crush-157 / hand-made

hand-made

This is an example to show how to add a local jar (i.e. not in a central Maven repository) to a Java Fn function.

To do this you need to do a Docker Multi - Stage build.

At the build stage, you will:

• add the local jar(s),
• install them into the Maven repository within the build container
• update the pom.xml
• run the Maven build

For the production stage, you copy the output of the build stage into the new image and update the CMD

This method only copies the runtime libraries from the fn-java-fdk image and so should work for jars that have been compiled using a later version of the JDK than is used in the FDK images.

Dockerfile

There is an example Dockerfile for each of the two functions in the repository.

They are very similar, so let's walk through the Dockerfile for online-order:

Builder

We need to run a Maven build, so start with:

FROM maven as builder

Local jar(s)

Set WORKDIR, copy in local jars and install them into the local Maven repository:

WORKDIR /fn-build/local-jars

# Copy in local jars from either another image or local filesystem
COPY ice-cream-1.0-SNAPSHOT.jar .

# Install each local jar into maven repository
RUN mvn install:install-file -Dfile=ice-cream-1.0-SNAPSHOT.jar \
  -DgroupId=com.oracle.emeatechnology -DartifactId=icecream \
  -Dversion=1.0 -Dpackaging=jar -DgeneratePom=true

Project files

Copy in the source and the pom.xml files for the project. The pom.xml must contain a dependency for each local jar.

# Copy in project files
WORKDIR /fn-build
COPY src src
COPY pom.xml .
# **Note:**
# The pom.xml file needs to reference the local jars as dependencies
# using the groupId, artifactId and version specified in the `mvn install`

Maven build

Then run the maven build in the builder stage.

# Run the maven build
RUN ["mvn", "package", "dependency:copy-dependencies", \
     "-DincludeScope=runtime", "-Dmdep.prependGroupId=true",\
     "-DoutputDirectory=target", "--fail-never"]

Runtime source

We need some libraries from the Fn Java FDK, and the easiest way to get them is from the fn-java-fdk image.

# Source for runtime jars and native library (libfnunixsocket.so)
FROM fnproject/fn-java-fdk as runtime-source

Runtime image

We need an up to date runtime image. In this case, we're using JDK14 on Oracle Linux.

We copy in the runtime libraries from the runtime-source stage, and the app and dependencies from the builder.

FROM openjdk:14.0.1-jdk-oraclelinux7
WORKDIR /function

# Copy in the runtime folder from the Fn Java base image
COPY --from=runtime-source /function/runtime/ /function/runtime

# Copy in the app and dependencies
COPY --from=builder /fn-build/target/*.jar /function/app/

Entrypoint

Set the ENTRYPOINT for the container, taking particular note of the java.library.path and classpath (-cp).

# Set the entrypoint for the image, making sure to include:
# -Djava.library.path (points to libfnunixsocket.so)
# -cp (classpath) entries for
#  /function/app/*
#  /function/runtime/*
ENTRYPOINT [ "java", \
     "-XX:-UsePerfData", \
     "-XX:+UseSerialGC", "-Xshare:on", \
     "-Djava.awt.headless=true" , \
     "-Djava.library.path=/function/runtime/lib", \
     "-cp", "/function/app/*:/function/runtime/*", \
     "com.fnproject.fn.runtime.EntryPoint" ]

Command (CMD)

Set the command to indicate the class and method that should be executed for the function.

CMD ["com.example.fn.OnlineOrder::handleRequest"]

Create a function

You want Fn to build the function using your custom Dockerfile. To do this run fn init:

$ fn init                                             [15:12:18]
Dockerfile found. Using runtime 'docker'.
func.yaml created.
$ cat func.yaml                                       [15:13:12]
schema_version: 20180708
name: online-order
version: 0.0.1
runtime: docker

Check that you can build from the Dockerfile: fn build --verbose

Deploy the function

if fn build --verbose works, then run fn deploy, e.g.

fn deploy --app hand-made
$ fn invoke hand-made online-order < bubblegum.json
14.3

Sadly, you don't get an ice cream :-(

Example

For a working example, see the code in this repository.