Summary

In DSE 5.0.4 the cassandra logback.xml is shipped with maxIndex = 50 for the SolrValidationErrorAppender.
This generates an error because the max index window is larger than than the limit maxWindowSize.

These messages are only warnings and there is no issue with cassandra, also because the maxIndex is reduced automatically.

Symptoms

The error that is thrown is quite self describing:

cassandra_1 | 21:11:59,515 |-WARN in ch.qos.logback.core.rolling.FixedWindowRollingPolicy@5fbe4146 - Large window sizes are not allowed. 
cassandra_1 | 21:11:59,515 |-WARN in ch.qos.logback.core.rolling.FixedWindowRollingPolicy@5fbe4146 - MaxIndex reduced to 21

Cause

The logback piece of code where this error is generated is here:

 final int maxWindowSize = getMaxWindowSize();
         if ((maxIndex - minIndex) > maxWindowSize) {
               addWarn("Large window sizes are not allowed.");
               maxIndex = minIndex + maxWindowSize;
               addWarn("MaxIndex reduced to " + maxIndex);
        }

Ref: http://logback.qos.ch/xref/ch/qos/logback/core/rolling/FixedWindowRollingPolicy.html

Workaround

Reducing the maxIndex for SolrValidationErrorAppender from 50 to 20, in the cassandra logback.xml, will avoid the warning messages.

Solution

An internal jira has been logged for this: DSP-12061