dnsdist: add pooling support for RemoteLoggerInterface

[esensar]

Short description

This adds a new kind of RemoteLoggerInterface: RemoteLoggerPool. It can take multiple other RemoteLoggerInterfaces and pass data to them in round-robin order by default.

This also adds additional option to newRemoteLogger, newFrameStreamTcpLogger and newFrameStreamUnixLogger: connectionCount, which can be used to generate a pool with multiple connections.

Closes: #14861

Checklist

I have:

• read the CONTRIBUTING.md document
• compiled this code
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)

[esensar]

There is a lot of noise in pdns/dnsdistdist/dnsdist-lua-bindings-protobuf.cc due to formatting. Let me know if that needs to be fixed or if I should add formatting in a separate PR.

[miodvallat]

Can you split this work in two commits, one with most of the formatting/whitespace changes and another with the actual work? This would indeed help reviewing.

[coveralls]

Pull Request Test Coverage Report for Build 13174750599

Details

• 77 of 191 (40.31%) changed or added relevant lines in 4 files are covered.
• 212 unchanged lines in 19 files lost coverage.
• Overall coverage decreased (-0.05%) to 64.671%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pdns/remote_logger_pool.hh	0	13	0.0%
pdns/remote_logger_pool.cc	0	22	0.0%
pdns/dnsdistdist/dnsdist-configuration-yaml.cc	5	34	14.71%
pdns/dnsdistdist/dnsdist-lua-bindings-protobuf.cc	72	122	59.02%

Files with Coverage Reduction	New Missed Lines	%
pdns/recursordist/negcache.hh	2	88.24%
modules/gsqlite3backend/gsqlite3backend.cc	2	94.44%
pdns/backends/gsql/gsqlbackend.cc	2	82.2%
ext/json11/json11.cpp	2	62.72%
pdns/recursordist/test-syncres_cc2.cc	3	88.91%
pdns/misc.hh	3	87.62%
pdns/packethandler.cc	3	72.49%
pdns/axfr-retriever.cc	3	67.34%
pdns/recursordist/lwres.cc	3	69.23%
pdns/iputils.hh	3	77.94%

Totals
Change from base Build 13160155488:	-0.05%
Covered Lines:	128299
Relevant Lines:	167314

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💛 - Coveralls

[miodvallat]

Can't comment about the usefulness, but the code reads ok.

Can you update the meson rules so that the CI gets a chance to pass?

[esensar]

Can't comment about the usefulness, but the code reads ok.

Can you update the meson rules so that the CI gets a chance to pass?

Thank you. I went for a very simple approach for now. There was a discussion of different strategies (for picking the interface(s) to pass data to), but I think these are easy to add onto this, since it really just forwards data to one of the interfaces.

[miodvallat]

One concern, though, is that RemoteLoggerPool::queueData() is not thread-safe. Are you sure that there is no risk of multiple threads attempting to invoke it? If so, you need to protect the d_pool_it value changes with some serialization object.

[esensar]

One concern, though, is that RemoteLoggerPool::queueData() is not thread-safe. Are you sure that there is no risk of multiple threads attempting to invoke it? If so, you need to protect the d_pool_it value changes with some serialization object.

You are right. I have overlooked that. I can see that RemoteLogger has a lock in queueData, so I guess there is that risk, so something similar needs to be done here.

[esensar]

Also, I was wondering if I should change the implementation of toString() for this class. Right now it could produce a very long string, because it is showing information of all the underlying loggers.

The alternative would be to just show number of loggers and stats, but then that would hide the addresses. This also brings me to the name and address implementation. I am not sure what their exact purpose is, so I was not sure how to implement them for this, since it is not guaranteed that all loggers will be the same (it is right now, because the only usage is in generating multiple instances of the same logger, but in general case, it is not).