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试图从一个巨大的表中卸载数据，下面是使用和输出的命令。

$ /home/cassandra/dsbulk-1.8.0/bin/dsbulk unload --driver.auth.provider PlainTextAuthProvider --driver.auth.username xxxx --driver.auth.password xxxx --datastax-java-driver.basic。接触点 123.123.123.123 -查询“从某个表中选择计数（*），其中包含聚类列和部分 pk 的位置——允许过滤”——connector.name json --driver.protocol.compression LZ4 --connector.json.mode MULTI_DOCUMENT -maxConcurrentFiles 1 -maxRecords -1 -url dsbulk --executor.continuousPaging.enabled false --executor.maxpersecond 2500 --driver.socket.timeout 240000

Setting dsbulk.driver.protocol.compression is deprecated and will be removed in a future release; please configure the driver directly using --datastax-java-driver.advanced.protocol.compression instead.
Setting dsbulk.driver.auth.* is deprecated and will be removed in a future release; please configure the driver directly using --datastax-java-driver.advanced.auth-provider.* instead.
Operation directory: /home/cassandra/logs/COUNT_20210423-070104-108326
total | failed | rows/s |      p50ms |      p99ms |     p999ms
    1 |      1 |      0 | 109,790.10 | 110,058.54 | 110,058.54
Operation COUNT_20210423-070104-108326 completed with 1 errors in 1 minute and 50 seconds.

以下是 dsbulk 记录——

cassandra@somehost> cd logs
cassandra@somehost> cd COUNT_20210423-070104-108326/
cassandra@somehost> ls
operation.log  unload-errors.log
cassandra@somehost> cat operation.log
2021-04-23 07:01:04 WARN  Setting dsbulk.driver.protocol.compression is deprecated and will be removed in a future release; please configure the driver directly using --datastax-java-driver.advanced.protocol.compression instead.
2021-04-23 07:01:04 WARN  Setting dsbulk.driver.auth.* is deprecated and will be removed in a future release; please configure the driver directly using --datastax-java-driver.advanced.auth-provider.* instead.
2021-04-23 07:01:04 INFO  Operation directory: /home/cassandra/logs/COUNT_20210423-070104-108326
2021-04-23 07:02:55 WARN  Operation COUNT_20210423-070104-108326 completed with 1 errors in 1 minute and 50 seconds.
2021-04-23 07:02:55 INFO  Records: total: 1, successful: 0, failed: 1
2021-04-23 07:02:55 INFO  Memory usage: used: 212 MB, free: 1,922 MB, allocated: 2,135 MB, available: 27,305 MB, total gc count: 4, total gc time: 98 ms
2021-04-23 07:02:55 INFO  Reads: total: 1, successful: 0, failed: 1, in-flight: 0
2021-04-23 07:02:55 INFO  Throughput: 0 reads/second
2021-04-23 07:02:55 INFO  Latencies: mean 109,790.10, 75p 110,058.54, 99p 110,058.54, 999p 110,058.54 milliseconds
2021-04-23 07:02:58 INFO  Final stats:
2021-04-23 07:02:58 INFO  Records: total: 1, successful: 0, failed: 1
2021-04-23 07:02:58 INFO  Memory usage: used: 251 MB, free: 1,883 MB, allocated: 2,135 MB, available: 27,305 MB, total gc count: 4, total gc time: 98 ms
2021-04-23 07:02:58 INFO  Reads: total: 1, successful: 0, failed: 1, in-flight: 0
2021-04-23 07:02:58 INFO  Throughput: 0 reads/second
2021-04-23 07:02:58 INFO  Latencies: mean 109,790.10, 75p 110,058.54, 99p 110,058.54, 999p 110,058.54 milliseconds

cassandra@somehost> cat unload-errors.log
Statement: com.datastax.oss.driver.internal.core.cql.DefaultBoundStatement@1083fef9 [0 values, idempotence: <UNSET>, CL: <UNSET>, serial CL: <UNSET>, timestamp: <UNSET>, timeout: <UNSET>]
SELECT batch_id from .... allow filtering (Cassandra timeout during read query at consistency LOCAL_ONE (1 responses were required but only 0 replica responded))
        at com.datastax.oss.dsbulk.executor.api.subscription.ResultSubscription.toErrorPage(ResultSubscription.java:534)
        at com.datastax.oss.dsbulk.executor.api.subscription.ResultSubscription.lambda$fetchNextPage$1(ResultSubscription.java:372)
        at com.datastax.oss.driver.internal.core.cql.CqlRequestHandler.setFinalError(CqlRequestHandler.java:447) [4 skipped]
        at com.datastax.oss.driver.internal.core.cql.CqlRequestHandler.access$700(CqlRequestHandler.java:94)
        at com.datastax.oss.driver.internal.core.cql.CqlRequestHandler$NodeResponseCallback.processRetryVerdict(CqlRequestHandler.java:859)
        at com.datastax.oss.driver.internal.core.cql.CqlRequestHandler$NodeResponseCallback.processErrorResponse(CqlRequestHandler.java:828)
        at com.datastax.oss.driver.internal.core.cql.CqlRequestHandler$NodeResponseCallback.onResponse(CqlRequestHandler.java:655)
        at com.datastax.oss.driver.internal.core.channel.InFlightHandler.channelRead(InFlightHandler.java:257)
        at java.lang.Thread.run(Thread.java:748) [24 skipped]
Caused by: com.datastax.oss.driver.api.core.servererrors.ReadTimeoutException: Cassandra timeout during read query at consistency LOCAL_ONE (1 responses were required but only 0 replica responded)

Cassandra 的 system.log 片段----

DEBUG [ScheduledTasks:1] 2021-04-23 00:01:48,539  MonitoringTask.java:152 - 1 operations timed out in the last 5015 msecs:
<SELECT * FROM my query being run with limit - LIMIT 5000>, total time 10004 msec, timeout 10000 msec/cross-node
INFO  [ScheduledTasks:1] 2021-04-23 00:02:38,540  MessagingService.java:1302 - RANGE_SLICE messages were dropped in last 5000 ms: 0 internal and 1 cross node
. Mean internal dropped latency: 0 ms and Mean cross-node dropped latency: 10299 ms
INFO  [ScheduledTasks:1] 2021-04-23 00:02:38,551  StatusLogger.java:114 -
Pool Name                    Active   Pending      Completed   Blocked  All Time Blocked
ReadStage                         1         0     1736872997         0                 0
ContinuousPagingStage             0         0            586         0                 0
RequestResponseStage              0         0     1483193130         0                 0
ReadRepairStage                   0         0        9079516         0                 0
CounterMutationStage              0         0              0         0                 0
MutationStage                     0         0      351841038         0                 0
ViewMutationStage                 0         0              0         0                 0
CommitLogArchiver                 0         0          32961         0                 0
MiscStage                         0         0              0         0                 0
CompactionExecutor                0         0       12034828         0                 0
MemtableReclaimMemory             0         0          68612         0                 0
PendingRangeCalculator            0         0              9         0                 0
AntiCompactionExecutor            0         0              0         0                 0
GossipStage                       0         0       20137208         0                 0
SecondaryIndexManagement          0         0              0         0                 0
HintsDispatcher                   0         0           3798         0                 0
MigrationStage                    0         0              8         0                 0
MemtablePostFlush                 0         0         338955         0                 0
PerDiskMemtableFlushWriter_0         0         0          66297         0                 0
ValidationExecutor                0         0         247600         0                 0
Sampler                           0         0              0         0                 0
MemtableFlushWriter               0         0          41757         0                 0
InternalResponseStage             0         0         525242         0                 0
AntiEntropyStage                  0         0         767527         0                 0
CacheCleanupExecutor              0         0              0         0                 0
Native-Transport-Requests         0         0      958717934         0                65
CompactionManager                 0         0
MessagingService                n/a       0/0
Cache Type                     Size                 Capacity               KeysToSave
KeyCache                  104857216                104857600                      all
RowCache                          0                        0                      all
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2 回答 2

2

问题是您在DSBulkunload中运行命令来执行 a这意味着它必须执行全表扫描才能返回单行。SELECT COUNT()

此外，ALLOW FILTERING除非您将查询限制为单个分区，否则不建议使用。在任何情况下，ALLOW FILTERING即使在最佳情况下，其性能也是非常不可预测的。

我建议您改用 DSBulkcount命令，该命令针对 Cassandra 中的行数或分区数进行了优化。有关详细信息，请参阅使用 DSBulk 计算数据示例。

在这个DSBulk Counting 博客文章中还有其他示例，Alex Ott 已经在他的回答中链接了这些示例。干杯!

于 2021-04-24T14:12:43.707 回答
0

扩展select count(*) from sometable with where on clustering column and partial pk -- allow filtering令牌范围的附加条件，如下所示：and partial pk token(full_pk) > :start and token(full_pk) <= :end- 在这种情况下，DSBulk 将对发送到多个节点的特定令牌范围执行许多查询，并且不会像您的情况那样在单个节点上创建负载。

查看-query option 的文档，以及关于 DSBulk 的本系列博客文章中的第 4 篇博客，它可以提供更多信息和示例：1、2、3、4、5、6

于 2021-04-24T08:06:51.680 回答