Minor - P4 The "setShardVersion failed!" log line has a needless newline in it; this should be changed to ":<space>", like the "setShardVersion success:" message above it. See SERVER-13069 for rationale.
src/mongo/s/version_manager.cpp:386
LOG(1) << " setShardVersion failed!\n" << result;
Verbose query planning logging makes use of newlines in log messages by necessity for readability purposes. This isn't a problem.
Additionally some log lines use "\n" as their terminator; these could be cleaned up to use endl instead:
$ ag 'LOG\(.*\\n' db/exec/multi_plan.cpp 125: LOG(5) << "Best plan errored out switching to backup\n"; 143: LOG(5) << "Best plan had a blocking stage, became unblocked\n"; 253: LOG(5) << "Winning solution:\n" << bestSolution->toString() << endl; 258: LOG(5) << "Winner has blocking stage, looking for backup plan...\n"; 261: LOG(5) << "Candidate " << ix << " is backup child\n"; db/repl/master_slave.cpp 865: LOG(2) << "sync_pullOpLog " << ns << " syncedTo:" << syncedTo.toStringLong() << '\n'; 916: LOG(2) << "tailing=true\n"; 939: LOG(2) << "tailing & no new activity\n"; 975: LOG(2) << "first op time received: " << nextOpTime.toString() << '\n'; 977: LOG(1) << "initial run\n"; db/storage/mmap_v1/mmap_v1_extent_manager.cpp 469: LOG(n < 512 ? 1 : 0) << "warning: newExtent " << n << " scanned\n"; db/query/planner_analysis.cpp 693: LOG(5) << "PROJECTION: Current plan is:\n" << solnRoot->toString() << endl; 699: LOG(5) << "PROJECTION: claims to require doc adding fetch.\n"; 710: LOG(5) << "PROJECTION: requires fields\n"; db/query/query_planner.cpp 420: LOG(5) << "Planner: solution constructed from the cache:\n" << soln->toString(); 468: LOG(5) << "Forcing a table scan due to hinted $natural\n"; 787: LOG(5) << "Planner: outputted " << out->size() << " indexed solutions.\n"; db/query/find.cpp 460: LOG(5) << "getMore returned " << numResults << " results\n"; 487: LOG(5) << "Running query:\n" << cq->toString(); 662: LOG(5) << "Not caching executor but returning " << numResults << " results.\n"; s/version_manager.cpp 386: LOG(1) << " setShardVersion failed!\n" << result; util/tcmalloc_server_status_section.cpp 69: LOG(1) << "tcmallocPoolSize: " << tcmallocPoolSize << "\n";