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https://github.com/mailscope/kumomta.git
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Wez Furlong
16fad7b260
It is useful enough and avoids some reptitions between the single node and docker swarm examples. closes: https://github.com/KumoCorp/kumomta/issues/359
67 lines
2.2 KiB
Lua
67 lines
2.2 KiB
Lua
local mod = {}
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local kumo = require 'kumo'
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-- Logically equivalent to kumo.dns.lookup_addr, except that
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-- function doesn't seem to work reliably with the docker service
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-- discovery DNS during early container startup.
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-- Instead this function uses the getent utility to resolve
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-- via the system resolver.
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-- If the endpoint_mode for the service is dnsrr this will
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-- return a list of the IPs of the constituent services.
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-- Otherwise it will return the load balancer IP
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local function resolve_docker_name(name)
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local result = {}
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local f = io.popen('getent ahostsv4 ' .. name, 'r')
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for line in f:lines() do
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local ip = string.match(line, '^(%d+%.%d+%.%d+%.%d+)%s+STREAM')
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if ip then
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table.insert(result, ip)
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end
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end
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-- print('resolve_docker_name', name, kumo.json_encode(result))
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return result
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end
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-- Employ a cache around the system resolver for resolve_docker_name
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mod.resolve_docker_name = kumo.memoize(resolve_docker_name, {
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name = 'resolve_docker_name',
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-- Not too long, so that we have lower latency for picking up
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-- scaling changes
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ttl = '1 minutes',
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capacity = 1024,
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})
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-- Resolve our hostname, then derive the docker network from that.
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-- This assumes that the network is a /24 and that HOSTNAME is
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-- injected by docker and resolves to the container IP on that network.
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local function resolve_docker_network()
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local hostname = os.getenv 'HOSTNAME'
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if not hostname then
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error 'HOSTNAME is not set in the environment'
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end
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local MY_IPS = mod.resolve_docker_name(hostname)
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local DOCKER_NETWORK = string.match(MY_IPS[1], '^(.*)%.%d+$') .. '.0/24'
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return DOCKER_NETWORK
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end
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mod.resolve_docker_network = kumo.memoize(resolve_docker_network, {
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name = 'resolve_docker_network',
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ttl = '1 hour',
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capacity = 1,
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})
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-- We resolve the tsa DNS record to obtain the list of IPs;
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-- this requires that the service be deployed with
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-- `endpoint_mode: dnsrr`.
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-- Map the list of IPs into a list of TSA HTTP endpoints.
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function mod.resolve_tsa_endpoints()
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local ips = mod.resolve_docker_name 'tsa'
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local result = {}
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for ip, _ in pairs(ips) do
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table.insert(result, string.format('http://%s:8008', ip))
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end
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return result
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end
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return mod
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