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pool.go
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pool.go
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// Package pool contains Telegram connections pool.
package pool
import (
"context"
"sync"
"github.com/go-faster/errors"
"go.uber.org/atomic"
"go.uber.org/zap"
"github.com/KoNekoD/td/bin"
"github.com/KoNekoD/td/tdsync"
)
// DC represents connection pool to one data center.
type DC struct {
id int
// Connection constructor.
newConn func() Conn
// Wrappers for external world, like logs or PRNG.
log *zap.Logger // immutable
// DC context. Will be canceled by Run on exit.
ctx context.Context // immutable
cancel context.CancelFunc // immutable
// Connections supervisor.
grp *tdsync.Supervisor
// Free connections.
free []*poolConn
// Total connections.
total int64
// Connection id monotonic counter.
nextConn atomic.Int64
freeReq *reqMap
// DC mutex.
mu sync.Mutex
// Limit of connections.
max int64 // immutable
// Signal connection for cases when all connections are dead, but all requests waiting for
// free connection in 3rd acquire case.
stuck *tdsync.ResetReady
closed atomic.Bool
}
// NewDC creates new uninitialized DC.
func NewDC(ctx context.Context, id int, newConn func() Conn, opts DCOptions) *DC {
ctx, cancel := context.WithCancel(ctx)
opts.setDefaults()
return &DC{
id: id,
newConn: newConn,
log: opts.Logger,
ctx: ctx,
cancel: cancel,
grp: tdsync.NewSupervisor(ctx),
freeReq: newReqMap(),
max: opts.MaxOpenConnections,
stuck: tdsync.NewResetReady(),
}
}
func (c *DC) createConnection(id int64) *poolConn {
conn := &poolConn{
Conn: c.newConn(),
id: id,
dc: c,
deleted: atomic.NewBool(false),
dead: tdsync.NewReady(),
}
c.grp.Go(func(groupCtx context.Context) (err error) {
defer c.dead(conn, err)
return conn.Run(groupCtx)
})
return conn
}
func (c *DC) dead(r *poolConn, deadErr error) {
if r.deleted.Swap(true) {
return // Already deleted.
}
c.mu.Lock()
defer c.mu.Unlock()
c.total--
remaining := c.total
if remaining < 0 {
panic("unreachable: remaining can't be less than zero")
}
idx := -1
for i, conn := range c.free {
// Search connection by pointer.
if conn.id == r.id {
idx = i
}
}
if idx >= 0 {
// Delete by index from slice tricks.
copy(c.free[idx:], c.free[idx+1:])
// Delete reference to prevent resource leaking.
c.free[len(c.free)-1] = nil
c.free = c.free[:len(c.free)-1]
}
r.dead.Signal()
c.stuck.Reset()
c.log.Debug("Connection died",
zap.Int64("remaining", remaining),
zap.Int64("conn_id", r.id),
zap.Error(deadErr),
)
}
func (c *DC) pop() (r *poolConn, ok bool) {
l := len(c.free)
if l > 0 {
r, c.free = c.free[l-1], c.free[:l-1]
return r, true
}
return
}
func (c *DC) release(r *poolConn) {
if r == nil {
return
}
c.mu.Lock()
defer c.mu.Unlock()
if c.freeReq.transfer(r) {
c.log.Debug("Transfer connection to requester", zap.Int64("conn_id", r.id))
return
}
c.log.Debug("Connection released", zap.Int64("conn_id", r.id))
c.free = append(c.free, r)
}
var errDCIsClosed = errors.New("DC is closed")
func (c *DC) acquire(ctx context.Context) (r *poolConn, err error) { // nolint:gocyclo
retry:
c.mu.Lock()
// 1st case: have free connections.
if r, ok := c.pop(); ok {
c.mu.Unlock()
select {
case <-r.Dead():
c.dead(r, nil)
goto retry
default:
}
c.log.Debug("Re-using free connection", zap.Int64("conn_id", r.id))
return r, nil
}
// 2nd case: no free connections, but can create one.
// c.max < 1 means unlimited
if c.max < 1 || c.total < c.max {
c.total++
c.mu.Unlock()
id := c.nextConn.Inc()
c.log.Debug("Creating new connection",
zap.Int64("conn_id", id),
)
conn := c.createConnection(id)
select {
case <-ctx.Done():
return nil, ctx.Err()
case <-c.ctx.Done():
return nil, errors.Wrap(c.ctx.Err(), "DC closed")
case <-conn.Ready():
return conn, nil
case <-conn.Dead():
c.dead(conn, nil)
goto retry
}
}
// 3rd case: no free connections, can't create yet one, wait for free.
key, ch := c.freeReq.request()
c.mu.Unlock()
c.log.Debug("Waiting for free connect", zap.Int64("request_id", int64(key)))
select {
case conn := <-ch:
c.log.Debug("Got connection for request",
zap.Int64("conn_id", conn.id),
zap.Int64("request_id", int64(key)),
)
return conn, nil
case <-c.stuck.Ready():
c.log.Debug("Some connection dead, try to create new connection, cancel waiting")
c.freeReq.delete(key)
select {
default:
case conn, ok := <-ch:
if ok && conn != nil {
return conn, nil
}
}
goto retry
case <-ctx.Done():
err = ctx.Err()
case <-c.ctx.Done():
err = errors.Wrap(c.ctx.Err(), "DC closed")
}
// Executed only if at least one of context is Done.
c.freeReq.delete(key)
select {
default:
case conn, ok := <-ch:
if ok && conn != nil {
c.release(conn)
}
}
return nil, err
}
// Invoke sends MTProto request using one of pool connection.
func (c *DC) Invoke(ctx context.Context, input bin.Encoder, output bin.Decoder) error {
if c.closed.Load() {
return errDCIsClosed
}
for {
conn, err := c.acquire(ctx)
if err != nil {
if errors.Is(err, ErrConnDead) {
continue
}
return errors.Wrap(err, "acquire connection")
}
c.log.Debug("DC Invoke")
err = conn.Invoke(ctx, input, output)
c.release(conn)
if err != nil {
c.log.Debug("DC Invoke failed", zap.Error(err))
return errors.Wrap(err, "invoke pool")
}
c.log.Debug("DC Invoke complete")
return err
}
}
// Close waits while all ongoing requests will be done or until given context is done.
// Then, closes the DC.
func (c *DC) Close() error {
if c.closed.Swap(true) {
return errors.New("DC already closed")
}
c.log.Debug("Closing DC")
defer c.log.Debug("DC closed")
c.cancel()
return c.grp.Wait()
}