google::cloud::LogSink Class Reference

A sink to receive log records. More...

#include <google/cloud/log.h>

Public Types
using	BackendId = long

Public Member Functions
	LogSink ()
bool	empty () const
	Return true if this object has no backends. More...
bool	is_enabled (Severity severity) const
	Return true if severity is enabled. More...
void	set_minimum_severity (Severity minimum)
Severity	minimum_severity () const
BackendId	AddBackend (std::shared_ptr< LogBackend > backend)
void	RemoveBackend (BackendId id)
void	ClearBackends ()
std::size_t	BackendCount () const
void	Log (LogRecord log_record)
void	Flush ()
	Flush all the current backends. More...

Static Public Member Functions
static constexpr bool	CompileTimeEnabled (Severity level)
	Return true if the severity is enabled at compile time. More...
static LogSink &	Instance ()
	Return the singleton instance for this application. More...
static void	EnableStdClog (Severity min_severity=Severity::GCP_LS_LOWEST_ENABLED)
	Enable std::clog on LogSink::Instance(). More...
static void	DisableStdClog ()
	Disable std::clog on LogSink::Instance(). More...

Detailed Description

A sink to receive log records.

Definition at line 248 of file log.h.

Member Typedef Documentation

BackendId

using google::cloud::LogSink::BackendId = long

Definition at line 313 of file log.h.

Constructor & Destructor Documentation

LogSink()

google::cloud::LogSink::LogSink

(

)

Member Function Documentation

AddBackend()

BackendId google::cloud::LogSink::AddBackend

(

std::shared_ptr< LogBackend >

backend

)

BackendCount()

std::size_t google::cloud::LogSink::BackendCount

(

)

const

ClearBackends()

void google::cloud::LogSink::ClearBackends

(

)

CompileTimeEnabled()

static constexpr bool google::cloud::LogSink::CompileTimeEnabled ( Severity  level )

inlinestaticconstexpr

Return true if the severity is enabled at compile time.

Definition at line 253 of file log.h.

DisableStdClog()

static void google::cloud::LogSink::DisableStdClog ( )

inlinestatic

Disable std::clog on LogSink::Instance().

Note that this will remove the default logging backend.

Definition at line 341 of file log.h.

empty()

bool google::cloud::LogSink::empty ( ) const

inline

Return true if this object has no backends.

We want to avoid synchronization overhead when checking if a log message is enabled. Most of the time, most messages will be disabled, so incurring the locking overhead on each message would be too expensive and would discourage developers from creating logs. Furthermore, missing a few messages while the change of state "propagates" to other threads does not affect the correctness of the program.

Note that memory_order_relaxed does not provide a compiler barrier either, so in theory stores into the atomic could be reordered by the optimizer. We have no reason to worry about that because all the writes are done inside a critical section protected by a mutex. The compiler cannot (or should not) reorder operations around those.

Definition at line 278 of file log.h.

EnableStdClog()

static void google::cloud::LogSink::EnableStdClog ( Severity  min_severity = Severity::GCP_LS_LOWEST_ENABLED )

inlinestatic

Enable std::clog on LogSink::Instance().

This is also enabled if the "GOOGLE_CLOUD_CPP_ENABLE_CLOG" environment variable is set.

Definition at line 331 of file log.h.

Flush()

void google::cloud::LogSink::Flush

(

)

Flush all the current backends.

Instance()

static LogSink& google::cloud::LogSink::Instance ( )

static

Return the singleton instance for this application.

is_enabled()

bool google::cloud::LogSink::is_enabled ( Severity  severity ) const

inline

Return true if severity is enabled.

We want to avoid synchronization overhead when checking if a log message is enabled. Most of the time, most messages will be disabled, so incurring the locking overhead on each message would be too expensive and would discourage developers from creating logs. Furthermore, missing a few messages while the change of state "propagates" to other threads does not affect the correctness of the program.

Note that memory_order_relaxed does not provide a compiler barrier either, so in theory stores into the atomic could be reordered by the optimizer. We have no reason to worry about that because all the writes are done inside a critical section protected by a mutex. The compiler cannot (or should not) reorder operations around those.

Definition at line 296 of file log.h.

Log()

void google::cloud::LogSink::Log

(

LogRecord

log_record

)

minimum_severity()

Severity google::cloud::LogSink::minimum_severity ( ) const

inline

Definition at line 304 of file log.h.

RemoveBackend()

void google::cloud::LogSink::RemoveBackend

(

BackendId

id

)

set_minimum_severity()

void google::cloud::LogSink::set_minimum_severity ( Severity  minimum )

inline

Definition at line 301 of file log.h.