summaryrefslogtreecommitdiffstats
path: root/docs/development/design/logging.rst
blob: 05f3f5b382968d17a4ba7f32eae7e0d6a08e979f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
#######
Logging
#######

************
Installation
************

Currently, we use the `sample configuration`_ in Istio to install fluentd::

    cd clover/logging
    kubectl apply -f install

.. _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