metrics: support relabel aggregate

[qiuqiu-007]

in order to aggregate metrics to node (or others) level, here add an optional to action, which is "aggregate_label". the usage is similar to action "drop_label". For example:

curl -X POST --header 'Content-Type: application/json' --header 'Accept: application/json' -d '[ \
   { \
     "source_labels": [ \
       "__name__" \
     ], \
     "action": "aggregate_label", \
     "target_label": "shard", \
     "regex": "column_family_live_sstable" \
   } \
 ]' 'http://localhost:10000/v2/metrics-config/'

Signed-off-by: qiulijuan2qiulijuan2_yewu@cmss.chinamobile.com

[amnonh]

I'm not sure if aggregate should be done on a metric level or on a metric family level, see my pr #2121

[qiuqiu-007]

I'm not sure if aggregate should be done on a metric level or on a metric family level, see my pr #2121

In my opinion, first of all, this way is convenient to set a single metric or a group metrics to be aggregated, so just add a function to relabel_config, secondly, it changes the minimum range of code.

[amnonh]

Most of the time, aggregation is on the metric family level, a single instance cannot be aggregated, which which metrics?
As far as I can tell, the code itself just adds a list of aggregate labels to a metric, but without changing the prometheus code it does not add any functionality.

Please do not merge

[qiuqiu-007]

In prometheus.cc, it seems that aggregate operation is done during http request ? And in registration time, it just sends the aggregate_labels arg to stored in map , right? @amnonh

[amnonh]

Prometheus takes the relabel from the metrics family, that's why it make more sense to put the configuration at that level

[qiuqiu-007]

Prometheus takes the relabel from the metrics family, that's why it make more sense to put the configuration at that level

Do u mean that add the aggregate_labels to struct of metric_info makes no sense, even thought send the aggregate_labels value to the metric_family_info ?

[qiuqiu-007]

@amnonh Here are three points I'm interested in :

• if update_aggregate_labels will be release in newer Scylla version, if yes, which version ?
• skip_when_empty is added to the relabel_config function, then why this aggregate_labels can not be an info added to metric_info? Both of them can be a member of metric label? What is the point to group metric level and metric_family level?
• How can I test Adding Metrics family config #2121 ? Is it similar to relabel_config which could update by http requests?

[qiuqiu-007]

ping @amnonh I am eager to receive your reply.