問題猜想
由於此問題不是必現,故不太好定位排查,根據關鍵異常資訊:EOF
一般指輸入流達到末尾,無法繼續從資料流中讀取; 懷疑可能是由於雙方(client<->server) 建立的連線,某一方主動close了,為了驗證以上猜想,筆者查閱了相關資料,以及做了一些簡單的程式碼實驗
如何解決
Github Issue or google or stackoverflow?
根據@edallagnol 描述,當兩次請求時間間隔超過server端配置的keep-alive timeout
,server端會主動關閉當前連線,Okhttp
連線池ConnectionPool
預設超時時間是5min,也就是說優先複用連線池中的連線,然而server已經主動close,導致輸入流中斷,進而丟擲EOF
異常。其中keep-alive
:兩次請求之間的最大間隔時間 ,超過這個間隔 伺服器會主動關閉這個連線, 主要是為了避免重新建立連線,已節約伺服器資源
問題復現:
// Note: 需要保證server端配置的keep-alive timeout 為60s
OkHttpClient client = new OkHttpClient.Builder()
.retryOnConnectionFailure(false)
.build();
try {
for (int i = 0; i != 10; i++) {
Response response = client.newCall(new Request.Builder()
.url("http://192.168.50.210:7080/common/version/demo")
.get()
.build()).execute();
try {
System.out.println(response.body().string());
} finally {
response.close();
}
Thread.sleep(61000);
}
} catch (Exception e) {
e.printStackTrace();
}
複製程式碼
原始碼分析
在進行常規的breakpoint
之後, 需要重點關注 RetryAndFollowUpInterceptor.java
Http1Codec.java
RealBufferedSource.java
這幾個類
RetryAndFollowUpInterceptor.java
public class RetryAndFollowUpInterceptor implements Interceptor {
//....
@Override public Response intercept(Chain chain) throws IOException {
//....
while(true) {
try {
response = realChain.proceed(request, streamAllocation, null, null);
releaseConnection = false;
} catch (IOException) {
// An attempt to communicate with a server failed. The request may have been sent.
boolean requestSendStarted = !(e instanceof ConnectionShutdownException);
// 此處非常重要,若不允許恢復,直接將異常向上丟擲(呼叫方接收),反之 迴圈繼續執行realChain.proceed()方法
if (!recover(e, streamAllocation, requestSendStarted, request)) throw e;
releaseConnection = false;
continue;
}
}
private boolean recover(IOException e, StreamAllocation streamAllocation,
boolean requestSendStarted, Request userRequest) {
// ....
/ The application layer has forbidden retries.
// 若客戶端配置 retryOnConnectionFailure 為false 則表明不允許重試,直接將異常拋給呼叫方
if (!client.retryOnConnectionFailure()) return false;
}
//....
}
複製程式碼
當執行realChain.proceed()
,將事件繼續分發給各個攔截器,最終執行到 Http1Codec#readResponseHeaders
方法
Http1Codec.java
public class Http1Codec implements HttpCodec {
//...
@Override public Response.Builder readResponseHeaders(boolean expectContinue) throws IOException {
try{
StatusLine statusLine = StatusLine.parse(readHeaderLine());
//後續程式碼根據statusLine 構造Response
} catch(EOFException e) {
// 原來異常資訊就是從這裡丟擲來的,接下來需要重點關注下readHeaderLine方法
// Provide more context if the server ends the stream before sending a response.
IOException exception = new IOException("unexpected end of stream on " + streamAllocation);
exception.initCause(e);
}
}
private String readHeaderLine() throws IOException {
// 繼續檢視RealBufferedSource#readUtf8LineStrict方法
String line = source.readUtf8LineStrict(headerLimit);
headerLimit -= line.length();
return line;
}
//...
}
複製程式碼
Http1Codec
用於Encode Http Request 以及 解析 Http Response的,上述程式碼用於獲取頭資訊相關引數
RealBufferedSource.java
final class RealBufferedSource implements BufferedSource {
//...
// 由於server端已經closed,故buffer == null 將EOF異常向上丟擲
@Override public String readUtf8LineStrict(long limit) throws IOException {
if (limit < 0) throw new IllegalArgumentException("limit < 0: " + limit);
long scanLength = limit == Long.MAX_VALUE ? Long.MAX_VALUE : limit + 1;
long newline = indexOf((byte) '\n', 0, scanLength);
if (newline != -1) return buffer.readUtf8Line(newline);
if (scanLength < Long.MAX_VALUE
&& request(scanLength) && buffer.getByte(scanLength - 1) == '\r'
&& request(scanLength + 1) && buffer.getByte(scanLength) == '\n') {
return buffer.readUtf8Line(scanLength); // The line was 'limit' UTF-8 bytes followed by \r\n.
}
Buffer data = new Buffer();
buffer.copyTo(data, 0, Math.min(32, buffer.size()));
throw new EOFException("\\n not found: limit=" + Math.min(buffer.size(), limit)
+ " content=" + data.readByteString().hex() + '…');
}
//...
}
複製程式碼
用一張圖總結:
可以看出 Okhttp 處理攔截器這塊,用到了責任鏈模式
解決方案
根據上述分析,在建立OkHttpClient
例項時,只需要將retryOnConnectionFailure
設定為true ,在丟擲EOF
異常時,讓其可以繼續去執行realChain.proceed
方法即可