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Re: [libvirt] [PATCH v2] virsh: add keepalive protocol in virsh



On 06/05/2012 02:36 AM, Guannan Ren wrote:
> Bugzilla:https://bugzilla.redhat.com/show_bug.cgi?id=822839
> add two general virsh options to support keepalive message protocol
> 
> -i | --keepalive_interval   interval time value (default 5 seconds)
> -n | --keepalive_count      number of heartbeats (default 5 times)
> 
> For non-p2p migration, start keepalive for remote driver to
> determine the status of network connection, aborting migrating job
> after defined amount of interval time.
> ---
>  tools/virsh.c |   88 +++++++++++++++++++++++++++++++++++++++++++++-----------
>  1 files changed, 70 insertions(+), 18 deletions(-)

Missing a counterpart documentation in virsh.pod.

> @@ -7213,6 +7219,12 @@ doMigrate (void *opaque)
>          dconn = virConnectOpenAuth (desturi, virConnectAuthPtrDefault, 0);
>          if (!dconn) goto out;
>  
> +        data->dconn = dconn;
> +        if (virConnectSetKeepAlive(dconn,
> +                                   ctl->keepalive_interval,
> +                                   ctl->keepalive_count) < 0)
> +             vshDebug(ctl, VSH_ERR_WARNING, "migrate: Failed to start keepalive\n");

This makes it impossible to migrate to an older server that lacks
virConnectSetKeepAlive() support.  You need to avoid doing this if
keepalive_interval and/or keepalive_count is set to a value that avoids
keepalive.  I think that also means you need to distinguish between a
normal default of 5 seconds with new servers but unspecified by the user
(where we just gracefully continue without keepalive), compared to an
explicit user request of 5 seconds (must fail if the keepalive request
cannot be honored), and compared to an explicit user request of no
keepalive.


> @@ -7329,6 +7342,13 @@ repoll:
>              goto cleanup;
>          }
>  
> +       if (data->dconn && virConnectIsAlive(data->dconn) <= 0) {
> +            virDomainAbortJob(dom);
> +            vshError(ctl, "%s",
> +                      _("Lost connection to destination host"));
> +            goto cleanup;
> +        }

Again, need to be careful of older servers that lack virConnectIsAlive()
support.


> @@ -18681,6 +18703,18 @@ vshCommandRun(vshControl *ctl, const vshCmd *cmd)
>          if (enable_timing)
>              GETTIMEOFDAY(&before);
>  
> +        /* start keepalive for remote driver */
> +        driver = virConnectGetType(ctl->conn);
> +        if (STREQ_NULLABLE(driver, "QEMU") ||
> +            STREQ_NULLABLE(driver, "xenlight") ||
> +            STREQ_NULLABLE(driver, "UML") ||
> +            STREQ_NULLABLE(driver, "LXC") ||
> +            STREQ_NULLABLE(driver, "remote"))

Why are you limiting this to particular hypervisors?  That feels wrong.
 Rather, you should blindly attempt it, and gracefully detect when it is
unsupported.


> @@ -19959,17 +19993,19 @@ vshUsage(void)
>      fprintf(stdout, _("\n%s [options]... [<command_string>]"
>                        "\n%s [options]... <command> [args...]\n\n"
>                        "  options:\n"
> -                      "    -c | --connect=URI      hypervisor connection URI\n"

> +                      "    -c | --connect=URI          hypervisor connection URI\n"

Rather than reindenting everything, I would just alter your new lines to
use multiple lines:


> +                      "    -i | --keepalive_interval   interval time value (default 5 seconds)\n"
> +                      "    -n | --keepalive_count      number of heartbeats (default 5 times)\n\n"

-c | --connect=URI      hypervisor connection URI
-i | --keepalive_interval
                        interval time value (default 5 seconds)

>  
>      /* Standard (non-command) options. The leading + ensures that no
>       * argument reordering takes place, so that command options are
>       * not confused with top-level virsh options. */
> -    while ((arg = getopt_long(argc, argv, "+d:hqtc:vVrl:e:", opt, NULL)) != -1) {
> +    while ((arg = getopt_long(argc, argv, "+d:hqtc:vVrl:e:i:n:", opt, NULL)) != -1) {

Pre-existing, but I would welcome an independent patch that cleaned this
up into alphabetic ordering to make it easier to find code for a given
option now that we have more options to deal with.

Looking forward to v3.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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