The five guards

Five guards stop a container that uses too much of the server.

Too much memory: the kernel stops the process. Then Docker starts it again.

1 / 5

Ferry puts five guards around each container that it starts. Each guard has a default value.

The defaults

Guard	Default	Set with
Memory	512 MiB	The service or the datastore. If not set: `--default-memory-limit`
CPU	1 CPU	The service or the datastore. If not set: `--default-cpu-limit`
Processes	1024	`--pids-limit`
Logs	10 MiB × 3 files	`--log-max-size`, `--log-max-files`
Free disk	1 GiB free	`--min-free-disk`

The flags are options of ferryd. See Server defaults.

Containers do not share a limit. A service with 3 instances can use 3 times its limit, plus the limit of each job that runs.

A limit is a cap. It does not reserve memory or CPU. Ferry does not make sure that all the limits together fit on the server.

Resource limits

Each container has a limit of memory and CPU. One bad app cannot stop your server.

The memory limit

A memory limit is the most memory that one container can use.