We have been using Heroku in the classroom to deploy a project developed by all the students together in each course. The project is different each year (examples at UdL-EPS-SoftArch · GitHub) and includes a Java Spring backend and an Angular frontend. The repositories include GitHub Actions to do CI/CD.
We are willing to migrate the CD part to fly.io using your free resources’ availability. For the moment, we have deployed the Spring API and attached it to a Postgres database for persistence. However, despite we limit the Spring JVM memory size using the following command:
/bin/sh -c java $JAVA_OPTS -Dspring.profiles.active=$PROFILE -jar app.jar
With JAVA_OPTS = “-Xmx214m -Xms128m”, the application is being killed continuously showing the following error:
[info] [ 17.753141] Out of memory: Killed process 520 (java) total-vm:2262688kB, anon-rss:201740kB, file-rss:0kB, shmem-rss:0kB, UID:0 pgtables:676kB oom_score_adj:0
This approach has been working with Heroku and their 512MB limit. Has anyone been able to run Spring on fly.io? Or is 256MB too low for it?
I’ve had some luck with using the openj9 jvm based docker image (eg ibm-semeru-runtimes:open-17-jre-focal) for jvm apps to make them (barely) fit in 256MB, where a hotspot based jvm (eg eclipse-temurin:17-jre-jammy) continuously hit the memory limit. fwiw I’m running with -XX:MaxRAM=70m which appeared to give the minimum heap for my app to start up successfully, and still get an average mem usage near the limit (currently @ 227 MB/232 MB)
I am facing the exactly same problem! I am trying to deploy a docker image of my application which is an angular + spring boot. My app only startup when I defined JAVA_OPS = " -Xmx214m -Xms128m” as you did. But my application which is using java 11 failed to startup complete because out of memory, showing the following message:
[info] [ 194.978636] Out of memory: Killed process 515 (java) total-vm:2224432kB, anon-rss:201256kB, file-rss:0kB, shmem-rss:0kB, UID:1000 pgtables:660kB oom_score_adj:0
I read in another forum post (https://community.fly.io/t/oom-errors-on-free-tier-on-a-bare-application/2621/2) that the " total-vm:2224432kB" meaning which is needed to startup, so is it need 2GB RAM?
@jjjoooeee could you share your Dockerfile config, please?
it’s pretty barebones, just running a shaded jar:
FROM ibm-semeru-runtimes:open-17-jre-focal
ARG CURRENT_VERSION
ADD server/target/server-${CURRENT_VERSION}-shaded.jar /app/server.jar
ENV PORT 8080
EXPOSE 8080
CMD java -XX:MaxRAM=70m -jar /app/server.jar
Thank you very much for your reply! As soon I try it out I will share the results with you 
It works as you said! My dockerfile to make it works:
FROM ibm-semeru-runtimes:open-11-jre-focal
MAINTAINER https://renanfranca.github.io/about.html
COPY target/baby-0.0.1-SNAPSHOT.jar baby-0.0.1-SNAPSHOT.jar
ENV _JAVA_OPTIONS="-XX:MaxRAM=70m"
CMD java $_JAVA_OPTIONS -Dspring.profiles.active=$SPRING_PROFILES_ACTIVE -Dspring.datasource.url=$SPRING_DATASOURCE_URL -Dspring.liquibase.url=$SPRING_LIQUIBASE_URL -Dspring.datasource.username=$SPRING_DATASOURCE_USERNAME -Dspring.datasource.password=$SPRING_DATASOURCE_PASSWORD -jar baby-0.0.1-SNAPSHOT.jar
I had a hard time because of the database URL connection! The postgres url server was wrong if you use it with java springboot and I didn’t pay attention into it. So I change the prefix postgres to PostgreSQL: jdbc:postgresql://example-postgres.internal:5432/databasename
I can’t thank you enough!
I wrote a blog post about the process of publishing an angular + spring boot solution at flyio:
Deploy jhipster monolithic (angular + spring boot) at fly.io for FREE
I will share with you my experience to publish an angular + spring boot + postgres database solution into fly.io for FREE. I opened source the Baby Care App as monolithic to let you put your hands on the code as I explain the step-by-step.
as an additional note, things run much better after also enabling swap as per Swap memory - #2 by OldhamMade – was getting memory issues a bit after startup without swap, but seems to be much more stable with swap
