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Merged
merged 5 commits into from
Oct 10, 2025
Merged

Reduce logging overhead further #552

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ae78fa0
Reduce logging overhead
stephen-webb Oct 9, 2025
a73d319
Simplify new code
stephen-webb Oct 9, 2025
a32267b
Simplify new code more
stephen-webb Oct 10, 2025
c8f212e
Overhead reduction does not require std::atomic<std::shared_ptr>'
stephen-webb Oct 10, 2025
d0af983
Clarify that the vector of appender pointers is immutable
stephen-webb Oct 10, 2025
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159 changes: 93 additions & 66 deletions src/main/cpp/appenderattachableimpl.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -23,11 +23,45 @@ using namespace LOG4CXX_NS::helpers;

IMPLEMENT_LOG4CXX_OBJECT(AppenderAttachableImpl)

using AppenderListPtr = std::shared_ptr<const AppenderList>;

/** A vector of appender pointers. */
struct AppenderAttachableImpl::priv_data
{
/** Array of appenders. */
AppenderList appenderList;
private: // Attributes
#ifdef __cpp_lib_atomic_shared_ptr
std::atomic<AppenderListPtr> pAppenderList;
#else // !defined(__cpp_lib_atomic_shared_ptr)
AppenderListPtr pAppenderList;
mutable std::mutex m_mutex;
#endif // !defined(__cpp_lib_atomic_shared_ptr)

public: // ...structors
priv_data(const AppenderList& newList = {})
: pAppenderList{ std::make_shared<const AppenderList>(newList) }
{}

public: // Accessors
AppenderListPtr getAppenders() const
{
#ifdef __cpp_lib_atomic_shared_ptr
return pAppenderList.load(std::memory_order_acquire);
#else // !defined(__cpp_lib_atomic_shared_ptr)
std::lock_guard<std::mutex> lock( m_mutex );
return pAppenderList;
#endif // !defined(__cpp_lib_atomic_shared_ptr)
}

public: // Modifiers
void setAppenders(const AppenderList& newList)
{
#ifdef __cpp_lib_atomic_shared_ptr
pAppenderList.store(std::make_shared<AppenderList>(newList), std::memory_order_release);
#else // !defined(__cpp_lib_atomic_shared_ptr)
std::lock_guard<std::mutex> lock( m_mutex );
pAppenderList = std::make_shared<const AppenderList>(newList);
#endif // !defined(__cpp_lib_atomic_shared_ptr)
}
};

AppenderAttachableImpl::AppenderAttachableImpl()
Expand All @@ -36,76 +70,62 @@ AppenderAttachableImpl::AppenderAttachableImpl()

#if LOG4CXX_ABI_VERSION <= 15
AppenderAttachableImpl::AppenderAttachableImpl(Pool& pool)
: m_priv()
{
}
#endif

AppenderAttachableImpl::~AppenderAttachableImpl()
{

}


void AppenderAttachableImpl::addAppender(const AppenderPtr newAppender)
{
// Null values for newAppender parameter are strictly forbidden.
if (!newAppender)
{
return;
}
if (!m_priv)
m_priv = std::make_unique<AppenderAttachableImpl::priv_data>();

std::lock_guard<std::mutex> lock( m_priv->m_mutex );
AppenderList::iterator it = std::find(
m_priv->appenderList.begin(), m_priv->appenderList.end(), newAppender);

if (it == m_priv->appenderList.end())
if (m_priv)
{
m_priv->appenderList.push_back(newAppender);
auto allAppenders = m_priv->getAppenders();
if (allAppenders->end() == std::find(allAppenders->begin(), allAppenders->end(), newAppender))
{
auto newAppenders = *allAppenders;
newAppenders.push_back(newAppender);
m_priv->setAppenders(newAppenders);
}
}
else
m_priv = std::make_unique<priv_data>(AppenderList{newAppender});
}

int AppenderAttachableImpl::appendLoopOnAppenders(
const spi::LoggingEventPtr& event,
Pool& p)
int AppenderAttachableImpl::appendLoopOnAppenders(const spi::LoggingEventPtr& event, Pool& p)
{
int numberAppended = 0;
int result = 0;
if (m_priv)
{
// FallbackErrorHandler::error() may modify our list of appenders
// while we are iterating over them (if it holds the same logger).
// So, make a local copy of the appenders that we want to iterate over
// before actually iterating over them.
AppenderList allAppenders = getAllAppenders();
for (auto appender : allAppenders)
auto allAppenders = m_priv->getAppenders();
for (auto& appender : *allAppenders)
{
appender->doAppend(event, p);
numberAppended++;
++result;
}
}

return numberAppended;
return result;
}

AppenderList AppenderAttachableImpl::getAllAppenders() const
{
AppenderList result;
if (m_priv)
{
std::lock_guard<std::mutex> lock( m_priv->m_mutex );
result = m_priv->appenderList;
}
result = *m_priv->getAppenders();
return result;
}

AppenderPtr AppenderAttachableImpl::getAppender(const LogString& name) const
{
AppenderPtr result;
if (m_priv && !name.empty())
if (m_priv)
{
std::lock_guard<std::mutex> lock( m_priv->m_mutex );
for (auto appender : m_priv->appenderList)
auto allAppenders = m_priv->getAppenders();
for (auto& appender : *allAppenders)
{
if (name == appender->getName())
{
Expand All @@ -122,8 +142,8 @@ bool AppenderAttachableImpl::isAttached(const AppenderPtr appender) const
bool result = false;
if (m_priv && appender)
{
std::lock_guard<std::mutex> lock( m_priv->m_mutex );
result = std::find(m_priv->appenderList.begin(), m_priv->appenderList.end(), appender) != m_priv->appenderList.end();
auto allAppenders = m_priv->getAppenders();
result = allAppenders->end() != std::find(allAppenders->begin(), allAppenders->end(), appender);
}
return result;
}
Expand All @@ -132,38 +152,42 @@ void AppenderAttachableImpl::removeAllAppenders()
{
if (m_priv)
{
for (auto a : getAllAppenders())
a->close();
std::lock_guard<std::mutex> lock( m_priv->m_mutex );
m_priv->appenderList.clear();
auto allAppenders = m_priv->getAppenders();
for (auto& appender : *allAppenders)
appender->close();
m_priv->setAppenders({});
}
}

void AppenderAttachableImpl::removeAppender(const AppenderPtr appender)
{
if (m_priv && appender)
{
std::lock_guard<std::mutex> lock( m_priv->m_mutex );
auto it = std::find(m_priv->appenderList.begin(), m_priv->appenderList.end(), appender);
if (it != m_priv->appenderList.end())
auto newAppenders = *m_priv->getAppenders();
auto pItem = std::find(newAppenders.begin(), newAppenders.end(), appender);
if (newAppenders.end() != pItem)
{
m_priv->appenderList.erase(it);
newAppenders.erase(pItem);
m_priv->setAppenders(newAppenders);
}
}
}

void AppenderAttachableImpl::removeAppender(const LogString& name)
{
if (m_priv && !name.empty())
if (m_priv)
{
std::lock_guard<std::mutex> lock( m_priv->m_mutex );
auto it = std::find_if(m_priv->appenderList.begin(), m_priv->appenderList.end()
auto newAppenders = *m_priv->getAppenders();
auto pItem = std::find_if(newAppenders.begin(), newAppenders.end()
, [&name](const AppenderPtr& appender) -> bool
{
return name == appender->getName();
});
if (it != m_priv->appenderList.end())
m_priv->appenderList.erase(it);
if (newAppenders.end() != pItem)
{
newAppenders.erase(pItem);
m_priv->setAppenders(newAppenders);
}
}
}

Expand All @@ -172,16 +196,17 @@ bool AppenderAttachableImpl::replaceAppender(const AppenderPtr& oldAppender, con
bool found = false;
if (m_priv && oldAppender && newAppender)
{
auto oldName = oldAppender->getName();
std::lock_guard<std::mutex> lock( m_priv->m_mutex );
auto it = std::find_if(m_priv->appenderList.begin(), m_priv->appenderList.end()
, [&oldName](const AppenderPtr& appender) -> bool
auto name = oldAppender->getName();
auto newAppenders = *m_priv->getAppenders();
auto pItem = std::find_if(newAppenders.begin(), newAppenders.end()
, [&name](const AppenderPtr& appender) -> bool
{
return oldName == appender->getName();
return name == appender->getName();
});
if (it != m_priv->appenderList.end())
if (newAppenders.end() != pItem)
{
*it = newAppender;
*pItem = newAppender;
m_priv->setAppenders(newAppenders);
found = true;
}
}
Expand All @@ -190,13 +215,15 @@ bool AppenderAttachableImpl::replaceAppender(const AppenderPtr& oldAppender, con

void AppenderAttachableImpl::replaceAppenders(const AppenderList& newList)
{
auto oldAppenders = getAllAppenders();
if (!m_priv)
m_priv = std::make_unique<AppenderAttachableImpl::priv_data>();
std::lock_guard<std::mutex> lock( m_priv->m_mutex );
for (auto a : oldAppenders)
a->close();
m_priv->appenderList = newList;
if (m_priv)
{
auto allAppenders = m_priv->getAppenders();
for (auto& a : *allAppenders)
a->close();
m_priv->setAppenders(newList);
}
else
m_priv = std::make_unique<priv_data>(newList);
}