Use Metrics

Metrics Access

Metrics can be presented on the final output stage within the emit select statement using a well formed metric query structure.

Declaratively

Users defined a metric query within the select statement with the results being added to the output event. The below example performs a metric lookup based upon the passed symbol value.

Example

emit:
  select: "symbol, BidMovingAverage.avg_bid_max;WHERE symbol=${symbol} 'avg_bid_max'"

Query Structure

The declarative query structure is formed of three required components and an optional override output alias.

<metric-family>.<metrics>;<predicate> '<output-alias>'

metric-family

This is the logical name of the group of metrics, which should correspond to a metric name declared within the compute section.

metrics

A comma delimited list of metrics or asterisk. Any defined metric needs to correspond the query projection attributes.

predicate

Matching and filtering statement using standard SQL. This is used to extract only those records that fulfill a specified condition.

-- Simple lookup using a 
WHERE symbol='IBM'

-- Parameter replace using the corresponding the event object symbol value
WHERE symbol=${symbol}

-- Apply additonal filtering criteria
WHERE symbol=${symbol} AND avg_bid_max > 120.88

Examples

-- Get all metrics from the BidMovingAverage metrics family for IBM 
BidMovingAverage.*;WHERE symbol='IBM'

-- Get the avg_bid_max metric from the BidMovingAverage metrics family all symbols matching the reference ${symbol} variable 
BidMovingAverage.avg_bid_max;WHERE symbol=${symbol}

-- Same as above with the ability to define a custom name for the resulting field
BidMovingAverage.avg_bid_max;WHERE symbol=${symbol} 'avg_bid_max'

-- Get the avg_bid_max and avg_bid_min metric from the BidMovingAverage metrics family
BidMovingAverage.avg_bid_max,avg_bid_min;WHERE symbol=${symbol}

Query Interface

Metrics can be used within custom processors my using the Metric Query API, see API documentation for details on how to leverage this capability.