Add proc for using tolerations on local-storage-operator Pods

[bobfuru]

BZ 1781233
Borrowing some content from https://docs.openshift.com/container-platform/4.2/logging/config/cluster-logging-kibana.html#cluster-logging-kibana-tolerations_cluster-logging-kibana to explain taint terminology and usage.

Doc update to be merged to master and CP to enterprise-4.3.

[bobfuru]

@huffmanca and @liangxia PTAL

[openshift-docs-preview-bot]

The preview will be available shortly at:

• https://BZ1781233--ocpdocs.netlify.com/

[bobfuru]

@huffmanca I've made a few comments and applied your suggestions. Thanks for your feedback!

[liangxia]

From oc adm taint --help,
A taint consists of a key, value, and effect. As an argument here, it is expressed as key=value:effect.

[bobfuru]

From https://docs.openshift.com/container-platform/4.2/nodes/scheduling/nodes-scheduler-taints-tolerations.html:
An operator ('Equal' in the following example of this module) allows you to leave one of these parameters empty.

I added this clarification as a note just before the prereqs. @liangxia Could I get an ack if this looks good, please?

[liangxia]

User will met https://bugzilla.redhat.com/show_bug.cgi?id=1781520

[bobfuru]

User will met https://bugzilla.redhat.com/show_bug.cgi?id=1781520

@liangxia I see that this ^^ bug was closed ("will be fixed in master"). So, does this documentation as written look good from QE perspective?

[liangxia]

Fix in master(currently for 4.4) means it will not fix in 4.3

[bobfuru]

@liangxia I updated key:value in tolerations spec to match, as explained in <2> annotation. So, will it work in QE if it uses the Equal operator (as described in the note, "An operator allows you to leave one of these parameters empty")?

Based on BZ1781520, I don't understand if all three (key-value-effect) are required, even with Equal/Exists operator. If so, what do you suggest for doc changes?

[liangxia]

• A taint consists of a key, value, and effect. As an argument here, it is expressed as key=value:effect.
• The key must begin with a letter or number, and may contain letters, numbers, hyphens, dots, and underscores, up to
  253 characters.
• Optionally, the key can begin with a DNS subdomain prefix and a single '/', like example.com/my-app
• The value is optional. If given, it must begin with a letter or number, and may contain letters, numbers, hyphens,
  dots, and underscores, up to 63 characters.
• The effect must be NoSchedule, PreferNoSchedule or NoExecute.
• Currently taint can only apply to node.

I would like we state here that the taint is "key=value:effect", so customer does not forgot adding the effect. Or else, customer will met the confusing error message describe in above bug.

[liangxia]

And QE confirmed that Equal operator does work as stated below in <2> annotation.

[bobfuru]

Thanks, Liang. This makes more sense now. I made a couple of small tweaks to the wording so that it states key=value:effect. PTAL and confirm that it looks good:

[IMPORTANT]
====
Taints and tolerations consist of a key, value, and effect. As an argument, it is expressed as key=value:effect. An operator allows you to leave one of these parameters empty.
====

[bmcelvee]

LGTM!

[liangxia]

/lgtm

[bobfuru]

/cherrypick enterprise-4.3

[openshift-cherrypick-robot]

@bobfuru: new pull request created: #18693

Details

In response to this:

/cherrypick enterprise-4.3

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