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conn.go
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conn.go
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package radix
import (
"container/list"
"context"
"errors"
"fmt"
"net"
"net/url"
"os"
"strings"
"sync"
"sync/atomic"
"time"
"github.com/mediocregopher/radix/v4/internal/proc"
"github.com/mediocregopher/radix/v4/resp"
"github.com/mediocregopher/radix/v4/resp/resp3"
)
// Conn is a Client wrapping a single network connection which synchronously
// reads/writes data using redis's RESP protocol.
//
// A Conn can be used directly as a Client, but in general you probably want to
// use a Pool instead.
type Conn interface {
// The Do method merely calls the Action's Perform method with the Conn as
// the argument.
Client
// EncodeDecode will encode marshal onto the connection, then decode a
// response into unmarshalInto (see resp3.Marshal and resp3.Unmarshal,
// respectively). If either parameter is nil then that step is skipped.
//
// If EncodeDecode is called concurrently on the same Conn then the order of
// decode steps will match the order of encode steps.
//
// NOTE If ctx is canceled then marshaling, and possibly unmarshaling, might
// still occur in the background even though EncodeDecode has returned.
EncodeDecode(ctx context.Context, marshal, unmarshalInto interface{}) error
}
////////////////////////////////////////////////////////////////////////////////
type wrappedNetConn struct {
net.Conn
prevBytesRead, totalBytesRead int
addr net.Addr
}
var _ net.Conn = new(wrappedNetConn)
func (c *wrappedNetConn) Read(b []byte) (int, error) {
n, err := c.Conn.Read(b)
c.totalBytesRead += n
prevBytesRead := c.prevBytesRead
c.prevBytesRead = n
if err == nil || !errors.Is(err, os.ErrDeadlineExceeded) || (prevBytesRead == 0 && n == 0) {
return n, err
}
// a timeout was reached, but there were bytes read before it was reached.
// In that case we pretend no timeout was reached. If there's more data to
// be pulled then we can do so, but if there's not more data to be pulled
// then a timeout will be returned the subsequent call to Read.
err = c.Conn.SetReadDeadline(time.Now().Add(500 * time.Millisecond))
return n, err
}
func (c *wrappedNetConn) resetBytesRead() {
c.prevBytesRead = 0
c.totalBytesRead = 0
}
func (c *wrappedNetConn) RemoteAddr() net.Addr {
return c.addr
}
////////////////////////////////////////////////////////////////////////////////
type connMarshalerUnmarshaler struct {
ctx context.Context
marshal, unmarshalInto interface{}
errCh chan error
readSeq uint64
}
type conn struct {
proc *proc.Proc
conn *wrappedNetConn
rOpts, wOpts *resp.Opts
br resp.BufferedReader
bw resp.BufferedWriter
rCh, wCh chan connMarshalerUnmarshaler
// the readSeq is used to track the current EncodeDecode call which the
// reader go-routine is operating on. readSeq is used to assign a uint64 to
// each connMarshalerUnmarshaler, and currReadSeq will be updated to reflect
// the readSeq that the reader is currently operating on.
//
// this mechanism is only used during error cases, primarily when the
// context deadline is exceeded and the EncodeDecode call wants to pre-empt
// the currently active resp3.Unmarshal call.
readSeqL sync.Mutex
readSeq, currReadSeq uint64
// errChPool is a buffered channel used as a makeshift pool of chan errors,
// so we don't have to make a new one on every EncodeDecode call.
errChPool chan chan error
}
var _ Conn = new(conn)
func (c *conn) Close() error {
return c.proc.PrefixedClose(c.conn.Close, nil)
}
func (c *conn) reader(ctx context.Context) {
discardList := list.New()
doneCh := ctx.Done()
for {
select {
case <-doneCh:
return
case mu := <-c.rCh:
c.readSeqL.Lock()
var skip bool
if err := mu.ctx.Err(); err != nil {
mu.errCh <- fmt.Errorf("checking context before read: %w", err)
skip = true
} else if err := c.conn.SetReadDeadline(time.Time{}); err != nil {
mu.errCh <- fmt.Errorf("unsetting read deadline: %w", err)
skip = true
}
if !skip {
c.currReadSeq = mu.readSeq
}
c.readSeqL.Unlock()
if skip {
if mu.marshal != nil {
discardList.PushBack(mu)
}
continue
}
var err error
c.conn.resetBytesRead()
buffered := c.br.Buffered()
// Discard messages queued up on the wire which aren't for this
// EncodeDecode call. Only discard messages if the EncodeDecode
// gives a value to marshal, as that indicates there's a specific
// response message in the queue which corresponds to it. If no
// value to marshal is given then the EncodeDecode will read in
// whatever the next message in the queue is.
if mu.marshal != nil {
for {
el := discardList.Front()
if el == nil {
break
}
discardMU := el.Value.(connMarshalerUnmarshaler)
if err = resp3.Unmarshal(c.br, discardMU.unmarshalInto, c.rOpts); err != nil {
break
}
discardList.Remove(el)
}
}
// if discarding didn't fail then read the actual desired response.
if err == nil {
if err = resp3.Unmarshal(c.br, mu.unmarshalInto, c.rOpts); err == nil && discardList.Len() > 0 {
discardList.Remove(discardList.Front())
}
}
// simplify things for the caller by translating network timeouts
// into the context error, since that's actually what happened.
var canceled bool
if canceled = errors.Is(err, os.ErrDeadlineExceeded); canceled {
if err = mu.ctx.Err(); err == nil {
// there might be some crazy edge case where this can
// happen, I'm not sure... go contexts are not pleasant to
// work with.
err = context.Canceled
}
}
if err != nil {
err = fmt.Errorf("unmarshaling message off Conn: %w", err)
}
if canceled {
if buffered == c.br.Buffered() && c.conn.totalBytesRead == 0 {
err = resp.ErrConnUsable{Err: err}
if mu.marshal != nil {
discardList.PushBack(mu)
}
} else {
// if Unmarshal returned a context error but data was also
// read it means that a message was only partially read off
// the wire. The Conn is unusable at this point, close it
// and bail.
go c.Close()
mu.errCh <- fmt.Errorf("after partial read off Conn: %w", err)
return
}
} else if err != nil && !errors.As(err, new(resp.ErrConnUsable)) {
go c.Close()
mu.errCh <- fmt.Errorf("unexpected error on Conn: %w", err)
return
}
mu.errCh <- err
}
}
}
func (c *conn) getErrCh() chan error {
select {
case errCh := <-c.errChPool:
return errCh
default:
return make(chan error, 1)
}
}
func (c *conn) putErrCh(errCh chan error) {
select {
case c.errChPool <- errCh:
default:
}
}
func (c *conn) EncodeDecode(ctx context.Context, m, u interface{}) error {
mu := connMarshalerUnmarshaler{
ctx: ctx,
marshal: m,
unmarshalInto: u,
errCh: c.getErrCh(),
readSeq: atomic.AddUint64(&c.readSeq, 1),
}
doneCh := ctx.Done()
closedCh := c.proc.ClosedCh()
select {
case <-doneCh:
return fmt.Errorf("writing EncodeDecode to Conn channel: %w", ctx.Err())
case <-closedCh:
return proc.ErrClosed
case c.wCh <- mu:
}
select {
case <-doneCh:
// To ensure that we don't miss messages which might come in _just_ as
// the deadline is exceeded, we only return the ctx.Err after hearing
// back from the reader. We call SetReadDeadline with a past value (but
// only if the reader is currently working on our message!) to unblock
// it, if it's blocked. If the reader returns nil then the message was
// successfully read despite the context being canceled.
c.readSeqL.Lock()
if c.currReadSeq == mu.readSeq {
if err := c.conn.SetReadDeadline(time.Unix(0, 0)); err != nil {
c.readSeqL.Unlock()
return fmt.Errorf("canceling Conn read from EncodeDecode: %w", err)
}
}
c.readSeqL.Unlock()
select {
case err := <-mu.errCh:
c.putErrCh(mu.errCh)
if err != nil {
err = fmt.Errorf("waiting for response from Conn: %w", ctx.Err())
}
return err
case <-closedCh:
return proc.ErrClosed
}
case <-closedCh:
return proc.ErrClosed
case err := <-mu.errCh:
// it's important that we only put the error channel back in the pool if
// it's actually been used, otherwise it might still end up with
// something written to it.
c.putErrCh(mu.errCh)
if err != nil {
err = fmt.Errorf("response returned from Conn: %w", err)
}
return err
}
}
func (c *conn) Do(ctx context.Context, a Action) error {
return a.Perform(ctx, c)
}
func (c *conn) Addr() net.Addr {
return c.conn.RemoteAddr()
}
////////////////////////////////////////////////////////////////////////////////
// Dialer is used to create Conns with particular settings. All fields are
// optional, all methods are thread-safe.
type Dialer struct {
// CustomConn indicates that this callback should be used in place of Dial
// when Dial is called. All behavior of Dialer/Dial is superceded when this
// is set.
CustomConn func(ctx context.Context, network, addr string) (Conn, error)
// AuthPass will cause Dial to perform an AUTH command once the connection
// is created, using AuthUser (if given) and AuthPass.
//
// If this is set and a redis URI is passed to Dial which also has a password
// set, this takes precedence.
AuthUser, AuthPass string
// SelectDB will cause Dial to perform a SELECT command once the connection
// is created, using the given database index.
//
// If this is set and a redis URI is passed to Dial which also has a
// database index set, this takes precedence.
SelectDB string
// Protocol can be used to automatically set the RESP protocol version.
//
// If Protocol is not empty the Dialer will send a HELLO command with the
// value of Protocol as version, otherwise no HELLO command will be send.
Protocol string
// NetDialer is used to create the underlying network connection.
//
// Defaults to net.Dialer.
NetDialer interface {
DialContext(context.Context, string, string) (net.Conn, error)
}
// WriteFlushInterval indicates how often the Conn should flush writes
// to the underlying net.Conn.
//
// Conn uses a bufio.Writer to write data to the underlying net.Conn, and so
// requires Flush to be called on that bufio.Writer in order for the data to
// be fully written. By delaying Flush calls until multiple concurrent
// EncodeDecode calls have been made Conn can reduce system calls and
// significantly improve performance in that case.
//
// All EncodeDecode calls will be delayed up to WriteFlushInterval, with one
// exception: if more than WriteFlushInterval has elapsed since the last
// EncodeDecode call then the next EncodeDecode will Flush immediately. This
// allows Conns to behave well during both low and high activity periods.
//
// Defaults to 0, indicating Flush will be called upon each EncodeDecode
// call without delay.
WriteFlushInterval time.Duration
// NewRespOpts returns a fresh instance of a *resp.Opts to be used by the
// underlying connection. This maybe be called more than once.
//
// Defaults to resp.NewOpts.
NewRespOpts func() *resp.Opts
}
func (d Dialer) withDefaults() Dialer {
if d.NetDialer == nil {
d.NetDialer = new(net.Dialer)
}
if d.NewRespOpts == nil {
d.NewRespOpts = resp.NewOpts
}
return d
}
func parseRedisURL(urlStr string, d Dialer) (string, Dialer) {
// do a quick check before we bust out url.Parse, in case that is very
// unperformant
if !strings.HasPrefix(urlStr, "redis://") {
return urlStr, d
}
u, err := url.Parse(urlStr)
if err != nil {
return urlStr, d
}
q := u.Query()
if d.AuthUser == "" {
d.AuthUser = q.Get("username")
if n := u.User.Username(); n != "" {
d.AuthUser = n
}
}
if d.AuthPass == "" {
d.AuthPass = q.Get("password")
if p, ok := u.User.Password(); ok {
d.AuthPass = p
}
}
if d.SelectDB == "" {
d.SelectDB = q.Get("db")
if u.Path != "" && u.Path != "/" {
d.SelectDB = u.Path[1:]
}
}
return u.Host, d
}
// Dial creates a Conn using the Dialer configuration.
//
// In place of a host:port address, Dial also accepts a URI, as per:
// https://www.iana.org/assignments/uri-schemes/prov/redis
// If the URI has an AUTH password or db specified Dial will attempt to perform
// the AUTH and/or SELECT as well.
func (d Dialer) Dial(ctx context.Context, network, addr string) (Conn, error) {
if d.CustomConn != nil {
return d.CustomConn(ctx, network, addr)
}
d = d.withDefaults()
addr, d = parseRedisURL(addr, d)
netConn, err := d.NetDialer.DialContext(ctx, network, addr)
if err != nil {
return nil, err
}
// If the netConn is a net.TCPConn (or some wrapper for it) and so can have
// keepalive enabled, do so with a sane (though slightly aggressive)
// default.
{
type keepaliveConn interface {
SetKeepAlive(bool) error
SetKeepAlivePeriod(time.Duration) error
}
if kaConn, ok := netConn.(keepaliveConn); ok {
if err = kaConn.SetKeepAlive(true); err != nil {
netConn.Close()
return nil, err
} else if err = kaConn.SetKeepAlivePeriod(10 * time.Second); err != nil {
netConn.Close()
return nil, err
}
}
}
wrappedNetConn := &wrappedNetConn{
Conn: netConn,
// wrap the conn so that it will return exactly what was used for
// dialing when Addr is called. If Conn's normal RemoteAddr is used then
// it returns the fully resolved form of the host.
addr: rawAddr{network: network, addr: addr},
}
conn := &conn{
proc: proc.New(),
conn: wrappedNetConn,
rOpts: d.NewRespOpts(),
wOpts: d.NewRespOpts(),
rCh: make(chan connMarshalerUnmarshaler, 128),
wCh: make(chan connMarshalerUnmarshaler, 128),
errChPool: make(chan chan error, 16),
}
conn.br = conn.rOpts.GetBufferedReader(wrappedNetConn)
conn.bw = conn.wOpts.GetBufferedWriter(wrappedNetConn)
conn.proc.Run(conn.reader)
conn.proc.Run(func(ctx context.Context) {
conn.writer(ctx, d.WriteFlushInterval)
})
if d.Protocol != "" {
args := []string{d.Protocol}
if d.AuthUser != "" {
args = append(args, "AUTH", d.AuthUser, d.AuthPass)
} else if d.AuthPass != "" {
args = append(args, "AUTH", "default", d.AuthPass)
}
if err := conn.Do(ctx, Cmd(nil, "HELLO", args...)); err != nil {
conn.Close()
return nil, err
}
} else if d.AuthUser != "" {
if err := conn.Do(ctx, Cmd(nil, "AUTH", d.AuthUser, d.AuthPass)); err != nil {
conn.Close()
return nil, err
}
} else if d.AuthPass != "" {
if err := conn.Do(ctx, Cmd(nil, "AUTH", d.AuthPass)); err != nil {
conn.Close()
return nil, err
}
}
if d.SelectDB != "" {
if err := conn.Do(ctx, Cmd(nil, "SELECT", d.SelectDB)); err != nil {
conn.Close()
return nil, err
}
}
return conn, nil
}
// Dial is a shortcut for calling Dial on a zero-value Dialer.
func Dial(ctx context.Context, network, addr string) (Conn, error) {
return (Dialer{}).Dial(ctx, network, addr)
}