Lowering memory consumption for lab 15.1 on anynines a9s 1G free tier

andrewmoore

If you are on the free tier of anynines, you'll find that by using the java_buildpack, you will be unable to run all three roster , web-ui , and rate-limit apps on the 1GB memory limit.

Instead, you can combine custom parameters to the java buildpack along with cf scale, to decrease the memory footprint and therefore stay within quota.

If you don't do this, when you cf push the app, it will complain about memory quota.

memory quota_exceeded
FAILED

If you simply scale down the memory limit, it will crash on launching the instance

name:              rate-limit
requested state:   started
routes:            
last uploaded:     Thu 04 Feb 11:26:16 AEDT 2021
stack:             cflinuxfs3
buildpacks:        
    name             version                                                            detect output   buildpack name
    java_buildpack   v4.35-https://github.com/cloudfoundry/java-buildpack.git#895590c   java            java

type:           web
sidecars:       
instances:      0/1
memory usage:   128M
     state     since                  cpu    memory      disk        details
#0   crashed   2021-02-04T01:53:10Z   0.0%   0 of 128M   0 of 512M   

type:           task
sidecars:       
instances:      0/0
memory usage:   256M
There are no running instances of this process.

In the logs will be this similar message

   2021-02-04T13:08:32.79+1100 [APP/PROC/WEB/0] ERR Cannot calculate JVM memory configuration: There is insufficient memory remaining for heap. Memory available for allocation 128M is less than allocated memory 633090K (-XX:ReservedCodeCacheSize=240M, -XX:MaxDirectMemorySize=10M, -XX:MaxMetaspaceSize=121090K, -Xss1M * 250 threads)

Take this corrective action, by lowering the threads used in the memory calculator.
cf set-env roster JBP_CONFIG_OPEN_JDK_JRE '{ memory_calculator: { stack_threads: 10 } }'

Restage and scale the app

cf restage roster
cf scale roster -m 512M

Repeat for rate-limit
cf set-env rate-limit JBP_CONFIG_OPEN_JDK_JRE '{ memory_calculator: { stack_threads: 5 } }'

Restage and scale the app

cf restage rate-limit
cf scale rate-limit -m 425M

If you need to scale down any task memory limits, use the --process task argument, like so:
cf scale rate-limit -m 32M --process task

Source: https://github.com/cloudfoundry/java-buildpack#configuration-and-extension