监控网络状态以减少延迟

网络监控API目前正处于Apollo Kotlin中的

Android和Apple的目标提供API来监控你的设备网络状态。

ConnectivityManager在Android目标中使用。
NWPathMonitor在Apple目标中使用。

您可以配置您的ApolloClient，通过使用NetworkMonitor API来改进请求的延迟：

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// androidMain
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val networkMonitor = NetworkMonitor(context)
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// appleMain
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val networkMonitor = NetworkMonitor()
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// commonMain
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val apolloClient = ApolloClient.Builder()
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    .serverUrl("https://example.com/graphql")
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    .retryOnErrorInterceptor(RetryOnErrorInterceptor(networkMonitor))
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    .build()

`failFastIfOffline`

当配置了NetworkMonitor后，您可以使用failFastIfOffline来避免设备离线时尝试发送请求：

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// Opt-in `failFastIfOffline` on all queries
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val apolloClient = ApolloClient.Builder()
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    .serverUrl("https://example.com/graphql")
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    .failFastIfOffline(true)
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    .build()
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val response = apolloClient.query(myQuery).execute()
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println(response.exception?.message)
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// "The device is offline"
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// Opt-out `failFastIfOffline` on a single query
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val response = apolloClient.query(myQuery).failFastIfOffline(false).execute()

`retryOnError`

当配置了NetworkMonitor后，retryOnError会使用NetworkMonitor.waitForNetwork()而不是默认的指数退避算法，以便在连接恢复后更快地重新连接。

自定义重试算法

您可以通过定义自己的拦截器进一步自定义重试算法

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val apolloClient = ApolloClient.Builder()
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    .retryOnErrorInterceptor(MyRetryOnErrorInterceptor())
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    .build()
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class MyRetryOnErrorInterceptor : ApolloInterceptor {
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  object RetryException : Exception()
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  override fun <D : Operation.Data> intercept(request: ApolloRequest<D>, chain: ApolloInterceptorChain): Flow<ApolloResponse<D>> {
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    var attempt = 0
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    return chain.proceed(request).onEach {
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      if (request.retryOnError == true && it.exception != null && it.exception is ApolloNetworkException) {
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        throw RetryException
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      } else {
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        attempt = 0
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      }
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    }.retryWhen { cause, _ ->
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      if (cause is RetryException) {
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        attempt++
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        delay(2.0.pow(attempt).seconds)
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        true
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      } else {
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        // Not a RetryException, probably a programming error, pass it through
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        false
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      }
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    }
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  }
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}