cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From benjamin roth <brs...@gmail.com>
Subject Re: nodes are always out of sync
Date Sat, 01 Apr 2017 19:17:08 GMT
Tl;Dr: there are race conditions in a repair and it is not trivial to fix
them. So we rather stay with these race conditions. Actually they don't
really hurt. The worst case is that ranges are repaired that don't really
need a repair.

Am 01.04.2017 21:14 schrieb "Chris Lohfink" <clohfink85@gmail.com>:

> Repairs do not have an ability to instantly build a perfect view of its
> data between your 3 nodes at an exact time. When a piece of data is written
> there is a delay between when they applied between the nodes, even if its
> just 500ms. So if a request to read the data and build the merkle tree of
> the data occurs and it finishes on node1 at 12:01 while node2 finishes at
> 12:02 the 1 minute or so delta (even if a few seconds, or if using snapshot
> repairs) between the partition/range hashes in the merkle tree can be
> different. On a moving data set its almost impossible to have the clusters
> perfectly in sync for a repair. I wouldnt worry about that log message. If
> you are worried about consistency between your read/writes use each or
> local quorum for both.
>
> Chris
>
> On Thu, Mar 30, 2017 at 1:22 AM, Roland Otta <Roland.Otta@willhaben.at>
> wrote:
>
>> hi,
>>
>> we see the following behaviour in our environment:
>>
>> cluster consists of 6 nodes (cassandra version 3.0.7). keyspace has a
>> replication factor 3.
>> clients are writing data to the keyspace with consistency one.
>>
>> we are doing parallel, incremental repairs with cassandra reaper.
>>
>> even if a repair just finished and we are starting a new one
>> immediately, we can see the following entries in our logs:
>>
>> INFO  [RepairJobTask:1] 2017-03-30 10:14:00,782 SyncTask.java:73 -
>> [repair #d0f651f6-1520-11e7-a443-d9f5b942818e] Endpoints /192.168.0.188
>> and /192.168.0.191 have 1 range(s) out of sync for ad_event_history
>> INFO  [RepairJobTask:2] 2017-03-30 10:14:00,782 SyncTask.java:73 -
>> [repair #d0f651f6-1520-11e7-a443-d9f5b942818e] Endpoints /192.168.0.188
>> and /192.168.0.189 have 1 range(s) out of sync for ad_event_history
>> INFO  [RepairJobTask:4] 2017-03-30 10:14:00,782 SyncTask.java:73 -
>> [repair #d0f651f6-1520-11e7-a443-d9f5b942818e] Endpoints /192.168.0.189
>> and /192.168.0.191 have 1 range(s) out of sync for ad_event_history
>> INFO  [RepairJobTask:2] 2017-03-30 10:14:03,997 SyncTask.java:73 -
>> [repair #d0fa70a1-1520-11e7-a443-d9f5b942818e] Endpoints /192.168.0.26
>> and /192.168.0.189 have 2 range(s) out of sync for ad_event_history
>> INFO  [RepairJobTask:1] 2017-03-30 10:14:03,997 SyncTask.java:73 -
>> [repair #d0fa70a1-1520-11e7-a443-d9f5b942818e] Endpoints /192.168.0.26
>> and /192.168.0.191 have 2 range(s) out of sync for ad_event_history
>> INFO  [RepairJobTask:4] 2017-03-30 10:14:03,997 SyncTask.java:73 -
>> [repair #d0fa70a1-1520-11e7-a443-d9f5b942818e] Endpoints /192.168.0.189
>> and /192.168.0.191 have 2 range(s) out of sync for ad_event_history
>> INFO  [RepairJobTask:1] 2017-03-30 10:14:05,375 SyncTask.java:73 -
>> [repair #d0fbd033-1520-11e7-a443-d9f5b942818e] Endpoints /192.168.0.189
>> and /192.168.0.191 have 1 range(s) out of sync for ad_event_history
>> INFO  [RepairJobTask:2] 2017-03-30 10:14:05,375 SyncTask.java:73 -
>> [repair #d0fbd033-1520-11e7-a443-d9f5b942818e] Endpoints /192.168.0.189
>> and /192.168.0.190 have 1 range(s) out of sync for ad_event_history
>> INFO  [RepairJobTask:4] 2017-03-30 10:14:05,375 SyncTask.java:73 -
>> [repair #d0fbd033-1520-11e7-a443-d9f5b942818e] Endpoints /192.168.0.190
>> and /192.168.0.191 have 1 range(s) out of sync for ad_event_history
>>
>> we cant see any hints on the systems ... so we thought everything is
>> running smoothly with the writes.
>>
>> do we have to be concerned about the nodes always being out of sync or
>> is this a normal behaviour in a write intensive table (as the tables
>> will never be 100% in sync for the latest inserts)?
>>
>> bg,
>> roland
>>
>>
>>
>

Mime
View raw message