CloudWatch metrics for your Network Load Balancer
Elastic Load Balancing publishes data points to Amazon CloudWatch for your load balancers and your targets. CloudWatch enables you to retrieve statistics about those data points as an ordered set of timeseries data, known as metrics. Think of a metric as a variable to monitor, and the data points as the values of that variable over time. For example, you can monitor the total number of healthy targets for a load balancer over a specified time period. Each data point has an associated time stamp and an optional unit of measurement.
You can use metrics to verify that your system is performing as expected. For example, you can create a CloudWatch alarm to monitor a specified metric and initiate an action (such as sending a notification to an email address) if the metric goes outside what you consider an acceptable range.
Elastic Load Balancing reports metrics to CloudWatch only when requests are flowing through the load balancer. If there are requests flowing through the load balancer, Elastic Load Balancing measures and sends its metrics in 60second intervals. If there are no requests flowing through the load balancer or no data for a metric, the metric is not reported. For Network Load Balancers with security groups, traffic rejected by the security groups is not captured in the CloudWatch metrics.
For more information, see the Amazon CloudWatch User Guide.
Contents
Network Load Balancer metrics
The AWS/NetworkELB
namespace includes the following metrics.
Metric  Description 

ActiveFlowCount 
The total number of concurrent flows (or connections) from clients to targets. This metric includes connections in the SYN_SENT and ESTABLISHED states. TCP connections are not terminated at the load balancer, so a client opening a TCP connection to a target counts as a single flow. Reporting criteria: Always reported. Statistics: The most useful
statistics are Dimensions

ActiveFlowCount_TCP 
The total number of concurrent TCP flows (or connections) from clients to targets. This metric includes connections in the SYN_SENT and ESTABLISHED state. TCP connections are not terminated at the load balancer, so a client opening a TCP connection to a target counts as a single flow. Reporting criteria: There is a nonzero value Statistics: The most useful
statistics are Dimensions

ActiveFlowCount_TLS 
The total number of concurrent TLS flows (or connections) from clients to targets. This metric includes connections in the SYN_SENT and ESTABLISHED state. Reporting criteria: There is a nonzero value. Statistics: The most useful
statistics are Dimensions

ActiveFlowCount_UDP 
The total number of concurrent UDP flows (or connections) from clients to targets. Reporting criteria: There is a nonzero value. Statistics: The most useful
statistics are Dimensions

ClientTLSNegotiationErrorCount 
The total number of TLS handshakes that failed during negotiation between a client and a TLS listener. Reporting criteria: There is a nonzero value. Statistics: The most useful
statistic is Dimensions

ConsumedLCUs 
The number of load balancer capacity units (LCU) used by your
load balancer. You pay for the number of LCUs that you use per
hour. For more information, see Elastic Load Balancing
Pricing Reporting criteria: Always reported. Statistics: All Dimensions

ConsumedLCUs_TCP 
The number of load balancer capacity units (LCU) used by your
load balancer for TCP. You pay for the number of LCUs that you
use per hour. For more information, see Elastic Load Balancing
Pricing Reporting criteria: There is a nonzero value. Statistics: All Dimensions

ConsumedLCUs_TLS 
The number of load balancer capacity units (LCU) used by your
load balancer for TLS. You pay for the number of LCUs that you
use per hour. For more information, see Elastic Load Balancing
Pricing Reporting criteria: There is a nonzero value. Statistics: All Dimensions

ConsumedLCUs_UDP 
The number of load balancer capacity units (LCU) used by your
load balancer for UDP. You pay for the number of LCUs that you
use per hour. For more information, see Elastic Load Balancing
Pricing Reporting criteria: There is a nonzero value. Statistics: All Dimensions

HealthyHostCount 
The number of targets that are considered healthy. This metric does not include any Application Load Balancers registered as targets. Reporting criteria: Reported if there are registered targets. Statistics: The most useful
statistics are Dimensions

NewFlowCount 
The total number of new flows (or connections) established from clients to targets in the time period. Reporting criteria: Always reported. Statistics: The most useful
statistic is Dimensions

NewFlowCount_TCP 
The total number of new TCP flows (or connections) established from clients to targets in the time period. Reporting criteria: There is a nonzero value. Statistics: The most useful
statistic is Dimensions

NewFlowCount_TLS 
The total number of new TLS flows (or connections) established from clients to targets in the time period. Reporting criteria: There is a nonzero value. Statistics: The most useful
statistic is Dimensions

NewFlowCount_UDP 
The total number of new UDP flows (or connections) established from clients to targets in the time period. Reporting criteria: There is a nonzero value. Statistics: The most useful
statistic is Dimensions

PeakPacketsPerSecond 
Highest average packet rate (packets processed per second), calculated every 10 seconds during the sampling window. This metric includes health check traffic. Reporting criteria: There is a nonzero value. Statistics: The most useful
statistic is Dimensions

PortAllocationErrorCount 
The total number of ephemeral port allocation errors during a client IP translation operation. A nonzero value indicates dropped client connections. Note: Network Load Balancers support 55,000 simultaneous connections or about 55,000 connections per minute to each unique target (IP address and port) when performing client address translation. To fix port allocation errors, add more targets to the target group. Reporting criteria: There is a nonzero value. Statistics: The most useful
statistic is Dimensions

ProcessedBytes 
The total number of bytes processed by the load balancer, including TCP/IP headers. This count includes traffic to and from targets, minus health check traffic. Reporting criteria: Always reported. Statistics: The most useful
statistic is Dimensions

ProcessedBytes_TCP 
The total number of bytes processed by TCP listeners. Reporting criteria: There is a nonzero value. Statistics: The most useful
statistic is Dimensions

ProcessedBytes_TLS 
The total number of bytes processed by TLS listeners. Reporting criteria: There is a nonzero value. Statistics: The most useful
statistic is Dimensions

ProcessedBytes_UDP 
The total number of bytes processed by UDP listeners. Reporting criteria: There is a nonzero value Statistics: The most useful
statistic is Dimensions

ProcessedPackets 
The total number of packets processed by the load balancer. This count includes traffic to and from targets, including health check traffic. Reporting criteria: There is a nonzero value. Statistics: The most useful
statistic is Dimensions

RejectedFlowCount 
The total number of flows (or connections) rejected by the load balancer. Reporting criteria: Always reported. Statistics: The most useful
statistics are Dimensions

RejectedFlowCount_TCP 
The number of TCP flows (or connections) rejected by the load balancer. Reporting criteria: There is a nonzero value. Statistics: The most useful statistic is Dimensions

SecurityGroupBlockedFlowCount_Inbound_ICMP 
The number of new ICMP messages rejected by the inbound rules of the load balancer security groups. Reporting criteria: There is a nonzero value. Statistics: The most useful
statistic is Dimensions

SecurityGroupBlockedFlowCount_Inbound_TCP 
The number of new TCP flows rejected by the inbound rules of the load balancer security groups. Reporting criteria: There is a nonzero value. Statistics: The most useful
statistic is Dimensions

SecurityGroupBlockedFlowCount_Inbound_UDP 
The number of new UDP flows rejected by the inbound rules of the load balancer security groups. Reporting criteria: There is a nonzero value. Statistics: The most useful
statistic is Dimensions

SecurityGroupBlockedFlowCount_Outbound_ICMP 
The number of new ICMP messages rejected by the outbound rules of the load balancer security groups. Reporting criteria: There is a nonzero value. Statistics: The most useful
statistic is Dimensions

SecurityGroupBlockedFlowCount_Outbound_TCP 
The number of new TCP flows rejected by the outbound rules of the load balancer security groups. Reporting criteria: There is a nonzero value. Statistics: The most useful
statistic is Dimensions

SecurityGroupBlockedFlowCount_Outbound_UDP 
The number of new UDP flows rejected by the outbound rules of the load balancer security groups. Reporting criteria: There is a nonzero value. Statistics: The most useful
statistic is Dimensions

TargetTLSNegotiationErrorCount 
The total number of TLS handshakes that failed during negotiation between a TLS listener and a target. Reporting criteria: There is a nonzero value. Statistics: The most useful
statistic is Dimensions

TCP_Client_Reset_Count 
The total number of reset (RST) packets sent from a client to a target. These resets are generated by the client and forwarded by the load balancer. Reporting criteria: Always reported. Statistics: The most useful
statistic is Dimensions

TCP_ELB_Reset_Count 
The total number of reset (RST) packets generated by the load balancer. For more information, see Troubleshooting. Reporting criteria: Always reported. Statistics: The most useful
statistic is Dimensions

TCP_Target_Reset_Count 
The total number of reset (RST) packets sent from a target to a client. These resets are generated by the target and forwarded by the load balancer. Reporting criteria: Always reported. Statistics: The most useful
statistic is Dimensions

UnHealthyHostCount 
The number of targets that are considered unhealthy. This metric does not include any Application Load Balancers registered as targets. Reporting criteria: Reported if there are registered targets. Statistics: The most useful
statistics are Dimensions

UnhealthyRoutingFlowCount 
The number of flows (or connections) that are routed using the routing failover action (fail open). Reporting criteria: There is a nonzero value. Statistics: The most useful
statistic is Dimensions

Metric dimensions for Network Load Balancers
To filter the metrics for your load balancer, use the following dimensions.
Dimension  Description 

AvailabilityZone 
Filters the metric data by Availability Zone. 
LoadBalancer 
Filters the metric data by load balancer. Specify the load balancer as follows: net/loadbalancername/1234567890123456 (the final portion of the load balancer ARN). 
TargetGroup 
Filters the metric data by target group. Specify the target group as follows: targetgroup/targetgroupname/1234567890123456 (the final portion of the target group ARN). 
Statistics for Network Load Balancer metrics
CloudWatch provides statistics based on the metric data points published by Elastic Load Balancing. Statistics are metric data aggregations over specified period of time. When you request statistics, the returned data stream is identified by the metric name and dimension. A dimension is a name/value pair that uniquely identifies a metric. For example, you can request statistics for all the healthy EC2 instances behind a load balancer launched in a specific Availability Zone.
The Minimum
and Maximum
statistics reflect the minimum
and maximum values of the data points reported by the individual load balancer nodes
in each sampling window. Increases in the maximum of HealthyHostCount
correspond to decreases in the minimum of UnHealthyHostCount
. It's
recommended to monitor maximum HealthyHostCount
, invoking the alarm when
the maximum HealthyHostCount
falls below your required minimum, or being
0
. This can help in identifying when your targets have become unhealthy.
It's also recommended to monitor minimum UnHealthyHostCount
, invoking the
alarm when the minimum UnHealthyHostCount
rises above 0
. This
allows you to become aware when there are no longer any registered targets.
The Sum
statistic is the aggregate value across all load balancer
nodes. Because metrics include multiple reports per period, Sum
is only
applicable to metrics that are aggregated across all load balancer nodes.
The SampleCount
statistic is the number of samples measured. Because
metrics are gathered based on sampling intervals and events, this statistic is
typically not useful. For example, with HealthyHostCount
,
SampleCount
is based on the number of samples that each load
balancer node reports, not the number of healthy hosts.
View CloudWatch metrics for your load balancer
You can view the CloudWatch metrics for your load balancers using the Amazon EC2 console. These metrics are displayed as monitoring graphs. The monitoring graphs show data points if the load balancer is active and receiving requests.
Alternatively, you can view metrics for your load balancer using the CloudWatch console.
To view metrics using the console
Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/
. 
To view metrics filtered by target group, do the following:

In the navigation pane, choose Target Groups.

Select your target group and choose Monitoring.

(Optional) To filter the results by time, select a time range from Showing data for.

To get a larger view of a single metric, select its graph.


To view metrics filtered by load balancer, do the following:

In the navigation pane, choose Load Balancers.

Select your load balancer and choose Monitoring.

(Optional) To filter the results by time, select a time range from Showing data for.

To get a larger view of a single metric, select its graph.

To view metrics using the CloudWatch console

Open the CloudWatch console at https://console.aws.amazon.com/cloudwatch/
. 
In the navigation pane, choose Metrics.

Select the NetworkELB namespace.

(Optional) To view a metric across all dimensions, type its name in the search field.
To view metrics using the AWS CLI
Use the following listmetrics command to list the available metrics:
aws cloudwatch listmetrics namespace AWS/NetworkELB
To get the statistics for a metric using the AWS CLI
Use the following getmetricstatistics command get statistics for the specified metric and dimension. Note that CloudWatch treats each unique combination of dimensions as a separate metric. You can't retrieve statistics using combinations of dimensions that were not specially published. You must specify the same dimensions that were used when the metrics were created.
aws cloudwatch getmetricstatistics namespace AWS/NetworkELB \ metricname UnHealthyHostCount statistics Average period 3600 \ dimensions Name=LoadBalancer,Value=net/myloadbalancer/50dc6c495c0c9188 \ Name=TargetGroup,Value=targetgroup/mytargets/73e2d6bc24d8a067 \ starttime 20170418T00:00:00Z endtime 20170421T00:00:00Z
The following is example output:
{
"Datapoints": [
{
"Timestamp": "20170418T22:00:00Z",
"Average": 0.0,
"Unit": "Count"
},
{
"Timestamp": "20170418T04:00:00Z",
"Average": 0.0,
"Unit": "Count"
},
...
],
"Label": "UnHealthyHostCount"
}