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Use OpenStack to run Java programs inside a Docker container

SEBASTIANO MIANO

TESINA PROTOCOLLI E ARCHITETTURE DI ROUTING

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Outline

• Problem presentation and proposed solution

• Implementation steps

• Performance Analysis

• Final Considerations

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OpenStack

OpenStack is a free and open-source cloud computing software platform. Users primarily deploy it as an infrastructure as service (IaaS) solution. 3/24

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VM migration: use case

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Hypervisor VMs vs. LXC vs. Docker LXC

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VM migration: Docker

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…also 400-500 MB

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Migrate Java programs instead VM

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VM migration problem: solution

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Implementation steps

Modify OpenStack so that recognizes this object (JAR) and lunches this object inside a Docker container with a JVM.

Create a bridge in C using libpcap library that forwards packets between 2 vNIC.

Integrate the previous prototype in Java.

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OpenStack and libvirt

In order to interact with the virtualization capabilities of VM, OpenStack uses the libvirt and its corresponding API to deploy an instance on the compute node.

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OpenStack and NovaDocker

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Transfer instance (JAR) from GlanceThe Glance project provides a service where users can upload and discover data assets that are meant to be used with other services. This currently includes images and metadata definitions.

os_command_line 12/24

image_id

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OpenStack and NovaJar

In order to load the Jar inside the Docker container and run it I developed two solutions:1. The first one uses docker data volumes to mount a Host

Directory as a Data Volume.2. The second one uses the new exec command included in

the docker API 1.15 that allows to run a command inside a running container.

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Solution with Data Volumes

With this solution I transfer the jar image in the host directory and when NovaJar receives a request from scheduler mount this directory in a directory on the just created container.

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Solution with Exec Command

With this solution I need to start the container and after that I have to inject the JAR image inside the container. There are not “official” solution to do this when a container is already running, but I solved this problem by copying the JAR retrieved from glance in this path -> /var/lib/docker/aufs/mnt/{container_id}. After that I use the exec command to run the jar inside the container.

Docker REST API

exec

/var/lib/docker/aufs/mnt/{container_id}

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Data Volumes VS Exec Command

Data Volumes• Good:

― Uses a feature of Docker’s API in order to use the JAR inside the container

― If the JAR does not use the network is possible to start it at container boot.

Exec Command• Good:

― Allows a user to spawn a process inside their Docker container via the Docker API.

• Bad:― If the JAR uses the network (all

times) the “pure” solution does not work because when the container starts the network is not yet available.

• Bad:― The command started using

docker exec will only run while the container’s primary process is running.

― Uses an “unofficial” solution in order to inject the JAR inside the container (other solution: Dockerfile).

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Third solution: merge of the previous

Data Volumes and Exec Command• Good:

― Uses a feature of Docker’s API in order to use the JAR inside the container

― Allows a user to spawn a process inside their Docker container via the Docker API.

• Bad:― The command started using

docker exec will only run while the container’s primary process is running (requires container already running). 17/24

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Changes to the controller: Nova-scheduler

Nova-scheduler is the module on the controller node that decide on which host run the instance selected. There are some standard filters available in nova.schedule.filters.We have to enable the ImagePropertiesFilter. It filters hosts based on properties defined on the instance’s image. It passes hosts that can support the specified image properties contained in the instance. In particular it filters hosts based on the architecture, hypervisor type, and virtual machine mode specified in the instance.

os_command_linehypervisor_type = nova_jar 18/24

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Performance Analysis

Ser ies1

0.167

0.707

0.207

0.129

Start JAR Bridge

Tim

e (s

)

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Performance Analysis

1 NIC 2 NIC 4 NIC 6 NIC 8 NIC 12 NIC0123456789

10

Time to start container

Container creation Container startRetrieve JAR First JAR output

1 NIC 2 NIC 4 NIC 6 NIC 8 NIC 12 NIC0123456789

10

Total Time

Total Time

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Performance Analysis

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Final Observations

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• Transfer JAVA programs is better than transfer VM images - not only java programs• Use the hybrid solution (volume + exec) is better - use only “official” API• Container start problem - OVS?• Container start delay can be solved - use a container already running - attach vNIC in this container at runtime• Nova-docker driver still under development - great start, but additional features needed for parity - additions to nova-docker driver could change cloud performance• Docker is still under development

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JavaBridge and libpcap wrapper

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eth0 eth2eth1

Java Bridge

Docker Container

JNI

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Thanks for your attention!

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