SERVER-29152 Do not cache logging ostream in threadlocal when in other thread-specific contexts

2 files changed, 16 insertions, 5 deletions

diff --git a/src/mongo/logger/logstream_builder.cpp b/src/mongo/logger/logstream_builder.cpp
index af055be3120..2378558bd4a 100644
--- a/src/mongo/logger/logstream_builder.cpp
+++ b/src/mongo/logger/logstream_builder.cpp
@@ -80,12 +80,14 @@ LogstreamBuilder::LogstreamBuilder(MessageLogDomain* domain,
 LogstreamBuilder::LogstreamBuilder(MessageLogDomain* domain,
                                    StringData contextName,
                                    LogSeverity severity,
-                                   LogComponent component)
+                                   LogComponent component,
+                                   bool shouldCache)
     : _domain(domain),
       _contextName(contextName.toString()),
       _severity(std::move(severity)),
       _component(std::move(component)),
-      _tee(nullptr) {}
+      _tee(nullptr),
+      _shouldCache(shouldCache) {}
 
 LogstreamBuilder::LogstreamBuilder(logger::MessageLogDomain* domain,
                                    StringData contextName,
@@ -110,7 +112,8 @@ LogstreamBuilder::~LogstreamBuilder() {
             _tee->write(_os->str());
         }
         _os->str("");
-        if (isThreadOstreamCacheInitialized && !threadOstreamCache.getMake()->get()) {
+        if (_shouldCache && isThreadOstreamCacheInitialized &&
+            !threadOstreamCache.getMake()->get()) {
             *threadOstreamCache.get() = std::move(_os);
         }
     }
@@ -124,7 +127,8 @@ void LogstreamBuilder::operator<<(Tee* tee) {
 
 void LogstreamBuilder::makeStream() {
     if (!_os) {
-        if (isThreadOstreamCacheInitialized && threadOstreamCache.getMake()->get()) {
+        if (_shouldCache && isThreadOstreamCacheInitialized &&
+            threadOstreamCache.getMake()->get()) {
             _os = std::move(*threadOstreamCache.get());
         } else {
             _os = stdx::make_unique<std::ostringstream>();
diff --git a/src/mongo/logger/logstream_builder.h b/src/mongo/logger/logstream_builder.h
index 1dac8462564..7c1cd62882f 100644
--- a/src/mongo/logger/logstream_builder.h
+++ b/src/mongo/logger/logstream_builder.h
@@ -73,11 +73,17 @@ public:
      * "contextName" is a short name of the thread or other context.
      * "severity" is the logging severity of the message.
      * "component" is the primary log component of the message.
+     *
+     * By default, this class will create one ostream per thread, and it
+     * will cache that object in a threadlocal and reuse it for subsequent
+     * logs messages. Set "shouldCache" to false to create a new ostream
+     * for each instance of this class rather than cacheing.
      */
     LogstreamBuilder(MessageLogDomain* domain,
                      StringData contextName,
                      LogSeverity severity,
-                     LogComponent component);
+                     LogComponent component,
+                     bool shouldCache = true);
 
     /**
      * Deprecated.
@@ -225,6 +231,7 @@ private:
     std::unique_ptr<std::ostringstream> _os;
     Tee* _tee;
     bool _isTruncatable = true;
+    bool _shouldCache;
 };