Re: Question about asyn and offline device

[Torsten Bögershausen <torsten.bogershausen@esss.se>]

On 10/09/14 00:28, Sonya Hoobler wrote:
> Hi Mark,
>
> At LCLS we have VME crates (and other devices) that we monitor and control with soft iocs using asyn + streamdevice.
> There are many crates and it is not uncommon for one or more to be offline.
Just curious: Why are they offlien ?
Is this intended, is it a problem with the network, or do the devices have problems their selves?
>
> We have noticed that if there is an offline device, it can take minutes for the monitoring soft ioc to exit.
> This delay is the time it takes for the connect() networking routine to try to connect to the offline device.
When the soft IOC is exiting, why does it try to connect to a device ?

(Or is it at the start of the IOC ?)
(Or do you start the IOC and stop it shortly after the start ?

> the socket is blocking and connect() takes about 3 minutes on our system.
Do we know why does it take 3 minutes ?
On a Debian Linux
"time telnet 10.0.0.1" reports 1 minute, 3 seconds, and the Scientific Linux 6.5 system reports the same
What does
"time telnet 10.0.0.2" give on your system ?

> (More detail: the delay occurs while drvAsynIPPort cleanup() waits for the synchronousLock mutex.
> The mutex is held by asynManager portThread() or connectAttempt() while drvAsynIPPort connectIt() calls connect().)
> I am curious what your thoughts are on this and whether you think it is worthwhile to pursue a change to reduce the shutdown time under these conditions.
> One option could be to modify connectIt() to temporarily set the socket to non-blocking during connect() and use select() to enforce a specified timeout.
> Then the socket could be set back to blocking. One potential downside of this could be introducing a new timeout which might not suit all systems.
>
> A little more detail about our system: the soft iocs run on Linux RHEL5 32-bit servers,
Isn't it that the cleanup() want to call epicsSocketDestroy(), which should result in a a simple close().

But, it is blocked because of the lockPort(), we need to wait for connect() to fail.

What would happen if we do like this:
(diff is taken from latest, so the line number may by different)


diff --git a/asyn/drvAsynSerial/drvAsynIPPort.c b/asyn/drvAsynSerial/drvAsynIPPort.c
index 07b96d3..2b2cfe6 100644
--- a/asyn/drvAsynSerial/drvAsynIPPort.c
+++ b/asyn/drvAsynSerial/drvAsynIPPort.c
@@ -236,6 +236,7 @@ cleanup (void *arg)
     ttyController_t *tty = (ttyController_t *)arg;
 
     if (!tty) return;
+    epicsSocketDestroy(tty->fd);
     status=pasynManager->lockPort(tty->pasynUser);
     if(status!=asynSuccess)
         asynPrint(tty->pasynUser, ASYN_TRACE_ERROR, "%s: cleanup locking error\n", tty->portName);
@@ -243,7 +244,6 @@ cleanup (void *arg)
     if (tty->fd != INVALID_SOCKET) {
         asynPrint(tty->pasynUser, ASYN_TRACE_FLOW, "%s: shutdown socket\n", tty->portName);
         tty->flags |= FLAG_SHUTDOWN; /* prevent reconnect */
-        epicsSocketDestroy(tty->fd);
         tty->fd = INVALID_SOCKET;
         /* If this delay is not present then the sockets are not always really closed cleanly */
         epicsThreadSleep(CLOSE_SOCKET_DELAY);


> soon to be RHEL6 64-bit. We are using base R3-14-12, asyn4-21, streamdevice-R2-5, TCP/IP telnet-style connections, e.g.:
>
> drvAsynIPPortConfigure ("crat-test-bd01","crat-test-bd01:23",0,0,0)
>
> Thanks,
>    Sonya
>
>
> Sonya Hoobler
> SLAC National Accelerator Laboratory
> sonya@slac.stanford.edu