Introduction

The aim of this repo is to measure some features of a Micronaut application and its Docker image. Instead of creating a new Micronaut demo from scratch, it is based on Micronaut migration of Spring PetClinic.

Size

Spring Boot artifact's size

Build PetClinic application:

git clone https://github.com/wearearima/micronaut-docker-study.git
cd micronaut-docker-study
./mvnw clean package

Measure the jar files:

ls -lh target/*.jar*

Result:

-rw-r--r--  1 inigotelleria  staff    37M Sep 18 22:12 target/micronaut-petclinic-0.1.0.BUILD-SNAPSHOT.jar
-rw-r--r--  1 inigotelleria  staff   637K Sep 18 22:12 target/original-micronaut-petclinic-0.1.0.BUILD-SNAPSHOT.jar

The file named micronaut-petclinic-0.1.0.BUILD-SNAPSHOT is the resulting fat jar because it includes PetClinic's code and its dependencies. The other file, prefixed .original, is just PetClinic's code without its dependencies. The result is that our code size is 637K and the dependencies' 37M.

Docker image's size

Build PetClinic's Docker image:

./mvnw jib:dockerBuild

Measure the image size:

docker image ls | grep micronaut-petclinic

Result:

micronaut-petclinic                                              0.1.0.BUILD-SNAPSHOT    7607b6166a45        49 years ago        129MB

We can see that size of the artifact has increased from 36M to 129MB. This is mainly because the Docker image includes the JDK and Linux images. Run this command to check it:

docker image history micronaut-petclinic:0.1.0.BUILD-SNAPSHOT

The result shows the different layers added to the Docker image:

[micronaut-docker-study] docker image history micronaut-petclinic:0.1.0.BUILD-SNAPSHOT                                                                                                                                                                       master  ✭ ✱
IMAGE               CREATED             CREATED BY                                      SIZE                COMMENT
7607b6166a45        49 years ago        jib-maven-plugin:1.5.1                          598kB               classes
<missing>           49 years ago        jib-maven-plugin:1.5.1                          936kB               resources
<missing>           49 years ago        jib-maven-plugin:1.5.1                          432kB               snapshot dependencies
<missing>           49 years ago        jib-maven-plugin:1.5.1                          37.2MB              dependencies
<missing>           3 days ago          /bin/sh -c #(nop)  ENV JAVA_HOME=/opt/java/o…   0B                  
<missing>           3 days ago          /bin/sh -c set -eux;     apk add --no-cache …   75.7MB              
<missing>           3 days ago          /bin/sh -c #(nop) COPY multi:cf4be6a9ef2b0c0…   15.6kB              
<missing>           3 days ago          /bin/sh -c #(nop)  ENV JAVA_VERSION=jdk8u222…   0B                  
<missing>           3 days ago          /bin/sh -c apk add --no-cache --virtual .bui…   8.88MB              
<missing>           3 days ago          /bin/sh -c #(nop)  ENV LANG=en_US.UTF-8 LANG…   0B                  
<missing>           4 weeks ago         /bin/sh -c #(nop)  CMD ["/bin/sh"]              0B                  
<missing>           4 weeks ago         /bin/sh -c #(nop) ADD file:fe64057fbb83dccb9…   5.58MB     

The 5.58MB image is the Alpine Linux image and the 75.7MB image is the JDK8 image. The sum of all layers results in an image of 129MB which includes Linux OS, JDK8, PetClinic's code and dependencies' jar.

Different Linux image comparison at https://github.com/gliderlabs/docker-alpine#why

Startup time

Before running PetClinic application the database must be started with this command:

docker-compose run --publish 5432:5432 db 

Afterwards, run PetClinic application with this command:

java -jar target/micronaut-petclinic-0.1.0.BUILD-SNAPSHOT.jar

The applications starts in 2,31 seconds using AdoptOpenJDK 1.8.0_222-b10:

Startup completed in 2310ms. Server Running: http://localhost:8080

Memory usage

After navigating through the application to make sure all beans are loaded, open JConsole or other profiler such as YourKit. Measure the heap after executing Garbage Collector (GC).

With no load the application's heap consumption is around 60MB . However, the memory consumption is bigger than just the heap, so let's measure it using ps command:

[micronaut-docker-study] ps aux 14526
USER    PID  %CPU %MEM      VSZ    RSS   TT  STAT STARTED      TIME COMMAND
inigo    14526   0.0  3.3 10414692 561908 s005  S+   10:17PM   0:10.81 /usr/bin/java -jar target/micronaut-petclinic-0.1.0.BUILD-SNAPSHOT.jar

We can see that PetClinic's process actually is using almost 560MB of memory.

Summary

Feature	Micronaut 1.2.2
Micronaut App disk usage	37M
Micronaut App disk usage (without dependencies)	637KB
Docker Container disk usage	129MB
Micronaut App startup time	2,31 seconds
Micronaut App heap consumption	60MB
Micronaut App memory usage	560MB

Credits

Original PetClinic by https://www.spring.io

Micronaut PetClinic by Graeme Rocher github repository