Consistent Hashing Matcher (proto)

This extension has the qualified name envoy.matching.matchers.consistent_hashing

Note

This extension is intended to be robust against untrusted downstream traffic. It assumes that the upstream is trusted.

Tip

This extension extends and can be used with the following extension category:

• envoy.matching.input_matchers

This extension must be configured with one of the following type URLs:

• type.googleapis.com/envoy.extensions.matching.input_matchers.consistent_hashing.v3.ConsistentHashing

extensions.matching.input_matchers.consistent_hashing.v3.ConsistentHashing

[extensions.matching.input_matchers.consistent_hashing.v3.ConsistentHashing proto]

The consistent hashing matchers computes a consistent hash from the input and matches if the resulting hash is within the configured threshold. More specifically, this matcher evaluates to true if hash(input, seed) % modulo >= threshold. Note that the consistency of the match result relies on the internal hash function (xxhash) remaining unchanged. While this is unlikely to happen intentionally, this could cause inconsistent match results between deployments.

{
  "threshold": ...,
  "modulo": ...,
  "seed": ...
}

threshold

(uint32) The threshold the resulting hash must be over in order for this matcher to evaluate to true. This value must be below the configured modulo value. Setting this to 0 is equivalent to this matcher always matching.

modulo

(uint32) The value to use for the modulus in the calculation. This effectively bounds the hash output, specifying the range of possible values. This value must be above the configured threshold.

seed

(uint64) Optional seed passed through the hash function. This allows using additional information when computing the hash value: by changing the seed value, a different partition of matching and non-matching inputs will be created that remains consistent for that seed value.