Spring Cloud microservices memory usage

Question

I'm running multiple microservices (Spring cloud + docker) in small/medium machines on AWS and recently I found that these machines are often exhausted and need rebooting. I'm investigating the causes of this loss of power, thinking of possible memory leaks or misconfigurations on the instance/container.

I tried to limit the amount of memory these containers can use by doing:

docker run -m 500M --memory-swap 500M -d my-service:latest

At this point my service (standard spring cloud service with one single endpoint that writes stuff to a Redis DB, using spring-data-redis) didn't even start.

Increased the memory to 760M and it worked, but monitoring it with docker I see the minimum is:

CONTAINER           CPU %               MEM USAGE / LIMIT       MEM %               NET I/O             BLOCK I/O             PIDS
cd5f64aa371e        0.18%               606.9 MiB / 762.9 MiB   79.55%              102.4 MB / 99 MB    1.012 MB / 4.153 MB   60

I added some parameters to limit the JVM memory heap but it doesn't seem to reduce it very much:

_JAVA_OPTIONS: "-Xms8m -Xss256k -Xmx512m"

I'm running

• Spring Cloud Brixton.M5
• Spring Boot 1.3.2
• Java 8 (Oracle JVM)
• Docker
• Spring data Redis 1.7.1

Is there a reason why such simple service uses so much memory to run? Are there any features I should disable to improve that?

Answer 1

We've investigated a number of things in a similar setup in terms of the JVM itself. A quick way to save some memory if using Java 8 is to use the following options:

-Xms256m -Xmx512m -XX:-TieredCompilation -Xss256k -XX:+UseG1GC -XX:+UseStringDeduplication

The G1GC is well documented, the UseStringDeduplication reduces heap usage by de-duplicating the storage of Strings in the heap (we found about 20% in a JSON/XML web service type environment), and the TieredCompilation makes a big difference in the use of CodeCache (from 70Mb down to 10Mb), as well as about 10% less Metaspace at the expense of about 10% startup time.