mirror of https://github.com/coder/coder.git
166 lines
4.2 KiB
Go
166 lines
4.2 KiB
Go
// Package wsconncache caches workspace agent connections by UUID.
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package wsconncache
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import (
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"context"
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"net/http"
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"sync"
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"time"
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"github.com/google/uuid"
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"go.uber.org/atomic"
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"golang.org/x/sync/singleflight"
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"golang.org/x/xerrors"
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"github.com/coder/coder/codersdk"
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)
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// New creates a new workspace connection cache that closes
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// connections after the inactive timeout provided.
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//
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// Agent connections are cached due to WebRTC negotiation
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// taking a few hundred milliseconds.
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func New(dialer Dialer, inactiveTimeout time.Duration) *Cache {
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if inactiveTimeout == 0 {
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inactiveTimeout = 5 * time.Minute
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}
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return &Cache{
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closed: make(chan struct{}),
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dialer: dialer,
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inactiveTimeout: inactiveTimeout,
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}
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}
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// Dialer creates a new agent connection by ID.
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type Dialer func(r *http.Request, id uuid.UUID) (*codersdk.WorkspaceAgentConn, error)
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// Conn wraps an agent connection with a reusable HTTP transport.
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type Conn struct {
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*codersdk.WorkspaceAgentConn
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locks atomic.Uint64
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timeoutMutex sync.Mutex
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timeout *time.Timer
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timeoutCancel context.CancelFunc
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transport *http.Transport
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}
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func (c *Conn) HTTPTransport() *http.Transport {
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return c.transport
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}
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// Close ends the HTTP transport if exists, and closes the agent.
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func (c *Conn) Close() error {
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if c.transport != nil {
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c.transport.CloseIdleConnections()
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}
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c.timeoutMutex.Lock()
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defer c.timeoutMutex.Unlock()
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if c.timeout != nil {
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c.timeout.Stop()
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}
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return c.WorkspaceAgentConn.Close()
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}
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type Cache struct {
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closed chan struct{}
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closeMutex sync.Mutex
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closeGroup sync.WaitGroup
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connGroup singleflight.Group
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connMap sync.Map
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dialer Dialer
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inactiveTimeout time.Duration
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}
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// Acquire gets or establishes a connection with the dialer using the ID provided.
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// If a connection is in-progress, that connection or error will be returned.
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//
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// The returned function is used to release a lock on the connection. Once zero
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// locks exist on a connection, the inactive timeout will begin to tick down.
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// After the time expires, the connection will be cleared from the cache.
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func (c *Cache) Acquire(r *http.Request, id uuid.UUID) (*Conn, func(), error) {
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rawConn, found := c.connMap.Load(id.String())
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// If the connection isn't found, establish a new one!
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if !found {
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var err error
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// A singleflight group is used to allow for concurrent requests to the
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// same identifier to resolve.
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rawConn, err, _ = c.connGroup.Do(id.String(), func() (interface{}, error) {
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c.closeMutex.Lock()
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select {
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case <-c.closed:
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c.closeMutex.Unlock()
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return nil, xerrors.New("closed")
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default:
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}
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c.closeGroup.Add(1)
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c.closeMutex.Unlock()
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agentConn, err := c.dialer(r, id)
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if err != nil {
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c.closeGroup.Done()
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return nil, xerrors.Errorf("dial: %w", err)
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}
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timeoutCtx, timeoutCancelFunc := context.WithCancel(context.Background())
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defaultTransport, valid := http.DefaultTransport.(*http.Transport)
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if !valid {
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panic("dev error: default transport is the wrong type")
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}
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transport := defaultTransport.Clone()
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transport.DialContext = agentConn.DialContext
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conn := &Conn{
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WorkspaceAgentConn: agentConn,
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timeoutCancel: timeoutCancelFunc,
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transport: transport,
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}
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go func() {
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defer c.closeGroup.Done()
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select {
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case <-timeoutCtx.Done():
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case <-c.closed:
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case <-conn.Closed():
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}
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c.connMap.Delete(id.String())
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c.connGroup.Forget(id.String())
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_ = conn.Close()
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}()
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return conn, nil
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})
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if err != nil {
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return nil, nil, err
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}
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c.connMap.Store(id.String(), rawConn)
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}
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conn, _ := rawConn.(*Conn)
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conn.timeoutMutex.Lock()
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defer conn.timeoutMutex.Unlock()
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if conn.timeout != nil {
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conn.timeout.Stop()
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}
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conn.locks.Inc()
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return conn, func() {
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conn.timeoutMutex.Lock()
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defer conn.timeoutMutex.Unlock()
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if conn.timeout != nil {
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conn.timeout.Stop()
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}
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conn.locks.Dec()
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if conn.locks.Load() == 0 {
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conn.timeout = time.AfterFunc(c.inactiveTimeout, conn.timeoutCancel)
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}
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}, nil
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}
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func (c *Cache) Close() error {
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c.closeMutex.Lock()
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defer c.closeMutex.Unlock()
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select {
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case <-c.closed:
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return nil
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default:
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}
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close(c.closed)
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c.closeGroup.Wait()
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return nil
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}
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