Meet Mesos

Interview: Mesos Cluster manager Proposed as Apache Project

Jessica Thornsby

Mesos provides finer grain resource sharing, better support for data intensive applications, and is more flexible than existing cluster schedulers.

JAXenter speaks to Ion Stoica, on the
Mesos project proposal
, and why it hopes to become a part of
the Apache ecosystem.

JAXenter: Mesos has just been proposed as an
Apache Incubator project. Can you give us an introduction to the
Mesos project?

Ion Stoica: Mesos is a cluster manager that
allows multiple applications, such as MapReduce, HBASE and MPI, to
share a cluster, the same way a traditional operating system allows
applications to share a single machine. Sharing improves cluster
utilization by allowing an application to take advantage of another
application’s resources that otherwise would remain unutilized. For
example, an analytics job can take advantage of the resources of a
frontend application during the off-peek hours. Mesos also enables
applications to share the same data set. The alternative of running
an application per cluster could be prohibitive for very large data
sets, since it would require the applications to either replicate
or access the data remotely. Finally, Mesos allows administrators
to perform rolling upgrades by slowly ramping up the new version of
an application.

To support the sophisticated schedulers of today’s cluster
computing applications, such as Hadoop or Dryad, Mesos uses a
distributed two-level scheduling mechanism. At the first level,
Mesos decides how many resources to offer each application; at the
second level, applications themselves decide which resources to
accept (of the ones offered by Mesos) and which computations to run
on them.

JAXenter: What are the potential problems of
having one instance control a whole cluster? And how does Mesos
solve this issue?

Ion Stoica: There are three key challenges that
Mesos needs to address: isolation, scale, and reliability. At the
cluster level, Mesos provides isolation by controlling how many
resources each application receives. At the node level, Mesos
ensures that an application does not use more resources than
allocated by leveraging existing isolation mechanisms such as VMs
and Linux Containers. Messos is highly scalable as it only
schedules resources across applications, while letting the
applications themselves deal with the more complex job of deciding
which computation to run, and where. Finally, to ensure
reliability, Mesos uses Zookeeper to detect and pick a new replica
to recover from failures.

JAXenter: What edge does Mesos have over
existing cluster schedulers, for example Sun Grid Engine and

Ion Stoica: Mesos provides finer grain resource
sharing, better support for data intensive applications, and is
more flexible than existing cluster schedulers. In part, these
properties are a consequence of targeting a different environment
and workload. Mesos targets data intensive applications running on
commodity clusters, where storage is distributed across machines.
In contrast, existing cluster schedulers typically assume
specialized hardware, such as Infiniband, and SANs, and target
computation intensive applications.

Mesos allocates resources at a task granularity where a task
(e.g., map or reduce) can take less than a minute to complete. This
fine grain sharing allows applications to achieve good data
locality by taking turns on the nodes where their input data is
located. In contrast, traditional cluster schedulers share
resources at the job granularity, where a job may take several
hours to complete, and assume that data can be efficiently accessed
remotely over a high speed network.

Mesos is flexible in that it allows applications to make their
own scheduling decisions. Systems, such as Sun Grid Engine and
Torque, ask applications to specify their requirements and employ a
centralized scheduler to make all scheduling decisions.

JAXenter: How will becoming an Apache Incubator
project, benefit Mesos?

Ion Stoica: We hope that by becoming an Apache
incubator, Mesos will attract both users and developers. We have
had good experience as a research team working with the open source
community (to add several scheduling features to Hadoop), and thus
we wanted to make Mesos part of the community from the beginning.
We hope this will enable developers from organizations already
using Mesos to become active contributors. Ultimately, we believe
that Apache’s model of encouraging a community with varied goals
and interests around a software project is critical to Mesos’

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