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kumo.set_lruttl_cache_capacity(NAME, CAPACITY)

Since: Version 2025.03.19-1d3f1f67

The functionality described in this section requires version 2025.03.19-1d3f1f67 of KumoMTA, or a more recent version.

Allows you to configure the maximum capacity for a specific named pre-defined cache.

You may only update the capacity for caches defined inside kumomta's Rust code via declare_cache!. Other caches are assumed to be dynamically created and expose their capacity as part of their own individual configuration.

kumo.on('pre_init', function()
  -- Increase the mx cache size from its default of 64*1024 to 128,000
  kumo.set_lruttl_cache_capacity('dns_resolver_mx', 128000)
end)

Note

This function is intended to be used in pre_init, but it can be called at any time. Reducing the capacity while the cache holds data will trigger a partial eviction. The cache will eventually shrink to conform to the new size as the cache is operated upon and background processing trims the cache.