On Mon, Aug 12, 2013 at 4:11 PM, Clint Byrum <[email protected]> wrote:
> Excerpts from Doug Hellmann's message of 2013-08-12 12:08:58 -0700: > > On Fri, Aug 9, 2013 at 11:56 AM, Clint Byrum <[email protected]> wrote: > > > > > Excerpts from Sandy Walsh's message of 2013-08-09 06:16:55 -0700: > > > > > > > > On 08/08/2013 11:36 PM, Angus Salkeld wrote: > > > > > On 08/08/13 13:16 -0700, Clint Byrum wrote: > > > > >> Last night while reviewing a feature which would add more events > to > > > the > > > > >> event table, it dawned on me that the event table really must be > > > removed. > > > > > > > > > > > > > > >> > > > > >> https://bugs.launchpad.net/heat/+bug/1209492 > > > > >> > > > > >> tl;dr: users can write an infinite number of rows to the event > table > > > at > > > > >> a fairly alarming rate just by creating and updating a very large > > > stack > > > > >> that has no resources that cost any time or are even billable > (like an > > > > >> autoscaling launch configuration). > > > > >> > > > > >> The table has no purge function, so the only way to clear out old > > > events > > > > >> is to delete the stack, or manually remove them directly in the > > > database. > > > > >> > > > > >> We've all been through this before, logging to a database seems > great > > > > >> until you actually do it. > > > > >> > > > > >> I have some ideas for how to solve it, but I wanted to get a wider > > > > >> audience: > > > > >> > > > > >> 1) Make the event list a ring buffer. Have rows 0 - > $MAX_BUFFER_SIZE > > > in > > > > >> each stack, and simply write each new event to the next open > position, > > > > >> wrapping at $MAX_BUFFER_SIZE. Pros: little change to current code, > > > > >> just need an offset column added and code that will properly wrap > to 0 > > > > >> at $MAX_BUFFER_SIZE. Cons: still can incur heavy transactional > load on > > > > >> the database server.A > > > > >> > > > > >> 1.b) Same, but instead of rows, just maintain a blob and append > the > > > rows > > > > >> as json list. Lowers transactional load but would push some load > onto > > > > >> the API servers and such to parse these out, and would make > pagination > > > > >> challenging. Blobs also can be a drain on DB server performance. > > > > >> > > > > >> 2) Write a purge script. Delete old ones. Pros: No code change, > just > > > > >> new code to do purging. Cons: same as 1, plus more vulnerability > to an > > > > >> aggressive attacker who can fit a lot of data in between purges. > Also > > > > >> large scale deletes can be really painful (see: keystone sql token > > > > >> backend). > > > > >> > > > > >> 3) Log events to Swift. I can't seem to find information on how/if > > > > >> appending works there. Tons of tiny single-row files is an option, > > > but I > > > > >> want to hear from people with more swift knowledge if that is a > > > viable, > > > > >> performant option. Pros: Scale to the moon. Can charge tenant for > > > usage > > > > >> and let them purge events as needed. Cons: Adds swift as a > requirement > > > > >> of Heat. > > > > >> > > > > >> 4) Provide a way for users to receive logs via HTTP POST. Pros: > Simple > > > > >> and punts the problem to the users. Cons: users will be SoL if > they > > > > >> don't have a place to have logs posted to. > > > > >> > > > > >> 5) Provide a way for users to receive logs via messaging service > like > > > > >> Marconi. Pros/Cons: same as HTTP, but perhaps a little more > confusing > > > > >> and ambitious given Marconi's short existence. > > > > >> > > > > >> 6) Provide a pluggable backend for logging. This seems like the > way > > > most > > > > >> OpenStack projects solve these issues, which is to let the > deployers > > > > >> choose and/or provide their own way to handle a sticky problem. > Pros: > > > > >> Simple and flexible for the future. Cons: Would require writing at > > > least > > > > >> one backend provider that does what the previous 5 options > suggest. > > > > >> > > > > >> To be clear: Heat cannot really exist without this, as it is the > only > > > way > > > > >> to find out what your stack is doing or has done. > > > > > > > > > > btw Clint I have ditched that "Recorder" patch as Ceilometer is > > > > > getting a Alarm History api soon, so we can defer to that for that > > > > > functionality (alarm transitions). > > > > > > > > > > But we still need a better way to record events/logs for the user. > > > > > So I make this blueprint a while ago: > > > > > https://blueprints.launchpad.net/heat/+spec/user-visible-logs > > > > > > > > > > I am becomming more in favor of user options rather than deployer > > > > > options if possible. So provide resources for Marconi, Meniscus and > > > > > what ever... > > > > > Although what is nice about Marconi is you could then hook up what > > > > > ever you want to it. > > > > > > > > Logs are one thing (and Meniscus is a great choice for that), but > events > > > > are the very thing CM is designed to handle. Wouldn't it make sense > to > > > > push them back into there? > > > > > > > > > > I'm not sure these events make sense in the current Ceilometer (I > assume > > > that is "CM" above) context. These events are: > > > > > > ... Creating stack A > > > ... Creating stack A resource A > > > ... Created stack A resource A > > > ... Created stack A > > > > > > Users will want to be able to see all of the events for a stack, and > > > likely we need to be able to paginate through them as well. > > > > > > They are fundamental and low level enough for Heat that I'm not sure > > > putting them in Ceilometer makes much sense, but maybe I don't > understand > > > Ceilometer.. or "CM" is something else entirely. :) > > > > > > > CM is indeed ceilometer. > > > > The plan for the event API there is to make it admin-only (at least for > > now). If this is data the user wants to see, that may change the plan for > > the API or may mean storing it in ceilometer isn't a good fit. > > > > Visibility into these events is critical to tracking the progress of > any action done to a Heat stack: > > > +---------------------+----+------------------------+--------------------+----------------------+ > | logical_resource_id | id | resource_status_reason | resource_status | > event_time | > > +---------------------+----+------------------------+--------------------+----------------------+ > | AccessPolicy | 24 | state changed | CREATE_IN_PROGRESS | > 2013-08-12T19:45:36Z | > | AccessPolicy | 25 | state changed | CREATE_COMPLETE | > 2013-08-12T19:45:36Z | > | User | 26 | state changed | CREATE_IN_PROGRESS | > 2013-08-12T19:45:36Z | > | Key | 28 | state changed | CREATE_IN_PROGRESS | > 2013-08-12T19:45:38Z | > | User | 27 | state changed | CREATE_COMPLETE | > 2013-08-12T19:45:38Z | > | Key | 29 | state changed | CREATE_COMPLETE | > 2013-08-12T19:45:39Z | > | notcompute | 30 | state changed | CREATE_IN_PROGRESS | > 2013-08-12T19:45:40Z | > > +---------------------+----+------------------------+--------------------+----------------------+ > > So unless there is a plan to make this a user centric service, it does > not seem like a good fit. > > > Are these "events" transmitted in the same way as notifications? If so, > we > > may already have the data. > > > > The Heat engine records them while working on the stack. They have a > fairly narrow, well defined interface, so it should be fairly easy to > address the storage issue with a backend abstraction. > OK. The term "event" frequently means "notification" for ceilometer, but it sounds like it's completely different in this case. Doug > > _______________________________________________ > OpenStack-dev mailing list > [email protected] > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev >
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