On 23/09/2021 10:47, Mark Gray wrote:
> On 16/09/2021 16:37, Dumitru Ceara wrote:
>> Add a new command, 'ovsdb-server/log-db-ops DB TABLE on|off', which
>> allows the user to enable/disable transaction logging for specific
>> databases and tables.
>>
>> By default, logging is disabled.  Once enabled, logs are generated
>> with level INFO and are also rate limited.
>>
>> If used with care, this command can be useful in analyzing production
>> deployment performance issues, allowing the user to pin point
>> bottlenecks without the need to enable wider debug logs, e.g., jsonrpc.
>>
>> Signed-off-by: Dumitru Ceara <[email protected]>
>> ---
>> A sample use case is an ovn-kubernetes scaled deployment in which
>> we're interesting in reducing time to bring up PODs (represented by
>> OVN logical switch ports).  In order to determine exactly where the
>> bottleneck is when provisioning PODs (CMS/ovn-nbctl/client
>> IDLs/ovsdb-server/ovn-controller/etc) we need timestamps of when
>> operations happen at various places in the stack.
>>
>> Without this patch the only option for tracking when transactions
>> happen in the Northbound database is to enable jsonrpc debug logs in
>> ovsdb-server.  This generates a rather large amount of data.
>>
>> Instead, now, users would be able to just enable logging for the
>> Logical_Switch_Port table getting more relevant and precise
>> information.
>>
>> V2:
>> - rebased (fixed conflicts in NEWS).
> Generally ok and I also did a quick test but I have a few comments on
> the UI which wouldn't block an ACK and one small comment below in the code:
> 
> * My personal preference would be that the syntax somewhat followed the
> vlog/set one that seperates terms by ':'. Also a more memorable name.
> For example tlog/set DB:TABLE:on or something like that but feel free to
> choose to completely ignore me :) I just find it can sometimes be
> difficult to remember syntax so I prefer some consistency.
> 
> * One limititation is that I don't think we can add a log before a table
> is created (i.e. to see the first entry). For example, let's say I want
> to log the very first creation of a bridge using `ovs-vsctl add-br br0`.
> Is there any way around it? I couldn't think of one.
> 
> * Could you make the table and database names case-insensitive. For
> example, I can do `ovs-vsctl list open` even though the table name is
> actually Open_vSwitch? However, with this I need to specify the actual
> table name.
> 
> * There is no way to list the tables that are currently 'on'. Something
> like vlog/list.
> 
> * Would it be useful to be able to specify which level to log to?: e.g.
> 
> tlog/set DB:TABLE:info
> 
> * Would it be useful to have a non-verbose mode that only states that an
> insert/delete/update happened?
> 

Also, do we need to document this somewhere? I am not sure.

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