Fresco HTTP DNS Interceptor

FrescoHttpDNSInterceptor.kt

import okhttp3.Interceptor
import okhttp3.Response
import java.io.IOException

/**
 * Fresco无法直接设置request的header来传递Hostname
 * 通过提供Interceptor来添加和video相同的httpdns支持
 * 同时图片下载的成功与否也会用来对host进行评分
 * Created by quan.zhou on 2018/7/11.
 */
class FrescoHttpDNSInterceptor : Interceptor {

  private val mDnsResolver by lazy { KwaiApp.getDnsResolver() }

  override fun intercept(chain: Interceptor.Chain): Response {
    val request = chain.request()

    val uri = request.url().uri()
    val url = uri.toString()
    val host = uri.host

    val IPs = mDnsResolver.resolveHost(host)

    if (IPs.isNullOrEmpty()) {
      return chain.proceed(request)
    }

    var response: Response? = null
    var exception: Exception? = null
    IPs.forEach { ip ->
      exception = null
      response = null
      try {
        val req = request.newBuilder()
            .url(url.replace(host, ip.mIP))
            .header("Host", host)
            .build()

        response = chain.proceed(req)
        if (response != null && response!!.isSuccessful) {
          CDNProvider.requestHostSuccess(host)
          return response!!
        }

      } catch (e: Exception) {
        if (e is IOException) {
          if (e.message != "Canceled" && NetworkUtils.isNetworkConnected(KwaiApp.getAppContext())) {
            mDnsResolver.evictIp(ip.mIP)
          }
        }

        exception = e
        response = null
      }
    }

    if (NetworkUtils.isNetworkConnected(KwaiApp.getAppContext())) {
      CDNProvider.requestHostFailed(host)
    }

    if (response != null) {
      return response!!
    } else {
      throw exception!!
    }

  }

}