Promtail receiver draft

[mar4uk]

Description:

Added new promtail receiver component. It is draft version just to feel how it could look like

Link to tracking Issue:
#9800

Documentation:

Currently this receiver supports scrape_config static_configs and scrape_configs loki_push_api. I didn't check other scrape_config targets (syslog, kubernetes, window_events), some additional fixes probably needed to make them work
The config file could look like:

receivers:
  promtail:
    config:
      positions:
        filename: /tmp/positions.yaml
        sync_period: 10s
      scrape_configs:
        - job_name: system
          static_configs:
            - labels:
                job: varlogs
                __path__: /var/log/example.log
        - job_name: push
          loki_push_api:
            server:
              http_listen_port: 3101
              grpc_listen_port: 3600
            labels:
              pushserver: push1
            use_incoming_timestamp: true
      target_config:
        sync_period: 10s

processors:
  batch:

exporters:
  logging:
    logLevel: debug
  loki:
    endpoint: "http://localhost:3100/loki/api/v1/push"
    labels:
      attributes:
        pushserver:
        foo:

service:
  pipelines:
    logs:
      receivers: [ promtail ]
      processors: [ batch ]
      exporters: [ logging, loki ]

To send logs to loki via collector we can run curl:

curl -i -XPOST -H "Content-Type: application/json" "http://localhost:3101/loki/api/v1/push" -d '{
  "streams": [
    {
      "stream": {
        "foo": "bar"
      },
      "values": [
          [ "1652782740000000000", "def" ]
      ]
    }
  ]
}'

To send logs to loki via collector we tail file example.log. It could be tested with command:

echo "May 04 11:45:56 Irinas-MBP login[87256]: USER_PROCESS: 87256 ttys012" >> example.log

Open question:

• do we need to implement the whole promtail functionality in collector? (considering we already have filelog, syslog and other receivers in collector already). Or instead of adding the full functional promtail receiver we can add few receivers that are currently missing in collector like lokireceiver (loki_push_api functionality), k8sreceiver ([kubernetes_sd_config](https://grafana.com/docs/loki/latest/clients/promtail/configuration/#kubernetes_sd_config functionality)

More context could be found in discussions:

• in slack https://cloud-native.slack.com/archives/C01N6P7KR6W/p1649822054450679
• in issue New component: receiver/promtailreceiver #9800

[github-actions]

This PR was marked stale due to lack of activity. It will be closed in 14 days.

[djaglowski]

Closing this per conclusion of #9800. I hope we can find a way to support this in the future without requiring a copyleft dependency.