feat(mixin): Add grafana mixins support for postgres exporter

Signed-off-by: Kaviraj <kavirajkanagaraj@gmail.com>

postgres_mixin/.gitignore

@@ -0,0 +1,3 @@
+/alerts.yaml
+/rules.yaml
+dashboards_out

postgres_mixin/Makefile

@@ -0,0 +1,23 @@
+JSONNET_FMT := jsonnetfmt -n 2 --max-blank-lines 2 --string-style s --comment-style s
+
+default: build
+
+all: fmt lint build clean
+
+fmt:
+	find . -name 'vendor' -prune -o -name '*.libsonnet' -print -o -name '*.jsonnet' -print | \
+		xargs -n 1 -- $(JSONNET_FMT) -i
+
+lint:
+	find . -name 'vendor' -prune -o -name '*.libsonnet' -print -o -name '*.jsonnet' -print | \
+		while read f; do \
+			$(JSONNET_FMT) "$$f" | diff -u "$$f" -; \
+		done
+
+	mixtool lint mixin.libsonnet
+
+build:
+	mixtool generate all mixin.libsonnet
+
+clean:
+	rm -rf dashboards_out alerts.yaml rules.yaml

postgres_mixin/README.md

@@ -0,0 +1,26 @@
+# Postgres Mixin
+
+_This is a work in progress. We aim for it to become a good role model for alerts
+and dashboards eventually, but it is not quite there yet._
+
+The Postgres Mixin is a set of configurable, reusable, and extensible alerts and
+dashboards based on the metrics exported by the Postgres Exporter. The mixin creates
+recording and alerting rules for Prometheus and suitable dashboard descriptions
+for Grafana.
+
+To use them, you need to have `mixtool` and `jsonnetfmt` installed. If you
+have a working Go development environment, it's easiest to run the following:
+```bash
+$ go get github.com/monitoring-mixins/mixtool/cmd/mixtool
+$ go get github.com/google/go-jsonnet/cmd/jsonnetfmt
+```
+
+You can then build the Prometheus rules files `alerts.yaml` and
+`rules.yaml` and a directory `dashboard_out` with the JSON dashboard files
+for Grafana:
+```bash
+$ make build
+```
+
+For more advanced uses of mixins, see
+https://github.com/monitoring-mixins/docs.

postgres_mixin/go.mod

@@ -0,0 +1,3 @@
+module github.com/wrouesnel/postgres_exporter/postgres_mixin
+
+go 1.15

postgres_mixin/mixin.libsonnet

@@ -0,0 +1,13 @@
+{
+  grafanaDashboards: {
+    'postgres-overview.json': (import 'dashboards/postgres-overview.json'),
+  },
+
+  // Helper function to ensure that we don't override other rules, by forcing
+  // the patching of the groups list, and not the overall rules object.
+  local importRules(rules) = {
+    groups+: std.native('parseYaml')(rules)[0].groups,
+  },
+
+  prometheusAlerts+: importRules(importstr 'alerts/alerts.yaml'),
+}