ClickHouse

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#include <Core/ServerUUID.h>
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#include <IO/ReadBufferFromFile.h>
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#include <IO/WriteBufferFromFile.h>
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#include <IO/ReadHelpers.h>
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#include <IO/WriteHelpers.h>
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#include <Common/logger_useful.h>
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namespace DB
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{
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namespace ErrorCodes
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{
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    extern const int CANNOT_CREATE_FILE;
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}
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void ServerUUID::load(const fs::path & server_uuid_file, Poco::Logger * log)
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{
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    server_uuid = loadServerUUID(server_uuid_file, log);
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}
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UUID loadServerUUID(const fs::path & server_uuid_file, Poco::Logger * log)
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{
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    /// Write a uuid file containing a unique uuid if the file doesn't already exist during server start.
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    if (fs::exists(server_uuid_file))
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    {
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        try
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        {
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            UUID uuid;
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            ReadBufferFromFile in(server_uuid_file);
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            readUUIDText(uuid, in);
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            assertEOF(in);
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            return uuid;
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        }
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        catch (...)
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        {
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            /// As for now it's ok to just overwrite it, because persistency in not essential.
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            LOG_ERROR(log, "Cannot read server UUID from file {}: {}. Will overwrite it",
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                      server_uuid_file.string(), getCurrentExceptionMessage(true));
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        }
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    }
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    try
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    {
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        UUID new_uuid = UUIDHelpers::generateV4();
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        auto uuid_str = toString(new_uuid);
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        WriteBufferFromFile out(server_uuid_file);
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        out.write(uuid_str.data(), uuid_str.size());
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        out.sync();
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        out.finalize();
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        return new_uuid;
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    }
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    catch (...)
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    {
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        throw Exception(ErrorCodes::CANNOT_CREATE_FILE, "Caught Exception {} while writing the Server UUID file {}",
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                        getCurrentExceptionMessage(false), server_uuid_file.string());
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    }
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}
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}
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