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107 lines
1.8 KiB
107 lines
1.8 KiB
package connection
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import (
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"errors"
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"net/rpc"
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"sync"
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log "github.com/sirupsen/logrus"
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)
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// TODO(helin): add TCP re-connect logic
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// Conn is a connection to a parameter server
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type Conn struct {
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mu sync.Mutex
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client *rpc.Client
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waitConn chan struct{}
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}
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// New creates a new connection.
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func New() *Conn {
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c := &Conn{}
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return c
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}
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// Close closes the connection.
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func (c *Conn) Close() error {
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c.mu.Lock()
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defer c.mu.Unlock()
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if c.client == nil {
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return nil
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}
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return c.client.Close()
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}
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// Connect connects the connection to a address.
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func (c *Conn) Connect(addr string) error {
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c.mu.Lock()
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if c.client != nil {
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err := c.client.Close()
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if err != nil {
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c.mu.Unlock()
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return err
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}
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c.client = nil
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}
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c.mu.Unlock()
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client, err := rpc.DialHTTP("tcp", addr)
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if err != nil {
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return err
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}
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c.mu.Lock()
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defer c.mu.Unlock()
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if c.client == nil {
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c.client = client
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if c.waitConn != nil {
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close(c.waitConn)
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c.waitConn = nil
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}
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} else {
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err := client.Close()
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if err != nil {
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log.Errorln(err)
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}
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return errors.New("client already set from a concurrent goroutine")
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}
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return nil
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}
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// TODO(helin): refactor Call to be able to perform given retry
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// policy.
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// Call make a RPC call.
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//
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// Call will be blocked until the connection to remote RPC service
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// being established.
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func (c *Conn) Call(serviceMethod string, args interface{}, reply interface{}) error {
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c.mu.Lock()
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client := c.client
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var waitCh chan struct{}
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if client == nil {
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if c.waitConn != nil {
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waitCh = c.waitConn
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} else {
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waitCh = make(chan struct{})
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c.waitConn = waitCh
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}
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}
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c.mu.Unlock()
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if waitCh != nil {
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// wait until new connection being established
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<-waitCh
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return c.Call(serviceMethod, args, reply)
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}
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return client.Call(serviceMethod, args, reply)
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}
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