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diff --git a/docs/development/design/logging.rst b/docs/development/design/logging.rst index 196ba40..05f3f5b 100644 --- a/docs/development/design/logging.rst +++ b/docs/development/design/logging.rst @@ -26,3 +26,139 @@ It validates the installation with the following criterias #. existence of fluented pod #. fluentd input is configured correctly #. TBD + +************************** +Understanding how it works +************************** + +In clover stack, Istio is configured to automatically gather logs for services +in a mesh. More specificly, it is configured in `Mixer`_:: + +- when to log +- what to log +- where to log + +.. _Mixer: https://istio.io/docs/concepts/policy-and-control/mixer.html + +When to log +=========== + +Istio defines when to log by creating a custom resource ``rule``. For example: + +.. code-block:: yaml + + apiVersion: "config.istio.io/v1alpha2" + kind: rule + metadata: + name: newlogtofluentd + namespace: istio-system + spec: + match: "true" # match for all requests + actions: + - handler: handler.fluentd + instances: + - newlog.logentry + +This rule specifies that all instances of ``newlog.logentry`` that matches the +expression will be handled by the specified handler ``handler.fluentd``. We +shall explain ``instances`` and ``handler`` later. The expression ``true`` means +whenever a request arrive at Mixer, it will trigger the actions defined belows. + +``rule`` is a custom resource definition from `Istio installation`_. + +.. code-block:: yaml + + # Rule to send logentry instances to the fluentd handler + kind: CustomResourceDefinition + apiVersion: apiextensions.k8s.io/v1beta1 + metadata: + name: rules.config.istio.io + labels: + package: istio.io.mixer + istio: core + spec: + group: config.istio.io + names: + kind: rule + plural: rules + singular: rule + scope: Namespaced + version: v1alpha2 + +.. _Istio installation: https://github.com/istio/istio/blob/master/install/kubernetes/templates/istio-mixer.yaml.tmpl + +What to log +=========== + +The instance defines what content to be logged. + +> A (request) instance is the result of applying request attributes to the +> template mapping. The mapping is specified as an instance configuration. + +For example: + +.. code-block:: yaml + + # Configuration for logentry instances + apiVersion: "config.istio.io/v1alpha2" + kind: logentry + metadata: + name: newlog + namespace: istio-system + spec: + severity: '"info"' + timestamp: request.time + variables: + source: source.labels["app"] | source.service | "unknown" + user: source.user | "unknown" + destination: destination.labels["app"] | destination.service | "unknown" + responseCode: response.code | 0 + responseSize: response.size | 0 + latency: response.duration | "0ms" + monitored_resource_type: '"UNSPECIFIED"' + +The keys under ``spec`` should conform to the template. To learn what fields +are available and valid type, you may need to reference the corresponding +template, in this case, `Log Entry template`_. + +The values of each field could be either `Istio attributes`_ or an expression. + +> A given Istio deployment has a fixed vocabulary of attributes that it +> understands. The specific vocabulary is determined by the set of attribute +> producers being used in the deployment. The primary attribute producer in +> Istio is Envoy, although Mixer and services can also introduce attributes. + +Refer to the `Attribute Vocabulary`_ to learn the full set. + +By the way, ``logentry`` is also a custom resource definition created by Istio. + +.. _Istio attributes: https://istio.io/docs/concepts/policy-and-control/attributes.html +.. _Attribute Vocabulary: https://istio.io/docs/reference/config/mixer/attribute-vocabulary.html +.. _Log Entry template: https://istio.io/docs/reference/config/template/logentry.html + +Where to log +============ + +For log, the handler defines where these information will be handled, in this +example, a fluentd daemon on fluentd-es.logging:24224. + +.. code-block:: yaml + + # Configuration for a fluentd handler + apiVersion: "config.istio.io/v1alpha2" + kind: fluentd + metadata: + name: handler + namespace: istio-system + spec: + address: "fluentd-es.logging:24224" + +In this example, handlers (``handler.fluentd``) configure `Adapters`_ +(``fluentd``) to handle the data delivered from the created instances +(``newlog.logentry``). + +An adapter only accepts instance of specified kind. For example, +`fluentd adapter`_ accepts logentry but not other kinds. + +.. _Adapters: https://istio.io/docs/concepts/policy-and-control/mixer.html#adapters +.. _fluentd adapter: https://istio.io/docs/reference/config/adapters/fluentd.html |