Collecting Metrics and Logs

This task shows how to configure Mixer to automatically gather telemetry for a service within a cluster. At the end of this task, a new metric and a new log stream will be enabled for calls to a specific service within your cluster.

The BookInfo sample application is used as the example application throughout this task.

Before you begin

  • Install Istio in your kubernetes cluster and deploy an application.

  • Configure your environment to support calling istioctl mixer. This may require setting up port-forwarding for the Mixer Config API as described in the reference docs for istioctl mixer.

  • Configure your environment to support accessing the Istio dashboard, as described in the Installation Guide. This requires installing the optional add-ons (Prometheus and Grafana), as well as verifying access to the dashboard. The Istio dashboard will be used to verify task success.

Collecting new telemetry data

  1. Create a new YAML file to hold configuration for the new metric and log stream that Istio will generate and collect automatically.

    Save the following as new_rule.yaml:

  2. Pick a destination service for the new rule.

    If using the BookInfo sample, select reviews.default.svc.cluster.local. A fully-qualified domain name for the service is required in the following steps.

  3. Validate that the selected service has no service-specific rules already applied.

    istioctl mixer rule get reviews.default.svc.cluster.local reviews.default.svc.cluster.local
    

    The expected output is:

    Error: the server could not find the requested resource
    

    If your selected service has service-specific rules, update new_rule.yaml to include the existing rules appropriately. Append the rule from new_rule.yaml to the existing rules block and save the updated content back over new_rule.yaml.

  4. Push the new configuration to Mixer for a specific service.

    istioctl mixer rule create reviews.default.svc.cluster.local reviews.default.svc.cluster.local -f new_rule.yaml
    
  5. Send traffic to that service.

    For the BookInfo sample, visit http://$GATEWAY_URL/productpage in your web browser or issue the following command:

    curl http://$GATEWAY_URL/productpage
    

    For purposes of this task, please refresh the page several times or issue the curl command a few times to generate traffic.

  6. Verify that the new metric is being collected.

    Setup port-forwarding for Grafana:

    kubectl port-forward $(kubectl get pod -l app=grafana -o jsonpath='{.items[0].metadata.name}') 3000:3000 &
    

    Then open the Istio dashboard in a web browser: http://localhost:3000/dashboard/db/istio-dashboard

    One of the rows in the dashboard will be named “reviews”. If that row is not visible, please refresh the dashboard page. The “reviews” row contains a graph entitled “Response Size by Source And Version”. The graph displays a breakdown of the distribution of Response Sizes returned by the “reviews” service.

    The request from the previous step is reflected in the graphs. This looks similar to:

    Istio Dashboard for Reviews Service
    Istio Dashboard for Reviews Service
  7. Verify that the logs stream has been created and is being populated for requests.

    Search through the logs for the Mixer pod as follows:

    kubectl logs $(kubectl get pods -l istio=mixer -o jsonpath='{.items[0].metadata.name}') | grep \"combined_log\"
    

    The expected output is similar to:

    {"logName":"combined_log","labels":{"referer":"","responseSize":871,"timestamp":"2017-04-29T02:11:54.989466058Z","url":"/reviews","userAgent":"python-requests/2.11.1"},"textPayload":"- - - [29/Apr/2017:02:11:54 +0000] \"- /reviews -\" - 871 - python-requests/2.11.1"}
    

Understanding the new telemetry rule

In this task, you added a new rule for a service within your cluster. The new rule instructed Mixer to automatically generate and report a new metric and a new log stream for all traffic going to a specific service.

The new rule was comprised of a new aspect definitions. These aspect definitions were for the aspect kind of metrics and access-logs.

Understanding the rule’s metrics aspect

The metrics aspect directs Mixer to report metrics to the prometheus adapter. The adapter params tell Mixer how to generate metric values for any given request, based on the attributes reported by Envoy (and generated by Mixer itself).

The schema for the metric came from a predefined metric descriptor known to Mixer. In this task, the descriptor used was response_size. The response_size metric descriptor uses buckets to record a distribution of values, making it easier for the backend metrics systems to provide summary statistics for a bunch of requests in aggregate (as is often desirable when looking at response sizes).

The new rule instructs Mixer to generate values for the metric based on the values of the attribute response.size. A default values of 0 was added, in case Envoy does not report the values as expected.

A set of dimensions were also configured for the metric value, via the labels chunks of configuration. For the new metric, the dimensions were source, destination, service, version, method, and response_code.

Dimensions provide a way to slice, aggregate, and analyze metric data according to different needs and directions of inquiry. For instance, it may be desirable to only consider response sizes for non-error responses when troubleshooting the rollout of a new application version.

The new rule instructs Mixer to populate values for these dimensions based on attribute values. For instance, for the service dimension, the new rule requests that the value be taken from the destination.labels["app"] attribute. If that attribute value is not populated, the rule instructs Mixer to use a default value of "unknown".

At the moment, it is not possible to programmatically generate new metric descriptors for use within Mixer. As a result, all new metric configurations must use one of the predefined metrics descriptors: request_count, request_duration, request_size, and response_size.

Work is ongoing to extend the Mixer Config API to add support for creating new descriptors.

Understanding the rule’s access_logs aspect

The access-logs aspect directs Mixer to send access logs to the default adapter (typically, stdioLogger). The adapter params tell Mixer how to generate the access logs for incoming requests based on attributes reported by Envoy.

The logName parameter is used by Mixer to identify a logs stream. In this task, the log name combined_log was used to identify the log stream amidst the rest of the Mixer logging output. This name should be used to uniquely identify log streams to various logging backends.

The log section of the rule describes the shape of the access log that Mixer will generate when the rule is applied. In this task, the pre-configured definition for an access log named accesslog.combined was used. It is based on the well-known Combined Log Format.

Access logs use a template to generate a plaintext log from a set of named arguments. The template is defined in the configured descriptor for the aspect. In this task, the template used is defined in the descriptor named accesslog.combined. The set of inputs to the template_expressions is fixed in the descriptor and cannot be altered in aspect configuration.

The template_expressions describe how to translate attribute values into the named arguments for the template processing. For example, the value for userAgent is to be derived directly from the value for the attribute request.headers["user-agent"].

Mixer supports structured log generation in addition to plaintext logs. In this task, a set of labels to populate for structured log generation was configured. These labels are populated from attribute values according to attribute expressions, in exactly the same manner as the template_expressions.

While it is common practice to include the same set of arguments in the labels as in the template_expressions, this is not required. Mixer will generate the labels completely independently of the template_expressions.

As with metric descriptors, it is not currently possible to programmatically generate new access logs descriptors. Work is ongoing to extend the Mixer Config API to add support for creating new descriptors.

What’s next