代码如下：

local resolver = require "resty.dns.resolver"
local resolver_ins, err = resolver:new{
    nameservers = {"172.21.0.10"},
    retrans = 5,  -- 5 retransmissions on receive timeout
    timeout = 2000,  -- 2 sec
}
if not resolver_ins then
    ngx.say("failed to instantiate the resolver: ", err)
    return
end

-- query
local host = "test-0.test-svc"
local answers, err, tries = resolver_ins:query(host, nil, {})
if not answers then
    ngx.log(ngx.ERR, "failed to query the DNS server: ", err)
    ngx.log(ngx.ERR, "retry historie:\n  ", table.concat(tries, "\n  "))
    return
end
if answers.errcode then
    ngx.log(ngx.ERR, "server returned error code: ", answers.errcode,
            ", err: ", answers.errstr, ", hostname: ", host)
end

错误日志
[error] 66#66: *1352423 [lua] resolver.lua:42: resolve(): server returned error code: 3, err: name error, hostname: test-0.test-svc

但是nslookup可以查到

/ # nslookup test-0.test-svc 172.21.0.10
Server: 172.21.0.10
Address 1: 172.21.0.10 kube-dns.kube-system.svc.cluster.local

Name: test-0.test-svc
Address 1: 172.20.2.104 test-0.test-svc.test.svc.cluster.local

biello nslookup查询的是完整域名test-0.test-svc.test.svc.cluster.local，是系统自动添加了域名后缀，而resty.dns.resolver必须传入完整的域名。

vinsonzou 谢谢～我后来也发现了，最后用dnsmasq做dns server解决了