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https://github.com/infobip/jib-layer-with-modification-time-extension-maven

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Host: GitHub
URL: https://github.com/infobip/jib-layer-with-modification-time-extension-maven
Owner: infobip
License: apache-2.0
Created: 2021-02-19T09:04:05.000Z (over 3 years ago)
Default Branch: master
Last Pushed: 2021-02-22T07:15:13.000Z (over 3 years ago)
Last Synced: 2024-04-16T11:20:45.312Z (7 months ago)
Language: Java
Size: 23.4 KB
Stars: 4
Watchers: 10
Forks: 3
Open Issues: 0
Metadata Files:
- Readme: README.md
- License: LICENSE

Awesome Lists containing this project

README

# Layer With Modification Time (LWMT) JIB Extension

## Contents
1. [Purpose](#purpose)
2. [Usage](#usage)
3. [Example](#example)
4. [Interesting reads](#reads)
5. [Requirements](#requirements)
6. [Contributing](#contributing)
7. [License](#license)

## Purpose

[JIB's](https://github.com/GoogleContainerTools/jib) default layer packaging process causes all files to have their
timestamps set to `1970-01-01T00:00:01Z`. This is caused due to JIB plugin's
[reproducibility feature](https://github.com/GoogleContainerTools/jib/blob/master/docs/faq.md#why-is-my-image-created-48-years-ago)
and is a good practice for most use cases, but causes problems for our public-facing web services, because it messes up `Last-Modified` headers.
When hosting resources, Spring MVC can read file modification timestamp and use it to answer to client's `If-Modified-Since` header
(works with bundled archives as well). Without this information, browser caching can work incorrectly or less efficiently.

While modification time can be set using a plugin property `filesModificationTime`, it has some drawbacks:
- it can be set only in `all-or-nothing` principle, forcing you to choose between seamless browser caching support and
Docker layer caching. Usually we only need one or two files/libraries to have modified time set.
- it can not be set to take the current time, but rather needs to be passed the time as a property. Additionally, it
expects a certain time format which not all projects use. In order to support this we would need to introduce new
Maven profiles.

This extension aims to achieve the best of both worlds, by enabling users to define which files they want to move from
standard layers (that have modification time set to JIB's default) to a special layer that has last modified time set to
build time.

This extension is opinionated in a way that it only allows moving the files into a single new layer. Keep in mind that
changing modification time also changes the layer hash and makes it irreproducible. Therefore, number of files affected
by this extension should be kept to a minimum and only include the files which are a part of the project.

## Usage

The plugin will:
- Remove files matching the filter from layers and put them in a final layer called `layerWithModificationTime`
- Remove an original layer if it is empty after the files were moved

Here is an example of adding this plugin to a project's plugin management:
```

com.google.cloud.tools
jib-maven-plugin
${jib-maven-plugin.version}

com.infobip.jib
jib-layer-with-modification-time-extension-maven
${jib-layer-with-modification-time-extension-maven.version}

package

dockerBuild

com.infobip.jib.extension.lwmt.LayerWithModificationTimeJibExtension

**/resources/**
**/static/**
**/*${project.parent.artifactId}*.jar

...

```

## Example

If we had a layers organized like this:

```
- layer1
- a.file
- b.file
- c.file
- layer2
- d.file
- e.file
- layer3
- f.file
```

and we ran the plugin with filter `**/a.file`, we'd end up with:

```
- layer1
- b.file
- c.file
- layer2
- d.file
- e.file
- layer3
- f.file
- layerWithModificationTime
- a.file
```

while running the plugin with filter `**/f.file` would result in:

```
- layer1
- a.file
- b.file
- c.file
- layer2
- d.file
- e.file
- layerWithModificationTime
- f.file
```

## Interesting reads
- [JIB FAQ on reproducible builds](https://github.com/GoogleContainerTools/jib/blob/master/docs/faq.md#why-is-my-image-created-48-years-ago)
- [Reproducible builds](https://reproducible-builds.org/)
- [GitHub discussion](https://github.com/GoogleContainerTools/jib/issues/2021)

## Requirements:

- Java 11
- Maven

## Contributing

If you have an idea for a new feature or want to report a bug please use the issue tracker.

Pull requests are welcome!

## License

This library is licensed under the [Apache License, Version 2.0](/LICENSE).