vmagent

vmagent

vmagent is a tiny but brave agent, which helps you collect metrics from various sources and stores them in VictoriaMetrics or any other Prometheus-compatible storage system that supports the remote_write protocol.

Motivation

While VictoriaMetrics provides an efficient solution to store and observe metrics, our users needed something fast and RAM friendly to scrape metrics from Prometheus-compatible exporters to VictoriaMetrics. Also, we found that users’ infrastructure are snowflakes - no two are alike, and we decided to add more flexibility to vmagent (like the ability to push metrics instead of pulling them). We did our best and plan to do even more.

Features

• Can be used as drop-in replacement for Prometheus for scraping targets such as node_exporter. See Quick Start for details.
• Can add, remove and modify labels (aka tags) via Prometheus relabeling. Can filter data before sending it to remote storage. See these docs for details.
• Accepts data via all the ingestion protocols supported by VictoriaMetrics:
  • Influx line protocol via http://<vmagent>:8429/write. See these docs.
  • Graphite plaintext protocol if -graphiteListenAddr command-line flag is set. See these docs.
  • OpenTSDB telnet and http protocols if -opentsdbListenAddr command-line flag is set. See these docs.
  • 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.
  • Arbitrary CSV data via http://<vmagent>:8429/api/v1/import/csv. See these docs.
• Can replicate collected metrics simultaneously to multiple remote storage systems.
• Works in environments with unstable connections to remote storage. If the remote storage is unavailable, the collected metrics are buffered at -remoteWrite.tmpDataPath. The buffered metrics are sent to remote storage as soon as connection to remote storage is recovered. The maximum disk usage for the buffer can be limited with -remoteWrite.maxDiskUsagePerURL.
• Uses lower amounts of RAM, CPU, disk IO and network bandwidth compared to Prometheus.

Quick Start

Just download vmutils-* archive from releases page, unpack it and pass the following flags to vmagent binary in order to start scraping Prometheus targets:

• -promscrape.config with the path to Prometheus config file (it is usually located at /etc/prometheus/prometheus.yml)
• -remoteWrite.url with the remote storage endpoint such as VictoriaMetrics. The -remoteWrite.url argument can be specified multiple times in order to replicate data concurrently to an arbitrary amount of remote storage systems.

Example command line:

/path/to/vmagent -promscrape.config=/path/to/prometheus.yml -remoteWrite.url=https://victoria-metrics-host:8428/api/v1/write

If you only need to collect Influx data, then the following is sufficient:

/path/to/vmagent -remoteWrite.url=https://victoria-metrics-host:8428/api/v1/write

Then send Influx data to http://vmagent-host:8429. See these docs for more details.

vmagent is also available in docker images.

Pass -help to vmagent in order to see the full list of supported command-line flags with their descriptions.

Use cases

IoT and Edge monitoring

vmagent can run and collect metrics in IoT and industrial networks with unreliable or scheduled connections to the remote storage. It buffers the collected data in local files until the connection to remote storage becomes available and then sends the buffered data to the remote storage. It re-tries sending the data to remote storage on any errors. The maximum buffer size can be limited with -remoteWrite.maxDiskUsagePerURL.

vmagent works on various architectures from IoT world - 32-bit arm, 64-bit arm, ppc64, 386, amd64. See the corresponding Makefile rules for details.

Drop-in replacement for Prometheus

If you use Prometheus only for scraping metrics from various targets and forwarding these metrics to remote storage, then vmagent can replace such Prometheus setup. Usually vmagent requires lower amounts of RAM, CPU and network bandwidth comparing to Prometheus for such a setup. See these docs 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 is 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 unwanted samples via Prometheus-like relabeling before sending the collected data to remote storage. See these docs for details.

Splitting data streams among multiple systems

vmagent supports splitting the collected data between 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. Note that each destination can receive its own subset of the collected data thanks to per-destination relabeling via -remoteWrite.urlRelabelConfig.

Prometheus remote_write proxy

vmagent may be used as a proxy for Prometheus data sent via Prometheus remote_write protocol. It can accept data via remote_write API at /api/v1/write endpoint, apply relabeling and filtering and then proxy it to another remote_write systems. The vmagent can be configured to encrypt the incoming remote_write requests with -tls* command-line flags. Additionally, Basic Auth can be enabled for the incoming remote_write requests with -httpAuth.* command-line flags.

How to collect metrics in Prometheus format

Pass the path to prometheus.yml to -promscrape.config command-line flag. vmagent takes into account the following sections from Prometheus config file:

• global
• scrape_configs

All the other sections are ignored, including remote_write section. Use -remoteWrite.* command-line flags instead for configuring remote write settings.

The following scrape types in scrape_config section are supported:

• static_configs - for scraping statically defined targets. See these docs for details.
• file_sd_configs - for scraping targets defined in external files aka file-based service discover. See these docs for details.
• kubernetes_sd_configs - for scraping targets in Kubernetes (k8s). See kubernetes_sd_config for details.
• ec2_sd_configs - for scraping targets in Amazon EC2. See ec2_sd_config for details. vmagent doesn't support role_arn config param yet.
• gce_sd_configs - for scraping targets in Google Compute Engine (GCE). See gce_sd_config for details. vmagent provides the following additional functionality for gce_sd_config:
  • if project arg is missing, then vmagent uses the project for the instance where it runs;
  • if zone arg is missing, then vmagent uses the zone for the instance where it runs;
  • if zone arg equals to "*", then vmagent discovers all the zones for the given project;
  • zone may contain arbitrary number of zones, i.e. zone: [us-east1-a, us-east1-b].
• consul_sd_configs - for scraping targets registered in Consul. See consul_sd_config for details.
• dns_sd_configs - for scraping targets discovered from DNS records (SRV, A and AAAA). See dns_sd_config for details.

Note that vmagent doesn't support refresh_interval option these scrape configs. Use the corresponding -promscrape.*CheckInterval command-line flag instead. For example, -promscrape.consulSDCheckInterval=60s sets refresh_interval for all the consul_sd_configs entries to 60s. Run vmagent -help in order to see default values for -promscrape.*CheckInterval flags.

File feature requests at our issue tracker 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.

Relabeling

vmagent supports Prometheus relabeling. 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.
• keep_if_equal: keeps the entry if all label values from source_labels are equal.
• drop_if_equal: drops the entry if all the label values from source_labels are equal.

The relabeling can be defined in the following places:

• At scrape_config -> relabel_configs section in -promscrape.config file. This relabeling is applied to target labels.
• At scrape_config -> metric_relabel_configs section in -promscrape.config file. This relabeling is applied to all the scraped metrics in the given scrape_config.
• At -remoteWrite.relabelConfig file. This relabeling is aplied to all the collected metrics before sending them to remote storage.
• At -remoteWrite.urlRelabelConfig files. This relabeling is applied to metrics before sending them to the corresponding -remoteWrite.url.

Read more about relabeling in the following articles:

• Life of a label
• Discarding targets and timeseries with relabeling
• Dropping labels at scrape time
• Extracting labels from legacy metric names
• 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.

Troubleshooting

• It is recommended increasing the maximum number of open files in the system (ulimit -n) when scraping big number of targets, since vmagent establishes at least a single TCP connection per each target.

• 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 to increase -remoteWrite.queues if vmagent collects more than 100K samples per second and vmagent_remotewrite_pending_data_bytes metric exported at http://vmagent-host:8429/metrics page constantly grows.

• vmagent buffers scraped data at -remoteWrite.tmpDataPath directory until it is sent to -remoteWrite.url. The directory can grow large when remote storage is unavailable for extended periods of time and if -remoteWrite.maxDiskUsagePerURL isn't set. If you don't want to send all the data from the directory to remote storage, simply stop vmagent and delete the directory.

• If you see skipping duplicate scrape target with identical labels errors when scraping Kubernetes pods, then it is likely these pods listen multiple ports. Just add the following relabeling rule to relabel_configs section in order to filter out targets with unneeded ports:

- action: keep_if_equal
  source_labels: [__meta_kubernetes_pod_annotation_prometheus_io_port, __meta_kubernetes_pod_container_port_number]

How to build from sources

It is recommended using binary releases - vmagent is located in vmutils-* archives there.

Development build

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

Production build

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

Building docker images

Run make package-vmagent. It builds victoriametrics/vmagent:<PKG_TAG> docker image locally. <PKG_TAG> is auto-generated image tag, which depends on source code in the repository. The <PKG_TAG> may be manually set via PKG_TAG=foobar make package-vmagent.

By default the image is built on top of alpine image. It is possible to build the package on top of any other base image by setting it via <ROOT_IMAGE> environment variable. For example, the following command builds the image on top of scratch image:

ROOT_IMAGE=scratch make package-vmagent

Profiling

vmagent provides handlers for collecting the following Go profiles:

• Memory profile. It can be collected with the following command:

curl -s http://<vmagent-host>:8429/debug/pprof/heap > mem.pprof

• CPU profile. It can be collected with the following command:

curl -s http://<vmagent-host>:8429/debug/pprof/profile > cpu.pprof

The command for collecting CPU profile waits for 30 seconds before returning.

The collected profiles may be analyzed with go tool pprof.