我们使用 java datastax cassandra 驱动程序2.1.2。我们使用的 Cassandra 版本是2.0.9.
我们有我们构建的语句，QueryBuilder并且我们正在将一致性级别设置为TWO显式的语句。
Select selectStatement = QueryBuilder.select().from(ARTICLES);
selectStatement.where(eq(ORGANIZATION_ID, organizationId));
selectStatement.setConsistencyLevel(ConsistencyLevel.TWO);
final ResultSet rs = session.execute(selectStatement);
//call to all() will be removed since it is enough to iterate over result set
//and then you get pagination for free instead of loading everything in
//memory
List<Row> rows = rs.all();
for (final Row row : rows) {
//do something with Row, convert to POJO
}
我们得到这样的异常：
com.datastax.driver.core.exceptions.ReadTimeoutException: Cassandra timeout during read query at consistency ALL (3 responses were required but only 2 replica responded)
com.datastax.driver.core.exceptions.ReadTimeoutException.copy (ReadTimeoutException.java:69)
com.datastax.driver.core.DefaultResultSetFuture.extractCauseFromExecutionException (DefaultResultSetFuture.java:259)
com.datastax.driver.core.ArrayBackedResultSet$MultiPage.prepareNextRow (ArrayBackedResultSet.java:279)
com.datastax.driver.core.ArrayBackedResultSet$MultiPage.isExhausted (ArrayBackedResultSet.java:239)
com.datastax.driver.core.ArrayBackedResultSet$1.hasNext (ArrayBackedResultSet.java:122)
com.datastax.driver.core.ArrayBackedResultSet.all (ArrayBackedResultSet.java:111)
I know that calling all() on ResultSet makes it load all articles for organization in memory and work with it and creates load on cassandra. This will be removed as noted in comments. This can cause read timeout but I am still puzzled why in exception message there is ALL.
Question is why exception is telling that consistency level ALL is used when we set it to TWO for original statement. Is all() internally doing something with query and using CL ALL by default?