tengine (nginx) backend process healthcheck in lua

gistfile1.txt

    location /health.pgrep {
      default_type text/plain;
      access_log off;
      content_by_lua '
      local io = require "io"

      if (ngx.var.arg_q ~= nil and ngx.var.arg_q ~= "") then
        -- Note: Testing this over 127.0.0.1 will always succeed.
        local arg_q = ngx.var.arg_q:gsub("[;&|/\\\\ ]", "")
        local c = assert(io.popen("/usr/bin/pgrep -f "..arg_q))
        local p = tonumber(c:read())
        c:close()
        if (p == nil) then
          ngx.status = 503
          ngx.say(arg_q.." is not found")
          ngx.exit(503)
        else
          ngx.say(arg_q.." is found at pid "..p)
        end
      else
        ngx.status = 503
        ngx.say("query term is empty or missing")
        ngx.exit(503)
      end
      ';
    }