The main repository is located at https://gitlab.otonokizaka.moe/Umi/til

Today I Learned

Collection of small writeups from my daily learning.

This document is best edited with emacs org-mode.

Docker

Use Docker buildkit with docker-compose

Docker has a new build backend called buildkit, which is an improvement over the original docker build backend.

You can activate it by exporting the DOCKER_BUILDKIT environment variable like so:

export DOCKER_BUILDKIT=1

This works great with docker build, however it doesn’t work with docker-compose build.

You can fix that by exporting one more environment variable like so:

export COMPOSE_DOCKER_CLI_BUILD=1

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Emacs

Insert heading in org-mode

There are commands for inserting a heading below the current line in org-mode, so you don’t have to type out the * yourself.

The most useful one is probably org-insert-heading-respect-content, which inserts a new heading at the end of the current subtree.

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Jenkins

Trigger job with cURL

To trigger a Jenkins job with cURL, you will need to get an API token for your user. Go to https://JENKINS_URL/user/JENKINS_USER/configure, then create a new API token under the API Token section.

Then, to trigger a job, run:

curl -X POST https://JENKINS_API_TOKEN@JENKINS_USER:JENKINS_URL/job/JOB_NAME/build

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Kubernetes

Fix HPA resource stuck at syncing in ArgoCD

Due to a bug in Kubernetes, HPA resources managed by ArgoCD might be stuck at syncing forever.

The fix is to reorder the metrics (placing memory before cpu). For example:

@@ -48,13 +48,13 @@ autoscaling:
   metrics:
     - type: Resource
       resource:
-        name: cpu
+        name: memory
         target:
           type: Utilization
           averageUtilization: 60
     - type: Resource
       resource:
-        name: memory
+        name: cpu
         target:
           type: Utilization
           averageUtilization: 60

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Python

Fix libffi error

When the underlying system upgrades libffi, and you are using a Python version installed with pyenv, you might run into this error:

>>> import ctypes
Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
    File "/home/umi/.pyenv/versions/3.8.1/lib/python3.8/ctypes/__init__.py", line 7, in <module>
        from _ctypes import Union, Structure, Array
ImportError: libffi.so.6: cannot open shared object file: No such file or directory

The reason is that libffi.so.6 no longer exists and is repalced by a newer version of libffi

The fix is simply recompile your Python:

pyenv install -f 3.8.1 # or whatever version

Scala

Access global build info

It is often helpful to access global build info in your sbt files.

One might attempt to do something like this:

val version_ = (version in ThisBuild).value

someTask := // do something with version_

However, the above doesn’t work, to proper way is to do this:

someTask := {
    val version_ = (version in ThisBuild).value
    // do something with version_
}

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Select repository based on snapshot

If you’re using Maven repositories you will also have to select the right repository depending on your artifacts: SNAPSHOT versions go to the /snapshot repository while other versions go to the /releases repository. Doing this selection can be done by using the value of the isSnapshot SettingKey:

publishTo := {
  val nexus = "https://my.artifact.repo.net/"
  if (isSnapshot.value)
    Some("snapshots" at nexus + "content/repositories/snapshots")
  else
    Some("releases"  at nexus + "service/local/staging/deploy/maven2")
}

Vim

Fix indentation

The shortcut to fix code indentation in vim is =.

You can use visual mode to select a block of code and use = to fix indentation for that selection.

You can also use =G to fix indentation for every line below the cursor.

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Resize windows automatically

CTRL+w =

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