增量超时；重试后设置总是成功 [英] Increment times out; set always succeeds after retry

问题描述

我在memcached中遇到了奇怪的行为，特别是在一致性方面很奇怪的行为.这是我的测试:

I'm getting strange behavior in memcached, in particular, behavior that is strange in its consistency. Here is my test:

@Test
public void testMemc() {
    logger.info("Setting head.");
    memc.set(env.memcachedQueueKeys().head, 3600, 0);
    logger.info("Set head; incrementing.");
    memc.incr(env.memcachedQueueKeys().head, 1);
    logger.info("Incremented.");
}

这是输出:

28 11:04:52.932 INFO;放下头.

28 11:04:52.932 INFO; Setting head.

2014-01-28 11:04:52.933警告net.spy.memcached.MemcachedConnection:无法重新分配到另一个节点，请重试q:unittest:scannedemails:w的主节点.

2014-01-28 11:04:52.933 WARN net.spy.memcached.MemcachedConnection: Could not redistribute to another node, retrying primary node for q:unittest:scannedemails:w.

28 11:04:52.933 INFO;机头；递增.

28 11:04:52.933 INFO; Set head; incrementing.

2014-01-28 11:04:52.935警告net.spy.memcached.MemcachedConnection:无法重新分发到另一个节点，重试q:unittest:scannedemails:w的主节点.

2014-01-28 11:04:52.935 WARN net.spy.memcached.MemcachedConnection: Could not redistribute to another node, retrying primary node for q:unittest:scannedemails:w.

失败:testMemc net.spy.memcached.OperationTimeoutException:突变操作超时，无法修改计数器[q:unittest:scannedemails:w]
在net.spy.memcached.MemcachedClient.mutate(MemcachedClient.java:1484)
在net.spy.memcached.MemcachedClient.incr(MemcachedClient.java:1529)
在me.unroll.emailroller.ActOnScanResultsTest.testMemc(ActOnScanResultsTest.java:295)

FAILED: testMemc net.spy.memcached.OperationTimeoutException: Mutate operation timed out,unable to modify counter [q:unittest:scannedemails:w]
at net.spy.memcached.MemcachedClient.mutate(MemcachedClient.java:1484)
at net.spy.memcached.MemcachedClient.incr(MemcachedClient.java:1529)
at me.unroll.emailroller.ActOnScanResultsTest.testMemc(ActOnScanResultsTest.java:295)

我对这种错误的大多数直觉在这里使我失望.以下都是奇怪的事情:

Most of my intuition for this kind of error fails me here. The following things are all strange:

1. 为什么总是总是一次设置失败?
2. 为什么它似乎在设定成功后就永远无法递增?

这是在高负载服务器上的(是的，在承重服务器上运行测试是有点错误的，但是如果它捕获到这样的问题，则至少有一些优势).是什么导致这种持续的故障?只有一个节点.

This is on a high-load server (yes, it's a little wrong to be running a test on a load-bearing server, but if it catches issues like this there's at least some advantage). What can cause this consistent failure? There is only one node.

推荐答案

问题是我根本无法连接 .这是spymemcached中的一个错误，因为set操作没有抛出异常，即使它没有用于执行set的内存缓存服务器.

Problem is I couldn't connect at all. This is a bug in spymemcached, since the set operation did not throw an exception even though it had no memcached server to perform set on.

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