DNS解析优化

背景

使用了cloudflare的proxy,在阿里云上请求到cf代理的域名上,经常出现dns解析失败,基本上是一次成功,下次失败. 而用dns查询工具可以看到,cf的ip基本都是那两个,在国内各省市,有的能解析成功,有的解析不成功.

于是,做一层内存缓存:

okhttp实现

static Map<String, List<InetAddress>> dnsMap = new HashMap<>();

okHttpClient = new OkHttpClient.Builder()
                .readTimeout(Duration.ofSeconds(50))
                .writeTimeout(Duration.ofSeconds(50))
                .connectTimeout(Duration.ofSeconds(50))
                .dns(new Dns() {
                    @NotNull
                    @Override
                    public List<InetAddress> lookup(@NotNull String host) throws UnknownHostException {
                        try {
                            InetAddress[] allByName = InetAddress.getAllByName(host);
                            if(allByName != null && allByName.length >0){
                                List<InetAddress> addresses = new ArrayList<>();
                                for (InetAddress inetAddress : allByName) {
                                    addresses.add(inetAddress);
                                }
                                dnsMap.put(host,addresses);
                                return addresses;
                            }
                            List<InetAddress> addresses = dnsMap.get(host);
                            if(addresses != null && !addresses.isEmpty()){
                                return addresses;
                            }else {
                                throw new UnknownHostException(" ---> can not resole host: "+host);
                            }
                        }catch (Throwable throwable){
                            List<InetAddress> addresses = dnsMap.get(host);
                            StaticLog.warn(throwable,"UnknownHostException then read cache : "+ host+"--->"+addresses);
                            if(addresses != null && !addresses.isEmpty()){
                                return addresses;
                            }else {
                                throw new UnknownHostException(" ---> can not resole host2: "+host);
                            }
                        }


                    }
                })

效果

使用缓存后,看api日志, 再也没有出现UnknownHostException了.