Monitoring concurrency
Lambda emits Amazon CloudWatch metrics to help you monitor concurrency for your functions. This topic explains these metrics and how to interpret them.
General concurrency metrics
Use the following metrics to monitor concurrency for your Lambda functions. The granularity for each metric is 1 minute.
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ConcurrentExecutions– The number of active concurrent invocations at a given point in time. Lambda emits this metric for all functions, versions, and aliases. For any function in the Lambda console, Lambda displays the graph forConcurrentExecutionsnatively in the Monitoring tab, under Metrics. View this metric using MAX. -
UnreservedConcurrentExecutions– The number of active concurrent invocations that are using unreserved concurrency. Lambda emits this metric across all functions in a region. View this metric using MAX.
Provisioned concurrency metrics
Use the following metrics to monitor Lambda functions using provisioned concurrency. The granularity for each metric is 1 minute.
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ProvisionedConcurrentExecutions– The number of execution environment instances that are actively processing an invocation on provisioned concurrency. Lambda emits this metric for each function version and alias with provisioned concurrency configured. View this metric using MAX.
ProvisionedConcurrentExecutions is not the same as the total number of
provisioned concurrency that you allocate. For example, suppose you allocate 100 units of
provisioned concurrency to a function version. During any given minute, if at most 50 out
of those 100 execution environments were handling invocations simultaneously, then the
value of MAX(ProvisionedConcurrentExecutions)
is 50.
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ProvisionedConcurrentInvocations– The number of times Lambda invokes your function code using provisioned concurrency. Lambda emits this metric for each function version and alias with provisioned concurrency configured. View this metric using SUM.
ProvisionedConcurrentInvocations differs from
ProvisionedConcurrentExecutions in that
ProvisionedConcurrentInvocations counts total number of invocations, while
ProvisionedConcurrentExecutions counts number of active environments. To
understand this distinction, consider the following scenario:
In this example, suppose that you receive 1 invocation per minute, and each invocation takes 2 minutes to complete. Each orange horizontal bar represents a single request. Suppose that you allocate 10 units of provisioned concurrency to this function, such that each request runs on provisioned concurrency.
In between minutes 0 and 1, Request 1 comes in.
At minute 1, the value for
MAX(ProvisionedConcurrentExecutions)
is 1, since at most 1 execution environment was active during the past minute.
The value for
SUM(ProvisionedConcurrentInvocations)
is also 1, since 1 new request came in during the past minute.
In between minutes 1 and 2, Request 2 comes in, and
Request 1 continues to run. At minute 2,
the value for
MAX(ProvisionedConcurrentExecutions)
is 2, since at most 2 execution environments were active during the past minute.
However, the value for
SUM(ProvisionedConcurrentInvocations)
is 1, since only 1 new request came in during the past minute. This metric behavior
continues until the end of the example.
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ProvisionedConcurrencySpilloverInvocations– The number of times Lambda invokes your function on standard (reserved or unreserved) concurrency when all provisioned concurrency is in use. Lambda emits this metric for each function version and alias with provisioned concurrency configured. View this metric using SUM. The value ofProvisionedConcurrentInvocations+ProvisionedConcurrencySpilloverInvocationsshould be equal to the total number of function invocations (i.e. theInvocationsmetric).ProvisionedConcurrencyUtilization– The percentage of provisioned concurrency in use (i.e. the value ofProvisionedConcurrentExecutionsdivided by the total amount of provisioned concurrency allocated). Lambda emits this metric for each function version and alias with provisioned concurrency configured. View this metric using MAX.
For example, suppose you provision 100 units of provisioned concurrency to a
function version. During any given minute, if at most 60 out of those 100
execution environments were handling invocations simultaneously, then the value of
MAX(ProvisionedConcurrentExecutions)
is 60, and the value of
MAX(ProvisionedConcurrentUtilization)
is 0.6.
A high value for ProvisionedConcurrencySpilloverInvocations
may indicate that you need to allocate additional provisioned concurrency for your
function. Alternatively, you can
configure Application Auto Scaling to handle automatic scaling of provisioned concurrency
based on pre-defined thresholds.
Conversely, consistently low values for ProvisionedConcurrencyUtilization
may indicate that you over-allocated provisioned concurrency for your function.