Internal Load Balancing Logging and Monitoring

Internal Load Balancing exports monitoring data to Stackdriver. Monitoring metrics can be used for the following purposes:

  • Evaluate an internal load balancer's configuration, usage, and performance
  • Troubleshoot problems
  • Improve resource utilization and user experience

In addition to the predefined dashboards in Stackdriver, you can create custom dashboards, set up alerts, and query the metrics through the Stackdriver monitoring API.

Viewing Stackdriver monitoring dashboards

  1. Go to Stackdriver in the Google Cloud Platform Console.
    Go to Stackdriver
  2. Select Resources > Google Cloud Load Balancers.
  3. Click the name of your load balancer.

In the left pane, you can see various details for this internal load balancer. In the right pane you can see timeseries graphs. Click the Breakdowns link to see specific breakdowns. The left pane presents currently configured data, while the right pane can present data served by historical configurations not currently reflected in the left pane.

Defining Stackdriver alerts

You can define Stackdriver alerts over various Internal Load Balancing metrics:

  1. Go to Stackdriver in the Google Cloud Platform Console.
    Go to Stackdriver
  2. Select Alerting > Create a Policy.
  3. Click on Add Condition and select condition type.
  4. Select metrics and filters. For metrics, the resource type is either Internal TCP Load Balancer or Internal UDP Load Balancer.
  5. Click Save Condition.
  6. Enter the policy name and click Save Policy.

Defining Stackdriver custom dashboards

You can create custom Stackdriver dashboards over Internal Load Balancing metrics:

  1. Go to Stackdriver in the Google Cloud Platform Console.
    Go to Stackdriver
  2. Select Dashboards > Create Dashboard.
  3. Click on Add Chart.
  4. Give the chart a title.
  5. Select metrics and filters. For metrics, the resource type is Google Cloud TCP Load Balancer (Internal) Rule (internal_tcp_lb_rule) or Google Cloud UDP Load Balancer (Internal) Rule (internal_udp_lb_rule).
  6. Click Save.

Metrics for internal load balancers

The following metrics for internal load balancers are reported into Stackdriver.

Metric Description
Inbound Throughput The number of bytes sent towards internal load balancer forwarding rules, as received by the backends.
Inbound Packets The number of packets sent towards internal load balancer forwarding rules, as received by the backends.
Outbound Throughput The number of bytes sent by internal load balanced backends on connections bound to forwarding rule IPs.
Outbound Packets The number of packets sent by internal load balanced backends on connections bound to forwarding rule IPs.
Latency(*) A by packets distribution of the RTT measured for bundles of packets over each internal load balanced connection. Typically reduced to 95th-%tile in Stackdriver views.

(*) Available only for TCP traffic.

Filtering Dimensions for Internal Load Balancer Metrics

Metrics are aggregated for each internal load balancer. Metrics can be further broken down by the following dimensions:

Property Description
INSTANCE GROUP The name of the instance group that received the connection.
BACKEND SCOPE The scope (region or zone) of the instance group that received the connection.
BACKEND ZONE If the instance group was a zonal instance group, the zone of the instance group that served the connection.
CLIENT NETWORK The network from which the instance that connected to internal load balancing sends traffic.
CLIENT SUBNETWORK The subnetwork from which the instance that connected to internal load balancing sends traffic.
CLIENT ZONE The Google Cloud Platform zone of the instance that connected to internal load balancing forwarding rule.
FORWARDING RULE The name of the forwarding rule used by the instance to connect to the internal load balancer.

Metric Reporting Frequency and Retention

Metrics for the internal load balancers are exported to Stackdriver in 1-minute granularity batches. Monitoring data is retained for six (6) weeks. The dashboard provides data analysis in default intervals of 1H (one hour), 6H (six hours), 1D (one day), 1W (one week), and 6W (six weeks). You can manually request analysis in any interval from 6W to 1 minute.

Troubleshooting Internal Load Balancing access across VPN and Interconnect

Internal Load Balancing access across VPN and Interconnect combines two GCP products. To isolate any issues, we recommend that you first attempt to access the internal load balancer from a client GCP VM instance in the same network and region as the VPN tunnel.

If you can successfully access the internal load balancer from the client VM instance, check the rest of this section for common issues that you might encounter.

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