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/pipeline.go

@@ -0,0 +1,142 @@
+package redis
+
+import (
+	"context"
+	"sync"
+
+	"github.com/go-redis/redis/v7/internal/pool"
+)
+
+type pipelineExecer func(context.Context, []Cmder) error
+
+// Pipeliner is an mechanism to realise Redis Pipeline technique.
+//
+// Pipelining is a technique to extremely speed up processing by packing
+// operations to batches, send them at once to Redis and read a replies in a
+// singe step.
+// See https://redis.io/topics/pipelining
+//
+// Pay attention, that Pipeline is not a transaction, so you can get unexpected
+// results in case of big pipelines and small read/write timeouts.
+// Redis client has retransmission logic in case of timeouts, pipeline
+// can be retransmitted and commands can be executed more then once.
+// To avoid this: it is good idea to use reasonable bigger read/write timeouts
+// depends of your batch size and/or use TxPipeline.
+type Pipeliner interface {
+	StatefulCmdable
+	Do(args ...interface{}) *Cmd
+	Process(cmd Cmder) error
+	Close() error
+	Discard() error
+	Exec() ([]Cmder, error)
+	ExecContext(ctx context.Context) ([]Cmder, error)
+}
+
+var _ Pipeliner = (*Pipeline)(nil)
+
+// Pipeline implements pipelining as described in
+// http://redis.io/topics/pipelining. It's safe for concurrent use
+// by multiple goroutines.
+type Pipeline struct {
+	cmdable
+	statefulCmdable
+
+	ctx  context.Context
+	exec pipelineExecer
+
+	mu     sync.Mutex
+	cmds   []Cmder
+	closed bool
+}
+
+func (c *Pipeline) init() {
+	c.cmdable = c.Process
+	c.statefulCmdable = c.Process
+}
+
+func (c *Pipeline) Do(args ...interface{}) *Cmd {
+	cmd := NewCmd(args...)
+	_ = c.Process(cmd)
+	return cmd
+}
+
+// Process queues the cmd for later execution.
+func (c *Pipeline) Process(cmd Cmder) error {
+	c.mu.Lock()
+	c.cmds = append(c.cmds, cmd)
+	c.mu.Unlock()
+	return nil
+}
+
+// Close closes the pipeline, releasing any open resources.
+func (c *Pipeline) Close() error {
+	c.mu.Lock()
+	_ = c.discard()
+	c.closed = true
+	c.mu.Unlock()
+	return nil
+}
+
+// Discard resets the pipeline and discards queued commands.
+func (c *Pipeline) Discard() error {
+	c.mu.Lock()
+	err := c.discard()
+	c.mu.Unlock()
+	return err
+}
+
+func (c *Pipeline) discard() error {
+	if c.closed {
+		return pool.ErrClosed
+	}
+	c.cmds = c.cmds[:0]
+	return nil
+}
+
+// Exec executes all previously queued commands using one
+// client-server roundtrip.
+//
+// Exec always returns list of commands and error of the first failed
+// command if any.
+func (c *Pipeline) Exec() ([]Cmder, error) {
+	return c.ExecContext(c.ctx)
+}
+
+func (c *Pipeline) ExecContext(ctx context.Context) ([]Cmder, error) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if c.closed {
+		return nil, pool.ErrClosed
+	}
+
+	if len(c.cmds) == 0 {
+		return nil, nil
+	}
+
+	cmds := c.cmds
+	c.cmds = nil
+
+	return cmds, c.exec(ctx, cmds)
+}
+
+func (c *Pipeline) Pipelined(fn func(Pipeliner) error) ([]Cmder, error) {
+	if err := fn(c); err != nil {
+		return nil, err
+	}
+	cmds, err := c.Exec()
+	_ = c.Close()
+	return cmds, err
+}
+
+func (c *Pipeline) Pipeline() Pipeliner {
+	return c
+}
+
+func (c *Pipeline) TxPipelined(fn func(Pipeliner) error) ([]Cmder, error) {
+	return c.Pipelined(fn)
+}
+
+func (c *Pipeline) TxPipeline() Pipeliner {
+	return c
+}