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From David McLaughlin <dmclaugh...@apache.org>
Subject Re: Support instance-specific TaskConfig in CreateJob API
Date Mon, 15 Aug 2016 17:49:00 GMT
On Mon, Aug 15, 2016 at 10:40 AM, Mauricio Garavaglia <
mauriciogaravaglia@gmail.com> wrote:

> Hi,
>
> WRT the constraint use case:
>
> Let's say I have two instances of a service, these instances would need
> different Docker arguments:
>

But that's less about using Docker and more how you're using Docker in
particular? Also the features of your executor? For example, if you're
using Thermos you can access the instance id in your process definition.



>
> - Labels. Log drivers uses container labels to identify who is producing
> this logs. The container name doesn't work with Mesos of course. So you
> have loglabel=serviceA-instance-0 and the other instance has
> loglabel=serviceA-instance-1.
> - Volumes. Each instance must read/write on its own volume. In the similar
> way each aurora instance writes to its own distributed log instance.
> - Ip addresses, etc.
>
> That means having separated jobs would be the thing to do right now. But if
> for HA reasons we don't want to let aurora schedule them on the same rack,
> the solution would be to add constraints on both jobs manually assigning
> them to a predefined set of racks.
>
> Coping with constraints is not the only use case; the same goes for rolling
> updates. Having different jobs means that the rolling update process needs
> to be manually implemented on top of the aurora api instead of using the
> one that is provided out of the box.
>
>
>
>
> On Mon, Aug 15, 2016 at 2:05 PM, Maxim Khutornenko <maxim@apache.org>
> wrote:
>
> > I would love to hear more about constraint use cases that don't work
> across
> > jobs to see if/how we can extend Aurora to support them.
> >
> > As far as heterogeneous jobs go, that effort would require rethinking
> quite
> > a few assumptions around fundamental Aurora principles to ensure we don't
> > lock ourselves into the corner wrt future features by accepting an "easy
> to
> > do" change short-term. I am -1 on supporting anything specific for
> > adhoc jobs only. IMO, this has to be an all-or-nothing feature adding
> > support for heterogeneous jobs across the stack.
> >
> > If you guys feel strongly about this idea, please craft a high-level
> design
> > summary for the community to explore and review.
> >
> > On Sat, Aug 13, 2016 at 7:43 AM, Mauricio Garavaglia <
> > mauriciogaravaglia@gmail.com> wrote:
> >
> > > Hi,
> > >
> > > We have been experimenting with the idea of having heterogeneous tasks
> > in a
> > > job. Mainly to support different docker container configurations (like
> > > volumes to let tasks have different storage, different labels for
> logging
> > > purposes, or ip addresses).
> > > The main reason for using this instead of separate jobs is that
> > scheduling
> > > constraints doesn't work across jobs, and we may want to have rack
> > > anti-affinity for the different instances.
> > >
> > > You can check how it works on the README in the repo [
> > > https://github.com/medallia/aurora/tree/0.13.0-medallia]. Basically
> the
> > > job
> > > includes a list of parameters that are later interpolated in the task
> > > config during mesos task creation, so this happens at a latter time and
> > the
> > > different values to apply to each instance are held in the config. We
> can
> > > start discussing if you think the design sounds or the feature could be
> > > helpful and start working to move it upstream.
> > >
> > > We used StartJobUpdate to achieve the same purpose but required
> > > some gymnastics during deployment that we wanted to avoid. Regarding
> Min
> > > Cal's issue about short-lived tasks finishing before the update starts,
> > we
> > > solved it by initially configuring all the tasks with a dummy NOP ("no
> > > operation") process that just sits there waiting to be updated.
> > >
> > > Mauricio
> > >
> > >
> > > On Fri, Aug 12, 2016 at 3:17 PM, Min Cai <mincai@gmail.com> wrote:
> > >
> > > > Thanks Maxim. Please see my previous email to David's comments for
> more
> > > > detailed response.
> > > >
> > > > On Fri, Aug 12, 2016 at 9:24 AM, Maxim Khutornenko <maxim@apache.org
> >
> > > > wrote:
> > > >
> > > > > I am cautious about merging createJob and startJobUpdate as we
> don't
> > > > > support updates of adhoc jobs. It's logically unclear what adhoc
> job
> > > > update
> > > > > would mean as adhoc job instances are not intended to survive
> > terminal
> > > > > state.
> > > > >
> > > >
> > > > +1. Our adhoc job instances could be short-lived and finished way
> > before
> > > > StartJobUpdate calls are made to Aurora.
> > > >
> > > >
> > > > >
> > > > > Even if we decided to do so I am afraid it would not help with the
> > > > scenario
> > > > > of creating a new heterogeneous job as the updater only supports
a
> > > single
> > > > > TaskConfig target.
> > > > >
> > > >
> > > > We will have to make N StartJobUpdate calls to update N distinct task
> > > > configs so it will be expensive if N is large like > 10K.
> > > >
> > > >
> > > > >
> > > > > Speaking broadly, Aurora is built around the idea of homogenous
> jobs.
> > > > It's
> > > > > possible to have different task configs to support canaries and
> > update
> > > > > rolls but we treat that state as *temporary* until config
> > > reconciliation
> > > > > completes.
> > > > >
> > > >
> > > > Agreed that the homogeneous jobs are important design consideration
> for
> > > > *long-running* jobs like Services. However, most adhoc jobs are
> > > > heterogenous by nature. For example, they might need to process
> > different
> > > > input files and write to different output files. Or they might take
> > > > different parameters etc. It would be nice to extend Aurora to
> support
> > > > heterogenous tasks so that it can be used for broader use cases as a
> > > > meta-scheduler.
> > > >
> > > > Thanks, - Min
> > > >
> > > >
> > > > > On Fri, Aug 12, 2016 at 8:03 AM, David McLaughlin <
> > > > dmclaughlin@apache.org>
> > > > > wrote:
> > > > >
> > > > > > Hi Min,
> > > > > >
> > > > > > I'd prefer to add support for ad-hoc jobs to startJobUpdate
and
> > > > > completely
> > > > > > remove the notion of job create.
> > > > > >
> > > > > > " Also, even the
> > > > > > > StartJobUpdate API is not scalable to a job with 10K ~
100K
> task
> > > > > > instances
> > > > > > > and each instance has different task config since we will
have
> to
> > > > > invoke
> > > > > > > StartJobUpdate for each distinct task config."
> > > > > >
> > > > > >
> > > > > > What is the use case for that? Aurora was designed to have those
> as
> > > > > > separate jobs.
> > > > > >
> > > > > > Thanks,
> > > > > > David
> > > > > >
> > > > > > On Thu, Aug 11, 2016 at 2:56 PM, Min Cai <mincai@gmail.com>
> wrote:
> > > > > >
> > > > > > > Hey fellow Aurora team:
> > > > > > >
> > > > > > > We would like to propose a simple and backwards compatible
> > feature
> > > in
> > > > > > > CreateJob API so that we can support instance-specific
> > TaskConfigs.
> > > > The
> > > > > > use
> > > > > > > case here is for an Adhoc job which has different resource
> > settings
> > > > as
> > > > > > well
> > > > > > > as different command line arguments for each task instance.
> > Aurora
> > > > > today
> > > > > > > already support heterogenous tasks for the same job via
> > > > StartJobUpdate
> > > > > > API,
> > > > > > > i.e. we can update the job instances to use different task
> > configs.
> > > > > This
> > > > > > > works reasonably well for long running tasks like Services.
> > > However,
> > > > it
> > > > > > is
> > > > > > > not feasible for Adhoc jobs where each task will finish
right
> > away
> > > > > before
> > > > > > > we even have a chance to invoke StartJobUpdate. Also, even
the
> > > > > > > StartJobUpdate API is not scalable to a job with 10K ~
100K
> task
> > > > > > instances
> > > > > > > and each instance has different task config since we will
have
> to
> > > > > invoke
> > > > > > > StartJobUpdate for each distinct task config.
> > > > > > >
> > > > > > > The proposal we have is to add an optional field in
> > > JobConfiguration
> > > > > for
> > > > > > > instance specific task config. It will be override the
default
> > task
> > > > > > config
> > > > > > > for given instance ID ranges if specific. Otherwise, everything
> > > will
> > > > be
> > > > > > > backwards compatibility as current API. The implementation
of
> > this
> > > > > change
> > > > > > > also seems to be very simple. We only need to plumb instance
> > > specific
> > > > > > tasks
> > > > > > > configs when we call statemanager.insertPendingTasks in
> > > > > > > SchedulerThriftInterface.createJob function.
> > > > > > >
> > > > > > >  /**
> > > > > > >   * Description of an Aurora job. One task will be scheduled
> for
> > > each
> > > > > > > instance within the job.
> > > > > > >   */
> > > > > > > @@ -328,13 +343,17 @@ struct JobConfiguration {
> > > > > > >    4: string cronSchedule
> > > > > > >    /** Collision policy to use when handling overlapping
cron
> > runs.
> > > > > > > Default is KILL_EXISTING. */
> > > > > > >    5: CronCollisionPolicy cronCollisionPolicy
> > > > > > > -  /** Task configuration for this job. */
> > > > > > > +  /** Default task configuration for all instances of
this
> job.
> > */
> > > > > > >    6: TaskConfig taskConfig
> > > > > > >    /**
> > > > > > >     * The number of instances in the job. Generated instance
> IDs
> > > for
> > > > > > tasks
> > > > > > > will be in the range
> > > > > > >     * [0, instances).
> > > > > > >     */
> > > > > > >    8: i32 instanceCount
> > > > > > > +  /**
> > > > > > > +   * The instance specific task configs that override
the
> > default
> > > > task
> > > > > > > config for given
> > > > > > > +   * instanceId ranges.
> > > > > > > +   */
> > > > > > > +  10: optional set<InstanceTaskConfig> instanceTaskConfigs
> > > > > > >  }
> > > > > > >
> > > > > > > Please let us know your comments and suggestions.
> > > > > > >
> > > > > > > Thanks, - Min
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>

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