Monitoring Interface

TypeScript Support

A monitoring object has an associated TypeScript type:

• Type Name - Monitoring
• Package - @resolve-js/core

A monitoring object's interface is the same as the interface of a monitoring adapter except for the getMetrics and clearMetrics methods that require a monitoring adapter ID as an argument.

A monitoring object exposes the following API:

Member Name	Description
error	Registers an occurred error.
execution	Registers an execution of an operation.
duration	Registers the duration of an operation.
time	Starts execution time measurement.
timeEnd	Ends execution time measurement and registers the resulting duration.
custom	Registers a custom metric.
publish	Defined by an implementation, publishes the collected metrics to the intended destination.
rate	Registers operation execution rate during the specified time interval in seconds.
group	Creates a monitoring group.
getMetrics	Gets a list of collected metrics.
clearMetrics	Clears the list of collected metrics.

error

Registers an occurred error. The default implementation increments the count of the "Errors" metric.

Example

try {
  ...
} catch (error) {
  monitoring.error(error)
}

Arguments

Argument Name	Type	Description
error	An error object.	An error to add to monitoring metrics.

execution

Registers an operation's execution. The default implementation increments the count of the "Executions" metric. The execution method can also be passed an optional error parameter. If this parameter is not null, the function registers the error in metrics.

Example

monitoring.execution()

Arguments

Argument Name	Type	Description
error?	An error object or null	An error to add to monitoring metrics.

duration

Registers the duration of an operation. The default implementation adds the specified value in milliseconds to the "Duration" metric.

Example

monitoring.duration(
  'myOperation',
  duration / operations.length,
  operations.length
)

Arguments

Argument Name	Type	Description
label	string	A text label to add to the 'Label' dimension.
duration	number	An operation duration in milliseconds.
count?	number	A number to add to the metric's count. Defaults to 1.

time

Starts a timer to measure execution time.

Example

monitoring.time('Execution', startTimestamp)

Arguments

Argument Name	Type	Description
name	string	The ID of the started timer.
timestamp?	number	A moment in time from which to start counting. Defaults to Date.now().

timeEnd

Ends time measurement and registers the resulting duration. The default implementation adds the measured time value in milliseconds to the "Duration" metric.

Example

monitoring.timeEnd('Execution')

Arguments

Argument Name	Type	Description
name	string	The ID of the timer to stop.
timestamp?	number	A moment in time at which to stop counting. Defaults to Date.now().

custom

Registers the specified custom metric. If the metric object's value and/or count fields are not specified, the default implementation sets them to 1.

Example

monitoring.custom(myMetric)

Arguments

Argument Name	Type	Description
metricData	A custom metric object.	Specifies a custom metric's data.

publish

Defined by an implementation, publishes the collected metrics to the intended destination.

Example

await monitoring.publish()

Arguments

Argument Name	Type	Description
options?	object	Specifies additional options for the publish operation.

Result

The returned value is a promise that resolves when the monitoring information is successfully published.

The monitoring adapters shipped with reSolve implement the publish function as follows:

Module Name	Description
@resolve-js/monitoring-console	Prints metrics to the text console.
@resolve-js/monitoring-aws-cloudwatch	Publishes metrics to AWS CloudWatch.

rate

Registers operation execution rate during the specified time interval in seconds. The default implementation adds a value in times per N seconds to the specified metric.

Example

monitoring.rate('ReadModelFeedingRate', eventCount, applyDuration / 1000)

Arguments

Argument Name	Type	Description
metricName	string	The name of the metric to add.
count	number	A number to add to the metric's count.
seconds?	number	The number of seconds for which to count the rate. Defaults to 1.

group

Creates a monitoring group and returns a monitoring adapter instance for this group.

Example

const groupMonitoring = monitoring.group({ Part: 'ReadModel' })

Arguments

Argument Name	Type	Description
config	A key-value pair object.	A key-value pair that identifies the group.

Result

A monitoring object instance that operates on the created group.

getMetrics

Gets a list of collected metrics.

Example

const metrics = getMetrics('default')

Argument Name	Type	Description
id	string	The metrics adapter ID as specified in the application configuration.

Result

The returned value is an array of metric objects.

clearMetrics

Example

monitoring.clearMetrics('default')

Clear the list of collected metrics.

Argument Name	Type	Description
id	string	The metrics adapter ID as specified in the application configuration.