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#######
Logging
#######
************
Installation
************
Currently, we use the `sample configuration`_ in Istio to install fluentd::
cd clover/logging
First, install logging stack Elasticsearch, Fluentd and Kibana::
kubectl apply -f install/logging-stack.yaml
Then configure fluentd for istio::
kubectl apply -f install/fluentd-istio.yaml
Note that, it must be done in two steps. If you run ``kubectl apply -f install``
instead, the mixer adapter may fail to intialize because the target service can
not be found. You may find an error message from mixer container::
2018-05-09T02:43:14.435156Z error Unable to initialize adapter:
snapshot='6', handler='handler.fluentd.istio-system', adapter='fluentd',
err='adapter instantiation error: dial tcp: lookup fluentd-es.logging on
10.96.0.10:53: no such host'.
.. _sample configuration: https://istio.io/docs/tasks/telemetry/fluentd.html
********
Validate
********
The scripts in ``clover/logging`` validates fluentd installation::
python clover/logging/validate.py
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
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