[Ovirt-devel] [PATCH server] Fixed db-omatic so it doesn't die due to an unhandled ActiveRecord::StaleObjectError exception.

[Scott Seago]

Arjun Roy wrote:
> The error is caused by the save! method updating an object that another
> thread (most likely in taskomatic) already updated.
>
> In the case of this race condition, we retry saving. However, a proper fix
> would involve fixing the locking.
> ---
>  src/db-omatic/db_omatic.rb |   23 ++++++++++++++++++++---
>  1 files changed, 20 insertions(+), 3 deletions(-)
>
> diff --git a/src/db-omatic/db_omatic.rb b/src/db-omatic/db_omatic.rb
> index d2540e1..60ea9f7 100755
> --- a/src/db-omatic/db_omatic.rb
> +++ b/src/db-omatic/db_omatic.rb
> @@ -215,7 +217,14 @@ class DbOmatic < Qpid::Qmf::Console
>          end
>  
>          vm.state = state
> -        vm.save!
> +        
> +        begin
> +            vm.save!
> +        rescue ActiveRecord::StaleObjectError => e
> +            @logger.error "Optimistic locking failed for VM #{vm.description}, retrying."
> +            @logger.error e.backtrace
> +            return update_domain_state(domain, state_override)
> +        end
>  
>          domain[:synced] = true
>      end
> @@ -234,7 +243,14 @@ class DbOmatic < Qpid::Qmf::Console
>              #db_host.lock_version = 2
>              # XXX: This would just be for init..
>              #db_host.is_disabled = 0
> -            db_host.save!
> +            
> +            begin
> +                db_host.save!
> +            rescue ActiveRecord::StaleObjectError => e
> +                @logger.error "Optimistic locking failure on host #{host_info['hostname']}, retrying."
> +                @logger.error e.backtrace
> +                return update_host_state(host_info, state)
> +            end
>              host_info[:synced] = true
>  
>              if state == Host::STATE_AVAILABLE
>   
OK I pushed this but replacing the "retry" return statements with blanke 
return statements, as we have not yet been able to test the 
StaleObjectError retries.

Scott