/// <summary>Returns a "null" context - one which does nothing.</summary>
public static MetricsContext GetNullContext(string contextName)
{
lock (typeof(ContextFactory))
{
MetricsContext nullContext = nullContextMap[contextName];
if (nullContext == null)
{
nullContext = new NullContext();
nullContextMap[contextName] = nullContext;
}
return(nullContext);
}
}
/// <summary>
/// Returns the named MetricsContext instance, constructing it if necessary
/// using the factory's current configuration attributes.
/// </summary>
/// <remarks>
/// Returns the named MetricsContext instance, constructing it if necessary
/// using the factory's current configuration attributes. <p/>
/// When constructing the instance, if the factory property
/// <i>contextName</i>.class</code> exists,
/// its value is taken to be the name of the class to instantiate. Otherwise,
/// the default is to create an instance of
/// <code>org.apache.hadoop.metrics.spi.NullContext</code>, which is a
/// dummy "no-op" context which will cause all metric data to be discarded.
/// </remarks>
/// <param name="contextName">the name of the context</param>
/// <returns>the named MetricsContext</returns>
/// <exception cref="System.IO.IOException"/>
/// <exception cref="System.TypeLoadException"/>
/// <exception cref="InstantiationException"/>
/// <exception cref="System.MemberAccessException"/>
public virtual MetricsContext GetContext(string refName, string contextName)
{
lock (this)
{
MetricsContext metricsContext = contextMap[refName];
if (metricsContext == null)
{
string classNameAttribute = refName + ContextClassSuffix;
string className = (string)GetAttribute(classNameAttribute);
if (className == null)
{
className = DefaultContextClassname;
}
Type contextClass = Runtime.GetType(className);
metricsContext = (MetricsContext)System.Activator.CreateInstance(contextClass);
metricsContext.Init(contextName, this);
contextMap[contextName] = metricsContext;
}
return(metricsContext);
}
}
