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

Note that, it must be done in separated 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'.

Then configure fluentd for istio:

kubectl apply -f install/fluentd-istio.yaml

Configure fluentd for node level logging:

kubectl apply -f install/fluentd-daemonset-elasticsearch-rbac.yaml

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

When to log¶

Istio defines when to log by creating a custom resource rule. For example:

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.

# 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

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:

# 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.

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.

# 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.