zrepl/docs/configuration/logging.rst
2017-11-11 23:25:12 +01:00

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Logging
=======
zrepl uses structured logging to provide users with easily processable log messages.
Configuration
-------------
Logging outlets are configured in the `global` section of the [configuration file]({{< relref "install/_index.md#configuration-files" >}}).<br />
Check out {{< sampleconflink "random/logging.yml" >}} for an example on how to configure multiple outlets:
::
global:
logging:
- outlet: OUTLET_TYPE
level: MINIMUM_LEVEL
format: FORMAT
- outlet: OUTLET_TYPE
level: MINIMUM_LEVEL
format: FORMAT
...
jobs: ...
Default Configuration
~~~~~~~~~~~~~~~~~~~~~
By default, the following logging configuration is used
::
global:
logging:
- outlet: "stdout"
level: "warn"
format: "human"
.. ATTENTION::
Output to **stderr** should always be considered a **critical error**.<br />
Only errors in the logging infrastructure itself, e.g. IO errors when writing to an outlet, are sent to stderr.
Building Blocks
---------------
The following sections document the semantics of the different log levels, formats and outlet types.
Levels
~~~~~~
::
| Level | SHORT | Description |
|-------|-------|-------------|
|`error`|`ERRO` | immediate action required |
|`warn` |`WARN` | symptoms for misconfiguration, soon expected failure, etc.|
|`info` |`INFO` | explains what happens without too much detail |
|`debug`|`DEBG` | tracing information, state dumps, etc. useful for debugging. |
Incorrectly classified messages are considered a bug and should be reported.
Formats
~~~~~~~
::
| Format | Description |
|--------|---------|
|`human` | emphasized context by putting job, task, step and other context variables into brackets before the actual message, followed by remaining fields in logfmt style|
|`logfmt`| [logfmt](https://brandur.org/logfmt) output. zrepl uses [github.com/go-logfmt/logfmt](github.com/go-logfmt/logfmt).|
|`json` | JSON formatted output. Each line is a valid JSON document. Fields are marshaled by `encoding/json.Marshal()`, which is particularly useful for processing in log aggregation or when processing state dumps.
Outlets
~~~~~~~
Outlets are ... well ... outlets for log entries into the world.
**`stdout`**
^^^^^^^^^^^^
::
| Parameter | Default | Comment |
|-----------| --------- | ----------- |
|`outlet` | *none* | required |
|`level` | *none* | minimum [log level](#levels), required |
|`format` | *none* | output [format](#formats), required |
Writes all log entries with minimum level `level` formatted by `format` to stdout.
Can only be specified once.
**`syslog`**
^^^^^^^^^^^^
::
| Parameter | Default | Comment |
|-----------| --------- | ----------- |
|`outlet` | *none* | required |
|`level` | *none* | minimum [log level](#levels), required, usually `debug` |
|`format` | *none* | output [format](#formats), required|
|`retry_interval`| 0 | Interval between reconnection attempts to syslog |
Writes all log entries formatted by `format` to syslog.
On normal setups, you should not need to change the `retry_interval`.
Can only be specified once.
**`tcp`**
^^^^^^^^^
::
| Parameter | Default | Comment |
|-----------| --------- | ----------- |
|`outlet` | *none* | required |
|`level` | *none* | minimum [log level](#levels), required |
|`format` | *none* | output [format](#formats), required |
|`net`|*none*|`tcp` in most cases|
|`address`|*none*|remote network, e.g. `logs.example.com:10202`|
|`retry_interval`|*none*|Interval between reconnection attempts to `address`|
|`tls`|*none*|TLS config (see below)|
Establishes a TCP connection to `address` and sends log messages with minimum level `level` formatted by `format`.
If `tls` is not specified, an unencrypted connection is established.
If `tls` is specified, the TCP connection is secured with TLS + Client Authentication.
This is particularly useful in combination with log aggregation services that run on an other machine.
::
|Parameter|Description|
|---------|-----------|
|`ca`|PEM-encoded certificate authority that signed the remote server's TLS certificate|
|`cert`|PEM-encoded client certificate identifying this zrepl daemon toward the remote server|
|`key`|PEM-encoded, unencrypted client private key identifying this zrepl daemon toward the remote server|
.. NOTE::
zrepl uses Go's `crypto/tls` and `crypto/x509` packages and leaves all but the required fields in `tls.Config` at their default values.
In case of a security defect in these packages, zrepl has to be rebuilt because Go binaries are statically linked.