[libvirt] [PATCH 04/10] qemu: agent: handle agent connection errors in one place

[Nikolay Shirokovskiy]

On 26.10.2016 22:57, John Ferlan wrote:
> 
> There's no commit message...

This is simple refactoring.

> 
> You're altering qemuConnectAgent to return -1 on the only error and
> perform the VIR_WARN plus agentError = true on other "soft" failures.
> 
> Not exactly nothing going on!

This is what already present in code, I've just moved soft failures
in qemuConnectAgent.

> 
> On 10/04/2016 02:56 AM, Nikolay Shirokovskiy wrote:
>> ---
>>  src/qemu/qemu_driver.c    |  8 +------
>>  src/qemu/qemu_migration.c | 13 ++---------
>>  src/qemu/qemu_process.c   | 58 ++++++++++++-----------------------------------
>>  3 files changed, 17 insertions(+), 62 deletions(-)
>>
> 
> This idea seems to have merit too - something that I've thought now that
> I've read the first 3 patches...
> 
> I think you should have started with this patch, it probably would have
> made the others easier to think about. In fact, I'm curious if with just
> this change and the suggestion in patch 3 for clearing agentError
> whether you can reproduced the bug you're trying to fix/resolve without
> any of the other patches.
> 
>> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
>> index 12ddbc0..edff973 100644
>> --- a/src/qemu/qemu_driver.c
>> +++ b/src/qemu/qemu_driver.c
>> @@ -4397,7 +4397,6 @@ processSerialChangedEvent(virQEMUDriverPtr driver,
>>      virObjectEventPtr event = NULL;
>>      virDomainDeviceDef dev;
>>      qemuDomainObjPrivatePtr priv = vm->privateData;
>> -    int rc;
>>  
>>      if (connected)
>>          newstate = VIR_DOMAIN_CHR_DEVICE_STATE_CONNECTED;
>> @@ -4450,13 +4449,8 @@ processSerialChangedEvent(virQEMUDriverPtr driver,
>>  
>>      if (STREQ_NULLABLE(dev.data.chr->target.name, "org.qemu.guest_agent.0")) {
>>          if (newstate == VIR_DOMAIN_CHR_DEVICE_STATE_CONNECTED) {
>> -            if (!priv->agent) {
>> -                if ((rc = qemuConnectAgent(driver, vm)) == -2)
>> +            if (!priv->agent && qemuConnectAgent(driver, vm) < 0)
> 
> FWIW:
> qemuConnectAgent returns 0 "if (priv->agent)", so there's one less check
> here too.  Could just be "if (qemuConnectAgent(driver, vm) < 0)"

It depends on patch 3. If we clear the error early in qemuConnectAgent then
we'd better check before calling this function.

> 
>>                      goto endjob;
> 
> The indention for this is off (remove leading 4 spaces)
> 
>> -
>> -                if (rc < 0)
>> -                    priv->agentError = true;
>> -            }
>>          } else {
>>              if (priv->agent) {
>>                  qemuAgentClose(priv->agent);
>> diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
>> index e2ca330..0a02236 100644
>> --- a/src/qemu/qemu_migration.c
>> +++ b/src/qemu/qemu_migration.c
>> @@ -6171,7 +6171,6 @@ qemuMigrationFinish(virQEMUDriverPtr driver,
>>      unsigned short port;
>>      unsigned long long timeReceived = 0;
>>      virObjectEventPtr event;
>> -    int rc;
>>      qemuDomainJobInfoPtr jobInfo = NULL;
>>      bool inPostCopy = false;
>>      bool doKill = true;
>> @@ -6244,16 +6243,8 @@ qemuMigrationFinish(virQEMUDriverPtr driver,
>>                                        QEMU_ASYNC_JOB_MIGRATION_IN) < 0)
>>          goto endjob;
>>  
>> -    if ((rc = qemuConnectAgent(driver, vm)) < 0) {
>> -        if (rc == -2)
>> -            goto endjob;
>> -
>> -        VIR_WARN("Cannot connect to QEMU guest agent for %s",
>> -                 vm->def->name);
>> -        virResetLastError();
>> -        priv->agentError = true;
>> -    }
>> -
>> +    if (qemuConnectAgent(driver, vm) < 0)
>> +        goto endjob;
>>  
>>      if (flags & VIR_MIGRATE_PERSIST_DEST) {
>>          if (qemuMigrationPersist(driver, vm, mig, !v3proto) < 0) {
>> diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
>> index 42f7f84..d7c9ce3 100644
>> --- a/src/qemu/qemu_process.c
>> +++ b/src/qemu/qemu_process.c
>> @@ -206,7 +206,6 @@ int
>>  qemuConnectAgent(virQEMUDriverPtr driver, virDomainObjPtr vm)
>>  {
>>      qemuDomainObjPrivatePtr priv = vm->privateData;
>> -    int ret = -1;
>>      qemuAgentPtr agent = NULL;
>>      virDomainChrDefPtr config = qemuFindAgentConfig(vm->def);
>>  
>> @@ -252,8 +251,7 @@ qemuConnectAgent(virQEMUDriverPtr driver, virDomainObjPtr vm)
>>          qemuAgentClose(agent);
>>          virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
>>                         _("guest crashed while connecting to the guest agent"));
>> -        ret = -2;
>> -        goto cleanup;
>> +        return -1;
>>      }
>>  
>>      if (virSecurityManagerClearSocketLabel(driver->securityManager,
>> @@ -264,18 +262,16 @@ qemuConnectAgent(virQEMUDriverPtr driver, virDomainObjPtr vm)
>>          goto cleanup;
>>      }
>>  
>> -
>>      priv->agent = agent;
>>  
>> -    if (priv->agent == NULL) {
>> -        VIR_INFO("Failed to connect agent for %s", vm->def->name);
> 
> Interesting a "marker" of sorts to know the virAgentOpen "failed" is
> that we'd get an Informational "Failed to connect..." followed shortly
> thereafter by a Warning "Cannot connect..." (depending of course on
> one's message display severity level).
> 
> I think if you "restore" this without the goto cleanup (below) and of
> course the removal of the {}, then at least message parity is
> achieved...  I suppose it could move up into the "if (agent == NULL)"
> too, but then it could be given even though an Error is reported.
> 
> It's not that important, but it does leave some breadcrumbs.

Agree. Even though I'm still wondering how useful this message is as
this patch is intended to be refactoring let's keep this message.

> 
> Again I'd like to see the breadcrumbs with just this patch applied to
> reproduced what you're chasing in patches 1-4...
> 

Sorry, not possible. The situation I've described in patch 1 is based on analysis. However
after applying the patches 1-3 the bug is not occured in our test system anymoree.

Nikolay