 // BlpopExCtx uses passed in redis connection to execute blpop command.
 // The difference against Blpop is that this method returns a bool to indicate success.
+//
+// For blocking operations, you must create a dedicated RedisNode using CreateBlockingNode.
+// See Blpop for usage examples.
 func (s *Redis) BlpopExCtx(ctx context.Context, node RedisNode, key string) (string, bool, error) {
 	if node == nil {
 		return "", false, ErrNilNode
@@ -297,12 +325,18 @@ func (s *Redis) BlpopExCtx(ctx context.Context, node RedisNode, key string) (str
 
 // BlpopWithTimeout uses passed in redis connection to execute blpop command.
 // Control blocking query timeout
+//
+// For blocking operations, you must create a dedicated RedisNode using CreateBlockingNode.
+// See Blpop for usage examples.
 func (s *Redis) BlpopWithTimeout(node RedisNode, timeout time.Duration, key string) (string, error) {
 	return s.BlpopWithTimeoutCtx(context.Background(), node, timeout, key)
 }
 
 // BlpopWithTimeoutCtx uses passed in redis connection to execute blpop command.
 // Control blocking query timeout
+//
+// For blocking operations, you must create a dedicated RedisNode using CreateBlockingNode.
+// See Blpop for usage examples.
 func (s *Redis) BlpopWithTimeoutCtx(ctx context.Context, node RedisNode, timeout time.Duration,
 	key string) (string, error) {
 	if node == nil {
@@ -1840,6 +1874,29 @@ func (s *Redis) XInfoStreamCtx(ctx context.Context, stream string) (*red.XInfoSt
 
 // XReadGroup reads messages from Redis streams as part of a consumer group.
 // It allows for distributed processing of stream messages with automatic message delivery semantics.
+//
+// For blocking operations, you must create a dedicated RedisNode using CreateBlockingNode to avoid
+// exhausting the connection pool. Blocking commands hold connections for extended periods and should
+// not share the regular connection pool.
+//
+// Example usage:
+//
+//	node, err := redis.CreateBlockingNode(rds)
+//	if err != nil {
+//	    // handle error
+//	}
+//	defer node.Close()
+//
+//	streams, err := rds.XReadGroup(
+//	    node,              // RedisNode created with CreateBlockingNode
+//	    "mygroup",         // consumer group name
+//	    "consumer1",       // consumer ID
+//	    10,                // max number of messages to read
+//	    5*time.Second,     // block duration
+//	    false,             // noAck flag
+//	    "mystream",        // stream name
+//	)
+//
 // Doesn't benefit from pooling redis connections of blocking queries.
 func (s *Redis) XReadGroup(node RedisNode, group string, consumerId string, count int64,
 	block time.Duration, noAck bool, streams ...string) ([]red.XStream, error) {
@@ -1847,6 +1904,10 @@ func (s *Redis) XReadGroup(node RedisNode, group string, consumerId string, coun
 }
 
 // XReadGroupCtx is the context-aware version of XReadGroup.
+//
+// For blocking operations, you must create a dedicated RedisNode using CreateBlockingNode to avoid
+// exhausting the connection pool. See XReadGroup for usage examples.
+//
 // Doesn't benefit from pooling redis connections of blocking queries.
 func (s *Redis) XReadGroupCtx(ctx context.Context, node RedisNode, group string, consumerId string,
 	count int64, block time.Duration, noAck bool, streams ...string) ([]red.XStream, error) {

core/stores/redis/redisblockingnode.go

@@ -13,7 +13,37 @@ type ClosableNode interface {
 	Close()
 }
 
-// CreateBlockingNode returns a ClosableNode.
+// CreateBlockingNode creates a dedicated RedisNode for blocking operations.
+//
+// Blocking Redis commands (like BLPOP, BRPOP, XREADGROUP with block parameter) hold connections
+// for extended periods while waiting for data. Using them with the regular Redis connection pool
+// can exhaust all available connections, causing other operations to fail or timeout.
+//
+// CreateBlockingNode creates a separate Redis client with a minimal connection pool (size 1) that
+// is dedicated to blocking operations. This ensures blocking commands don't interfere with regular
+// Redis operations.
+//
+// Example usage:
+//
+//	rds := redis.MustNewRedis(redis.RedisConf{
+//	    Host: "localhost:6379",
+//	    Type: redis.NodeType,
+//	})
+//
+//	// Create a dedicated node for blocking operations
+//	node, err := redis.CreateBlockingNode(rds)
+//	if err != nil {
+//	    // handle error
+//	}
+//	defer node.Close() // Important: close the node when done
+//
+//	// Use the node for blocking operations
+//	value, err := rds.Blpop(node, "mylist")
+//	if err != nil {
+//	    // handle error
+//	}
+//
+// The returned ClosableNode must be closed when no longer needed to release resources.
 func CreateBlockingNode(r *Redis) (ClosableNode, error) {
 	timeout := readWriteTimeout + blockingQueryTimeout