Provide a scoped guard for recording elapsed time.
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Namespaces |
namespace | balm |
Detailed Description
- Outline
-
-
- Purpose:
- Provide a scoped guard for recording elapsed time.
-
- Classes:
-
- See also:
- Component balm_metricsmanager, Component balm_defaultmetricsmanager, Component balm_metric
-
- Description:
- This component provides a scoped guard class intended to simplify the task of recording (to a metric) the elapsed time of a block of code. The
balm::StopwatchScopedGuard
is supplied the identity of a metric on construction, and an optional enumerated constant indicating the time units to report values in (by default, values are reported in seconds). The guard measures the elapsed time between its construction and destruction, and on destruction records that elapsed time, in the indicated time units, to the supplied metric.
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- Alternative Systems for Telemetry:
- Bloomberg software may alternatively use the GUTS telemetry API, which is integrated into Bloomberg infrastructure.
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- Choosing Between balm::StopwatchScopedGuard and Macros:
- The
balm::StopwatchScopedGuard
class and the macros defined in the balm_metrics
component provide the same basic functionality. Clients may find that using a balm::StopwatchScopedGuard
object (in coordination with a balm::Metric
object) is better suited to collecting metrics associated with a particular instance of a stateful object, while macros are better suited to collecting metrics associated with a particular code path (rather than an object instance). In most instances, however, choosing between the two is a matter of taste.
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- Thread Safety:
balm::StopwatchScopedGuard
is const thread-safe, meaning that accessors may be invoked concurrently from different threads, but it is not safe to access or modify a balm::StopwatchScopedGuard
in one thread while thread modifies the same object. Note however, that at this another time balm::StopwatchScopedGuard
provides no manipulator methods.
-
- Usage:
- The following examples demonstrate how to record the elapsed time of a block of code using a
balm::StopwatchScopedGuard
.
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- Example 1: Create and Configure the Default balm::MetricsManager Instance:
- This example demonstrates how to create the default
balm::MetricManager
instance and perform a trivial configuration.
- First we create a
balm::DefaultMetricsManagerScopedGuard
, which manages the lifetime of the default metrics manager instance. At construction, we provide the scoped guard an output stream (stdout
) that it will publish metrics to. Note that the default metrics manager is intended to be created and destroyed by the owner of main
. An instance of the manager should be created during the initialization of an application (while the task has a single thread) and destroyed just prior to termination (when there is similarly a single thread). Once the default instance has been created, it can be accessed using the instance
operation: Note that the default metrics manager will be released when managerGuard
exits this scoped and is destroyed. Clients that choose to explicitly call the balm::DefaultMetricsManager::create
method must also explicitly call the balm::DefaultMetricsManager::release
method.
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- Example 2: Metric Collection with balm::StopwatchScopedGuard:
- Alternatively, we can use the
balm::StopwatchScopedGuard
to record metric values. In the following example we implement a hypothetical request processor similar to the one in example 3. We use a balm::Metric
(d_elapsedTime
) and a balm::StopwatchScopedGuard
(guard
) to record the elapsed time of the request-processing function. class RequestProcessor {
balm::Metric d_elapsedTime;
public:
RequestProcessor()
: d_elapsedTime("MyCategory", "RequestProcessor/elapsedTime")
{}
int processRequest(const bsl::string& request)
{
(void)request;
int returnCode = 0;
balm::StopwatchScopedGuard guard(&d_elapsedTime);
return returnCode;
}
};
RequestProcessor processor;
processor.processRequest("ab");
processor.processRequest("abc");
processor.processRequest("abc");
processor.processRequest("abdef");
manager->publishAll();
processor.processRequest("ab");
processor.processRequest("abc");
processor.processRequest("abc");
processor.processRequest("abdef");
processor.processRequest("a");
processor.processRequest("abc");
processor.processRequest("abc");
processor.processRequest("abdefg");
manager->publishAll();