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fix concurrency issue #22

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fix concurrency issue #22

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2516d10
fix concurrency
irgendwr Feb 8, 2019
94d0c84
fixed TestConcurrency
irgendwr Feb 10, 2019
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12 changes: 11 additions & 1 deletion client.go
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@ import (
"net"
"regexp"
"strings"
"sync"
"time"
)

Expand Down Expand Up @@ -57,6 +58,7 @@ type Client struct {
notify chan Notification
disconnect chan struct{}
res []string
mutex sync.Mutex

Server *ServerMethods
}
Expand Down Expand Up @@ -234,7 +236,15 @@ func (c *Client) ExecCmd(cmd *Cmd) ([]string, error) {
return nil, ErrNotConnected
}

c.work <- cmd.String()
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c.mutex.Lock()
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I'm in too minds if we want to do this, it adds the lock overhead to a client which can only perform one request at a time. This falls under the remit of nothing being concurrent safe unless documented to be so.

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@irgendwr irgendwr Feb 10, 2019 •
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I can try to think of a better solution to solve this but it should definitely be concurrent safe imho (the fact that two people reported the issue suggests that it's expected despite not being "documented to be so").
Is the tiny overhead really that significant in this use case?

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My issue doesn't come from trying to use the library from multiple goroutines at once.

My issue happens once unhandled timeout/connection closed errors occur. (for example: read: connection reset by peer)

Because the next time I execute a command on that closed connection, the conn.Write() call freezes indefinitely, causing the issue.

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enabling keepalive on the connection should fix this

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conn.Write() should also never freeze "indefinitely", only as long as the Timeout that is specified/DefaultTimout, since there's a Deadline set before calling it.

defer c.mutex.Unlock()

select {
case c.work <- cmd.String():
// continue
case <-time.After(c.timeout):
return nil, ErrTimeout
}

select {
case err := <-c.err:
Expand Down
33 changes: 33 additions & 0 deletions client_test.go
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Expand Up @@ -230,3 +230,36 @@ func TestClientBadHeader(t *testing.T) {
// Should never get here
assert.NoError(t, c.Close())
}

func TestConcurrency(t *testing.T) {
s := newServer(t)
if s == nil {
return
}
defer func() {
assert.NoError(t, s.Close())
}()

c, err := NewClient(s.Addr, Timeout(time.Millisecond*100))
if !assert.NoError(t, err) {
return
}

wait := make(chan struct{})
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go func() {
for i := 0; i <= 10; i++ {
_, err = c.Server.GroupList()
assert.NoError(t, err)
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}
wait <- struct{}{}
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}()

for i := 0; i <= 10; i++ {
_, err = c.Server.GroupList()
assert.NoError(t, err)
}

// wait for go routine to finish
<-wait
}