I wanted a simple way to have a dashboard to show if hosts and services are alive & didn’t want to write much code and/or run up a nagios instance (or anything like that). All I care is whether it’s green or red. I’d already been setting up HAProxy for a proxy forwarder, so I …
Category Archive: Docker
Mar 30
Interesting Feature of Dockerfile Volume Directives
I’ve been rewriting a cleanroom version of the hadoop-in-a-box — just about finished. And, truth be told, the code, all in all, is a bit tighter than the original encumbered version. However, I ran into an interesting feature of Volumes — I had thought perhaps to optimize things a bit, but it caused some unexpected …
Mar 17
Docker, Cgroups, Memory Constraints, and Java: A Cautionary Tale, or Here be Reapers (sometimes)
TL;DR: Java and cgroups/Docker memory constraints don’t always behave as you might expect. Always explicitly specify JVM heap sizes. Also be aware that kernel features may not be enabled. And Linux… lies. I’ve recently discovered an interesting “quirk” in potential interactions between Java, cgroups, Docker, and the kernel which can cause some surprising results. Unless …
Mar 15
Zombie Apocalypse! Docker AUFS + Java + Low Memory …. Hadoop in a Box Cloudera Manager Cluster
TL;DR — When using AUFS in a memory constrained environment, Java can spawn (lots!) of Zombies. A workaround is to change the storage driver to the device mapper. In working on the Hadoop in a box CDH cluster with Cloudera Manager, I’ve discovered a few interesting things about AUFS. These experiences are with Ubuntu 14.04 …
Feb 11
Docker: Could not find container for entity id
I had an instance where the docker filesystem ran out of space. After cleaning up with docker rm and docker rmi, I got:
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Could not find container for entity id |
I followed iwidanalage‘s suggestion from “Creating fail with Could not find container for entity id after upgrading to 1.9.0 · Issue #17691 · docker/docker”
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cd /var/lib/docker sudo sqlite3 linkgraph.db update edge set name='some-random-container-name' where name='failing-container-name'; .quit |
After this, it worked.
Jan 28
Cloudera Manager, Embedded DB and Docker
If you ever see a message like:
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could not open session |
on startup and the Cloudera manager won’t start, it’s because you did not start the container in privileged mode:
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docker run -d --hostname=master --privileged=true --name=master cdh-master |
Oct 07
Hypriot Does it Again
Many thanks and kudos to the most excellent people at Hypriot on their latest release! Hypriot has made Docker on the Pi easy — prior to their distribution it took a lot of blood, sweat, and tears to compile and get Docker working on the Pi. (Trust me!!! Been there, done that, have the t-shirt). …
Oct 02
Multifarious v2
While at a DevOps Birds of a Feather session at Ohio Linux Fest today I was describing to John Willis (@botchagalupe) my experiments with Docker and the Pi Swarm. Along the way, I mentioned that I’d gotten heterogenous docker swarms working using Powerstrip — aka Multifarious, first described in Heterogenous Docker Swarms Teaser. In so …
Sep 25
Containers and Open Source Vulnerabilities
I have a guest article on BlackDuck’s OpenSource Delivers Blog — Containers and Open Source Vulnerabilities.
Sep 07
Bulk Adding Hosts to a Pi Swarm
I’ve refreshed my stack and am rebuilding the cluster. I’m using Hypriot for the linux distribution, but I’m a smart sysadmin (read lazy) and don’t want to manually add them each time. Also, I want to make a script so that I can quickly rebuild. This is inspired by Let Docker Swarm all over your …
