feat: implement extra info (tag, field)

[c3y1huang]

longhorn/longhorn#5235

[innobead]

In general, LGTM.

Let Phan do the final review. Also, I am curious why kubernetes_version is able to collect now. I did not see the code here before this implementation. Or we use a different branch for Longhorn?

@PhanLe1010 Please do the review before merging.

[PhanLe1010]

Since we are creating continuous queries automatically for app developers. Suggesting to modify the documentation

upgrade-responder/README.md

Lines 128 to 153 in b5b3035

	### Add kubernetesVersion extra field
	For example, if you want to keep track of the number of your application instances by each Kubernetes version, you may want to include Kubernetes version into `extraInfo` in the request's body sent to Upgrade Responder server.
	The request's body may look like this:
	```json
	{
	"appVersion": "v0.8.1",
	"extraInfo": {
	"kubernetesVersion": "v1.19.1"
	}
	}
	```
	In order to display statical information about Kubernetes version on Grafana dashboard, you need to do:
	1. Create a continuous query in the InfluxDB to periodically group data by Kubernetes version
	```
	CREATE CONTINUOUS QUERY "cq_by_kubernetes_version_down_sampling" ON "<application-name>_upgrade_responder" BEGIN SELECT count("value") as total INTO "by_kubernetes_version_down_sampling" FROM "upgrade_request" GROUP BY time(1h),"kubernetes_version" END
	```
	where:
	* `cq_by_kubernetes_version_down_sampling` is the name of the new continuous query (chosen by you)
	* `<application-name>_upgrade_responder` is the name of the database prefixed by your application's name
	* `by_kubernetes_version_down_sampling` is the name of the new measurement (chosen by you)
	* `upgrade_request` is the original measurement where Upgrade Responder server records data to
	* `1h` is the query period. Make sure that this value is the same as `--query-period`
	* `kubernetes_version` is the tag to grouping data. This is derived from the camelcase form of `kubernetesVersion` to its snakecase form.
	1. Create a Grafana panel that pull data from the new measurement `by_kubernetes_version_down_sampling` similar to this:
	

Also, we need to update the Grafanar dashboard afterward.

[PhanLe1010]

After this PR, the upgrade-responder server will create a continuous query for each user-submitted tag value. This can potentially be abused by a malicious user sending a request with a lot of tags and crashing our database. I am thinking to verify the user-submitted data based on a config file similar to https://github.com/longhorn/upgrade-responder/blob/b5b303538e1e2920a97f0afb7e6fb1ce5e2ea143/config/response.json#L1-L26

This will be tracked at the ticket https://github.com/longhorn/upgrade-responder/issues/47

[innobead]

That's possible, especially right now this service is quite public and anonymous. It's better to use white list to achieve that.

[PhanLe1010]

I have created the PR #48 which contains the logic of this PR as well as the logic for user-data verification. Is it ok to use that PR in favor of this PR @c3y1huang @innobead? Thank you very much

[PhanLe1010]

Iwith this AddPoint() and the one below it, we are adding 2 points for 1 request which will make the number of node count double because the number of nodes == number of requests

[PhanLe1010]

I am thinking that the main focus for the extra tag info and extra field info is to understand the distribution of different values/settings currently. Therefore, I think we don't need to create continuous queries because we can use the data in the last hour to visualize all kind of distribution. What do you think?

[innobead]

I have created the PR #48 which contains the logic of this PR as well as the logic for user-data verification. Is it ok to use that PR in favor of this PR @c3y1huang @innobead? Thank you very much

I am OK with that. @c3y1huang WDYT?

[c3y1huang]

I have created the PR #48 which contains the logic of this PR as well as the logic for user-data verification. Is it ok to use that PR in favor of this PR @c3y1huang @innobead? Thank you very much

I am fine with this.