Prometheus的relabel_configs和metric_relabel_configs解释及用法示例

配置释义

先看两个配置的所处位置： 

global:
    ......
# A list of scrape configurations.
scrape_configs:
  # The job name assigned to scraped metrics by default.
  - job_name: <job_name>
    ........
    # List of target relabel configurations.
    relabel_configs:
      [ - <relabel_config> ... ]

    # List of metric relabel configurations.
    metric_relabel_configs:
      [ - <relabel_config> ... ]

<relabel_config> relabel_config | Prometheus

# The source labels select values from existing labels. Their content is concatenated
# using the configured separator and matched against the configured regular expression
# for the replace, keep, and drop actions.
[ source_labels: '[' <labelname> [, ...] ']' ]

# Separator placed between concatenated source label values.
[ separator: <string> | default = ; ]

# Label to which the resulting value is written in a replace action.
# It is mandatory for replace actions. Regex capture groups are available.
[ target_label: <labelname> ]

# Regular expression against which the extracted value is matched.
[ regex: <regex> | default = (.*) ]

# Modulus to take of the hash of the source label values.
[ modulus: <int> ]

# Replacement value against which a regex replace is performed if the
# regular expression matches. Regex capture groups are available.
[ replacement: <string> | default = $1 ]

# Action to perform based on regex matching.
[ action: <relabel_action> | default = replace ]

区别：relabel_configs用于在抓取metrics之前修改target的已有标签，已有标签也即配置中的source_labels包括（可从Prometheus UI的target页面查看）__address__、__meta_filepath、__metrics_path__、__scheme__、job以及target中手动添加的其他标签。

metric_relabel_configs用于修改抓取后得到的metric的标签，可用的source_labels包括instance、job已经target中手动添加的其他标签。

用法示例

使用已有标签创建一个新标签

例如给指标添加一个IP标签，使用如下配置实现：

# relabel_config
  - job_name: 'node'
    file_sd_configs:
    - refresh_interval: 1m
      files:
      - node_targets.yml
    relabel_configs:
      - source_labels: ['__address__']
        regex: (.*):.*
        target_label: 'IP'

或者使用metric_relabel_configs，注意该配置不对up指标生效。

# metric_relabel_config
  - job_name: 'node'
    file_sd_configs:
    - refresh_interval: 1m
      files:
      - node_targets.yml
    metric_relabel_configs:
      - source_labels: ['instance']
        regex: (.*):.*
        target_label: 'IP'

给一组job中指标添加一个全新标签

例如添加一个公共标签env=“test”：

  - job_name: 'node'
    file_sd_configs:
    - refresh_interval: 1m
      files:
      - config/node_targets.yml
    relabel_configs:
      - target_label: 'env'
        replacement: 'test'

这里使用relabel_configs或者metric_relabel_configs均可，因为不涉及source_labels直接使用了字符串替代。