背景
最近因为工作原理，需要研究一下各种 client 的 read timeout 的配置和原理
包括 Apache HttpClient 和 jedis
简单分析了一下，把结论分享在这里
（注意，只是 read timeout, 还有很多 timeout, 这里不展开研究）
Apache HttpClient timeout 配置
这里贴一个常用的工具类
import org.apache.http.client.HttpClient;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.impl.client.HttpClientBuilder;
public class HttpClientUtils {
public static final String DEFAULT_CHARSET = "UTF-8";
//默认值参数在 org.apache.http.impl.conn.PoolingHttpClientConnectionManager.PoolingHttpClientConnectionManager
//设置最大连接数,默认值是 20
private static final int MAX_CONN_TOTAL = 800;
//每个路由最大连接数(一个 host:port就是一个连接)，默认 2
private static final int MAX_CONN_PER_ROUTE = 400;
private static final int CONNECTION_POOL_TIMEOUT = 1000; //从连接池中获取连接的超时时间, 1000毫秒
private static final int CONNECTION_TIMEOUT = 1000; //与服务器连接超时, 1 秒
private static final int SOCKET_TIMEOUT = 10 * 1000; //读取服务器返回的数据 超时, 10 秒
/**
* <br>默认提供一个 client
*/
public static final HttpClient DEFAULT_CLIENT;
static {
RequestConfig clusterConfig = RequestConfig.custom()
.setConnectionRequestTimeout(CONNECTION_POOL_TIMEOUT)
.setConnectTimeout(CONNECTION_TIMEOUT) // 与服务器连接超时
.setSocketTimeout(SOCKET_TIMEOUT) // 读取服务器返回的数据 超时
.build();
//参数含义参考 下面两个博客
//https://blog.csdn.net/shootyou/article/details/6615051
//https://blog.csdn.net/shootyou/article/details/6415248
DEFAULT_CLIENT = HttpClientBuilder.create()
.setDefaultRequestConfig(clusterConfig)
.setMaxConnTotal(MAX_CONN_TOTAL)
.setMaxConnPerRoute(MAX_CONN_PER_ROUTE)
.build();
}
}
可以看到 read timeout 其实就是 socket timeout， 也就是这行代码
.setSocketTimeout(SOCKET_TIMEOUT) // 读取服务器返回的数据 超时
原理
那么是怎么实现的呢？
我们写一个接口，阻塞 11秒， 看下堆栈就知道了
java.net.SocketTimeoutException: Read timed out
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
at java.net.SocketInputStream.read(SocketInputStream.java:171)
at java.net.SocketInputStream.read(SocketInputStream.java:141)
at org.apache.http.impl.conn.LoggingInputStream.read(LoggingInputStream.java:84)
at org.apache.http.impl.io.SessionInputBufferImpl.streamRead(SessionInputBufferImpl.java:137)
at org.apache.http.impl.io.SessionInputBufferImpl.fillBuffer(SessionInputBufferImpl.java:153)
at org.apache.http.impl.io.SessionInputBufferImpl.readLine(SessionInputBufferImpl.java:280)
at org.apache.http.impl.conn.DefaultHttpResponseParser.parseHead(DefaultHttpResponseParser.java:138)
at org.apache.http.impl.conn.DefaultHttpResponseParser.parseHead(DefaultHttpResponseParser.java:56)
at org.apache.http.impl.io.AbstractMessageParser.parse(AbstractMessageParser.java:259)
at org.apache.http.impl.DefaultBHttpClientConnection.receiveResponseHeader(DefaultBHttpClientConnection.java:163)
at org.apache.http.impl.conn.CPoolProxy.receiveResponseHeader(CPoolProxy.java:157)
at org.apache.http.protocol.HttpRequestExecutor.doReceiveResponse(HttpRequestExecutor.java:273)
at org.apache.http.protocol.HttpRequestExecutor.execute(HttpRequestExecutor.java:125)
at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:272)
at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:186)
at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:89)
at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:110)
at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:185)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:83)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:108)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:56)
Native Method 我们看不到代码，那去看下 java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
// wrap native call to allow instrumentation
/**
* Reads into an array of bytes at the specified offset using
* the received socket primitive.
* @param fd the FileDescriptor
* @param b the buffer into which the data is read
* @param off the start offset of the data
* @param len the maximum number of bytes read
* @param timeout the read timeout in ms
* @return the actual number of bytes read, -1 is
* returned when the end of the stream is reached.
* @exception IOException If an I/O error has occurred.
*/
private int socketRead(FileDescriptor fd,
byte b[], int off, int len,
int timeout)
throws IOException {
return socketRead0(fd, b, off, len, timeout);
}
可以看到，是jdk 提供了timeout参数，实现了这个超时功能， HttpClient 只是使用了这个特性
JedisPool
配置
我们看下 redis.clients.jedis.JedisPool 的构造方法源码
下面是一个构造 JedisPool 的样例
private static JedisPool initJedisPool(String url) {
JedisPoolConfig jedisPoolConfig = new JedisPoolConfig();
jedisPoolConfig.setMaxTotal(200);
jedisPoolConfig.setMaxIdle(50);
jedisPoolConfig.setMaxWaitMillis(10000L);
jedisPoolConfig.setTestOnBorrow(true);
return new JedisPool(jedisPoolConfig, URI.create(url));
}
看下这个两个参数的构造方法
public JedisPool(final GenericObjectPoolConfig poolConfig, final URI uri) {
this(poolConfig, uri, Protocol.DEFAULT_TIMEOUT);
}
这个常量是下面这样的，也就是2秒
public static final int DEFAULT_TIMEOUT = 2000;
再继续看下三个参数的构造方法
public JedisPool(final GenericObjectPoolConfig poolConfig, final URI uri, final int timeout) {
this(poolConfig, uri, timeout, timeout);
}
public JedisPool(final GenericObjectPoolConfig poolConfig, final URI uri,
final int connectionTimeout, final int soTimeout) {
super(poolConfig, new JedisFactory(uri, connectionTimeout, soTimeout, null, false,
null, null, null));
}
可以看到，Protocol.DEFAULT_TIMEOUT 被设置到两个值里面去了
分别是 connectionTimeout 和 soTimeout
soTimeout 应该全称是 socket timeout
原理
我们也试着让 redis 慢点返回，看看异常堆栈
redis.clients.jedis.exceptions.JedisConnectionException: java.net.SocketTimeoutException: Read timed out
at redis.clients.util.RedisInputStream.ensureFill(RedisInputStream.java:202)
at redis.clients.util.RedisInputStream.readByte(RedisInputStream.java:40)
at redis.clients.jedis.Protocol.process(Protocol.java:153)
at redis.clients.jedis.Protocol.read(Protocol.java:218)
at redis.clients.jedis.Connection.readProtocolWithCheckingBroken(Connection.java:341)
at redis.clients.jedis.Connection.getBinaryBulkReply(Connection.java:260)
at redis.clients.jedis.Connection.getBulkReply(Connection.java:249)
at redis.clients.jedis.Jedis.get(Jedis.java:156)
Caused by: java.net.SocketTimeoutException: Read timed out
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
at java.net.SocketInputStream.read(SocketInputStream.java:171)
at java.net.SocketInputStream.read(SocketInputStream.java:141)
at java.net.SocketInputStream.read(SocketInputStream.java:127)
at redis.clients.util.RedisInputStream.ensureFill(RedisInputStream.java:196)
... 14 common frames omitted
可以看到超时的原理差不多，都是jdk提供的特性
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