Allow common redis and leveldb connections (#12385)

* Allow common redis and leveldb connections

Prevents multiple reopening of redis and leveldb connections to the same
place by sharing connections.

Further allows for more configurable redis connection type using the
redisURI and a leveldbURI scheme.

Signed-off-by: Andrew Thornton <art27@cantab.net>

* add unit-test

Signed-off-by: Andrew Thornton <art27@cantab.net>

* as per @lunny

Signed-off-by: Andrew Thornton <art27@cantab.net>

* add test

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Update modules/cache/cache_redis.go

* Update modules/queue/queue_disk.go

* Update modules/cache/cache_redis.go

* Update modules/cache/cache_redis.go

* Update modules/queue/unique_queue_disk.go

* Update modules/queue/queue_disk.go

* Update modules/queue/unique_queue_disk.go

* Update modules/session/redis.go

Co-authored-by: techknowlogick <techknowlogick@gitea.io>
Co-authored-by: Lauris BH <lauris@nix.lv>

vendor/github.com/go-redis/redis/v7/error.go

@@ -0,0 +1,108 @@
+package redis
+
+import (
+	"context"
+	"io"
+	"net"
+	"strings"
+
+	"github.com/go-redis/redis/v7/internal/pool"
+	"github.com/go-redis/redis/v7/internal/proto"
+)
+
+var ErrClosed = pool.ErrClosed
+
+type Error interface {
+	error
+
+	// RedisError is a no-op function but
+	// serves to distinguish types that are Redis
+	// errors from ordinary errors: a type is a
+	// Redis error if it has a RedisError method.
+	RedisError()
+}
+
+var _ Error = proto.RedisError("")
+
+func isRetryableError(err error, retryTimeout bool) bool {
+	switch err {
+	case nil, context.Canceled, context.DeadlineExceeded:
+		return false
+	case io.EOF:
+		return true
+	}
+	if netErr, ok := err.(net.Error); ok {
+		if netErr.Timeout() {
+			return retryTimeout
+		}
+		return true
+	}
+
+	s := err.Error()
+	if s == "ERR max number of clients reached" {
+		return true
+	}
+	if strings.HasPrefix(s, "LOADING ") {
+		return true
+	}
+	if strings.HasPrefix(s, "READONLY ") {
+		return true
+	}
+	if strings.HasPrefix(s, "CLUSTERDOWN ") {
+		return true
+	}
+	return false
+}
+
+func isRedisError(err error) bool {
+	_, ok := err.(proto.RedisError)
+	return ok
+}
+
+func isBadConn(err error, allowTimeout bool) bool {
+	if err == nil {
+		return false
+	}
+	if isRedisError(err) {
+		// Close connections in read only state in case domain addr is used
+		// and domain resolves to a different Redis Server. See #790.
+		return isReadOnlyError(err)
+	}
+	if allowTimeout {
+		if netErr, ok := err.(net.Error); ok && netErr.Timeout() {
+			return false
+		}
+	}
+	return true
+}
+
+func isMovedError(err error) (moved bool, ask bool, addr string) {
+	if !isRedisError(err) {
+		return
+	}
+
+	s := err.Error()
+	switch {
+	case strings.HasPrefix(s, "MOVED "):
+		moved = true
+	case strings.HasPrefix(s, "ASK "):
+		ask = true
+	default:
+		return
+	}
+
+	ind := strings.LastIndex(s, " ")
+	if ind == -1 {
+		return false, false, ""
+	}
+	addr = s[ind+1:]
+	return
+}
+
+func isLoadingError(err error) bool {
+	return strings.HasPrefix(err.Error(), "LOADING ")
+}
+
+func isReadOnlyError(err error) bool {
+	return strings.HasPrefix(err.Error(), "READONLY ")
+}