* Can add, remove and modify labels (aka tags) via Prometheus relabeling. Can filter data before sending it to remote storage. See [these docs](#relabeling) for details.
* Accepts data via all the ingestion protocols supported by VictoriaMetrics:
* Influx line protocol via `http://<vmagent>:8429/write`. See [these docs](https://github.com/VictoriaMetrics/VictoriaMetrics/blob/master/README.md#how-to-send-data-from-influxdb-compatible-agents-such-as-telegraf).
* Graphite plaintext protocol if `-graphiteListenAddr` command-line flag is set. See [these docs](https://github.com/VictoriaMetrics/VictoriaMetrics/blob/master/README.md#how-to-send-data-from-graphite-compatible-agents-such-as-statsd).
* OpenTSDB telnet and http protocols if `-opentsdbListenAddr` command-line flag is set. See [these docs](https://github.com/VictoriaMetrics/VictoriaMetrics/blob/master/README.md#how-to-send-data-from-opentsdb-compatible-agents).
* Prometheus remote write protocol via `http://<vmagent>:8429/api/v1/write`.
* JSON lines import protocol via `http://<vmagent>:8429/api/v1/import`. See [these docs](https://github.com/VictoriaMetrics/VictoriaMetrics/blob/master/README.md#how-to-import-time-series-data).
* Arbitrary CSV data via `http://<vmagent>:8429/api/v1/import/csv`. See [these docs](https://github.com/VictoriaMetrics/VictoriaMetrics/blob/master/README.md#how-to-import-csv-data).
Then send Influx data to `http://vmagent-host:8429`. See [these docs](https://github.com/VictoriaMetrics/VictoriaMetrics/blob/master/README.md#how-to-send-data-from-influxdb-compatible-agents-such-as-telegraf) for more details.
then `vmagent` can replace such Prometheus setup. Usually `vmagent` requires lower amounts of RAM, CPU and network bandwidth comparing to Prometheus for such setup.
See [these docs](#how-to-collect-metrics-in-prometheus-format) for details.
#### Replication and high availability
`vmagent` replicates the collected metrics among multiple remote storage instances configured via `-remoteWrite.url` args.
If a single remote storage instance temporarily goes out of service, then the collected data remains available in another remote storage instances.
`vmagent` buffers the collected data in files at `-remoteWrite.tmpDataPath` until the remote storage becomes available again.
Then it sends the buffered data to the remote storage in order to prevent data gaps in the remote storage.
#### Relabeling and filtering
`vmagent` can add, remove or update labels on the collected data before sending it to remote storage. Additionally,
it can remove unneeded samples via Prometheus-like relabeling before sending the collected data to remote storage.
See [these docs](#relabeling) for details.
#### Splitting data streams among multiple systems
`vmagent` supports splitting of the collected data among muliple destinations with the help of `-remoteWrite.urlRelabelConfig`,
which is applied independently for each configured `-remoteWrite.url` destination. For instance, it is possible to replicate or split
data among long-term remote storage, short-term remote storage and real-time analytical system [built on top of Kafka](https://github.com/Telefonica/prometheus-kafka-adapter).
Note that each destination can receive its own subset of the collected data thanks to per-destination relabeling via `-remoteWrite.urlRelabelConfig`.
Pass the path to `prometheus.yml` to `-promscrape.config` command-line flag. `vmagent` takes into account the following
sections from [Prometheus config file](https://prometheus.io/docs/prometheus/latest/configuration/configuration/):
*`global`
*`scrape_configs`
All the other sections are ignored, including [remote_write](https://prometheus.io/docs/prometheus/latest/configuration/configuration/#remote_write) section.
The following scrape types in [scrape_config](https://prometheus.io/docs/prometheus/latest/configuration/configuration/#scrape_config) section are supported:
*`static_configs` - for scraping statically defined targets. See [these docs](https://prometheus.io/docs/prometheus/latest/configuration/configuration/#static_config) for details.
*`file_sd_configs` - for scraping targets defined in external files aka file-based service discover.
See [these docs](https://prometheus.io/docs/prometheus/latest/configuration/configuration/#file_sd_config) for details.
File feature requests at [our issue tracker](https://github.com/VictoriaMetrics/VictoriaMetrics/issues) if you need other service discovery mechanisms to be supported by `vmagent`.
### Adding labels to metrics
Labels can be added to metrics via the following mechanisms:
* Via `global -> external_labels` section in `-promscrape.config` file. These labels are added only to metrics scraped from targets configured in `-promscrape.config` file.
* Via `-remoteWrite.label` command-line flag. These labels are added to all the collected metrics before sending them to `-remoteWrite.url`.
Additionally it provides the following extra actions:
*`replace_all`: replaces all the occurences of `regex` in the values of `source_labels` with the `replacement` and stores the result in the `target_label`.
*`labelmap_all`: replaces all the occurences of `regex` in all the label names with the `replacement`.
The relabeling can be defined in the following places:
* At `scrape_config -> relabel_configs` section in `-promscrape.config` file. This relabeling is applied to targets when parsing the file during `vmagent` startup
or during config reload after sending `SIGHUP` signal to `vmagent` via `kill -HUP`.
* At `scrape_config -> metric_relabel_configs` section in `-promscrape.config` file. This relabeling is applied to metrics after each scrape for the configured targets.
Read more about relabeling in the following articles:
* [Life of a label](https://www.robustperception.io/life-of-a-label)
* [Discarding targets and timeseries with relabeling](https://www.robustperception.io/relabelling-can-discard-targets-timeseries-and-alerts)
* [Dropping labels at scrape time](https://www.robustperception.io/dropping-metrics-at-scrape-time-with-prometheus)
* [Extracting labels from legacy metric names](https://www.robustperception.io/extracting-labels-from-legacy-metric-names)
* [relabel_configs vs metric_relabel_configs](https://www.robustperception.io/relabel_configs-vs-metric_relabel_configs)
### Monitoring
`vmagent` exports various metrics in Prometheus exposition format at `http://vmagent-host:8429/metrics` page. It is recommended setting up regular scraping of this page
either via `vmagent` itself or via Prometheus, so the exported metrics could be analyzed later.
`vmagent` also exports target statuses at `http://vmagent-host:8429/targets` page in plaintext format. This page also exports information on improperly configured scrape configs.
* When `vmagent` scrapes many unreliable targets, it can flood error log with scrape errors. These errors can be suppressed
by passing `-promscrape.suppressScrapeErrors` command-line flag to `vmagent`. The most recent scrape error per each target can be observed at `http://vmagent-host:8429/targets`.
It is recommended using [binary releases](https://github.com/VictoriaMetrics/VictoriaMetrics/releases) - `vmagent` is located in `vmutils-*` archives there.
