[IMPALA-10598] test_cache_reload_validation is flaky

• Type: Test
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: Impala 4.0.0
• Labels: flaky-test
• Epic Color: ghx-label-4
• Assignee: Vihang Karajgaonkar
• Reporter: Vihang Karajgaonkar
• Created: 19/Mar/21 20:52
• Updated: 26/Mar/21 19:41
• Resolved: 26/Mar/21 19:41

Description

I noticed that when I run

bin/impala-py.test tests/query_test/test_hdfs_caching.py -k test_cache_reload_validation

I see a the following failure on master branch.

 TestHdfsCachingDdl.test_cache_reload_validation[protocol: beeswax | exec_option: {'batch_size': 0, 'num_nodes': 0, 'disable_codegen_rows_threshold': 5000, 'disable_codegen': False, 'abort_on_error': 1, 'exec_single_node_rows_threshold': 0} | table_format: text/none] 
tests/query_test/test_hdfs_caching.py:269: in test_cache_reload_validation
    assert num_entries_pre + 4 == get_num_cache_requests(), \
E   AssertionError: Adding the tables should be reflected by the number of cache directives.
E   assert (2 + 4) == 7
E    +  where 7 = get_num_cache_requests()

This failure is reproducible for me every time but I am not sure why the jenkins job don't show this test failure. When I looked into this I found that the test depends on the method
get the number of cache directives on the hdfs.

  def get_num_cache_requests_util():
    rc, stdout, stderr = exec_process("hdfs cacheadmin -listDirectives -stats")
    assert rc == 0, 'Error executing hdfs cacheadmin: %s %s' % (stdout, stderr)
    return len(stdout.split('\n'))

This output of this command when there are no entries is

Found 0 entries

when there are entries the output looks like

Found 4 entries
  ID POOL       REPL EXPIRY  PATH                                                    BYTES_NEEDED  BYTES_CACHED  FILES_NEEDED  FILES_CACHED
 225 testPool      8 never   /test-warehouse/cachedb.db/cached_tbl_reload                       0             0             0             0
 226 testPool      8 never   /test-warehouse/cachedb.db/cached_tbl_reload_part                  0             0             0             0
 227 testPool      8 never   /test-warehouse/cachedb.db/cached_tbl_reload_part/j=1              0             0             0             0
 228 testPool      8 never   /test-warehouse/cachedb.db/cached_tbl_reload_part/j=2              0             0             0             0

When there are no entries there is also a additional new line which is counted.
So when there are no entries the method outputs 2 and when there are 4 entries the method outputs 7 which causes the failure because the test expects 2+4.