Why linkToDbNative must be called before linkToDb?

[kcudnik]

According to this comment https://github.com/Azure/sonic-swss-common/blob/master/common/logger.h#L81, why? If this is public API it should not be dependent of call order. Could this method be private or this issue should be fixed in proper way.

[mikeberesford]

I'd add that if the call order is required and changing the public API isn't possible, the API should probably enforce the call order - once linkToDbNative is called, calls to linkToDb should probably result in an error instead of succeeding silently.

[kcudnik]

btw. calling linkToDbNative twiece will carash beceuse previous thread is still running when dtr is called

#0  0x00007f5d1d85920b in raise () from /lib64/libc.so.6
#1  0x00007f5d1d83b524 in abort () from /lib64/libc.so.6
#2  0x00007f5d1dc04657 in ?? () from /usr/lib64/libstdc++.so.6
#3  0x00007f5d1dc0fef6 in ?? () from /usr/lib64/libstdc++.so.6
#4  0x00007f5d1dc0ff41 in std::terminate() () from /usr/lib64/libstdc++.so.6
#5  0x00007f5d1ddf82ca in std::thread::~thread (this=<optimized out>, __in_chrg=<optimized out>) at /usr/include/c++/9.1.0/thread:139
#6  std::default_delete<std::thread>::operator() (this=0x7f5d1de5b380 <swss::Logger::getInstance()::m_logger+160>, __ptr=<optimized out>)
    at /usr/include/c++/9.1.0/bits/unique_ptr.h:81
#7  std::unique_ptr<std::thread, std::default_delete<std::thread> >::reset (__p=<optimized out>, this=0x7f5d1de5b380 <swss::Logger::getInstance()::m_logger+160>)
    at /usr/include/c++/9.1.0/bits/unique_ptr.h:399
#8  swss::Logger::linkToDbNative (dbName="syncd") at logger.cpp:152

[kcudnik]

also, why we need to create new thread every time linkToDbNative is called ?

[kcudnik]

i was looking on logger code for half day and i couldn't figure out why linkToDbNative must be called before linkToDb :(

[qiluo-msft]

@marian-pritsak Could you help check this issue?