Tag Archives: Mesosphere

Looking Back at EMC World 2016

Wow! How quickly a week can go by. Like many of you, EMC World 2016 was my first time in attendance and it also happen to be the first time I have been given the opportunity to be a presenter for a larger audience. I though the experience exceeded my expectations and based on some of the preliminary numbers and feedback that we have been getting on the sessions the EMC {code} team had presented, a good number of you agree the sessions content and presentations were of value to you. Thanks again for attending the sessions and providing your feedback.

Couldn’t make it this year?

For those that couldn’t make it out this year, a number of people in {code} have starting posting the materials and slide decks for our sessions. Official EMC World slide decks should be posted in the coming weeks, but there have been a large number of requests to get a hold of the material ASAP and many of us on the team have been happy to oblige. As for my sessions, you can find the materials below.

Introduction To Mesos & Mesosphere

Here is the session material for Introduction To Mesos & Mesosphere (Monday May 2 at 8:30) which just as the title says is a Apache Mesos 101 type session.

You can download the “Introduction To Mesos & Mesosphere” powerpoint presentation HERE. The video of the demonstration used at the end of the session highlighting Mesos using persistent external storage can be found on YouTube below:

The source code for the MVC Web Application written in Golang can be found in my GitHub repo. The two projects used in demo were RestServer and RestClient.

To launch the MVC Application with external persistent storage, you first need to have each of your Mesos Agent/Slave nodes running Mesos DNS and configured for persistent external storage using this Guide. Once you have those prerequisites in your Mesos Cluster, you can find the Marathon JSON files to launch tasks here. To start up the application, perform the following:

Start PostgreSQL:
curl -k -XPOST -d @postgres-mvc.json -H "Content-Type: application/json" YourMarathonIP:8080/v2/apps

Start RestServer:
curl -k -XPOST -d @restapi.json -H "Content-Type: application/json" YourMarathonIP:8080/v2/apps

Start RestClient:
curl -k -XPOST -d @ui.json -H "Content-Type: application/json" YourMarathonIP:8080/v2/apps

Deep Dive With Mesos & Persistent Storage For Applications

Here is the session material for Deep Dive With Mesos & Persistent Storage For Applications (Tuesday May 3 at 3:00) which covered the importance of Apache Mesos Frameworks and the powerful capabilities that 2 layer scheduling provides in your Datacenter and Mesos cluster.

You can download the “Deep Dive With Mesos & Persistent Storage For Applications” powerpoint presentation HERE. The video of the demonstration used at the end of the session highlighting the Elastic Search Mesos Framework using persistent external storage can be found on YouTube below:

To launch the Elastic Search Framework with external persistent storage, you first need to have at least a 3 Agent/Slave nodes in your Mesos cluster and each of your Mesos Agent/Slave nodes configured for persistent external storage using this Guide. To start the ElasticSearch scheduler, you can find the Marathon JSON files to launch task here. To start up the Scheduler, perform the following:

Start ElasticSearch Scheduler:
curl -k -XPOST -d @elasticsearch.json -H "Content-Type: application/json" YourMarathonIP:8080/v2/apps

If you want to run some of the advanced ElasticSearch functionality used in the demo, you can find additional information in this file here.

What’s Next…

After recharging for a bit, we have already started on our post-EMC World plans and deliverables. Hopefully this will bring a forth a bunch of interesting ideas and projects for the community. To keep up to date with the things that I will be working on, please follow me on Twitter at @dvonthenen. If anyone has any questions about the EMC World presentations, you can always catch me on the {code} Community Slack channel.

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Getting Ready for EMC World 2016

We are getting closer and closer to EMC World 2016. I have to admit, its approaching crazy fast. This will be my first time attending EMC World. Seems odd saying that as I have attended many conferences in my career, but never the one my company throws. This time its going to be a different conference going experience as I will be presenting two sessions in the “Code and Modern Operations” track this year. I am very excited for this opportunity to talk about things that are interesting to me and I hope that are of interest to others out there in the open source community.

Apache Mesos

The first session is Introduction To Mesos & Mesosphere. This is basically an Apache Mesos 101 type session with a focus on the company, Mesosphere, whom pushes the direction of Mesos. I will be co-presenting this session with Somik Behera from Mesosphere. For those that haven’t heard about Mesos or looking to learn more about it, this is a excellent session outlining why Mesos is among the best workload schedulers in the datacenter and why its the preferred choice among companies looking to scale their applications. You can catch us both Monday morning (May 2) at 8:30am. Yes, you read that right. Going to be difficult for people to drag themselves out of bed that early in the morning… this is Las Vegas after all. Hope you all can make it!

Deep Dive

My second session is Deep Dive With Mesos & Persistent Storage For Applications. After getting some time to digest the information in my previous Mesos 101 session, this will dive into some of the internals of Mesos as we explore Mesos Frameworks and 2 layer scheduling. We will discuss what 2 layer scheduling means and how external storage can enhance the story around applications leveraging Frameworks. For the architects, operators, and consumers of Mesos, this session is packed with things you need to know in order to make your applications function efficiently and be highly available in order to avoid the train wreck. Ultimately the goal of talk is to enable you to put things on autopilot so you don’t need to manage the application.

Train Wreck

If you haven’t purchases tickets for EMC World, I would highly recommend you do as soon as possible. The EMC {code} team has a huge presence this year as we have our own booth along with our own session track, Code and Modern Operations, which I eluded to earlier. The {code} team collectively has 21 sessions at the conference this year talking about everything from Docker, managing larger open source communities, Mesos, and contributing to open source just to name a few. I will have a follow up blog post just before EMC World highlighting some of the other sessions you might want to check out. Catch you all later!

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Difficulties with Multi-Version Mesos Support

I have been working with Apache Mesos for some time now and after a recent meeting with the Mesosphere team (the company largely driving the roadmap and development effort), I have come to learn that some Mesos users sit on the bleeding edge of releases and others that are sensitive to things like security, change management, and stability are more inclined to be a couple or several versions behind. This practice isn’t anything new, it took EMC IT a long time to adopt Windows 7… heck, Windows 10 is out now and we are still sitting at Windows 7. Not saying that is necessarily a bad thing..

Why you wait for the first Service Pack

So we have to accept the fact that we need to support multiple versions and take that into consideration when building components for Mesos. This takes us to the most recent release (0.4.0) of mesos-module-dvdi which supports multiple versions spanning from 0.23.1 to the most recent release of mesos, 0.26.0. A side note, for those not familiar with mesos-module-dvdi its a Mesos isolator module that can create and mount external storage volumes, such as ScaleIO, Amazon EBS, or etc, and provide persistent storage for Applications created on Mesos. If you are interested, you can find more information on its GitHub page.

Where’s the Beef?

The mesos-module-dvdi is a C++11 project and as such needs to implement defined Mesos interfaces so that the module can be loaded and invoked from a Mesos slave (think of it as a simple node that launches tasks). If you take a look at the Isolator interface between versions, you will immediately notice that the interface varies wildly between versions and that modules created for one version will not work on another version of Mesos. Heck, even the interface class name you need to implement has changed:

In 0.23.1:
class IsolatorProcess : public process::Process

process::Future<Nothing> recover(
const std::list<ExecutorRunState>& states,
const hashset<ContainerID>& orphans);

process::Future<Option<CommandInfo>> prepare(
const ContainerID& containerId,
const ExecutorInfo& executorInfo,
const std::string& directory,
const Option<std::string>& rootfs,
const Option<std::string>& user);

In 0.24.1:
class DockerVolumeDriverIsolator: public mesos::slave::Isolator

virtual process::Future<Nothing> recover(
const std::list<ContainerState>& states,
const hashset<ContainerID>& orphans);

virtual process::Future<Option<ContainerPrepareInfo>> prepare(
const ContainerID& containerId,
const ExecutorInfo& executorInfo,
const std::string& directory,
const Option<std::string>& user);

This is not good. This is basically Mesos’ version of Microsoft’s DLL Hell. As an experienced C++ developer, defining a C++ interface that is going to ensure backwards compatibility is very difficult. In previous projects I have worked on, the interfaces not only needed to be backwards compatible but also cross-platform (yes, Windows support) all from a single code base. That adds further complexity. These days some of these difficulties can easily be side stepped by standing up a REST endpoint. Even the worst REST APIs by in large “get the job done” even if the API is horribly designed. For example, some might argue if the API does not follow CRUD, HATEOAS, or etc they are bad designs, but I digress.

DLL Hell

A Meh Solution

So the current solution to support multiple versions of the Mesos Isolator interface from a single code base has been to use ifdefs. Yea, unfortunately the solution isn’t as elegant as it could be, but with the break in backwards compatibility in the Isolator interface, it leaves us with very little choice. This is also compounded by the fact that this isn’t the only interface that is changing between versions. There are other Mesos support libraries in which the interface is in flux and adding an abstraction layer among all these functions, classes, and structures might take you down a rabbit hole that will leave you rocking yourself in the fetal position for months crying “so many functions”.

Since we are using ifdefs, that unfortunately means our solution is a compile time solution and we therefore need to build every version that we plan on supporting. We do that in our Makefile as see below.

In the Makefile on lines 8 and 818 respectively:
ISO_VERSIONS := 0.23.1 0.24.1 0.25.0 0.26.0

$(foreach V,$(ISO_VERSIONS),$(eval $(call ISOLATOR_BUILD_RULES,$(V))))

Then we take that version and create an integer representation of the version by stripping out the periods from the version we are compiling. Represented by the MESOS_VERSION_INT preprocessor directive below. An example of that would be version 0.24.1 becomes 0241.

In the Makefile lines 790-795:
$$(ISO_MAKEFILE_$1): CXXFLAGS=-I$$(GLOG_OPT_DIR)/include
-I$$(PICOJSON_OPT_DIR)/include
-I$$(BOOST_OPT_DIR)
-I$$(PBUF_OPT_DIR)/include
-DMESOS_VERSION_INT=$$(subst .,,$1)
$$(ISO_MAKEFILE_$1): $$(ISO_CONFIGURE_$1) $$(ISO_DEPS_$1)

Then we compile the project using the MESOS_VERSION_INT and make alterations to the code to handle the ifdefs.

In the docker_volume_driver_isolator.hpp:
if MESOS_VERSION_INT != 0 && MESOS_VERSION_INT < 0240<br />
class DockerVolumeDriverIsolator: public mesos::slave::IsolatorProcess<br />
else<br />
class DockerVolumeDriverIsolator: public mesos::slave::Isolator<br />
endif

if MESOS_VERSION_INT != 0 && MESOS_VERSION_INT < 0240<br />
process::Future<Nothing> recover(
const std::list<ExecutorRunState>& states,
const hashset<ContainerID>& orphans);<br />
else<br />
virtual process::Future<Nothing> recover(
const std::list<ContainerState>& states,
const hashset<ContainerID>& orphans);<br />
endif

if MESOS_VERSION_INT != 0 && MESOS_VERSION_INT < 0240<br />
process::Future<Option<CommandInfo>> prepare(
const ContainerID& containerId,
const ExecutorInfo& executorInfo,
const std::string& directory,
const Option<std::string>& rootfs,
const Option<std::string>& user);<br />
else<br />
process::Future<Option<ContainerPrepareInfo>> prepare(
const ContainerID& containerId,
const ExecutorInfo& executorInfo,
const std::string& directory,
const Option<std::string>& user);<br />
endif

So that is it. Again, not the most elegant solution but unfortunately addressing the backwards compatibility is going to be very difficult to resolve going forward as it would require retrofitting older versions of Mesos. That could get pretty ugly to change architecture in the form of patches or even a minor release. Odds are this is not going to go away any time soon. I hope this helps other developers out there looking to create Mesos Isolators (and Mesos Frameworks because it looks like the Framework interfaces may have the same problem).

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