[IMPALA-8179] Backend tests are flaky: time-based srand

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: Impala 3.2.0
• Component/s: Backend
• Epic Color: ghx-label-3
• Assignee: Joe McDonnell
• Reporter: Jim Apple
• Created: 11/Feb/19 01:15
• Updated: 16/Feb/19 00:01

Description

https://gerrit.cloudera.org/#/c/12124/9/be/src/service/unified-betest-main.cc added

    uint32_t seed = time(NULL);
    cout << "seed = " << seed << endl;
    srand(seed);

There is no way to force the seed, and backend tests using rand() are then flaky by default. We should make them unflaky by default (using a specific random seed) and we should also provide a way to override this by setting it by time or to a specific seed for just one run, to help with debugging.

If we want the coverage that comes from running with a different seed each time, we could run a test multiple times.