Let us take a close look at the mem_limit docker compose. At Bobares our Docker support services will give you d detailed note it and how the mem_lmit can help in memory management.

Docker Compose

Docker compose acts as a handy tool. When deploying your Dockerized application, it saves time and reduces errors. Running the entire stack, including the frontend, database server, and so on, from within a single container is usually not a good idea.

Use Docker Compose to easily spin up different containers to handle different workloads of an application. Each logically distinct workload is listed as a separate service. The frontend http server, for example, will be listed as a frontend service running an Apache or Nginx image as a container. A docker-compose.yml file can specify all of the services, their networking requirements, storage requirements, and so on. We will concentrate on memory utilization here.

mem_limit

Before getting into mem_limit docker compose let us take a look at mem_limit.  Memory Limit or mem-limit, in general, imposes an upper limit on the amount of memory that a Docker container can potentially use. A Docker container, like any other system process, can use the Docker host’s entire available memory by default. This can result in an Out-of-Memory-Exception, and the system may crash.

Even if this never happens, it can still deprive other processes (including other containers) of valuable resources, lowering performance. Memory Limits ensure that resource-hungry containers do not exceed a certain threshold. This restricts a poorly written application’s blast radius to a few containers rather than the entire host.

The mem_limit Docker compose file, this parameter corresponds to mem limit. This field is optional in Docker compose version 3 and must be specified in the ECS params file rather than the compose file. This field in Docker compose version 2 can be specified in either the compose or ECS params file. The value specified in the ECS params file takes precedence over the value specified in the compose file.

The “docker stats” command can be used to determine the mem_ limit set for running Docker containers. If the container name is “repository 1,” run the following command:

docker stats repository_1

CONTAINER CPU % MEM USAGE/LIMIT MEM % NET I/O
repository_1 1.93% 4.609 MiB/60 MiB 7.20% 1.832 KiB/648 B

Specifying mem_limits

Version 2

The option for version 2 for mem_limit docker compose is as follows. Type in the following:

version: '2.4'
services:
my-nginx:
image: nginx:latest
ports:
- "80:80"
mem_limit: 300m

The final line limits the size of the my-nginx service to 300MiB for mem_limit docker compose. Use k for KiB, g for GiB, and b for bytes only. The preceding number, however, must be an integer. Use values like 2.4m can’t be used, instead, use 2400k instead. Now, when running:

docker stat --all

CONTAINER ID  NAME
CPU%  MEM USAGE/LIMIT MEM % NET I/O   BLOCK I/O PIDS
44114d785d0a my-compose_my-nginx_1 0.00%  2.141MiB/300MiB 0.71% 1.16kB/0B    0B/0B   2

Version 3

To use version three, for mem_limit docker compose; Docker must be running in swarm mode. Enable it in the Docker settings menu for Windows and Mac. Linux users must execute docker swarm init. It is not, however, a required step, and if you have not enabled it, that is also fine. This section is for people who are already using swarm mode and can benefit from the newer version.

version: '3'
services:
my-nginx:
image: nginx:latest
ports:
- "80:80"
deploy:
resources:
limits:
memory: 300m
reservations:
memory: 100m

[Need assistance with similar queries? We are here to help]

Conclusion

To conclude, the mem_limit docker compose; The “docker stats” tool may be used to determine the RAM limit imposed for running Docker containers.