My SSH Issue Docker Swarm hosts

That one time you all of sudden could not SSH into your Docker Swarm hosts?

I am writing this so I will remember to be smarter next time.

Ever Get this?

minas-tirith:~ jowings$ ssh scarif
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!

I started to flip out and wondered why this just all of sudden happened on all four host in my swarm cluster. Was something actually nasty happening? Probably not, but you never know. I thought I broke the pub key on my mac. because I went into .ssh/known_hosts and removed the entry for my hosts as I quite commonly see this because I rebuild vm’s and hosts all the time. Then I got something different and got the same exact error from my Windows 10 machine.

Permission denied (publickey).

Pretty sure I didn’t break 2 different ssh clients on 2 different computers.
What did I do?

$docker stack deploy -c gitlab.yml gitlab

So I am keeping local git copies and thoughs I would be smart to have Gitlab to run this service in my home lab.

Problem in my zeal to have git use stander ssh tcp port 22 to push my repos up to the server I did this:

version: '3'
services:
web:
image: 'gitlab/gitlab-ce:latest'
restart: always
hostname: 'gitlab1'
environment:
GITLAB_OMNIBUS_CONFIG: |
external_url 'http://gitlab.2vcps.local'
ports:
- '80:80'
- '443:443'
- '22:22'

So basically my gitlab service was now available using tcp/22 on my entire cluster. Even though the container is only on one host they way Docker overlay networking works is any host in that cluster will forward the request for tcp/22 to that container. The container without my public key, the container that no matter my hostname does not have the same SSH “ID” as my actual hosts.
Bad move JO.
So don’t do that and stuff.

To fix:

version: '3'
services:
web:
image: 'gitlab/gitlab-ce:latest'
restart: always
hostname: 'gitlab1'
environment:
GITLAB_OMNIBUS_CONFIG: |
external_url 'http://gitlab.2vcps.local'

ports:
- '80:80'
- '443:443'
- '12022:22'

I changed the port mapping for now. I can use HAPROXY later to use the virtual hostname and point traffic to the container.

$docker stack deploy -c gitlab.yml gitlab

and it updates the service with the new port mapping.

CockroachDB with Persistent Data

There IS an Official Whitepaper!

While I was writing this post the awesome Simon Dodsley was writing a great whitepaper on Persistent storage with Pure. As you can see there is some very different ways to deploy CockroachDB but the main goal is to keep your important data persistent no matter what happens to the containers as the scale, live and die.

I know most everyone loved seeing the demo of the most mission critical app in my house. I also want to show a few quick ways to leverage the Pure plugin to provide persistent data to a database. I am posting my files I used to create the demo here https://github.com/2vcps/crdb-demo-pure

First note
I started with the instructions provided here by Cockroach Labs.
This is an insecure installation for demo purposes. They do provide the instructions for a more Prod ready version. This is good enough for now.

Second note
The loadbalancer I used was created for my environment using the intructions to output the HAProxy file found here on the Cockroach Labs website:
https://www.cockroachlabs.com/docs/stable/generate-cockroachdb-resources.html

My yaml file refers to a docker image I built for the HAproxy loadbalancer. If it works for you cool! If not please follow the instructions above to create your own. If you really need to know more I can write another post showing how to take the Dockerfile and copy the CFG generated by CRDB into a new image just for you.

 

My nice little docker swarm

media_1501095950777.png

I have three VMware VM’s running Ubuntu 16.04. With Docker CE and the Pure plugin already installed. Read more here if you want to install the plugin.

media_1501096079095.png

Run the deploy

https://github.com/2vcps/crdb-demo-pure/blob/master/3node-cockroachdb-pure.yml

version: '3.1'
services:
    db1:
      image: cockroachdb/cockroach:v1.0.2
      deploy:
            mode: replicated
            replicas: 1
      ports:
            - 8888:8080
      command: start --advertise-host=cockroach_db1 --logtostderr --insecure
      networks:
            - cockroachdb
      volumes:
            - cockroachdb-1:/cockroach/cockroach-data
    db2:
      image: cockroachdb/cockroach:v1.0.2
      deploy:
         mode: replicated
         replicas: 1
      command: start --advertise-host=cockroach_db2 --join=cockroach_db1:26257 --logtostderr --insecure
      networks:
         - cockroachdb
      volumes:
         - cockroachdb-2:/cockroach/cockroach-data
    db3:
      image: cockroachdb/cockroach:v1.0.2
      deploy:
         mode: replicated
         replicas: 1
      command: start --advertise-host=cockroach_db3 --join=cockroach_db1:26257 --logtostderr --insecure
      networks:
         - cockroachdb
      volumes:
         - cockroachdb-3:/cockroach/cockroach-data
    crdb-proxy:
      image: jowings/crdb-proxy:v1
      deploy:
         mode: replicated
         replicas: 1
      ports:
         - 26257:26257
      networks: 
         - cockroachdb

networks:
    cockroachdb:
        external: true

volumes:
    cockroachdb-1:
      driver: pure
    cockroachdb-2:
      driver: pure
    cockroachdb-3:
      driver: pure

 

#docker stack deploy -c 3node-cockroachdb-pure.yml cockroach

Like it shows in the compose file This command deploys 4 services. 3 database nodes and 1 HAproxy. Each database node gets a brand new volume attached directly to the path by the Pure Docker Volume Plugin.

New Volumes

media_1501098437804.png

Each new volume created and attached to the host via iSCSI and mounted into the container.

Cool Dashboard

media_1501098544719.png

Other than being no data do you notice something else?
First lets generate some data.
I run this from a client machine but you can attach to one of the DB containers and run this command to generate some sample data.

cockroach gen example-data | cockroach sql --insecure --host [any host ip of your docker swam]

media_1501098910914.png

I am also going to create a “bank” database and use a few containers to start inserting data over and over.

cockroach sql --insecure --host 10.21.84.7
# Welcome to the cockroach SQL interface.
# All statements must be terminated by a semicolon.
# To exit: CTRL + D.
[email protected]:26257/> CREATE database bank;
CREATE DATABASE
[email protected]:26257/> set database = bank;
SET
[email protected]:26257/bank> create table accounts (
-> id INT PRIMARY KEY,
-> balance DECIMAL
-> );
CREATE TABLE
r[email protected]:26257/bank> ^D

I created a program in golang to insert some data into the database just to make the charts interesting. This container starts, inserts a few thousand rows then exits. I run it as a service with 12 replicas so it is constantly going, I call it gogogo because I am funny.

media_1501108005294.png

gogogo

media_1501108062456.png
media_1501108412285.png

You can see the data slowly going into the volumes.

media_1501171172944.png

Each node remains balanced (roughly) as cockroachdb stores that data.

What happens if a container dies?

media_1501171487843.png

Lets make this one go away.

media_1501171632191.png

We kill it.
Swarm starts a new one. The Docker engine uses the Pure plugin and remounts the volume. The CRDB cluster keeps on going.
New container ID but the data is the same.

media_1501171737281.png

Alright what do I do now?

media_1501171851533.png

So you want to update the image to the latest version of Cockroach? Did you notice this in our first screenshot?

Also our database is getting a lot of hits, (not really but lets pretend), so we need to scale it out. What do we do now?

https://github.com/2vcps/crdb-demo-pure/blob/master/6node-cockroachdb-pure.yml

version: '3.1'
services:
    db1:
      image: cockroachdb/cockroach:v1.0.3
      deploy:
            mode: replicated
            replicas: 1
      ports:
            - 8888:8080
      command: start --advertise-host=cockroach_db1 --logtostderr --insecure
      networks:
            - cockroachdb
      volumes:
            - cockroachdb-1:/cockroach/cockroach-data
    db2:
      image: cockroachdb/cockroach:v1.0.3
      deploy:
         mode: replicated
         replicas: 1
      command: start --advertise-host=cockroach_db2 --join=cockroach_db1:26257 --logtostderr --insecure
      networks:
         - cockroachdb
      volumes:
         - cockroachdb-2:/cockroach/cockroach-data
    db3:
      image: cockroachdb/cockroach:v1.0.3
      deploy:
         mode: replicated
         replicas: 1
      command: start --advertise-host=cockroach_db3 --join=cockroach_db1:26257 --logtostderr --insecure
      networks:
         - cockroachdb
      volumes:
         - cockroachdb-3:/cockroach/cockroach-data
    crdb-proxy:
      image: jowings/crdb-haproxy:v2
      deploy:
         mode: replicated
         replicas: 1
      ports:
         - 26257:26257
      networks: 
         - cockroachdb
    db4:
      image: cockroachdb/cockroach:v1.0.3
      deploy:
         mode: replicated
         replicas: 1
      command: start --advertise-host=cockroach_db4 --join=cockroach_db1:26257 --logtostderr --insecure
      networks:
         - cockroachdb
      volumes:
         - cockroachdb-4:/cockroach/cockroach-data
    db5:
      image: cockroachdb/cockroach:v1.0.3
      deploy:
         mode: replicated
         replicas: 1
      command: start --advertise-host=cockroach_db5 --join=cockroach_db1:26257 --logtostderr --insecure
      networks:
         - cockroachdb
      volumes:
         - cockroachdb-5:/cockroach/cockroach-data
    db6:
      image: cockroachdb/cockroach:v1.0.3
      deploy:
         mode: replicated
         replicas: 1
      command: start --advertise-host=cockroach_db6 --join=cockroach_db1:26257 --logtostderr --insecure
      networks:
         - cockroachdb
      volumes:
         - cockroachdb-6:/cockroach/cockroach-data
networks:
    cockroachdb:
        external: true

volumes:
    cockroachdb-1:
      driver: pure
    cockroachdb-2:
      driver: pure
    cockroachdb-3:
      driver: pure
    cockroachdb-4:
      driver: pure
    cockroachdb-5:
      driver: pure
    cockroachdb-6:
      driver: pure
$docker stack deploy -c 6node-cockroachdb-pure.yml cockroach

(important to provide the name of the stack you already used, or else errors)

media_1501172007803.png

We are going to update the services with the new images.

  1. This will replace the container with the new version — v1.0.3
  2. This will attach the existing volumes for nodes db1,db2,db3 to the already created FlashArray volumes.
  3. Also create new empty volumes for the new scaled out nodes db4,db5,db6
  4. CockroachDB will begin replicating the data to the new nodes.
  5. My gogogo client “barage” is still running

This is kind of the shotgun approach in this non-prod demo environment. If you want no downtime upgrades to containers I suggest reading more on blue-green deployments. I will show how to make the application upgrade with no downtime and use blue-green in another post.

Cockroach DB begins to reblance the data.

media_1501172638117.png

6 nodes

media_1501172712079.png

If you notice the gap in the queries it is becuase I updated every node all at once. A better way would be to do one at a time and make sure each node is back up while they “roll” through the upgrade to the new image. Not prod remember?

media_1501172781312.png
media_1501172828992.png

Application says you are using 771MiB of your 192GB. While the FlashArray is using just maybe 105MB across these volumes.

A little while later…

media_1501175811897.png

Now we are mostly balanced with replicas in each db node.

Conclusion
This is just scratching the surface and running highly scalable data applications in containers with persistent data on a FlashArray. Are you a Pure customer or potential Pure customer about to run stateful/persistent apps on Docker/Kubernetes/DCOS? I want to hear from you. Leave a comment or send me a message on Twitter @jon_2vcps.

If you are a developer and have no clue what your infrastructure team does or is doing I am here to help make everyone’s life better. No more weekend long deployments or upgrades. Get out of doing storage performance troubleshooting.

Go to more of your kids soccer games.

My First DockerCon

Wrapping up my very first DockerCon. I learned great new things, was introduced to new tech and reconnected with some old friends.

This was my first convention in a very long time where I actually just attended the show and went to sessions. It was really nice. While people would usually read my blog looking for tips and tricks on how to do technical things and not my philosophic rambling. So I won’t try to be a pundit on announcements and competition and all that. Some cool things I learned:

  1. Share everything on GitHub. People use github as the defacto standard for sharing information. Usually it is code, but lots more is out there including presentations and demos for a lot for what happened at DockerCon. Exciting for me as someone that always loved sharing what I learn via this blog is that this is expected. I will post some of my notes and other things about specific sessions once the info is all posted.
  2. Being a “storage guy” for the past 6 years or so between Pure Storage and EMC it was good to see how many companies in the ecosystem have solutions built for CI/CD and Container Security. So much different than other shows where the Storage vendors dominate the mind share.
  3. Over the years friends and co-workers have gone there own way and ended up all over the industry. Some of my favorite people that always put a very high value on community and sharing seem to be the same people that gravitate to DockerCon. It was great to see all of you and meet some new people.

More to follow as I pull my notes together and find links to the sessions.

 

Kubernetes Anywhere and PhotonOS Template

Experimenting with Kubernetes to orchestrate and manage containers? If you are like me and already have a lot invested in vSphere (time, infra, knowledge) you might be exctied to use Kubernetes Anywhere to deploy it quickly. I won’t re-write the instruction found here:

https://github.com/kubernetes/kubernetes-anywhere

It works with

  • Google Compure Engine
  • Azure
  • vSphere

The vSphere option uses the Photon OS ova to spin up the container hosts and managers. So you can try it out easily with very little background in containers. That is dangerous as you will find yourself neck deep in new things to learn.

Don’t turn on the template!

media_1491484535602.png

If you are like me and *skim* instructions you could be in for hours of “Why do all my nodes have the same IP?” When you power on the Photon OS template the startup sequence generates a machine ID (and mac address). So even though I powered it back off, the cloning processes was producing identical VM’s for my kubernetes cluster. Those not hip to networking this is bad for communication.

Also, don’t try to be a good VMware Admin cad convert that VM to a VM Template. The Kubernetes Anywhere script won’t find it.

IF you do like me and skip a few lines reading (happens right) make sure to check this documenation out on Photon OS. It will help get you on the right track.

https://github.com/vmware/photon/blob/master/docs/photon-admin-guide.md#clearing-the-machine-id-of-a-cloned-instance-for-dhcp

This is clearly marked in the documentation now.