Manage flow logs

Use flow logs to save network traffic metadata, including 5-tuples, in Google Distributed Cloud (GDC) air-gapped to the observability stack in the form of queryable logs. Use these logs to:

  • Understand traffic flows for a particular service in an organization.
  • Understand and identify issues with the network health of a Kubernetes workload.
  • Verify Kubernetes network policies.

Flow log is a GDC feature based on the open source Hubble project: https://github.com/cilium/hubble. Configure flow logs using the FlowLog resource from the Networking API.

Before you begin

  • You must obtain authorization to manage or view flow logs from the GDC console. To view or manage flow logs, ask your Organization IAM Admin to grant you the corresponding flow log role.

    For information about setting role bindings from the GDC console, see Grant access to resources.

  • Before querying and viewing flow logs on dashboards, you must obtain access to the system monitoring instance. For more information, see Get access to dashboards.

Create a flow log

Create a flow log to save network traffic metadata that is filtered by a given set of specifications.

Create flow log with protocol and namespace filters

  1. Create a file called example-flowlog.yaml with the following contents:

    apiVersion: networking.gdc.goog/v1
kind: FlowLog
metadata:
  name: "FLOW_LOG_NAME"
  namespace: "platform"
spec:
  filters:
    - l4Protocols:
        - tcp
      source:
        namespacePodSelectors:
          - namespace: gpc-system
          - namespace: kube-system
      destination:
        namespacePodSelectors:
          - namespace: kube-system
  lifetime:
    duration: "1h"

    Replace FLOW_LOG_NAME with the chosen name for the flow log.

    In this example, the flow log captures all flows for which a TCP connection was started by any pod in the gpc-system or kube-system namespace to any pod in kube-system namespace. It stops recording logs one hour from when the object is created.

  2. Create the flow log object in target cluster:

    kubectl --kubeconfig ORG_ADMIN_CLUSTER_KUBECONFIG apply -f example-flowlog.yaml

    Replace ORG_ADMIN_CLUSTER_KUBECONFIG with the kubeconfig path of the org admin cluster.

  3. Verify that the FLOW_LOG_NAME value was correctly reconciled, and that the logging process has started by examining the Status field:

    kubectl --kubeconfig ORG_ADMIN_CLUSTER_KUBECONFIG describe -n platform FLOW_LOG_NAME

    Example status:

    Status:
  Clusters:
    Cluster:  org-1-system-cluster
    Conditions:
      Last Transition Time:  2024-01-19T01:46:11Z
      Message:
      Observed Generation:   1
      Reason:                ResourcesPropagated
      Status:                True
      Type:                  Propagated
    Name:                    cilium-flowlog-config
    Namespace:               kube-system
    Node:                    org-1-system
    Cluster:                 user-vm-1-cluster
    Conditions:
      Last Transition Time:  2024-01-19T01:46:11Z
      Message:
      Observed Generation:   1
      Reason:                ResourcesPropagated
      Status:                True
      Type:                  Propagated
    Name:                    cilium-flowlog-config
    Namespace:               kube-system
    Node:                    user-vm-1
    Cluster:                 user-vm-2-cluster
    Conditions:
      Last Transition Time:  2024-01-19T01:46:11Z
      Message:
      Observed Generation:   1
      Reason:                ResourcesPropagated
      Status:                True
      Type:                  Propagated
    Name:                    cilium-flowlog-config
    Namespace:               kube-system
    Node:                    user-vm-2
  Conditions:
    Last Transition Time:  2024-01-18T19:17:53Z
    Message:
    Observed Generation:   1
    Reason:                Active
    Status:                True
    Type:                  Logging
    Last Transition Time:  2024-01-19T01:46:11Z
    Message:
    Observed Generation:   1
    Reason:                ResourcesPropagated
    Status:                True
    Type:                  Propagated
    Last Transition Time:  2024-01-18T19:17:53Z
    Message:
    Observed Generation:   1
    Reason:                Succeeded
    Status:                True
    Type:                  Reconciled
  Start Time:              2024-01-18T19:17:53Z
  End Time:              2024-01-18T20:17:53Z

    This example output contains the following conditions:

    • Propagated: the flow log configuration was sent to clusters user-vm-1, user-vm-2, and org-1-system.
    • Reconciled: the flow log was successfully programmed on clusters user-vm-1, user-vm-2, and org-1-system.
    • Logging: the flow log is not expired or disabled, has not encountered any error, and may produce logs if the filters match the flows.
    • The Start Time and End Time indicate the job was started at 19:17:53, and expires at 20:17:53.

    For this flow log to be able to successfully produce log entries, all Propagated, Reconciled and Logging conditions must be true.

Modify flow log

To modify an existing flow log, modify the created flow log object definition in the example-flowlog.yaml file and apply it again:

kubectl --kubeconfig ORG_ADMIN_CLUSTER_KUBECONFIG apply -f example-flowlog.yaml

View flow logs in monitor dashboard

To view flow logs, ask users with the corresponding flow log role to check Query operational logs.

References