mirror of
https://github.com/ClickHouse/ClickHouse.git
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53 lines
2.1 KiB
C++
53 lines
2.1 KiB
C++
#include <city.h>
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#include <iostream>
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#include <IO/ReadBufferFromFileDescriptor.h>
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#include <IO/ReadHelpers.h>
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#include <base/hex.h>
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/** A tool to easily prove if "Checksum doesn't match: corrupted data"
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* errors are caused by random bit flips due to hardware issues.
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* It frequently happens due to bad memory on network switches
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* (at least about a few times a year in a fleet of ~1200 ClickHouse servers).
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*
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* These hardware errors don't cause any data corruption issues in ClickHouse,
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* because ClickHouse always validate it's own 128 bit checksums
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* and report errors if checksum doesn't match.
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*
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* Client can simply retry the query.
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* But ops engineers want to validate if the issue is real hardware error or not.
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* If checksum difference is caused by single bit flip,
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* we can be sure that this is hardware error, because random bit flips
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* have low probability to happen due to software bugs.
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*
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* Usage:
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echo -ne "\x82\x6b\x00\x00\x00\x62\x00\x00\x00\xf2\x3b\x01\x00\x02\xff\xff\xff\xff\x00\x01\x01\x2c\x75\x6e\x69\x71\x49\x66\x28\x44\x65\x76\x69\x63\x65\x49\x44\x48\x61\x73\x68\x2c\x20\x65\x71\x75\x61\x6c\x73\x28\x53\x65\x73\x73\x69\x6f\x6e\x54\x79\x70\x65\x2c\x20\x30\x29\x29\x28\x41\x67\x67\x72\x65\x67\x61\x74\x65\x46\x75\x6e\x63\x74\x69\x6f\x6e\x28\x3f\x00\xf0\x03\x2c\x20\x55\x49\x6e\x74\x36\x34\x2c\x20\x55\x49\x6e\x74\x38\x29\x00\x00" | ./checksum-for-compressed-block-find-bit-flips | grep 8b40502d2ffe5b712b52e03c505ca49f
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8b40502d2ffe5b712b52e03c505ca49f 32, 6
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*/
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std::string flipBit(std::string s, size_t pos)
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{
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s[pos / 8] ^= 1 << pos % 8;
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return s;
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}
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int main(int, char **)
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{
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using namespace DB;
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ReadBufferFromFileDescriptor in(STDIN_FILENO);
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std::string str;
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readStringUntilEOF(str, in);
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for (size_t pos = 0; pos < str.size() * 8; ++pos)
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{
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auto flipped = flipBit(str, pos);
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auto checksum = CityHash_v1_0_2::CityHash128(flipped.data(), flipped.size());
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std::cout << getHexUIntLowercase(checksum.first) << getHexUIntLowercase(checksum.second) << "\t" << pos / 8 << ", " << pos % 8 << "\n";
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}
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return 0;
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}
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