sysctl¶

Handler for the sysctl config.

This library allows your charm to create and configure sysctl options to the machine.

Validation and merge capabilities are added, for situations where more than one application are setting values. The following files can be created:

/etc/sysctl.d/90-juju-<app-name>

Requirements from one application requesting to configure the values.
/etc/sysctl.d/95-juju-sysctl.conf

Merged file resulting from all other 90-juju-* application files.

A charm using the sysctl lib will need a data structure like the following:

{
    "vm.swappiness": "1",
    "vm.max_map_count": "262144",
    "vm.dirty_ratio": "80",
    "vm.dirty_background_ratio": "5",
    "net.ipv4.tcp_max_syn_backlog": "4096",
}

Now, it can use that template within the charm, or just declare the values directly:

from charmlibs import sysctl

class MyCharm(CharmBase):

    def __init__(self, *args):
        ...
        self.sysctl = sysctl.Config(self.meta.name)

        self.framework.observe(self.on.install, self._on_install)
        self.framework.observe(self.on.remove, self._on_remove)

    def _on_install(self, _):
        # Alternatively, read the values from a template
        sysctl_data = {"net.ipv4.tcp_max_syn_backlog": "4096"}}

        try:
            self.sysctl.configure(config=sysctl_data)
        except (sysctl.ApplyError, sysctl.ValidationError) as e:
            logger.error(f"Error setting values on sysctl: {e.message}")
            self.unit.status = BlockedStatus("Sysctl config not possible")
        except sysctl.CommandError:
            logger.error("Error on sysctl")

    def _on_remove(self, _):
        self.sysctl.remove()