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docs/vmalert.md

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+## VM Alert
+
+`vmalert` executes a list of given MetricsQL expressions (rules) and
+sends alerts to [Alert Manager](https://github.com/prometheus/alertmanager).   
+
+### Features:
+* Integration with [VictoriaMetrics](https://github.com/VictoriaMetrics/VictoriaMetrics) TSDB;
+* VictoriaMetrics [MetricsQL](https://github.com/VictoriaMetrics/VictoriaMetrics/wiki/MetricsQL)
+ expressions validation;
+* Prometheus [alerting rules definition format](https://prometheus.io/docs/prometheus/latest/configuration/alerting_rules/#defining-alerting-rules)
+ support;
+* Integration with [Alertmanager](https://github.com/prometheus/alertmanager);
+* Lightweight without extra dependencies.
+
+### TODO:
+* Persist alerts state as timeseries in TSDB. Currently, alerts state is stored
+in process memory only and will be lost on restart;
+* Configuration hot reload.
+
+### QuickStart
+
+To build `vmalert` from sources:
+```
+git clone https://github.com/VictoriaMetrics/VictoriaMetrics
+cd VictoriaMetrics
+make vmalert
+```
+The build binary will be placed to `VictoriaMetrics/bin` folder.
+
+To start using `vmalert` you will need the following things:
+* list of alert rules - PromQL/MetricsQL expressions to execute;
+* datasource address - reachable VictoriaMetrics instance for rules execution;
+* notifier address - reachable Alertmanager instance for processing, 
+aggregating alerts and sending notifications.
+
+Then configure `vmalert` accordingly:
+```
+./bin/vmalert -rule=alert.rules \
+		-datasource.url=http://localhost:8428 \
+        -notifier.url=http://localhost:9093
+```
+
+Example for `.rules` file may be found [here](https://github.com/VictoriaMetrics/VictoriaMetrics/blob/master/app/vmalert/testdata/rules0-good.rules)
+
+`vmalert` runs evaluation for every group in a separate goroutine.
+Rules in group evaluated one-by-one sequentially. 
+
+`vmalert` also runs a web-server (`-httpListenAddr`) for serving metrics and alerts endpoints:
+* `http://<vmalert-addr>/api/v1/alerts` - list of all active alerts;
+* `http://<vmalert-addr>/api/v1/<groupName>/<alertID>/status" ` - get alert status by ID.
+Used as alert source in AlertManager.
+* `http://<vmalert-addr>/metrics` - application metrics.
+
+### Configuration
+
+The shortlist of configuration flags is the following:
+```
+Usage of vmalert:
+  -datasource.url string
+        Victoria Metrics or VMSelect url. Required parameter. e.g. http://127.0.0.1:8428
+  -datasource.basicAuth.password string
+        Optional basic auth password to use for -datasource.url
+  -datasource.basicAuth.username string
+        Optional basic auth username to use for -datasource.url
+  -evaluationInterval duration
+        How often to evaluate the rules. Default 1m (default 1m0s)
+  -external.url string
+        External URL is used as alert's source for sent alerts to the notifier
+  -httpListenAddr string
+        Address to listen for http connections (default ":8880")
+  -notifier.url string
+        Prometheus alertmanager URL. Required parameter. e.g. http://127.0.0.1:9093
+  -remotewrite.url string
+        Optional URL to remote-write compatible storage where to write timeseriesbased on active alerts. E.g. http://127.0.0.1:8428
+  -rule value
+        Path to the file with alert rules. 
+        Supports patterns. Flag can be specified multiple times. 
+        Examples:
+         -rule /path/to/file. Path to a single file with alerting rules
+         -rule dir/*.yaml -rule /*.yaml. Relative path to all .yaml files in "dir" folder, 
+        absolute path to all .yaml files in root.
+  -rule.validateTemplates
+        Indicates to validate annotation and label templates (default true)
+```
+
+Pass `-help` to `vmalert` in order to see the full list of supported 
+command-line flags with their descriptions.
+
+### Contributing
+
+`vmalert` is mostly designed and built by VictoriaMetrics community.
+Feel free to share your experience and ideas for improving this 
+software. Please keep simplicity as the main priority.