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Tiny Maven Proxy

Is exactly what it says it is - a tiny proxy server for Maven, which you can run on your local network. The only thing it does (at present) is proxy stuff Maven downloads and cache it.

If you have a slow-ish internet connection, and you have multiple machines or a team that will all be building and downloading, this is the project for you.

It is a tiny server you can run with java -jar somewhere on your network, and configure Maven to use. It is written with acteur and Netty, meaning that it is asynchronous, with a small memory footprint and low memory usage (microscopic if you're used to Java EE - -Xmx16M is reasonable).

By default it runs on port 5956. It has a minimal web-ui.

You give it a list of repository URLs to proxy, and a folder to cache files in, and run it. Then configure your ~/.m2/settings.xml to use it. That's all.

Download a recent build here

Configuration

There are two properties you'll want to set. You can either set them from the command-line, or in a tiny-maven-proxy.properties file that can live in /etc, /opt/local/etc, /~ or ./ (these override each other in that order).

Example

java -jar tiny-maven-proxy.jar --maven.dir /var/lib/maven --mirror https://repo1.maven.org/maven2,http://bits.netbeans.org/maven2/

or you could create /etc/tiny-maven-proxy.properties and put in it:

maven.dir=/var/lib/maven
mirror=https://repo1.maven.org/maven2,http://bits.netbeans.org/maven2/

Other properties that affect Acteur that may be useful:

• port - the port to run on
• cors.enabled - whether or not to answer CORS preflight requests affirmitively - on by default
• workerThreads - the number of threads used to answer requests (one thread can work on multiple requests at a time with netty, so 4-8 is usually enough)
• log.file - log to a file

Defaults

If maven.dir is not set, it will create a /maven directory in the system temporary dir (on most OSs this is wiped on reboot).

The following is the list of Maven repositories it proxies by default, if you do not set the mirror setting:

* https://repo1.maven.org/maven2
* http://bits.netbeans.org/maven2/
* http://bits.netbeans.org/nexus/content/repositories/snapshots/
* https://timboudreau.com/builds/plugin/repository/everything/
* https://maven.java.net/content/groups/public/
* https://oss.sonatype.org/

What This Project Is Not

It is not a full-featured Maven proxy, such as Nexus or Artifactory. Those are great if you need to manage complex mirroring setups, authentication, etc.

It does no authentication, validation, checksum checking (but your Maven client will, so you'll get the same result as if you'd downloaded things directly).

Indexing

IDEs and other tools will try to download a Nexus-style maven index. A companion project next to this makes it simple to automate index generation. It embeds the nexus-cli tool in a single fat-jar and runs it appropriately.

Since plexus depends on a version of Guice from the dawn of time, we cannot embed the indexer directly in tiny-maven-proxy. However, it is trivial to set up as a cron job. Here is an example crontab:

@hourly /usr/bin/java -jar /opt/tiny-maven-proxy/tiny-maven-indexer.jar --repositoryId dr.timboudreau.org --repositoryDir /space/maven/repository

To build it, simply build the companion project with mvn install, copy tiny-maven-indexer.jar to wherever you need it, and set it up to run periodically as the same user tiny-maven-proxy runs as on the target server.

Logging

The project uses bunyan-java for logging in JSON format - more about bunyan-java here. That makes it easy to collect metrics and stats and process log files using the bunyan command-line utility (to get that, install NodeJS and then run nbm install -g bunyan on the command-line).

To-Dos

• Clean out -SNAPSHOT dependencies periodically

Under The Hood

Tiny Maven Proxy uses netty-http-client for downloads, and acteur for the server piece. On a request for a non-cached file, it simultaneously attempts downloads from all the servers it knows about, and when one succeeds, cancels the others.

Command-line and configuration file management is done with giulius.

Footprint

While the default Java 64Mb heap is preferred, especially if the server will be heavily used, just to prove you can run this with a minimal memory footprint, you can run it and use it with an 7Mb heap - the following command-line sets up a JDK 8 vm appropriately:

java -XX:-UseConcMarkSweepGC -Xmx7M -jar tiny-maven-proxy.jar --log.level=fatal 
	--acteur.fork.join false --download.chunk.size 256

A bunch of care is taken to ensure as few memory copies as possible are performed, and that downloads are read and written chunk by chunk, so the whole file is never dragged into memory at once.

Hopefully this demonstrates what you can do with non-blocking I/O and a bit of care :-)