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Improve cgroup_regex docs with examples (elastic#20425)
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Signed-off-by: chrismark <chrismarkou92@gmail.com>
(cherry picked from commit e48f5c8)
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ChrsMark committed Aug 4, 2020
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Expand Up @@ -72,23 +72,29 @@ field will be present in the output.

`host_path`:: (Optional) By default, the `host_path` field is set to the root
directory of the host `/`. This is the path where `/proc` is mounted. For
different runtime configurations of Kubernetes or Docker, the `host_path` can
different runtime configurations of Kubernetes or Docker, the `host_path` can
be set to overwrite the default.

`cgroup_prefixes`:: (Optional) By default, the `cgroup_prefixes` field is set
to `/kubepods` and `/docker`. This is the prefix where the container ID is
inside cgroup. For different runtime configurations of Kubernetes or Docker,
the `cgroup_prefixes` can be set to overwrite the defaults.

`cgroup_regex`:: (Optional) By default, the container id is extracted from
cgroup file based on `cgroup_prefixes`. This can be overwritten by specifying
regular expression with capture group for capturing container id from cgroup
path. For example: `^\/.+\/.+\/.+\/([0-9a-f]{64}).*`

`cgroup_cache_expire_time`:: (Optional) By default, the
`cgroup_regex`:: (Optional) By default, the container id is extracted from
cgroup file based on `cgroup_prefixes`. This can be overwritten by specifying
regular expression with capture group for capturing container id from cgroup
path. Examples:
. `^\/.+\/.+\/.+\/([0-9a-f]{64}).*` will match the container id of a cgroup
like `/kubepods/besteffort/pod665fb997-575b-11ea-bfce-080027421ddf/b5285682fba7449c86452b89a800609440ecc88a7ba5f2d38bedfb85409b30b1`
. `^\/.+\/.+\/.+\/docker-([0-9a-f]{64}).scope` will match the container id of a cgroup
like `/kubepods.slice/kubepods-burstable.slice/kubepods-burstable-pod69349abe_d645_11ea_9c4c_08002709c05c.slice/docker-80d85a3a585f1575028ebe468d83093c301eda20d37d1671ff2a0be50fc0e460.scope`
. `^\/.+\/.+\/.+\/crio-([0-9a-f]{64}).scope` will match the container id of a cgroup
like `/kubepods.slice/kubepods-burstable.slice/kubepods-burstable-pod69349abe_d645_11ea_9c4c_08002709c05c.slice/crio-80d85a3a585f1575028ebe468d83093c301eda20d37d1671ff2a0be50fc0e460.scope`

`cgroup_cache_expire_time`:: (Optional) By default, the
`cgroup_cache_expire_time` is set to 30 seconds. This is the length of time
before cgroup cache elements expire in seconds. It can be set to 0 to disable
the cgroup cache. In some container runtimes technology like runc, the
the cgroup cache. In some container runtimes technology like runc, the
container's process is also process in the host kernel, and will be affected by
PID rollover/reuse. The expire time needs to set smaller than the PIDs wrap
PID rollover/reuse. The expire time needs to set smaller than the PIDs wrap
around time to avoid wrong container id.

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