kumomta/assets/shaping.lua

local mod = {}
local kumo = require 'kumo'

-- Helper function that merges the values from `src` into `dest`
local function merge_into(src, dest)
  if src then
    for k, v in pairs(src) do
      dest[k] = v
    end
  end
end

--[[
Usage:

Create a `/opt/kumomta/etc/shaping.json` with contents like:

```json
{
  "gmail.com": {
    // "mx_rollup": false, // if false, is NOT shared with other domains with same mx
    "connection_limit": 3,

    // Entries that are themselves objects are considered to be
    // source configuration. These will take precendence over
    // the more general configuration for the domain/site
    "sources": {
      "source-0": {
        "connection_limit": 5
      }
    }
  }
}
```

---
local shaping = require 'shaping'
kumo.on('get_egress_path_config', shaping:setup_json())
---

]]

function mod:setup_json()
  local function load_shaping_data(filename)
    local data = kumo.json_load(filename)
    local result = {
      by_site = {},
      by_domain = {},
    }
    for domain, config in pairs(data) do
      local entry = {
        sources = {},
        params = {},
      }

      local mx_rollup = config.mx_rollup or true
      config.mx_rollup = nil

      for k, v in pairs(config) do
        if k == 'sources' then
          entry.sources = v
        else
          entry.params[k] = v
        end
      end

      if mx_rollup then
        local site_name = kumo.dns.lookup_mx(domain).site_name
        result.by_site[site_name] = entry
      else
        result.by_domain[domain] = entry
      end
    end
    return result
  end

  local cached_load_data = kumo.memoize(load_shaping_data, {
    name = 'shaping_data',
    ttl = '5 minutes',
    capacity = 10,
  })

  local function get_egress_path_config(domain, egress_source, site_name)
    local data = cached_load_data '/opt/kumomta/etc/shaping.json'

    local by_site = data.by_site[site_name]
    local by_domain = data.by_domain[domain]

    -- domain config takes precedence over shared site config
    local options = by_domain or by_site

    local params = {}
    -- apply basic/default configuration
    merge_into(data.by_domain['default'], params)

    -- then any overrides based on the site, domain, source
    if options then
      merge_into(options.params, params)
      merge_into(options.sources[egress_source], params)
    end

    return kumo.make_egress_path(params)
  end

  return get_egress_path_config
end

return mod