VictoriaMetrics/app/vmalert/README.md

vmalert

vmalert executes a list of given alerting or recording rules against configured address.

Features:

• Integration with VictoriaMetrics TSDB;
• VictoriaMetrics MetricsQL support and expressions validation;
• Prometheus alerting rules definition format support;
• Integration with Alertmanager;
• Lightweight without extra dependencies.

Limitations:

• vmalert execute queries against remote datasource which has reliability risks because of network. It is recommended to configure alerts thresholds and rules expressions with understanding that network request may fail;
• by default, rules execution is sequential within one group, but persisting of execution results to remote storage is asynchronous. Hence, user shouldn't rely on recording rules chaining when result of previous recording rule is reused in next one;
• there is no query function support in templates yet;
• vmalert has no UI, just an API for getting groups and rules statuses.

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 rules - PromQL/MetricsQL expressions to execute;
• datasource address - reachable VictoriaMetrics instance for rules execution;
• notifier address - reachable Alert Manager instance for processing, aggregating alerts and sending notifications.
• remote write address - remote write compatible storage address for storing recording rules results and alerts state in for of timeseries. This is optional.

Then configure vmalert accordingly:

./bin/vmalert -rule=alert.rules \
		-datasource.url=http://localhost:8428 \
        -notifier.url=http://localhost:9093

Configuration for recording and alerting rules is very similar to Prometheus rules and configured using YAML. Configuration examples may be found in testdata folder. Every rule belongs to group and every configuration file may contain arbitrary number of groups:

groups:
  [ - <rule_group> ]

Groups

Each group has following attributes:

# The name of the group. Must be unique within a file.
name: <string>

# How often rules in the group are evaluated.
[ interval: <duration> | default = global.evaluation_interval ]

# How many rules execute at once. Increasing concurrency may speed
# up round execution speed. 
[ concurrency: <integer> | default = 1 ]

rules:
  [ - <rule> ... ]

Rules

There are two types of Rules:

• alerting - Alerting rules allows to define alert conditions via MetricsQL and to send notifications about firing alerts to Alertmanager.
• recording - Recording rules allow you to precompute frequently needed or computationally expensive expressions and save their result as a new set of time series.

vmalert forbids to define duplicates - rules with the same combination of name, expression and labels within one group.

Alerting rules

The syntax for alerting rule is following:

# The name of the alert. Must be a valid metric name.
alert: <string>

# The MetricsQL expression to evaluate.
expr: <string>

# Alerts are considered firing once they have been returned for this long.
# Alerts which have not yet fired for long enough are considered pending.
[ for: <duration> | default = 0s ]

# Labels to add or overwrite for each alert.
labels:
  [ <labelname>: <tmpl_string> ]

# Annotations to add to each alert.
annotations:
  [ <labelname>: <tmpl_string> ]

vmalert has no local storage and alerts state is stored in process memory. Hence, after reloading of vmalert process alerts state will be lost. To avoid this situation, vmalert may be configured via following flags:

• -remoteWrite.url - URL to Victoria Metrics or VMInsert. vmalert will persist alerts state into the configured address in form of timeseries with name ALERTS via remote-write protocol.
• -remoteRead.url - URL to Victoria Metrics or VMSelect. vmalert will try to restore alerts state from configured address by querying ALERTS timeseries.

Recording rules

The syntax for recording rules is following:

# The name of the time series to output to. Must be a valid metric name.
record: <string>

# The MetricsQL expression to evaluate.
expr: <string>

# Labels to add or overwrite before storing the result.
labels:
  [ <labelname>: <labelvalue> ]

For recording rules to work -remoteWrite.url must specified.

WEB

vmalert runs a web-server (-httpListenAddr) for serving metrics and alerts endpoints:

• http://<vmalert-addr>/api/v1/groups - list of all loaded groups and rules;
• 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.
• http://<vmalert-addr>/-/reload - hot configuration reload.

Configuration

The shortlist of configuration flags is the following:

Usage of vmalert:
  -datasource.basicAuth.password string
        Optional basic auth password for -datasource.url
  -datasource.basicAuth.username string
        Optional basic auth username for -datasource.url
  -datasource.url string
        Victoria Metrics or VMSelect url. Required parameter. E.g. http://127.0.0.1:8428
  -evaluationInterval duration
        How often to evaluate the rules (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")
  -metricsAuthKey string
        Auth key for /metrics. It overrides httpAuth settings
  -notifier.url string
        Prometheus alertmanager URL. Required parameter. e.g. http://127.0.0.1:9093
  -remoteRead.basicAuth.password string
        Optional basic auth password for -remoteRead.url
  -remoteRead.basicAuth.username string
        Optional basic auth username for -remoteRead.url
  -remoteRead.lookback duration
        Lookback defines how far to look into past for alerts timeseries. For example, if lookback=1h then range from now() to now()-1h will be scanned. (default 1h0m0s)
  -remoteRead.url vmalert
        Optional URL to Victoria Metrics or VMSelect that will be used to restore alerts state. This configuration makes sense only if vmalert was configured with `remoteWrite.url` before and has been successfully persisted its state. E.g. http://127.0.0.1:8428
  -remoteWrite.basicAuth.password string
        Optional basic auth password for -remoteWrite.url
  -remoteWrite.basicAuth.username string
        Optional basic auth username for -remoteWrite.url
  -remoteWrite.concurrency int
        Defines number of readers that concurrently write into remote storage (default 1)
  -remoteWrite.maxBatchSize int
        Defines defines max number of timeseries to be flushed at once (default 1000)
  -remoteWrite.maxQueueSize int
        Defines the max number of pending datapoints to remote write endpoint (default 100000)
  -remoteWrite.url string
        Optional URL to Victoria Metrics or VMInsert where to persist alerts state in form of timeseries. 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.validateExpressions
        Whether to validate rules expressions via MetricsQL engine (default true)
  -rule.validateTemplates
        Whether 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.

To reload configuration without vmalert restart send SIGHUP signal or send GET request to /-/reload endpoint.

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.

How to build from sources

It is recommended using binary releases

• vmalert is located in vmutils-* archives there.

Development build

1. Install Go. The minimum supported version is Go 1.13.
2. Run make vmalert from the root folder of the repository. It builds vmalert binary and puts it into the bin folder.

Production build

1. Install docker.
2. Run make vmalert-prod from the root folder of the repository. It builds vmalert-prod binary and puts it into the bin folder.