Custom metrics allow you to record arbitrary metrics via an API call. For example, you could report the value of each shopping cart as part of the checkout transaction. Then use Insights Metric Explorer to charts and track that metric. You can use custom metrics to unify your monitoring inside New Relic.
Collecting too many metrics can impact the performance of your application and your New Relic agent. To avoid data problems, keep the total number of unique custom metrics under 2000.
Metric names identify specific data values tracked by New Relic. When using the New Relic Ruby agent's API to track custom metrics, it's important to consider your metric naming and how the values will aggregate.
A custom metric name consists of the prefix
Custom/, the class or category name, and a label, each separated with a slash mark
Custom/<category>/<name> (for example,
- Metric names and paths
Metric names are paths delimited by a slash mark
/. For custom instrumentation use this pattern:
To override the default metric name, pass a second argument to
add_method_tracer. This may be necessary to specify a category other than the default
Custom, or if the method and class name do not represent the metric well.
Reserved categories include:
For custom metric names, use
- Metrics and stats in the Ruby agent
There are two basic data structures used to collect metric data:
MetricSpecis an identifier for which we have data. The following pseudo Ruby defines a metric:
class MetricSpec attr_accessor :name # String - metric name attr_accessor :scope # String - current controller action end
The name identifies what the metric represents. The optional scope is the name of the controller action handling the current request. A metric is "global" if the scope is empty.
Metric values are recorded by
Statstypically collects data about method execution but can store any interesting data. The following pseudo Ruby defines
class Stats attr_accessor :call_count # Integer - method invocation count attr_accessor :total_call_time # Float - total method call time (in seconds) attr_accessor :total_exclusive_time # Float - total time spent in the traced method minus any child time (in seconds) attr_accessor :min_call_time # Float - the smallest method invocation time (in seconds) attr_accessor :max_call_time # Float - the largest method invocation time (in seconds) attr_accessor :sum_of_squares # Float - the sum of squares of response times - used for standard deviation computation attr_accessor :begin_time # Time - the start of the time window for this data attr_accessor :end_time # Time - end of the time window for this data end
- Stat aggregation policy
One of New Relic's strengths is its ability to aggregate data over time. (Aggregation is the act of combining several things into one.) When collecting custom metrics, the aggregation policy can be important to know when collecting custom metrics. These include:
min_call_time: Min() of each min_call_time
max_call_time: Max() of each max_call_time
begin_time: Min() of each begin_time
end_time: Max() of each end_time
Recording custom metrics
increment_metric are thread safe.
record_metric should be used to record an event-based metric, usually associated with a particular duration.
metric_name must be a String following standard metric naming rules.
value will usually be a Numeric, but may also be a Hash.
value is a numeric value, it should represent the magnitude of a measurement associated with an event, e.g. the duration for a particular method call.
value is a Hash, it must contain
:sum_of_squares keys, all with Numeric values. This form is useful if you wish to aggregate metrics on your own and report them periodically (e.g. from a background thread). The provided stats will be aggregated with any previously collected values for the same metric. The names of the hash keys have been chosen to match the names of the keys used by the platform API.
increment_metric should be used to update a metric that acts as a simple counter. The count of the selected metric will be incremented by the specified amount.
Example custom metric
Here is an example that shows how you might use metrics to track currency flowing through a site:
class Cart def checkout() amount = compute_cart_total # computes the amount to charge the customer ::NewRelic::Agent.record_metric('Custom/Cart/charge_amount', amount) charge_customer(amount) ... end end
For more information about how data aggregates over time, see Stat aggregation policy.
Viewing custom metrics
To view these custom metrics, use Insights Metric Explorer to search metrics, create customizable charts, and add those charts to Insights dashboards.
For more help
Additional documentation resources include: