Docker based architecture

About Me7+ years as backend Software Engineer.

● Java/Scala● SQL/NoSQL databases● distributed caches, queuing● Hadoop/Spark● AWS,DevOps● REST, microservices

An approach to developing a single application as a suite of small services, each running in its own process and communicating with lightweight mechanisms

http://martinfowler.com/

Microservice architecture style

• Component decomposition• Independant development lifecycle and

technology freedom• Better extensibility• Fault isolation

Microservice benefits

• Deployment of much greater number of services and components

• Monitoring of many services for performance or issues

• Looking into log files from many micro-services• Versioning between services and environment

consistency

Microservice drawbacks

1. Multiple Service instances per host● conflicting resource requirements(CPU, memory, IO, etc.)● conflicting dependency versions

1. Single Service instance per host● potentially less efficient resource utilization● hosts provisioning and maintenance

1. Service Instance per VM ● building a VM image is slow and time consuming

1. Service instance per container● The infrastructure for deploying containers is not as rich as

the infrastructure for deploying virtual machines

Microservice deployment patterns

Containerization vs Virtualization

Containerization providersImplementations:● by vendors(Open Source,HP, IBM, Microsoft)● by OS (Linux, FreeBSD, Solaris, Windows)

http://en.wikipedia.org/wiki/Operating-system-level_virtualization#Implementations.

Docker has become the most popular nowadays.

Docker Ecosystem

How it works

http://en.wikipedia.org/wiki/Docker_(software)

Docker registry

Docker container overhead

Docker container network overhead

Basic docker usage scenario1. create Dockerfile 2. build image with specific name in format

[registry_url/]repository:imageTag , e.g

myhost:5000/mycompany/myservice:version1

3. push image into registry (private or Docker Hub)4. pull image by repository and tag (Optional)5. run container from image

Dockerfile• inherit existing images • add/copy files to container• set environment vars • run shell command• expose ports• set working dir• share host FS with container• --no-cache option• CMD and bootstrapping• CMD vs ENTRYPOINT

FROM mycompany/app-base:latest

RUN mkdir -p /opt/app

ADD core.jar /opt/app/core.jar

RUN curl http://3rd-paty.repo.org/download/component.zip &&

\

unzip component.zip -d /opt/app/ && rm -f component.zip

COPY lib/ /opt/app/lib

ADD bootstrap.sh /etc/mysevice/

RUN chmod +x /etc/mysevice/bootstrap.sh

ADD workspace-manager-core.jar

ADD logback.xml /opt/app/logback.xml

ENV MODE="PRODUCTION"

VOLUME /log

WORKDIR /opt/app/

EXPOSE 80

CMD /etc/myservice/bootstrap.sh &&

/usr/lib/jvm/latest/bin/java -cp

/opt/app/core.jar:/opt/app/lib \

-Xms256m \

-Xmx2048m \

-XX:+UseCompressedOops \

-XX:+UseG1GC \

-Dspark.kryoserializer.buffer.max.mb=128 \ -

Dlogback.configurationFile=/opt/app/logback.xml \

org.mycompany.app.Runner

Ready, set,go

• docker build -t mycompany/app:1.0• docker tag -t mycompany/app:1.0

registry.mycompany.com:5000/mycompany/app:1.0

• docker push registry.mycompany.com:5000/mycompany/app:1.0

Container entrypoint

• Container must have long leaving process - entrypoint

• Container will become stopped when process is ended/crashed

• Two strategies: process per container vs supervisord

Supervisord configuration

[supervisord]nodaemon = truelogfile = /var/log/supervisord.log

[program:hadoop-hdfs-namenode]command = /etc/init.d/hadoop-hdfs-namenode start

[program:mesos-master]command = /usr/local/sbin/mesos-master --work_dir=/mnt/mesos-work --hostname={{ MESOS_HOSTNAME }} --log_dir=/var/log/mesos

[program:vw-spanning-tree]command = /usr/local/bin/spanning_tree

FROM mycompany/mesos-general

MAINTAINER mycompany

#Configure namenode

RUN apt-get install -y hadoop-hdfs-namenode=2.5.0+cdh5.3.3*

#Add config templates

ADD hadoop-conf/core-site.xml /etc/hadoop/conf/core-site.xml.tpl

ADD hadoop-conf/hadoop-env.sh /etc/hadoop/conf/hadoop-env.sh

ADD hadoop-conf/hdfs-site.xml /etc/hadoop/conf/hdfs-site.xml.tpl

ADD bootstrap.sh /bootstrap.sh

RUN chmod +x /bootstrap.sh

COPY supervisord.conf /etc/supervisor/conf.d/supervisord.conf.tpl

CMD /bootstrap.sh && /usr/bin/supervisord

Master Dockerfile

#!/bin/bash

set -e mkdir -p /mnt/mesos-work mkdir -p /var/log/mesos source /resolve_ec2_hostname.sh

envtpl < /etc/hadoop/conf/core-site.xml.tpl > /etc/hadoop/conf/core-site.xml envtpl < /etc/hadoop/conf/hdfs-site.xml.tpl > /etc/hadoop/conf/hdfs-site.xml envtpl < /etc/supervisor/conf.d/supervisord.conf.tpl > /etc/supervisor/conf.d/supervisord.conf

Bootstrap.sh example

• Container identification (--name)

• Network settings

o --net = [none, bridge (default), host, container:<name|id>]

o -P vs -p

o --link

• Useful options for debug/testing

o --rm=true, -it

o docker exec -it running_container_name bash

• Env variables

• Runtime constraints on CPU and memory

• Volume mount

Run options

Environment example

Thank You!

References● http://martinfowler.com/articles/microservices.html● https://docs.docker.com/introduction/understanding-docker/● http://domino.research.ibm.com/library/cyberdig.nsf/papers/092905219

5DD819C85257D2300681E7B/$File/rc25482.pdf