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statsrelay (3.0)

A veritable toolkit, sidecar, or daemon(set) for sharding, aggregating, relaying and working with statsd and Prometheus based metrics sources, at scale.


MIT License Copyright (c) 2015-2020 Lyft Inc.

Originally based on statsrelay: Copyright (c) 2014 Uber Technologies, Inc.

Whats different in this version

Statsrelay 3.0 is a port of the original C statsrelay to Rust, with a number of new features designed to improve the operatability and scalability of the original daemon, moving beyond pure "relaying" and instead focusing on both sharding, as well as cascading aggregation. The original C daemon in this fork featured sampling support, but was limited by having the output format be statsd.



  • Rust (stable, 1.46+)


statsrelay 3.1.0

    statsrelay [OPTIONS]

    -h, --help       Prints help information
    -V, --version    Prints version information

    -c, --config <config>     [default: /etc/statsrelay.json]

Statsrelay logging is handled by the env_logger crate, which inherits a number of logging options from the environment. Consult the crate documentation for more information on options you can set.


Statsrelay understands:

  • statsd text line protocol
    • with sampling support (@sampling)
    • with extended data types (map, kv, sets, etc)
    • with "DogStatsD" extended tags (|#tags)
    • with Lyft internal tags (metric.__tag=value)

Configuration file

The configuration file is a JSON file originating from the original statsrelay structure. The original statsrelay configuration contract has been broken as of version 3.1 in order to fix a number of features.

Basic structure

    "statsd": {
        "bind": "",
        "validate": true,
        "backends": {
          "b1": {
            "shard_map": [""],
            "prefix": "myapp.",
            "suffix": ".suffix"
    "discovery": {
      "sources": {
        "source1": {
          "type": "s3",
          "bucket": "my-bucket",
          "key": "file.json",
          "interval": 10

Statsd inputs and routing is defined in the outer statsd block.

  • bind: sets the server bind address to accept statsd protocol messages. Statsrelay will bind on both UDP and TCP ports.
  • validate: turns on extended, more expensive validation of statsd line protocol messages, such as parsing of numerical fields, which may not be required for a pure relaying case.
  • backends forks the incoming statsd metrics down a number of parallel processing pipelines. By default, all incoming protocol lines from the statsd server are sent to all backends.

backends options

Each backend is named and can accept a number of options and rewrite steps for sending and processing StatsD messages.

  • shard_map: list of socket addresses that defines where to send statsd output to, from a list of servers. The same server can be specified more than once (allowing for virtual sharding). Output statsd lines are consistently hashed, and sent to the corresponding server based on a standard hash ring, in a compatible format to the original statsrelay code (Murmur3 hash). This list can be empty to not relay statsd messages.
  • shard_map_source: string value which defines a discovery source to use in-lieu of shard_map.
  • prefix: prepend this prefix string in front of every metric/statsd line before forwarding it to the shard_map servers. Useful for tagging metrics coming from a sidecar.
  • suffix: append a suffix. Works like prefix, just at the end.
  • max_queue: Number of messages to support queued up before dropping. Allows the sender to make overall progress in light of one backend being down. Defaults to 10,000.

discovery options

Each key in the discovery sources section defines a source which can be used by most backends to locate servers, sharding, or other network resources to communicate with. Each named discovery source is listed in the sources subkey:

  "sources": {
    "source_name_1": {
      "type": "static_file"
    "source_name_2": {
      "type": "s3"

For sources supporting a file input (s3, static_file), the following schema is assumed:

  "hosts": ["host:port", "host:port"]

Some sources may support rewriting to transform the input string into an output string (e.g., to add a port)

s3 source

An S3 source represents an AWS S3 compatible source. Statsrelay uses rusoto_s3 to access S3 and supports the vast majority of metadata sources, configuration, and environment variables in order to locate credentials.

The following keys are supported for the S3 source:

  • bucket - The S3 bucket where the file lives
  • key - The key/path instead the S3 bucket
  • interval - An integer number of seconds to wait before re-polling the contents of the S3 key to detect changes.
  • format - A simple text subsitution to run on the incoming text, where {} is replaced by the value of each host entry. Valuable to append information, such as a port number by specifying "format": "{}:8125"


A consistent-hashing relay for statsd and carbon metrics




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