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/internal/pool/conn.go

@@ -0,0 +1,118 @@
+package pool
+
+import (
+	"context"
+	"net"
+	"sync/atomic"
+	"time"
+
+	"github.com/go-redis/redis/v7/internal/proto"
+)
+
+var noDeadline = time.Time{}
+
+type Conn struct {
+	netConn net.Conn
+
+	rd *proto.Reader
+	wr *proto.Writer
+
+	Inited    bool
+	pooled    bool
+	createdAt time.Time
+	usedAt    int64 // atomic
+}
+
+func NewConn(netConn net.Conn) *Conn {
+	cn := &Conn{
+		netConn:   netConn,
+		createdAt: time.Now(),
+	}
+	cn.rd = proto.NewReader(netConn)
+	cn.wr = proto.NewWriter(netConn)
+	cn.SetUsedAt(time.Now())
+	return cn
+}
+
+func (cn *Conn) UsedAt() time.Time {
+	unix := atomic.LoadInt64(&cn.usedAt)
+	return time.Unix(unix, 0)
+}
+
+func (cn *Conn) SetUsedAt(tm time.Time) {
+	atomic.StoreInt64(&cn.usedAt, tm.Unix())
+}
+
+func (cn *Conn) SetNetConn(netConn net.Conn) {
+	cn.netConn = netConn
+	cn.rd.Reset(netConn)
+	cn.wr.Reset(netConn)
+}
+
+func (cn *Conn) Write(b []byte) (int, error) {
+	return cn.netConn.Write(b)
+}
+
+func (cn *Conn) RemoteAddr() net.Addr {
+	return cn.netConn.RemoteAddr()
+}
+
+func (cn *Conn) WithReader(ctx context.Context, timeout time.Duration, fn func(rd *proto.Reader) error) error {
+	err := cn.netConn.SetReadDeadline(cn.deadline(ctx, timeout))
+	if err != nil {
+		return err
+	}
+	return fn(cn.rd)
+}
+
+func (cn *Conn) WithWriter(
+	ctx context.Context, timeout time.Duration, fn func(wr *proto.Writer) error,
+) error {
+	err := cn.netConn.SetWriteDeadline(cn.deadline(ctx, timeout))
+	if err != nil {
+		return err
+	}
+
+	if cn.wr.Buffered() > 0 {
+		cn.wr.Reset(cn.netConn)
+	}
+
+	err = fn(cn.wr)
+	if err != nil {
+		return err
+	}
+
+	return cn.wr.Flush()
+}
+
+func (cn *Conn) Close() error {
+	return cn.netConn.Close()
+}
+
+func (cn *Conn) deadline(ctx context.Context, timeout time.Duration) time.Time {
+	tm := time.Now()
+	cn.SetUsedAt(tm)
+
+	if timeout > 0 {
+		tm = tm.Add(timeout)
+	}
+
+	if ctx != nil {
+		deadline, ok := ctx.Deadline()
+		if ok {
+			if timeout == 0 {
+				return deadline
+			}
+			if deadline.Before(tm) {
+				return deadline
+			}
+			return tm
+		}
+	}
+
+	if timeout > 0 {
+		return tm
+	}
+
+	return noDeadline
+}