Record Prometheus metrics from nginx stub_status module using https://github.com/knyar/nginx-lua-prometheus

nginx_stub_status.lua

-- A module to export Prometheus metrics from nginx stub_status module.
local ngx = ngx
local ngx_var = ngx.var
local prometheus = prometheus
local select = select
local tonumber = tonumber
local find = string.find
local capture = ngx.location.capture
local log = ngx.log
local ERR = ngx.ERR

local _M = {_VERSION = "0.0.1"}
local mt = {__index = _M}


function _M.new(_, opts)
    if not opts then
        return nil, "no options table specified"
    end

    return setmetatable({
        -- Location block with "stub_status;".
        location=opts.location or "/nginx_status",
    }, mt)
end


--- Connect, read, and parse metrics.
function _M.set_metrics(self)
    local r = capture(self.location)
    if r.status ~= 200 then
        prometheus:inc("nginx_stub_status_failure_total")
        local err_msg = "failure querying stub_status location, " .. tostring(self.location)
        log(ERR, err_msg)
        return err_msg
    end
    local accepted, handled, total = select(3, find(r.body, "accepts handled requests\n (%d*) (%d*) (%d*)"))
    prometheus:set_key("nginx_connections_accepted_total", tonumber(accepted))
    prometheus:set_key("nginx_connections_handled_total", tonumber(handled))
    prometheus:set_key("nginx_connections_total", tonumber(total))
    prometheus:set_key("nginx_connections_active", tonumber(ngx_var.connections_active))
    prometheus:set_key("nginx_connections_reading", tonumber(ngx_var.connections_reading))
    prometheus:set_key("nginx_connections_writing", tonumber(ngx_var.connections_writing))
    prometheus:set_key("nginx_connections_waiting", tonumber(ngx_var.connections_waiting))
end


return _M