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monitoring-metrics.md

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Working with AWS Lambda function metrics

When your function finishes processing an event, Lambda sends metrics about the invocation to Amazon CloudWatch. You can build graphs and dashboards with these metrics in the CloudWatch console, and set alarms to respond to changes in utilization, performance, or error rates. Use dimensions to filter and sort function metrics by function name, alias, or version.

To view metrics in the CloudWatch console

  1. Open the Amazon CloudWatch console Metrics page (AWS/Lambda namespace).

  2. Choose a dimension.

    • By Function Name (FunctionName) – View aggregate metrics for all versions and aliases of a function.
    • By Resource (Resource) – View metrics for a version or alias of a function.
    • By Executed Version (ExecutedVersion) – View metrics for a combination of alias and version. Use the ExecutedVersion dimension to compare error rates for two versions of a function that are both targets of a weighted alias.
    • Across All Functions (none) – View aggregate metrics for all functions in the current AWS Region.

  3. Choose metrics to add them to the graph.

By default, graphs use the Sum statistic for all metrics. To choose a different statistic and customize the graph, use the options on the Graphed metrics tab.

The timestamp on a metric reflects when the function was invoked. Depending on the duration of the execution, this can be several minutes before the metric is emitted. If, for example, your function has a 10-minute timeout, look more than 10 minutes in the past for accurate metrics.

For more information about CloudWatch, see the https://docs.aws.amazon.com/AmazonCloudWatch/latest/DeveloperGuide/.

Topics

Using invocation metrics

Invocation metrics are binary indicators of the outcome of an invocation. For example, if the function returns an error, Lambda sends the Errors metric with a value of 1. To get a count of the number of function errors that occurred each minute, view the Sum of the Errors metric with a period of one minute.

You should view the following metrics with the Sum statistic.

Invocation metrics

  • Invocations – The number of times your function code is executed, including successful executions and executions that result in a function error. Invocations aren't recorded if the invocation request is throttled or otherwise resulted in an invocation error. This equals the number of requests billed.
  • Errors – The number of invocations that result in a function error. Function errors include exceptions thrown by your code and exceptions thrown by the Lambda runtime. The runtime returns errors for issues such as timeouts and configuration errors. To calculate the error rate, divide the value of Errors by the value of Invocations.
  • DeadLetterErrors – For asynchronous invocation, the number of times Lambda attempts to send an event to a dead-letter queue but fails. Dead-letter errors can occur due to permissions errors, misconfigured resources, or size limits.
  • DestinationDeliveryFailures – For asynchronous invocation, the number of times Lambda attempts to send an event to a destination but fails. Delivery errors can occur due to permissions errors, misconfigured resources, or size limits.
  • Throttles – The number of invocation requests that are throttled. When all function instances are processing requests and no concurrency is available to scale up, Lambda rejects additional requests with TooManyRequestsException. Throttled requests and other invocation errors don't count as Invocations or Errors.
  • ProvisionedConcurrencyInvocations – The number of times your function code is executed on provisioned concurrency.
  • ProvisionedConcurrencySpilloverInvocations – The number of times your function code is executed on standard concurrency when all provisioned concurrency is in use.

Using performance metrics

Performance metrics provide performance details about a single invocation. For example, the Duration metric indicates the amount of time in milliseconds that your function spends processing an event. To get a sense of how fast your function processes events, view these metrics with the Average or Max statistic.

Performance metrics

  • Duration – The amount of time that your function code spends processing an event. For the first event processed by an instance of your function, this includes initialization time. The billed duration for an invocation is the value of Duration rounded up to the nearest 100 milliseconds.
  • IteratorAge – For event source mappings that read from streams, the age of the last record in the event. The age is the amount of time between when the stream receives the record and when the event source mapping sends the event to the function.

Duration also supports percentile statistics. Use percentiles to exclude outlier values that skew average and maximum statistics. For example, the P95 statistic shows the maximum duration of 95 percent of executions, excluding the slowest 5 percent.

Using concurrency metrics

Lambda reports concurrency metrics as an aggregate count of the number of instances processing events across a function, version, alias, or AWS Region. To see how close you are to hitting concurrency limits, view these metrics with the Max statistic.

Concurrency metrics

  • ConcurrentExecutions – The number of function instances that are processing events. If this number reaches your concurrent executions limit for the Region, or the reserved concurrency limit that you configured on the function, additional invocation requests are throttled.
  • ProvisionedConcurrentExecutions – The number of function instances that are processing events on provisioned concurrency. For each invocation of an alias or version with provisioned concurrency, Lambda emits the current count.
  • ProvisionedConcurrencyUtilization – For a version or alias, the value of ProvisionedConcurrentExecutions divided by the total amount of provisioned concurrency allocated. For example, .5 indicates that 50 percent of allocated provisioned concurrency is in use.
  • UnreservedConcurrentExecutions – For an AWS Region, the number of events that are being processed by functions that don't have reserved concurrency.