This document provides an overview of microservices, containers, scheduling and orchestration. It defines microservices as small, autonomous services that work together with bounded contexts. Containers provide operating system-level virtualization and isolation for microservices. Container cluster managers like Docker Swarm, Kubernetes and Mesosphere DC/OS provide scheduling, service discovery, load balancing and other orchestration capabilities for containers. The document examines characteristics of moving from monolithic to microservice architectures and different deployment patterns using containers, VMs and hardware virtualization.
3. 3
Key Definitions: Microservice
‘There is not one single definition for the term “microservice,” two are very
helpful:
• Microservices are small, autonomous services that work together; and
• Loosely coupled service-oriented architecture with bounded contexts.’ [1]
Microservices is a style of Application Architecture, evolving from Service-Oriented
Architecture (SOA), designed to solve problems for systems that are ‘too big’.
They are really about replaceability not maintenability, a way of working with
systems in which scale is a predominant factor, focused on the goal of improving
changeability of these systems.
Microservices are typically composed into whole application solutions using
patterns of industry proven arrangement, just like SOA services. Patterns address
Deployment (more of which later), Communication, Service Discovery, Reliability,
Data Management, Observability, Security, Testing and so on. For example,
microservices should own and manage their own data. Databases can be sharded
to provide isolation within a shared RDBMS context, or be physically separate
stores of information. Regardless, the Command Query Responsibility Segregation
(CQRS) pattern will be an essential approach when writing queries across these
disparate data sources. [2]
[1] Microservice Architecture – Aligning Principles, Practices and Culture
Nadareshvili, Mitra, McLarty, Amundsen
Published by O’Reilly 06/2016
[2] Chris Richardson maintains the site microservices.io which has a great section on microservice patterns
http://microservices.io/patterns/index.html
4. 4
Microservice Characteristics and Moving from Monolith to Microservice [3]
James Lewis and Martin Fowler provided a reasonable common set of
characteristics that fit most of the microservices architectures:
• Componentization via services
• Organized around business capabilities
• Products not projects
• Smart endpoints and dumb pipes
• Decentralized governance
• Decentralized data
management
• Infrastructure automation
• Design for failure
• Evolutionary design
Each microservice should have its own separate database,
or shard within a shared database
https://en.wikipedia.org/wiki/Shard_(database_architecture)
Most asked
question: How
do I evolve my
monolithic
(legacy)
database?
[3] Migrating to Microservices Databases – from Relational Monolith to
Distributed Data
Edson Yanaga
When developing a strategy for moving from Monolithic code and (relational) databases to
microservices and distributed data, there are some key undertakings:
• Implement the Strangler Pattern;
• Follow a Domain Driven Development approach;
• Ensure Zero Downtime by employing:
o Blue / Green Deployments; and
o Smart Canary Deployments via Smart Routers and / or Feature Toggles.
• Have a mature DevOps team and
culture;
• Have a mature CI/CD pipeline;
Another key element of each microservice is how to handle application state:
• transient or ephemeral – handle in memory during run with services like Redis or
Memcached so that there is no state loss during deployment given they back their in
memory caches with on disk storage;
• persistent – distributed databases, one per microservice, or isolated shard within a
single database i.e. as indicated by the Decentralised Data Management point above.
5. 5
Key Definitions: Container
Containers are a method of operating system virtualization that allow you to run an
application and its dependencies as resource-isolated processes.
• You are able to package an application's code, configurations, and dependencies
into easy to use building blocks.
• Containers, coupled with automation methods, provide rapid, reliable and
consistent deployments and provide fine grained control over infrastructure
resources.
• The result is environmental consistency, increased operational efficiency,
developer productivity, and sound version control practices.
A container need not be used for a microservice, but they are a good way to develop
and deploy them.
Containers are built from images - pre-built components
that can be layered together to build up applications and
dependencies. A prime benefit is that it is easy to
“overwrite” an individual container with images while the
application is still running – less scheduled downtime
which means better business continuity.
Containers can be clustered and their constituent (microservice) applications
scheduled as a unit through Container Cluster Managers – broadly discussed under
the topic Container Orchestration.
6. 6
Container Benefits
• Agile application creation and deployment: Increased ease and efficiency of
container image creation compared to VM image use;
• Continuous development, integration, and deployment: Provides for reliable and
frequent container image build and deployment with quick and easy rollbacks (due
to image immutability);
• Dev and Ops separation of concerns: Create application container images at
build/release time rather than deployment time, thereby decoupling applications
from infrastructure;
• Environmental consistency across development, testing, and production: Runs the
same on a laptop as it does in the cloud;
• Cloud and OS distribution portability: Runs on Ubuntu, RHEL, CoreOS, on-prem,
Google Container Engine, and anywhere else;
• Application-centric management: Raises the level of abstraction from running an
OS on virtual hardware to run an application on an OS using logical resources;
• Loosely coupled, distributed, elastic, liberated micro-services: Applications are
broken into smaller, independent pieces and can be deployed and managed
dynamically – not a fat monolithic stack running on one big single-purpose
machine;
• Resource isolation: Predictable application performance; and
• Resource utilization: High efficiency and density.
7. 7
Microservice Runtime Deployment Patterns / Architectures
Microservices don’t
have to use Containers
– it’s an architectural
style, not a technology.
Microservices that
use Containers
provide OS level
virtualisation when
installed on bare
metal…
Containers, using
a Container OS
Microservices don’t
have to use hardware
virtualisation, but it
brings many benefits
and enables multi-
tenancy and varying
Guest OS’ and
configurations.
Hypervisor
Host Operating System
Hardware
Virtual Machine
Micro-
service
Bins/Libs
Guest OS
Micro-
service
Virtual Machine
Micro-
service
Bins/Libs
Guest OS
Micro-
service
Bins / Libs
Host Operating System
Hardware
MicroserviceMicroservice
Container Engine
Bins/Libs
Microservice
C
Microservice
B
Microservice
C
Microservice
C
Microservice
A
Bins/
Libs
Bins/
Libs
Host Operating
System
Hardware
…and can be combined with
hardware virtualisation for further
efficiency, with a measure of added
complexity.
Host Operating System
Hardware
Hypervisor
Virtual Machine
Guest OS
Container Engine
Bins/Libs
Microservice
C
Microservice
B
Microservice
C
Microservice
C
Microservice
A
Bins/
Libs
Bins/
Libs
Virtual Machine
Guest OS
Container Engine
Bins/Libs
Microservice
C
Microservice
B
Microservice
C
Microservice
C
Microservice
A
Bins/
Libs
Bins/
Libs
8. 8
Layered Container Technology Architecture
Container
Orchestration
Container
Engine
Container OS
Bins / Libs
Microservi
ce
Container
Application
Support Services
10. 10
Limitations of Single Container Instances: The Need for Container Cluster
Managers
• Single point of failure;
• Resource constraints;
• No auto healing & autoscaling features;
• Limited container orchestration features;
and
• Limited service discovery features.
Container Engine
Bins/Libs
Microservice
C
Microservice
B
Microservice
C
Microservice
C
Microservice
A
Bins/
Libs
Bins/
Libs
Host Operating
System
Hardware
Containers, using
a Container OS Single Container Instances – despite the benefits, there are
production issues which they can’t address stand alone:
11. 11
Orchestrating Container Clusters and Scheduling Applications: Container
Cluster Managers
Load Balancer
Host Operating
System
Hardware
Container Engine
Bins/Libs
Microservice
C
Microservice
B
Microservice
C
Microservice
C
Microservice
A
Bins/
Libs
Bins/
Libs
Host Operating System
Hardware
Agent
Scheduler DNS
Container Engine
Bins/Libs
Microservice
C
Microservice
B
Microservice
C
Microservice
C
Microservice
A
Bins/
Libs
Bins/
Libs
Host Operating System
Hardware
Agent
Container Engine
Bins/Libs
Microservice
C
Microservice
B
Microservice
C
Microservice
C
Microservice
A
Bins/
Libs
Bins/
Libs
Host Operating System
Hardware
Agent
Overlay Network
Physical Network
Container Cluster Managers provide the following benefits and
capabilities:
• Container grouping by namespace;
• Container clustering by application component;
• Application health checking;
• Auto healing;
Hosted Container Cluster Manager Reference
Architecture
• Horizontal autoscaling;
• Domain naming and service
discovery;
• Dynamic load balancing;
• Centralised log access; and
• Multi-tenancy.CCMs should also be supported by:
• Identity and authorization systems;
and
• Mounting storage systems.
12. 12
Leading Container Orchestration Technology: Docker Engine Swarm Mode
Docker Engine Swarm Mode Features
• Same API as Docker;
• Built-in service discovery;
• Mesh Routing;
• Multi-host networking;
• Rolling updates;
• Integrates directly with Docker Compose;
• Secure using TLS encryption;
• Securely manage, transmit and store secrets
between nodes.
Services, Tasks and Manager Nodes
• Services use a declarative model;
• Deploy by submitting a service definition to
a manager node;
• Manager node dispatches units of work
called tasks to worker nodes for execution;
• A single elected manager node maintains the
desired state of the swarm by performing
orchestration and cluster management
functions;
• Agent on the worker node reports assigned
task state to manager so desired state can
be maintained.
Swarm Mode vs. Standalone Containers
• When you use Docker engines (Container Engine component of the Reference Architecture) without
using swarm mode, you execute commands on standalone containers.
• Docker engines, or nodes, using swarm mode participate in a managed and orchestrated cluster.
• You can run swarm services and standalone containers on the same Docker instances.
Docker Swarm
and Docker
Engine in Swarm
Mode are not the
same thing – the
latter is an
evolution of the
former.
13. 13
Mesosphere DC/OS
Leading Container Orchestration Technology: Mesosphere DC/OS
Apache Mesos
Marathon
Container (Docker, rkt)
Chronos
HAProxy
ZooKeepe
r
Kubernetes
Docker
Engine
Swarm
Mode
Marathon and
Docker Swarm
Mode can operate
concurrently on
the same Mesos
Cluster.
Logical Component
Stack
Framework designed
to simplify execution
of long running
applications in a
clustered
environment
Open source
load balancer
and reverse
proxy
Open source,
distributed and
fault-tolerant
scheduler
open source cluster
manager that
simplifies running
applications on a
scalable cluster of
servers
e.g. Chronos
e.g.
Marathon
e.g.
Docker
Containe
r
Mesosphere’s
distribution
14. 14
Leading Container Orchestration Technology: Kubernetes
Kubernetes is:
• Portable: public, private, hybrid, multi-cloud
• Extensible: modular, pluggable, hookable, composable
• Self-healing: auto-placement, auto-restart, auto-replication, auto-scaling
Service - logical set of Pods running
somewhere in the cluster, all provide the
same functionality, assigned a unique IP
address.
kube-proxy is responsible for
implementing a form of virtual IP
for Services
Container
(Docker)
Labels
applied to
Pods
Collections of
co-scheduled
Containers
Cluster
worker
node
Exposed by kube-
apiserver as the
main management
point for the
control plane
kube-
controller-
manager
manages the
lifecycle of
pods
kube-scheduler
assigns workloads to
specific pods
Node agent, ensures
containers within pods are
running and healthy
Docker Engine
(not in Swarm
Mode!)
Container
resource &
performance
collator
15. 15
(Unordered)
Container PaaS Vendor Landscape
Vendor Product CCM Container
s
Commentary
Cloud Foundry
Foundation
Cloud
Foundry
Diego Garden IBM, SAP, Pivotal base their PaaS strategy on Cloud Foundry.
Cloud Foundry is an open source, multi cloud application PaaS governed by
the Cloud Foundry Foundation – a Linux Foundation project.
The software was originally developed by VMware and then transferred to
Pivotal Software, a joint venture by EMC, VMware and General Electric.
A commercial version called Pivotal Cloud Foundry (PCF) is available from
Pivotal. It provides extra tools for installation and administration and a
Marketplace of packaged offerings e.g Spring Cloud Services. Pivotal Web
Services (PWS), however, is an instance of Pivotal Cloud Foundry hosted on
Amazon Web Services (AWS).
Uses the same OCI low-level container execution code as Docker and
Kubernetes, so container images run identically across all three platforms.
Amazon Web
Services (AWS)
EC2 Container
Service (ECS)
ECS,
Blox
Docker Images stored in the ECS Registry (ECR). CloudWatch for metrics monitoring.
Can also be combined with other AWS services like IAM, VPC & ELB. AWS
Simplified Workflow is also tightly integrated with AWS ECS to use Docker CLI
commands (e.g. push, pull, list, tag).
Blox is a collection of open source projects for container management and
orchestration on Amazon ECS. Blox gives you more control over how your
containerized applications run on Amazon ECS, enabling you to build
schedulers and integrate third-party schedulers on top of ECS, while
leveraging Amazon ECS to fully manage and scale your clusters.
Docker Inc Docker Cloud Docker
Engine in
Swarm
Mode
Docker Docker Cloud uses the hosted Docker Cloud Registry, which allows you to
publish Dockerized images on the internet either publicly or privately.
Docker Cloud can also store pre-built images, or link to your source code so
it can build the code into Docker images, and optionally test the resulting
images before pushing them to a repository.
Docker Cloud allows you to link to your infrastructure or cloud services
provider so you can provision new nodes automatically. Once you have nodes
set up, you can deploy images directly from Docker Cloud repositories.
With Beta Swarm Mode, you can create new swarms from within Docker
Cloud, register existing swarms to Docker Cloud, or provision swarms to
your cloud providers.
Once you’ve built an image, you can use it to deploy services (which are
composed of one or more containers created from an image), or use Docker
Cloud’s stackfiles to combine it with other services and microservices, to
form a full application.
Eldarion Eldarion
Cloud
Kubernete
s + Kel
Docker Kubernetes on GCP coupled with Kel (kelproject.com), a layer of Eldarion-
developed open-source tools and components written in Python & Go to
16. 16
(Unordered)
Container PaaS Vendor Landscape
Vendor Product CCM Container
s
Commentary
Flockport Flockport LXC
Installer,
Flockport
Utility,
FlockBox
LXC Flockport
Apps (LXC
format)
Flockport is a startup focused on building an App store based on LXC
containers that users can deploy in seconds on any server, any cloud and any
provider. Flockport is focused on simplicity, making things just work, giving
users a cloud-like flexibility of portable instances and workloads that can be
moved across servers easily.
Flockport LXC Installer creates a fully functioning LXC out of the box, the
Flockport Utility let's you view and download containers directly to your
system from the Flockport App Store.
Flockbox is a minimal VM that lets you use LXC and the Flockport App store
in seconds. Images available for Virtualbox, VMware and KVM.
Linux Containers (LXC) is an open source Linux container project. LXC is a
container manager and provides a set of tools to manage containers, a wide
choice of container OS templates and advanced networking and storage
capabilities for things like cloning and snapshotting.
DigitalOcean Droplet,
Block Storage,
Networking,
etc. (typical
IaaS services)
Docker
Swarm 1,
Kubernete
s, Mesos
2, Dokku
OS Image
(VM),
Docker
DigitalOcean is a cloud infrastructure provider which allows developers to
build and deploy microservices by creating so-called Droplets (i.e. units of
work) on their global cloud data centers, plus leveraging block storage and
networking features. A droplet can be an instance of an operating system
image, but also a Docker container application. DigitalOcean takes care of
provisioning, monitoring and other platform requirements for the Droplets. It
can be combined with different orchestration tools such as Docker Swarm,
Kubernetes, Apache Mesos or Dokku (a Docker-powered mini-Heroku PaaS).
Therefore, DigitalOcean is more like a IaaS - comparable to AWS EC2 - but
focusing on ease-of-use to deploy and run microservices clusters.
Google Google
Container
Engine
Kubernete
s
Docker Google Cloud Platform (GCP) contains Google Container Engine, amongst
other services, a Kubernetes based cluster manager and orchestration PaaS
for running Docker containers, providing flexibility to take advantage of on-
premises, hybrid, or public cloud infrastructure.
Google Container Registry makes it easy to store and access your private
Docker images.
Enable Stackdriver Logging and Stackdriver Monitoring with simple checkbox
configurations, making it easy to gain insight into how your application is
running.
Container Engine is fully managed by Google reliability engineers, ensuring
clusters are available and up-to-date, including both auto-upgrading and
auto-repairing master and nodes. The Google Cloud Container Engine
Service Level Agreement commitment is a Monthly Uptime Percentage to
Customer of at least 99.5%.
Reserve an IP address range for your container cluster, allowing your cluster
1 Not clear if this is Docker Swarm or Docker Engine in Swarm Mode
2 Not clear if this is Apache Mesos or Mesosphere DC/OS
17. 17
(Unordered)
Container PaaS Vendor Landscape
Vendor Product CCM Container
s
Commentary
CoreOS Tectonic,
Quay
Kubernete
s
Docker CoreOS previously promoted fleet for distributed compute cluster
management. They subsequently recognised Kubernetes as the de-facto
standard, deprecated fleet 02/18.
Quay is a secure container registry that builds and stores container images.
Able to sync container images between data centres, automatically build and
push images when developers commit code, automatically scan images for
known security vulnerabilities etc.
Tectonic includes Kubernetes installers to get up and running quickly, a
console to visually investigate clusters, and security features to permit
integration with existing security frameworks. Tectonic ships Operators in
order to better manage its open source components, like Kubernetes, etcd,
and Prometheus. Operators will be able to perform in-place updates, as well
as backup, restore, and scale up and down instances of software as needed.
A powerful, user-friendly console provides a full view of running apps, and
deploy new versions using rolling upgrades, canary instances, and
blue/green deployments. Available on bare metal or AWS - available in a free
tier for small clusters.
Deis Workflow,
Helm,
Steward
Kubernete
s
Docker Deis builds open source tools for Kubernetes. Now acquired by Microsoft.
Workflow – nginx, etcd, kubernetes, docker, core OS – integrated into a self
service platform that makes it easy to deploy and manage container-based
apps through a simple Heroku-inspired command line interface. Features
such as user and log management, buildpack support, edge routing and easy
release and rollback controls. Open source.
Helm – package manager - helps you manage Kubernetes applications using
Helm Charts (YML) to define, install, and upgrade complex Kubernetes
applications. Charts are easy to create, version, share, and publish, provide
repeatable application installation, and serve as a single point of authority.
The latest version of Helm is maintained by the Cloud Native Computing
Foundation CNCF.io - in collaboration with Microsoft, Google, Bitnami and
the Helm contributor community.
Steward – service broker - endpoint that manages a set of services. Now
continuing evolutionary development under the service-catalog project (in
incubation) to bring integration with service brokers to the Kubernetes
ecosystem via the Open Service Broker API.
Rackspace As yet
unnamed,
release ‘18
Q3+
Kubernete
s
Docker Carina (Magnum OpenStack, running Docker Swarm) killed April 2017 as it
wasn’t aligning with the roadmap: managed Kubernetes service running on
top of private OpenStack clouds, then bare metal, followed by layering the
service on top of other Public Clouds. Kubernetes cluster federation opens up
some interesting use cases for private/public deployments. Target of
18. 18
Container PaaS Vendor Landscape
Vendor Product CCM Container
s
Commentary
RedHat OpenShift Kubernete
s
Docker Provides a platform for provisioning, building, and deploying applications
and their components in a self-service fashion e.g. the source-to-image (S2I)
automated workflow which gets source code from version control to ready-
to-run, docker-formatted (and thus portable) container images, integrating
with CICD tooling on the way.
Gives IT operations a secure, enterprise-grade Kubernetes that provides
policy-based control and automation for applications, security features
preventing tenants application or underlying host compromise. Support for
stateless and stateful applications on a single platform due to ability to
attach persistent storage directly to Linux containers.
Other features: rich set of command-line tools; multidevice web console;
Eclipse-based integrated development environments; CloudForms enables
users to get real-time visibility into individual containers to the entire
infrastructure; ecosystem of partners; can easily scale to thousands of
instances across hundreds of nodes in a matter of seconds.
Install OpenShift on OpenStack, AWS, Azure, GCP, VMware’s vCenter,
https://blog.openshift.com/openshift-container-platform-reference-
architecture-implementation-guides/
VMware Photon
Platform,
Photon OS
Kubernete
s,
Cloud
Foundry
Docker Photon Controller sits between infrastructure and container cluster manager,
similar to Mesos, it has a Service Manager and a REST API and is open source.
Add Cloud Foundry and / or Kubernetes, then Docker containers and Harbor
(container registry server). Features: A scale-out control plane that turns
compute hosts into an easy-to-manage single system; Aggregates and
exposes IaaS services for secure container and modern app runtimes via IaaS
APIs; Simplifies deployment and life cycle management of compute,
networking, security, storage and operations functions; Complete life-cycle
management of advanced developer services (Kubernetes and Harbor)
Photon OS – A lightweight open source operating system optimized for
containers.
All sits on VMware’s ESXi hypervisor for hardware virtualisation.
Rancher Labs Rancher,
RancherOS
Docker
Swarm 1,
Kubernete
s, Mesos
2,
Cattle
Docker Open source platform, takes virtual or physical Linux compute from any
public or private cloud and implements a portable (container based) layer of
infrastructure services designed for containerized apps, including
networking, storage, load balancer, DNS, and security.
Cattle is Rancher’s own CCM and is used to orchestrate infrastructure
services as well as set up, manage, and upgrade Swarm, Kubernetes, and
Mesos clusters.
Application Catalog provides a one click deploy for an entire multi-container
clustered app & perform fully automated upgrades. Public community catalog
1 Not clear if this is Docker Swarm or Docker Engine in Swarm Mode
2 Not clear if this is Apache Mesos or Mesosphere DC/OS
19. 19
(Unordered)
Container PaaS Vendor Landscape
Vendor Product CCM Container
s
Commentary
IBM IBM Bluemix
Container
Service
Kubernet
es
Docker Based on Cloud Foundry
Deploy clusters into Bluemix Public cloud environment and connect to any
service in the Bluemix catalogue and choose between dedicated or shared
levels of hardware isolation for the worker nodes. Alternatively use Container
Service in Bluemix Dedicated private cloud. Both leverage Bluemix
Infrastructure (aka SoftLayer) resources.
Store, share and restore data between pods with the integrated and secure
volume service. Fully managed Kubernetes master that is highly available and
continuously monitored by IBM.
Image security compliance with Vulnerability Advisor - automatic scanning of
images in your private and secure Bluemix image registry. Review
recommendations specific to the operating system used in the image to fix
potential vulnerabilities.
Define custom policies to scale apps based on CPU and memory
consumption.
Use the cluster dashboard to manage cluster health and container
deployments.
Detailed consumption metrics via IBM Monitoring Service
Review logging information using the IBM Logging Service to see detailed
cluster activities.
Private overlay networks with full load balancer and Ingress support to make
your apps publicly available and balance workloads. Use a public IP, an IBM
provided route, or own custom domain to access cluster services from the
internet.
Potential to integrate Bluemix services, such as Watson APIs, Blockchain, data
services, IoT etc.
Microsoft Azure
Container
Service,
Azure Service
Fabric,
Docker
Swarm 1,
Kubernet
es,
Mesosphe
re DC/OS.
Azure
Service
Fabric
Docker
Docker
Windows
Developed in conjunction with Docker, PaaS can manage clusters of
containers with “master machines” for orchestration i.e. any of Swarm,
DC/OS or Kubernetes – you select the appropriate ARM template.
Mesosphere Universe of services are included with ACS DC/OS deployment –
permits addition of Spark, Hadoop, Cassandra etc.
Microsoft Azure Service Fabric is a microservices framework and container
orchestration engine. It is not dependent on Microsoft Azure, but also usable
on premises and in other clouds (the term “Azure” is somewhat misleading).
Service Fabric leverages Docker for container management on both Linux and
Windows containers. It allows devs to use different programming languages
(e.g. C#, Java, Powershell). Service Fabric powers many Microsoft services
today, including Azure SQL Database, Cosmos DB, Cortana, Power BI, Intune,
Azure Event Hubs, Azure IoT Hub, Dynamics 365, Skype for Business, and
1 This is legacy Docker Swarm - Docker Engine in Swarm Mode is not supported at the time of
writing. If you want to deploy a Swarm mode cluster in Azure, use the open-source ACS Engine,
a community-contributed quickstart template, or a Docker solution in the Azure Marketplace.
20. 20
Watching Brief – Container Initiatives – CNCF and OCI
Cloud Native Computing Foundatio (CNCF) cncf.io
Mission to create and drive the adoption of a new computing paradigm that is optimized for modern
distributed systems environments capable of scaling to tens of thousands of self healing multi-tenant
nodes.
a) Container packaged. Running apps and processes in containers as an isolated unit of deployment, and
achieve high levels of resource isolation. Improves development, fosters code and component reuse
and simplifies cloud native application operations.
b) Dynamically managed. Actively scheduled and managed by a central orchestrating process. Radically
improve machine efficiency and resource utilization while reducing the ops and maintenance costs.
c) Micro-services oriented. Loosely coupled with dependencies explicitly described (e.g. through service
endpoints). Increase app agility and maintainability of applications. CNCF will shape the evolution of the
technology to advance the state of the art for application management, and to make the technology
ubiquitous and easily available through reliable interfaces.
Open Container Initiative (OCI) opencontainers.org, A Linux Foundation Project
A lightweight, open governance structure (project) to create open industry standards around container
formats and runtime. Launched ‘15 by Docker (who donated its container format and runtime, runC),
CoreOS and other industry leaders, OCI currently contains two specifications: runtime-spec and image-spec.
runtime-spec outlines how to run a “filesystem bundle” that is unpacked on disk. At a high-level an OCI
implementation would download an OCI Image then unpack that image into an OCI Runtime filesystem
bundle. At this point the OCI Runtime Bundle would be run by an OCI Runtime. This workflow must support
the ability to run an image with no additional arguments, thus:
docker run example.com/org/app:v1.0.0
rkt run example.com/org/app,version=v1.0.0
To support this user experience the OCI Image Format contains sufficient information to launch the
application on the target platform (e.g. command, arguments, environment variables, etc). This specification
defines how to create an OCI Image, which will generally be done by a build system, and output an image
manifest, a filesystem serialization, and an image configuration. At a high level the image manifest contains
metadata about the contents and dependencies of the image including the content-addressable identity of
one or more filesystem serialization archives that will be unpacked to make up the final runnable filesystem.
The image configuration includes information such as application arguments, environments, etc. The
21. 21
Watching Brief – Rapid Changes – Recent Developments
The technology in this space is changing very quickly – the crowded landscape grows more
complex. However, it’s also very obvious that there are two de-facto technology approaches
to containers & CCMs:
Docker and Kubernetes
As such, much of the recent innovation has taken place in relation to these technologies.
Some recent developments include:
• Kubernetes open source projects:
o Ksonnet - A Jsonnet library that compiles Jsonnet code to Kubernetes YAML;
o Kubeval - kubeval is a tool for validating a Kubernetes YAML or JSON configuration file;
o Istio - An open platform to connect, manage, and secure microservices; and
o Kubermesh - A bare-metal, self-hosted, self-healing, self-provisioning, partial-mesh network
Kubernetes cluster!
• IBM’s Microservice Builder developer.ibm.com/microservice-builder/ on Bluemix Container Service.
By the time you read this, the landscape will have evolved further, so while the core
principles remain the same, keep a watching brief over the technology.
