java-什么会导致JVM无法在负载下解析DNS？
作者：互联网
我正在调查我们的服务问题,该服务无法解析负载下的s3存储桶名称.
我强调一个c1.medium ec2实例：
root@ip-10-243-126-111:/mnt/log# uname -a
Linux ip-10-243-126-111 2.6.35-30-virtual #56-Ubuntu SMP Mon Jul 11 23:41:40 UTC 2011 i686 GNU/Linux
root@ip-10-243-126-111:/mnt/log# cat /etc/issue
Ubuntu 10.10 \n \l
root@ip-10-243-126-111:/mnt/log# free
total used free shared buffers cached
Mem: 1746008 1681752 64256 0 29600 1582508
-/+ buffers/cache: 69644 1676364
Swap: 917500 32 917468
该应用程序以-server,jvm build 1.6.0_23-b05,32bit运行
我看到的行为是网络通信开始变得“有趣”,有时套接字超时从我们的mongo连接驱动程序发生,如下所示：
Caused by: java.net.SocketTimeoutException: Read timed out
at java.net.SocketInputStream.socketRead0(Native Method) ~[na:1.6.0_23]
at java.net.SocketInputStream.read(SocketInputStream.java:129) ~[na:1.6.0_23]
at java.io.BufferedInputStream.fill(BufferedInputStream.java:218) ~[na:1.6.0_23]
at java.io.BufferedInputStream.read1(BufferedInputStream.java:258) ~[na:1.6.0_23]
at java.io.BufferedInputStream.read(BufferedInputStream.java:317) ~[na:1.6.0_23]
at org.bson.io.Bits.readFully(Bits.java:35) ~[mongo-java-driver-2.5.3.jar:na]
at org.bson.io.Bits.readFully(Bits.java:28) ~[mongo-java-driver-2.5.3.jar:na]
at com.mongodb.Response.<init>(Response.java:35) ~[mongo-java-driver-2.5.3.jar:na]
at com.mongodb.DBPort.go(DBPort.java:110) ~[mongo-java-driver-2.5.3.jar:na]
at com.mongodb.DBPort.go(DBPort.java:75) ~[mongo-java-driver-2.5.3.jar:na]
at com.mongodb.DBPort.call(DBPort.java:65) ~[mongo-java-driver-2.5.3.jar:na]
at com.mongodb.DBTCPConnector.call(DBTCPConnector.java:201) ~[mongo-java-driver-2.5.3.jar:na]
... 43 common frames omitted
有时会发生以下情况
Caused by: java.net.UnknownHostException: bucket-system.s3.amazonaws.com
at java.net.InetAddress.getAllByName0(InetAddress.java:1158) ~[na:1.6.0_23]
at java.net.InetAddress.getAllByName(InetAddress.java:1084) ~[na:1.6.0_23]
at java.net.InetAddress.getAllByName(InetAddress.java:1020) ~[na:1.6.0_23]
at org.apache.http.impl.conn.DefaultClientConnectionOperator.resolveHostname(DefaultClientConnectionOperator.java:242) ~[httpclient-4.1.jar:4.1]
at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:130) ~[httpclient-4.1.jar:4.1]
at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:149) ~[httpclient-4.1.jar:4.1]
at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:121) ~[httpclient-4.1.jar:4.1]
at org.apache.http.impl.client.DefaultRequestDirector.tryConnect(DefaultRequestDirector.java:562) ~[httpclient-4.1.jar:4.1]
at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:415) ~[httpclient-4.1.jar:4.1]
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:820) ~[httpclient-4.1.jar:4.1]
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:754) ~[httpclient-4.1.jar:4.1]
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:732) ~[httpclient-4.1.jar:4.1]
at com.amazonaws.http.AmazonHttpClient.executeHelper(AmazonHttpClient.java:240) ~[aws-java-sdk-1.2.5.jar:na]
... 48 common frames omitted
这是可重现的,但不一致.一旦在计算机上开始加载(50个并发的http请求),计算机就会在两次正确响应的周期之间持续约5分钟,然后使所有请求失败10秒钟,然后再进行一次正确响应的周期.
什么会导致这种行为？我可能会尝试调整任何ulimit或其他系统设置以对此进行改进吗？还有其他寻找线索的指针吗？
我怀疑的另一个选择是亚马逊(美国东部1地区)的基础设施,我怀疑那里的路由器在服务上启用了某种DoS预防策略,因为请求几乎立即从0跳到了50.时间稳定在并发速率稳定在50,这时硬件会适应新的流量.牵强？我在任何地方都没有提到这种类型的模式.
解决方法:
看起来您正在尝试仅对Amazon DNS服务器进行DoS.
缓存您要访问的主机的IP,并定期更新缓存.这也将提高应用程序的整体性能
更新：
从跟踪中可以看出,DNS主机只是没有响应您的请求.如果要达到一个ulimit,您将面临另一个Exception(类似于无法创建套接字的东西).
标签：amazon-ec2,linux-kernel,load,linux,java 来源： https://codeday.me/bug/20191202/2085629.html