Unit test failures when using multiple jobs and RANDOM_CTX

hodlinator commented at 2:41 pm on August 22, 2024: contributor

Is there an existing issue for this?

I have searched the existing issues

Current behaviour

While testing #30571 using:

0RANDOM_CTX_SEED=1 make -j16 check

…I discovered that 97e16f57042cab07e5e73f6bed19feec2006e4f7 from #29625 leads to test failures within the first 10 seconds in blockfilter_index_tests/blockfilter_index_initial_sync, argsman_tests/util_datadir or addrman_tests (probably more).

Running without the environment variable, or single-threaded, passes:

0make -j16 check
1RANDOM_CTX_SEED=1 make -j1 check

Expected behaviour

Should always work, as it did before 97e16f57042cab07e5e73f6bed19feec2006e4f7.

Steps to reproduce

Console command:

0RANDOM_CTX_SEED=1 make -j8 check

Relevant log output

Excerpts:

02024-08-22T14:07:48.334146Z (mocktime: 2020-08-31T15:34:12Z) [basic block filter index] [util/thread.cpp:20] [TraceThread] basic block filter index thread start
12024-08-22T14:07:48.334255Z (mocktime: 2020-08-31T15:34:12Z) [basic block filter index] [flatfile.cpp:69] [Allocate] [validation] Pre-allocating up to position 0x100000 in fltr00000.dat
22024-08-22T14:07:48.334479Z (mocktime: 2020-08-31T15:34:12Z) [basic block filter index] [index/base.cpp:206] [Sync] Syncing basic block filter index with block chain from height 0
32024-08-22T14:07:48.345502Z (mocktime: 2020-08-31T15:34:12Z) [basic block filter index] [index/base.cpp:220] [Sync] basic block filter index is enabled at height 100
42024-08-22T14:07:48.345523Z (mocktime: 2020-08-31T15:34:12Z) [basic block filter index] [util/thread.cpp:22] [TraceThread] basic block filter index thread exit
52024-08-22T14:07:48.434324Z (mocktime: 2020-08-31T15:34:12Z) [test] [flatfile.cpp:44] [Open] Unable to open file /run/user/1001/test_common_Bitcoin Core/cd149241dcbf7d8e2e5ebaf5a96aafdab9953a29260dce4e20e44f11a4b6efa5/regtest/indexes/blockfilter/basic/fltr00000.dat
6test/blockfilter_index_tests.cpp(46): error: in "blockfilter_index_tests/blockfilter_index_initial_sync": check filter_index.LookupFilter(block_index, filter) has failed
72024-08-22T14:07:48.434406Z (mocktime: 2020-08-31T15:34:12Z) [test] [flatfile.cpp:44] [Open] Unable to open file /run/user/1001/test_common_Bitcoin Core/cd149241dcbf7d8e2e5ebaf5a96aafdab9953a29260dce4e20e44f11a4b6efa5/regtest/indexes/blockfilter/basic/fltr00000.dat
8test/blockfilter_index_tests.cpp(48): error: in "blockfilter_index_tests/blockfilter_index_initial_sync": check filter_index.LookupFilterRange(block_index->nHeight, block_index, filters) has failed
9test/blockfilter_index_tests.cpp(55): error: in "blockfilter_index_tests/blockfilter_index_initial_sync": check filter.GetHash() == expected_filter.GetHash() has failed [9a538906e6466ebd2617d321f71bc94e56056ce213d366773699e28158e00614 != b17ba25562f198a43d1fc5e4b7114ac5346c5dcc85b95ed19278bbfa30de301f]

 0test/argsman_tests.cpp(25): Entering test suite "argsman_tests"
 1test/argsman_tests.cpp(27): Entering test case "util_datadir"
 22024-08-22T14:21:36Z SeedRandomForTest: Setting random seed for current tests to RANDOM_CTX_SEED=0000000000000000000000000000000000000000000000000000000000000001
 32024-08-22T14:21:36.227485Z [test] [init/common.cpp:149] [LogPackageVersion] Bitcoin Core version v27.99.0-97e16f57042c (release build)
 42024-08-22T14:21:36.227525Z [test] [node/chainstatemanager_args.cpp:57] [ApplyArgsManOptions] Script verification uses 15 additional threads
 52024-08-22T14:21:36.227556Z [test] [kernel/context.cpp:18] [Context] Using the 'sse4(1way),sse41(4way),avx2(8way)' SHA256 implementation
 62024-08-22T14:21:36.227561Z [test] [random.cpp:114] [ReportHardwareRand] Using RdSeed as an additional entropy source
 72024-08-22T14:21:36.227563Z [test] [random.cpp:117] [ReportHardwareRand] Using RdRand as an additional entropy source
 82024-08-22T14:21:36.233950Z [test] [script/sigcache.cpp:104] [InitSignatureCache] Using 16 MiB out of 16 MiB requested for signature cache, able to store 524288 elements
 92024-08-22T14:21:36.239326Z [test] [validation.cpp:2108] [InitScriptExecutionCache] Using 16 MiB out of 16 MiB requested for script execution cache, able to store 524288 elements
10test/argsman_tests.cpp(27): Leaving test case "util_datadir"; testing time: 12446us
11test/argsman_tests.cpp(171): Entering test case "util_CheckValue"
12test_bitcoin: test/util/setup_common.cpp:294: void ChainTestingSetup::LoadVerifyActivateChainstate(): Assertion `status == node::ChainstateLoadStatus::SUCCESS' failed.
13make[3]: *** [Makefile:22560: test/argsman_tests.cpp.test] Error 1

0Entering test module "Bitcoin Core Test Suite"
1test/addrman_tests.cpp(62): Entering test suite "addrman_tests"
2test/addrman_tests.cpp(64): Entering test case "addrman_simple"
3terminate called after throwing an instance of 'std::filesystem::__cxx11::filesystem_error'
4  what():  filesystem error: cannot remove all: No such file or directory [/run/user/1001/test_common_Bitcoin Core/cd149241dcbf7d8e2e5ebaf5a96aafdab9953a29260dce4e20e44f11a4b6efa5] [/run/user/1001/test_common_Bitcoin Core/cd149241dcbf7d8e2e5ebaf5a96aafdab9953a29260dce4e20e44f11a4b6efa5/regtest/blocks/rev00000.dat]
5make[3]: *** [Makefile:22560: test/addrman_tests.cpp.test] Error 1

How did you obtain Bitcoin Core

Compiled from source

What version of Bitcoin Core are you using?

97e16f57042cab07e5e73f6bed19feec2006e4f7

Operating system and version

NixOS unstable (Linux)

Machine specifications

16 logical cores, intel SSD

maflcko added the label Tests on Aug 22, 2024

maflcko commented at 3:19 pm on August 22, 2024: member

Nice fine. RANDOM_CTX_SEED is only really for debugging single unit tests after the fact that they failed, but it would be nice to fix this nonetheless.

hodlinator commented at 1:19 pm on August 23, 2024: contributor

Thinking about it some more, it makes sense that if we give all jobs the same random seed and 97e16f57042cab07e5e73f6bed19feec2006e4f7 makes the test folder generation deterministic, the jobs will trample over each other. If that is the case, it’s probably better bring back some non-determinism in the folder generation.

maflcko commented at 1:38 pm on August 23, 2024: member

Correct. The easiest fix would be to just use GetStrongRandBytes, however, I am not sure how slow that’d be in the worst case.

Another possible fix would be to move the SeedRandomForTest after the fuzz target’s init function, but before ResetCoverageCounters. However that’d still break if the fuzz target spun up a TestingSetup.

Another possible fix would be to instead use the hash of the current folder generator, as well as the hash of the pid. Which may obviously break once the kernel wraps the pids, but I am not sure how likely that is.

hodlinator commented at 2:07 pm on August 23, 2024: contributor

Top of setup_common.cpp is a bit damning:

0/** Random context to get unique temp data dirs. Separate from g_insecure_rand_ctx, which can be seeded from a const env var */
1static FastRandomContext g_insecure_rand_ctx_temp_path;

Together with the comment added in #29625 in test/util/random.cpp (“GetRandHash is no longer truly random”):

0    // Do this once, on the first call, regardless of seedtype, because once
1    // MakeRandDeterministicDANGEROUS is called, the output of GetRandHash is
2    // no longer truly random. It should be enough to get the seed once for the
3    // process.

Folder generation runs const auto rand_str{g_insecure_rand_ctx_temp_path.rand256().ToString()} which internally calls:

0void FastRandomContext::fillrand(Span<std::byte> output) noexcept
1{
2    if (requires_seed) RandomSeed();
3    rng.Keystream(output);
4}

..which uses the now deterministic GetRandHash().

0void FastRandomContext::RandomSeed() noexcept
1{
2    uint256 seed = GetRandHash();
3    rng.SetKey(MakeByteSpan(seed));
4    requires_seed = false;
5}

=> :boom: @sipa Would you be okay with us undoing the move of SeedRandomForTest from your 97e16f57042cab07e5e73f6bed19feec2006e4f7 so it happens after the folder name generation like it used to, meaning that part would not be affected by a deterministic seed (potentially being the same for multiple jobs if RANDOM_CTX_SEED is set)?

sipa commented at 2:10 pm on August 23, 2024: member

@hodlinator I probably won’t have time to look into this the next two weeks, but I’m happy to defer to @maflcko on this.

Unit test failures when using multiple jobs and RANDOM_CTX_SEED #30696