worryg0d commented on code in PR #1822:
URL:
https://github.com/apache/cassandra-gocql-driver/pull/1822#discussion_r1803313311
##########
conn.go:
##########
@@ -474,8 +483,12 @@ func (s *startupCoordinator) startup(ctx context.Context,
supported map[string][
case error:
return v
case *readyFrame:
+ // Connection is successfully set up and ready to use Native
Protocol v5
+ s.conn.startupCompleted = true
Review Comment:
`startupCoordinator.setupConn` is complex, so I'll add its code to this
message for clarification
```go
func (s *startupCoordinator) setupConn(ctx context.Context) error {
var cancel context.CancelFunc
if s.conn.timeout > 0 {
ctx, cancel = context.WithTimeout(ctx, s.conn.timeout)
} else {
ctx, cancel = context.WithCancel(ctx)
}
defer cancel()
startupErr := make(chan error)
go func() { // the reading goroutine
for range s.frameTicker {
err := s.conn.recv(ctx)
if err != nil {
select {
case startupErr <- err:
case <-ctx.Done():
}
return
}
}
}()
go func() { // the writing one
defer close(s.frameTicker)
err := s.options(ctx)
select {
case startupErr <- err:
case <-ctx.Done():
}
}()
select {
case err := <-startupErr:
if err != nil {
return err
}
case <-ctx.Done():
return errors.New("gocql: no response to connection startup
within timeout")
}
return nil
}
```
It runs two goroutines: the first listening for response from C* and the
second for processing startup.
The first gorounite starts listening data from C* when the
`startupCoordinator.frameTicker` chan is not empty.
The second goroutine sends queries to C* via
[startupCoordinator.write](https://github.com/apache/cassandra-gocql-driver/blob/953e0df999cabb3f5eef714df9921c00e9f632c2/conn.go#L417)
which also writes to `startupCoordinator.frameTicker` chan. So, the reading
from C* only starts when the **writing gouroutine** sends a query to the C*,
the both goroutines are synchronized by `startupCoordinator.frameTicker`. Once
the startup is completed, those goroutines are finished.
When `startupCoordinator.setupConn` is finished, `Conn.init` runs two new
goroutines: one for connection serving, and another one for a heartbeat, so
they both already have an updated state of `startupCompleted`.
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