From 6d13122a4d9b271cc765688d25fed1a8bf615882 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=A9r=C3=B4me=20Petazzoni?= <jerome.petazzoni@gmail.com>
Date: Tue, 9 May 2023 07:50:40 +0200
Subject: [PATCH] =?UTF-8?q?=E2=9E=95=20Add=20BuildKit=20RUN=20--mount=3Dty?=
 =?UTF-8?q?pe=3Dcache...?=
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---
 slides/containers/Buildkit.md           | 20 ++++++++++
 slides/containers/Multi_Stage_Builds.md | 51 +++++++++++++++++++++++++
 2 files changed, 71 insertions(+)

diff --git a/slides/containers/Buildkit.md b/slides/containers/Buildkit.md
index 4684e51e..68c40a7a 100644
--- a/slides/containers/Buildkit.md
+++ b/slides/containers/Buildkit.md
@@ -348,6 +348,26 @@ It will indicate which executables can be run on your engine.
 
 ---
 
+## Cache directories
+
+```bash
+RUN --mount=type=cache,target=/pipcache pip install --cache-dir /pipcache ...
+```
+
+- The `/pipcache` directory won't be in the final image
+
+- But it will persist across builds
+
+- This can simplify Dockerfiles a lot
+
+  - we no longer need to `download package && install package && rm package`
+
+  - download to a cache directory, and skip `rm` phase
+
+- Subsequent builds will also be faster, thanks to caching
+
+---
+
 ## More than builds
 
 - Buildkit is also used in other systems:
diff --git a/slides/containers/Multi_Stage_Builds.md b/slides/containers/Multi_Stage_Builds.md
index f944f17f..e885c687 100644
--- a/slides/containers/Multi_Stage_Builds.md
+++ b/slides/containers/Multi_Stage_Builds.md
@@ -296,6 +296,8 @@ virtually "free."
 
 ---
 
+class: extra-details
+
 ## Build targets
 
 * We can also tag an intermediary stage with the following command:
@@ -313,6 +315,55 @@ virtually "free."
 
   (instead of using multiple Dockerfiles, which could go out of sync)
 
+--
+
+class: extra-details
+
+## Dealing with download caches
+
+* In some cases, our images contain temporary downloaded files or caches
+
+  (examples: packages downloaded by `pip`, Maven, etc.)
+
+* These can sometimes be disabled
+
+  (e.g. `pip install --no-cache-dir ...`)
+
+* The cache can also be cleaned immediately after installing
+
+  (e.g. `pip install ... && rm -rf ~/.cache/pip`)
+
+---
+
+class: extra-details
+
+## Download caches and multi-stage builds
+
+* Download+install packages in a build stage
+
+* Copy the installed packages to a run stage
+
+* Example: in the specific case of Python, use a virtual env
+
+  (install in the virtual env; then copy the virtual env directory)
+
+---
+
+class: extra-details
+
+## Download caches and BuildKit
+
+* BuildKit has a caching feature for run stages
+
+* It can address download caches elegantly
+
+* Example:
+  ```bash
+  RUN --mount=type=cache,target=/pipcache pip install --cache-dir /pipcache ...
+  ```
+
+* The cache won't be in the final image, but it'll persist across builds
+
 ???
 
 :EN:Optimizing our images and their build process