[vmalert] initial

app/vmalert/README.md

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+## VM Alert
+
+#### Abstract
+The application which accepts the alert rules, executes them on given source, sends(fires) an alert to(in) alert management system
+
+### Components
+
+#### Alert Config Reader
+It accepts yaml config as input parameter in Prometheus format, parses it into Go struct.
+
+#### Source Caller
+Create own watchdog for every alert group (goroutines), which executes alert query on given source and issues an alert if source returns non-empty result. 
+Source can be any service which supports PromQL (MetricsQL). 
+
+#### Alert Management System Provider
+Send positive alert to alert management system, provides interface for every concrete implementation.
+Should be ingratiated with Prometheus alertmanager. 
+
+open questions:
+- do we really need alert group or can just run every alert in own goroutine?
+
+#### Web Server
+Expose metrics
+
+open questions:
+- should the tool provide API or UI for managing alerting rules? Where to store config updated via the API or UI?
+- should the tool provide “alerting rules validation mode” for validating and debugging alerting rules? This mode is useful when creating and debugging alerting rules.
+
+#### Requirements:
+- Stateless
+- Avoid external dependencies if possible
+- Reuse existing code from VictoriaMetrics repo
+- Makefile rules for common tasks – see Makefiles for other apps in the app/ dir 
+- Every package should be covered by tests 
+- Dockerfile
+- Graceful shutdown 
+- Helm template
+- Application uses command line flags for configuration
+
+
+![vmalert](https://github.com/VictoriaMetrics/VictoriaMetrics/tree/master/app/vmalert/vmalert.png "vmalert")