Add node-observ-lib (#25)

* Add node-observ-lib

* Remove trends support (not in 10.0 schema)

* Make filteringSelector for logs dashboard configurable

* Temp change dependency (until PR is merged for commonlib)

* Refactor config

* Update jsonnetfile.json

* Update README

* Add separate loki example

* Add sep file example

Author: v-zhuravlev

docs/node-observ-lib/README.md

@@ -0,0 +1,163 @@
+# Node exporter observability lib
+
+This jsonnet observability lib can be used to generate observability package for node exporter.
+
+## Import
+
+```sh
+jb init
+jb install https://github.com/grafana/node_exporter/docs/node-observ-lib
+```
+
+## Examples
+
+### Example 1: Basic example
+
+You can use observ-lib to fill in monitoring-mixin structure:
+
+```jsonnet
+// mixin.libsonnet file
+local nodelib = import 'node-observ-lib/main.libsonnet';
+
+local linux =
+  nodelib.new()
+  + nodelib.withConfigMixin({
+    filteringSelector: 'job=~".*node.*"',
+    groupLabels: ['job'],
+    instanceLabels: ['instance'],
+    dashboardNamePrefix: 'Node exporter / ',
+    dashboardTags: ['node-exporter-mixin'],
+    uid: 'node',
+    // enable loki logs
+    enableLokiLogs: true,
+  });
+
+{
+  grafanaDashboards+:: linux.grafana.dashboards,
+  prometheusAlerts+:: linux.prometheus.alerts,
+  prometheusRules+:: linux.prometheus.recordingRules,
+}
+
+```
+
+### Example 2: Fill in monitoring-mixin with default config values and enable loki logs:
+
+
+```jsonnet
+// mixin.libsonnet file
+local nodelib = import 'node-observ-lib/main.libsonnet';
+
+local linux =
+  nodelib.new()
+  + nodelib.withConfigMixin({
+    enableLokiLogs: true,
+  });
+
+{
+  grafanaDashboards+:: linux.grafana.dashboards,
+  prometheusAlerts+:: linux.prometheus.alerts,
+  prometheusRules+:: linux.prometheus.recordingRules,
+}
+
+```
+
+### Example 3: Override some of default config values from file:
+
+
+```jsonnet
+// overrides.libsonnet
+{
+  // Memory utilzation (%) level on which to trigger the
+  // 'NodeMemoryHighUtilization' alert.
+  memoryHighUtilizationThreshold: 80,
+
+  // Threshold for the rate of memory major page faults to trigger
+  // 'NodeMemoryMajorPagesFaults' alert.
+  memoryMajorPagesFaultsThreshold: 1000,
+
+  // Disk IO queue level above which to trigger
+  // 'NodeDiskIOSaturation' alert.
+  diskIOSaturationThreshold: 20,
+}
+
+// mixin.libsonnet file
+local configOverride = import './overrides.libsonnet';
+local nodelib = import 'node-observ-lib/main.libsonnet';
+
+local linux =
+  nodelib.new()
+  + nodelib.withConfigMixin(configOverride);
+
+{
+  grafanaDashboards+:: linux.grafana.dashboards,
+  prometheusAlerts+:: linux.prometheus.alerts,
+  prometheusRules+:: linux.prometheus.recordingRules,
+}
+
+```
+
+### Example 4: Modify specific panel before rendering dashboards
+
+```jsonnet
+local g = import './g.libsonnet';
+// mixin.libsonnet file
+local nodelib = import 'node-observ-lib/main.libsonnet';
+
+local linux =
+  nodelib.new()
+  + nodelib.withConfigMixin({
+    filteringSelector: 'job=~".*node.*"',
+    groupLabels: ['job'],
+    instanceLabels: ['instance'],
+    dashboardNamePrefix: 'Node exporter / ',
+    dashboardTags: ['node-exporter-mixin'],
+    uid: 'node',
+  })
+  + {
+      grafana+: {
+        panels+: {
+          networkSockstatAll+:
+            + g.panel.timeSeries.fieldConfig.defaults.custom.withDrawStyle('bars')
+        }
+      }
+    };
+
+{
+  grafanaDashboards+:: linux.grafana.dashboards,
+  prometheusAlerts+:: linux.prometheus.alerts,
+  prometheusRules+:: linux.prometheus.recordingRules,
+}
+
+```
+
+## Collectors used:
+
+Grafana Agent or combination of node_exporter/promtail can be used in order to collect data required.
+
+### Logs collection
+
+Loki logs are used to populate logs dashboard and also for annotations.
+
+To use logs, you need to opt-in, with setting `enableLokiLogs: true` in config.
+
+See example above.
+
+The following scrape snippet can be used in grafana-agent/promtail:
+
+```yaml
+    - job_name: integrations/node_exporter_journal_scrape
+      journal:
+        max_age: 24h
+        labels:
+          instance: '<your-instance-name>'
+          job: integrations/node_exporter
+      relabel_configs:
+      - source_labels: ['__journal__systemd_unit']
+        target_label: 'unit'
+      - source_labels: ['__journal__boot_id']
+        target_label: 'boot_id'
+      - source_labels: ['__journal__transport']
+        target_label: 'transport'
+      - source_labels: ['__journal_priority_keyword']
+        target_label: 'level'
+```