cc12b8947b
bcb0cacac28e98a39dc856c574a0872fe17059e9 reindex, log, test: fixes #21379 (mruddy)
Pull request description:
Fixes #21379.
The blocks/blk?????.dat files are mutated and become increasingly malformed, or corrupt, as a result of running the re-indexing process.
The mutations occur after the re-indexing process has finished, as new blocks are appended, but are a result of a re-indexing process miscalculation that lingers in the block manager's `m_blockfile_info` `nSize` data until node restart.
These additions to the blk files are non-fatal, but also not desirable.
That is, this is a form of data corruption that the reading code is lenient enough to process (it skips the extra bytes), but it adds some scary looking log messages as it encounters them.
The summary of the problem is that the re-index process double counts the size of the serialization header (magic message start bytes [4 bytes] + length [4 bytes] = 8 bytes) while calculating the blk data file size (both values already account for the serialization header's size, hence why it is over accounted).
This bug manifests itself in a few different ways, after re-indexing, when a new block from a peer is processed:
1. If the new block will not fit into the last blk file processed while re-indexing, while remaining under the 128MiB limit, then the blk file is flushed to disk and truncated to a size that is 8 greater than it should be. The truncation adds zero bytes (see `FlatFileSeq::Flush` and `TruncateFile`).
1. If the last blk file processed while re-indexing has logical space for the new block under the 128 MiB limit:
1. If the blk file was not already large enough to hold the new block, then the zeros are, in effect, added by `fseek` when the file is opened for writing. Eight zero bytes are added to the end of the last blk file just before the new block is written. This happens because the write offset is 8 too great due to the miscalculation. The result is 8 zero bytes between the end of the last block and the beginning of the next block's magic + length + block.
1. If the blk file was already large enough to hold the new block, then the current existing file contents remain in the 8 byte gap between the end of the last block and the beginning of the next block's magic + length + block. Commonly, when this occcurs, it is due to the blk file containing blocks that are not connected to the block tree during reindex and are thus left behind by the reindex process and later overwritten when new blocks are added. The orphaned blocks can be valid blocks, but due to the nature of concurrent block download, the parent may not have been retrieved and written by the time the node was previously shutdown.
ACKs for top commit:
LarryRuane:
tested code-review ACK bcb0cacac28e98a39dc856c574a0872fe17059e9
ryanofsky:
Code review ACK bcb0cacac28e98a39dc856c574a0872fe17059e9. This is a disturbing bug with an easy fix which seems well-worth merging.
mzumsande:
ACK bcb0cacac28e98a39dc856c574a0872fe17059e9 (reviewed code and did some testing, I agree that it fixes the bug).
w0xlt:
tACK bcb0cacac2
Tree-SHA512: acc97927ea712916506772550451136b0f1e5404e92df24cc05e405bb09eb6fe7c3011af3dd34a7723c3db17fda657ae85fa314387e43833791e9169c0febe51
Unit tests
The sources in this directory are unit test cases. Boost includes a unit testing framework, and since Bitcoin Core already uses Boost, it makes sense to simply use this framework rather than require developers to configure some other framework (we want as few impediments to creating unit tests as possible).
The build system is set up to compile an executable called test_bitcoin
that runs all of the unit tests. The main source file for the test library is found in
util/setup_common.cpp.
Compiling/running unit tests
Unit tests will be automatically compiled if dependencies were met in ./configure
and tests weren't explicitly disabled.
After configuring, they can be run with make check.
To run the unit tests manually, launch src/test/test_bitcoin. To recompile
after a test file was modified, run make and then run the test again. If you
modify a non-test file, use make -C src/test to recompile only what's needed
to run the unit tests.
To add more unit tests, add BOOST_AUTO_TEST_CASE functions to the existing
.cpp files in the test/ directory or add new .cpp files that
implement new BOOST_AUTO_TEST_SUITE sections.
To run the GUI unit tests manually, launch src/qt/test/test_bitcoin-qt
To add more GUI unit tests, add them to the src/qt/test/ directory and
the src/qt/test/test_main.cpp file.
Running individual tests
test_bitcoin accepts the command line arguments from the boost framework.
For example, to run just the getarg_tests suite of tests:
test_bitcoin --log_level=all --run_test=getarg_tests
log_level controls the verbosity of the test framework, which logs when a
test case is entered, for example. test_bitcoin also accepts the command
line arguments accepted by bitcoind. Use -- to separate both types of
arguments:
test_bitcoin --log_level=all --run_test=getarg_tests -- -printtoconsole=1
The -printtoconsole=1 after the two dashes redirects the debug log, which
would normally go to a file in the test datadir
(BasicTestingSetup::m_path_root), to the standard terminal output.
... or to run just the doubledash test:
test_bitcoin --run_test=getarg_tests/doubledash
Run test_bitcoin --help for the full list.
Adding test cases
To add a new unit test file to our test suite you need
to add the file to src/Makefile.test.include. The pattern is to create
one test file for each class or source file for which you want to create
unit tests. The file naming convention is <source_filename>_tests.cpp
and such files should wrap their tests in a test suite
called <source_filename>_tests. For an example of this pattern,
see uint256_tests.cpp.
Logging and debugging in unit tests
make check will write to a log file foo_tests.cpp.log and display this file
on failure. For running individual tests verbosely, refer to the section
above.
To write to logs from unit tests you need to use specific message methods
provided by Boost. The simplest is BOOST_TEST_MESSAGE.
For debugging you can launch the test_bitcoin executable with gdb or lldb and
start debugging, just like you would with any other program:
gdb src/test/test_bitcoin
Segmentation faults
If you hit a segmentation fault during a test run, you can diagnose where the fault
is happening by running gdb ./src/test/test_bitcoin and then using the bt command
within gdb.
Another tool that can be used to resolve segmentation faults is valgrind.
If for whatever reason you want to produce a core dump file for this fault, you can do
that as well. By default, the boost test runner will intercept system errors and not
produce a core file. To bypass this, add --catch_system_errors=no to the
test_bitcoin arguments and ensure that your ulimits are set properly (e.g. ulimit -c unlimited).
Running the tests and hitting a segmentation fault should now produce a file called core
(on Linux platforms, the file name will likely depend on the contents of
/proc/sys/kernel/core_pattern).
You can then explore the core dump using
gdb src/test/test_bitcoin core
(gbd) bt # produce a backtrace for where a segfault occurred