The Metrics facet implements the Instrumentation Facility to provide convenient access to metrics for the Ice run time and select Ice services. The metrics provided by this facet include the number of threads currently running and their state, the number of connections, information on invocations and dispatch, as well as connection establishment and endpoint name resolution.

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Metrics Terminology

Metrics Types

Metrics are specified as Slice classes defined in the Ice/Metrics.ice Slice file. All the metrics types are defined in the IceMX module.

The base class is IceMX::Metrics:

class Metrics
{
    string id;
    long total = 0;
    int current = 0;
    long totalLifetime = 0;
    int failures = 0;
}

A metrics object is an instance of IceMX::Metrics and represents metrics of one or more instrumented objects. An instrumented object can be anything that supports instrumentation. The Ice run time supports instrumentation of the following objects and activities:

• Threads
• Connections
• Invocations
• Dispatch
• Connection establishment
• Endpoint resolution

The id of a metric identifies the instrumented object(s). The total and current members specify the total and current number of instrumented objects created since the creation of the Ice communicator, respectively. The totalLifetime member is the sum of the lifetime of each instrumented object and failures is the number of failures that have occurred for the metrics object(s).

Failures are specified using a separate IceMX::MetricsFailures structure:

struct MetricsFailures
{
    string id;
    StringIntDict failures;
}

The failures dictionary provides the count of each type of failure for a metric identified by id. Failures are dependent on the instrumented objects. For example, failures for Ice connections are represented with the name of the exception that caused the connection to fail (e.g., Ice::ConnectionLostException or Ice::TimeoutException).

A metrics map is simply defined as a sequence of IceMX::Metrics objects, and a metrics view is defined as a dictionary of metrics map:

sequence<Metrics> MetricsMap;
dictionary<string, MetricsMap> MetricsView;

The key for the metrics view dictionary is a string that identifies the metrics map. The Ice run time supports the following metrics maps:

A metrics map can also contain sub-metrics maps. An example is the Invocation metrics map, which provides a Remote sub-metrics map to record metrics associated with remote invocations. The Slice class for remote invocation metrics is IceMX::Metrics.

The MetricsAdmin Interface

The Slice interface IceMX::MetricsAdmin allows you to retrieve the metrics associated with the Ice communicator:

module IceMX
{
    exception UnknownMetricsView {}

    interface MetricsAdmin
    {
        Ice::StringSeq getMetricsViewNames(out Ice::StringSeq disableViews);
        void enableMetricsView(string name)
            throws UnknownMetricsView;
        void disableMetricsView(string name)
            throws UnknownMetricsView;
        MetricsView getMetricsView(string view, out long timestamp)
            throws UnknownMetricsView;
        MetricsFailuresSeq getMapMetricsFailures(string view, string map)
            throws UnknownMetricsView;
        MetricsFailures getMetricsFailures(string view, string map, string id)
            throws UnknownMetricsView;
    }
}

The getMetricsViewName operation retrieves the names of the configured enabled and disabled views. The enableMetricsView and disableMetricsView allow to enable and disable a specific view. Calling those methods is equivalent to setting the view Disabled property to 1 or 0.The getMetricsView operation returns the metrics for the given view. The getMapMetricsFailures and getMetricsFailures operations retrieve the metrics failures for a given map or metrics id.

Obtaining the Local Metrics Facet

We already showed how to obtain a proxy for a remote administrative facet, but suppose you want to interact with the facet in your local address space. The code below shows the necessary steps:

auto obj = communicator->findAdminFacet("Metrics");
if(obj)
{ 
    // May be null if the facet is not enabled
    auto facet = std::dynamic_pointer_cast<Ice::MetricsAdmin>(obj);
    ...
}

Ice::ObjectPtr obj = communicator->findAdminFacet("Metrics");
if(obj)
{ 
    // May be null if the facet is not enabled
    Ice::MetricsAdminPtr facet = Ice::MetricsAdminPtr::dynamicCast(obj);
    ...
}

As shown here, the facet is registered with the name Metrics and a regular language cast is used to downcast the base object type to the MetricsAdmin interface.

Metrics Attributes

Metrics views are configured with IceMX Metrics properties.

The GroupBy, Accept and Reject properties are specified using attributes that are specific to each metrics map. The table below describes the attributes supported by the Ice run time's metrics maps.

The id, parent and none attributes are supported by all maps.

The value of the parent attribute depends on the map. For the Connection, Dispatch and Remote maps, the parent will either be "Communicator" if the connection is a client connection, or the object adapter name if it's a server connection. For the Invocation, EndpointLookup, and ConnectionEstablishment maps, it will always be "Communicator". The parent attribute enables the filtering of metrics based on the object adapter. When used with the GroupBy property it also allows you to obtain metrics at the object adapter level. For instance, the following configuration does not monitor any metrics for the Ice.Admin object adapter and it groups all the metrics based on the object adapter or communicator:

IceMX.Metrics.MyView.GroupBy=parent
IceMX.Metrics.MyView.Reject.parent=Ice\.Admin   # Escape the dot in Ice.Admin

This configuration enables the communicator to get metrics on a per object adapter or communicator basis.

You can also use the none attribute to get metrics for the communicator including the metrics from object adapters, e.g., IceMX.Metrics.MyView.GroupBy=none. This provides the lowest possible level of detail as all the statistics will be recorded by a single metrics object.

The id attribute allows you to get a higher level of detail by recording metrics on a per instrumented object or operation basis. If you specify IceMX.Metrics.MyView.GroupBy=id, the Metrics facet will record metrics for each individual object or operation.

See Also

• Instrumentation Facility
• Creating the admin Object
• Ice.Admin.*