Shrink container image with --no-cache option on apk

[OctopusET]

This option shrinks container image more than half.
result: 1.95 GB -> 882 MB

[apyrgio]

Hey @OctopusET, thanks a lot for the contribution. We really want to reduce the size of the container image, so I tested it locally as well. I found that the original image from main was 838MiB, and with your changes, it got reduced to 836MiB.

I was confused a bit so I checked out the size of the APK index under /var/cache/apk, and in my case, it was just 2MiB, which explains the size difference:

$ ls -lh /var/cache/apk/
total 2M     
-rw-r--r--    1 root     root      422.1K Jun 26 11:02 APKINDEX.49104001.tar.gz
-rw-r--r--    1 root     root        1.4M Jun 26 11:02 APKINDEX.884188d8.tar.gz

So, I have two questions here:

1. Could it be that the size difference that you're seeing is attributed to disabling image compression the first time? 1.95 GiB is the size of the uncompressed image, that's why I'm asking.
2. Using --no-cache is indeed a reasonable setting for container images, and it uncovered an issue in our Dockerfile, if we also add it to apk add. If you're ok with the following code, can you add it to your branch, so that I can merge it?

diff --git a/Dockerfile b/Dockerfile
index c247982..5e0f1c6 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -4,7 +4,7 @@ ARG TESSDATA_CHECKSUM=990fffb9b7a9b52dc9a2d053a9ef6852ca2b72bd8dfb22988b0b990a70
 
 # Install dependencies
 RUN apk --no-cache -U upgrade && \
-    apk add \
+    apk --no-cache add \
     ghostscript \
     graphicsmagick \
     libreoffice \
@@ -26,7 +26,6 @@ RUN apk --no-cache -U upgrade && \
 RUN mkdir tessdata && cd tessdata \
     && TESSDATA_VERSION=$(wget -O- -nv https://api.github.com/repos/tesseract-ocr/tessdata/releases/latest \
         | sed -n 's/^.*"tag_name": "\([0-9.]\+\)".*$/\1/p') \
-    && apk --purge del jq \
     && wget https://github.com/tesseract-ocr/tessdata/archive/$TESSDATA_VERSION/tessdata-$TESSDATA_VERSION.tar.gz \
     && echo "$TESSDATA_CHECKSUM  tessdata-$TESSDATA_VERSION.tar.gz" | sha256sum -c \
     && tar -xzvf tessdata-$TESSDATA_VERSION.tar.gz -C . \

[OctopusET]

Hello, thank you for the comment.

1. I'm not sure, but I checked the size with podman images. I just tried re-build whole image without/with my PR. It still shows 1.9GB. I think --no-cache option doesn't help shrinking size that much. I think I got around 900MB because podman somehow used the compressed image or it's just part of the image. But still I think --no-cache option would be good for the container image maintenance.

2. Thank you for the changes, I forgot to add it. I just added it.

It's not related to this PR.

This PR was made during I'm working on the adding a hwp supports.
But I have a problem, I managed to convert hwp, hwpx to pdf with extension (I mentioned on this comment.) in the container. But dangerzone fails when it's running pdfinfo.
I'd like to discuss about this, should I just open Draft PR first?

[apyrgio]

This PR was made during I'm working on the adding a hwp supports.

That's exciting!

But I have a problem, I managed to convert hwp, hwpx to pdf with extension (I mentioned on this #243 (comment).) in the container. But dangerzone fails when it's running pdfinfo.
I'd like to discuss about this, should I just open Draft PR first?

Sure, go ahead.

[OctopusET]

I just posted my draft PR #460!

Just curious, what was that line for?

&& apk --purge del jq

[apyrgio]

I just posted my draft PR #460!

Great, thanks! I'll comment there soon.

Just curious, what was that line for?

&& apk --purge del jq

Oh, good question. In order to get the Tesseract data version, I initially installed jq, parsed the version with it, and then deleted it. Once I figured out we can use sed instead of jq, I ditched the jq approach, but not the line that removes it.

This didn't cause any problem, up to the point where we removed the APK index. By doing so, this line would fail. So, I removed it.