我试图在Docker中使用Cassandra集群模拟提示切换。
提示切换有效：
root@2f5aa8d649e2:/# nodetool statushandoff
Hinted handoff is running
密钥空间的复制因子为3：
cqlsh> DESCRIBE KEYSPACE imdb;
CREATE KEYSPACE imdb WITH replication = {'class': 'NetworkTopologyStrategy', 'dc1': '2', 'dc2': '1'} AND durable_writes = true;
然后我关闭一个节点，打开跟踪并插入一个新行：
cqlsh:imdb> insert into movies_by_actor (actor, movie_id, character, movie_title, salary) values ('TomHanks', uuid(), 'Character', 'Title', 1000);
Tracing session: e4a2cc20-42ce-11e7-bd49-cf534e0135c6
activity | timestamp | source | source_elapsed | client
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------+------------+----------------+-----------
Execute CQL3 query | 2017-05-27 11:23:22.466000 | 172.13.0.2 | 0 | 127.0.0.1
Parsing insert into movies_by_actor (actor, movie_id, character, movie_title, salary) values ('TomHanks', uuid(), 'Character', 'Title', 1000); [Native-Transport-Requests-1] | 2017-05-27 11:23:22.467000 | 172.13.0.2 | 364 | 127.0.0.1
Preparing statement [Native-Transport-Requests-1] | 2017-05-27 11:23:22.467000 | 172.13.0.2 | 727 | 127.0.0.1
Determining replicas for mutation [Native-Transport-Requests-1] | 2017-05-27 11:23:22.468000 | 172.13.0.2 | 1354 | 127.0.0.1
Sending MUTATION message to /172.13.0.3 [MessagingService-Outgoing-/172.13.0.3-Small] | 2017-05-27 11:23:22.468000 | 172.13.0.2 | 1722 | 127.0.0.1
Sending MUTATION message to /172.13.0.6 [MessagingService-Outgoing-/172.13.0.6-Small] | 2017-05-27 11:23:22.468000 | 172.13.0.2 | 1722 | 127.0.0.1
MUTATION message received from /172.13.0.2 [MessagingService-Incoming-/172.13.0.2] | 2017-05-27 11:23:22.469000 | 172.13.0.3 | 30 | 127.0.0.1
MUTATION message received from /172.13.0.2 [MessagingService-Incoming-/172.13.0.2] | 2017-05-27 11:23:22.469000 | 172.13.0.6 | 35 | 127.0.0.1
Appending to commitlog [MutationStage-1] | 2017-05-27 11:23:22.469000 | 172.13.0.3 | 294 | 127.0.0.1
Appending to commitlog [MutationStage-1] | 2017-05-27 11:23:22.469000 | 172.13.0.6 | 292 | 127.0.0.1
Adding to movies_by_actor memtable [MutationStage-1] | 2017-05-27 11:23:22.469000 | 172.13.0.6 | 486 | 127.0.0.1
Enqueuing response to /172.13.0.2 [MutationStage-1] | 2017-05-27 11:23:22.469000 | 172.13.0.6 | 660 | 127.0.0.1
REQUEST_RESPONSE message received from /172.13.0.3 [MessagingService-Incoming-/172.13.0.3] | 2017-05-27 11:23:22.470000 | 172.13.0.2 | 3659 | 127.0.0.1
Processing response from /172.13.0.3 [RequestResponseStage-2] | 2017-05-27 11:23:22.470000 | 172.13.0.2 | 3820 | 127.0.0.1
Sending REQUEST_RESPONSE message to /172.13.0.2 [MessagingService-Outgoing-/172.13.0.2-Small] | 2017-05-27 11:23:22.472000 | 172.13.0.6 | 3533 | 127.0.0.1
REQUEST_RESPONSE message received from /172.13.0.6 [MessagingService-Incoming-/172.13.0.6] | 2017-05-27 11:23:22.473000 | 172.13.0.2 | 34 | 127.0.0.1
Processing response from /172.13.0.6 [RequestResponseStage-3] | 2017-05-27 11:23:22.473000 | 172.13.0.2 | 523 | 127.0.0.1
Request complete | 2017-05-27 11:23:22.469919 | 172.13.0.2 | 3919 | 127.0.0.1
从日志中可以看出，协调器节点172.13.0.2处理请求并联系节点172.13.0.3和172.13.0.6。我希望节点172.13.0.2保存提示的切换，因为第三个节点不可用。但是当我检查system.hints表时，它是空的：
cqlsh:imdb> select * from system.hints;
target_id | hint_id | message_version | mutation
-----------+---------+-----------------+----------
(0 rows)
一致性级别设置为默认ONE。有人可以解释一下存储的暗示切换的位置吗？
答案 0 :(得分：1)
最新版本的cassandra不会在>>> has_odd_number([0])
False
>>> has_odd_number([1])
True
表中存储提示。
提示存储在cassandra 3.0的平面文件中。如果使用大于3.0的cassandra版本，则必须查看system.hints
cassandra.yaml检查# Directory where Cassandra should store hints.
# If not set, the default directory is $CASSANDRA_HOME/data/hints.
hints_directory: "C:/Program Files/DataStax-DDC/data/hints"
# How often hints should be flushed from the internal buffers to disk.
# Will *not* trigger fsync.
hints_flush_period_in_ms: 10000
中的上述2个值并查找其中的提示。