open-telemetry / opentelemetry-demo

This documentation provides an in-depth look at how Docker is utilized within the development environment of the open-telemetry/opentelemetry-demo project. The focus is on the setup and use of Docker during the development phase, excluding any production-related aspects.

Dockerfile

The Dockerfile is critical for building the project using Docker. Below is an explanation of each part of the Dockerfile found in the repository.

FROM --platform=${BUILDPLATFORM} gradle:8-jdk17 AS builder

WORKDIR /usr/src/app/

COPY ./src/frauddetectionservice/ ./
COPY ./pb/ ./src/main/proto/
RUN gradle shadowJar

  1. Base Image: The Dockerfile begins with specifying a base image. Here, the Gradle image is being used, which has Java 17 installed. This image serves as the build environment.

  2. Working Directory: The WORKDIR instruction sets the working directory inside the container to /usr/src/app/. All subsequent commands will run from this directory.

  3. Copying Files: The COPY instructions replicate the necessary source files into the working directory. The contents of src/frauddetectionservice/ and protocol buffers located in pb/ are copied into the appropriate paths.

  4. Building the Application: The RUN gradle shadowJar command invokes Gradle to build the application and produce a shadow JAR file. This is crucial for combining all dependencies into a single executable JAR.

The second stage of the Dockerfile is as follows:

FROM gcr.io/distroless/java17-debian11

ARG OTEL_JAVA_AGENT_VERSION
WORKDIR /usr/src/app/

COPY --from=builder /usr/src/app/build/libs/frauddetectionservice-1.0-all.jar ./
ADD --chmod=644 https://github.com/open-telemetry/opentelemetry-java-instrumentation/releases/download/v$OTEL_JAVA_AGENT_VERSION/opentelemetry-javaagent.jar /app/opentelemetry-javaagent.jar
ENV JAVA_TOOL_OPTIONS=-javaagent:/app/opentelemetry-javaagent.jar

ENTRYPOINT [ "java", "-jar", "frauddetectionservice-1.0-all.jar" ]

  1. Distroless Image: The second stage uses a distroless image optimized for Java applications. This results in a smaller container size while eliminating unnecessary operating system components.

  2. Arguments: The ARG OTEL_JAVA_AGENT_VERSION line allows for passing in the version of the OpenTelemetry Java agent during the build process.

  3. Copying the JAR: The built shadow JAR file created in the previous stage is copied into this stage for runtime.

  4. Adding OpenTelemetry Java Agent: The ADD command fetches the OpenTelemetry Java agent from the specified URL and places it in the container. The --chmod=644 flag sets the permissions for the file.

  5. Setting Java Options: The ENV JAVA_TOOL_OPTIONS sets environment variables for Java, instructing it to use the OpenTelemetry agent when launching the application.

  6. Entry Point: Finally, the ENTRYPOINT command specifies how the container will be executed. It instructs Docker to run java -jar frauddetectionservice-1.0-all.jar.

Makefile

A Makefile is used to facilitate various development tasks, including building and managing the Docker images. Below is an excerpt regarding its usage:

The specific contents of the Makefile are not provided here, but it typically contains targets for building the Docker containers, managing dependencies, and executing tests.

The Makefile can include commands like the following:

build:
    docker build -t frauddetectionservice .

Here, the build target utilizes docker build to create an image called frauddetectionservice using the current directory’s Dockerfile.

By using the above definitions, developers can effectively utilize Docker in their development environment, managing dependencies, and compiling code in an isolated setting.

Sources: The code definitions and configuration details have been extracted directly from the project repository.