materialized view rebuild automatically after drop multiple views

Background:

Cassandra version: 3.0.12

Our cassandra cluster has 9 host for DC1 and 3 host for DC2,

each host :

by using nodetool status, node load in DC1 is about 1.5 TB, node load in DC2 is about 4 TB

QPS: 270

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Problem we met:

In DC1 1 node, enter the cql command line and execute command like following in sametime:

"drop materialized view if exists view1; 

drop materialized view if exists view2;

drop materialized view if exists view3;

drop materialized view if exists view4;"

after a while, command line display warning like "schema version mismatch detected..." (sorry we cannot find the exact output for that time)

After that we find view files in node: "DC1 7" hasn't be deleted yet.

at this moment, we find performance of cluster drop sharp, the cluster almost stop response to any request.

by runing:  select * from system.views_builds_in_progress;

we can see several views were building.

then we execte:

1,   nodetool stop VIEW_BUILD  in each node

2, in cql: delete from system.views_builds_in_progress where view_name=XXXX

3, rolling restart cassandra nodes

 

about an hours later, performance increase to normal.

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Why this happen?

How to avoid this problem?

Any better way to deal with this problem?