FedericoCeratto / Nim Morelogging

== Morelogging

A set of logging utilities for Nim.

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.Features: [none]

• [x] File rotation
• [x] Compression
• [x] Templated log file name
• [x] Templated log messages
• [x] Threaded log buffering
• [x] Async log buffering
• [x] Logging, file rotation and compression do not block the caller
• [x] Sensible defaults: log to "..log", daily log rotation
• [x] Log to systemd Journald. Support structured entries.
• [x] Support Linux, OSX, Windows
• [x] Functional-tested

.Roadmap:

• [ ] Logging hierarchy
• [ ] Do not crash the application on write failure (e.g. broken or full disk, permission errors) - switch to logging to stderr
• [ ] Rotate logfile on SIGHUP signal
• [ ] Structured logging and optional fields

.Installation [source,bash]

$ # install Nim using APT or from the upstream website $ sudo apt-get install nim $ # install nimble and then: $ nimble install morelogging

.Usage [source,nim]

import morelogging as log

let log = newAsyncFileLogger() log.debug("debug") log.info("info") log.warn("warn") log.error("error") log.fatal("fatal")

=== Log message formatting

The following formatters are supported:

$date $time $datetime $app $appdir $appname $levelid $levelname

Messages with level below level_threshold are ignored.

=== Async and threaded loggers

If buffer_size is positive, messages are buffered internally up to writeout_interval_ms

Messages with level >= flush_threshold are flushed out immediately.

[source,nim]

proc newAsyncFileLogger*( filename_tpl = "$app.$y$MM$dd.log", flush_threshold = lvlError, fmtStr = "$datetime $levelname ", level_threshold = lvlAll, mode: FileMode = fmAppend, writeout_interval_ms = 100, buffer_size = 1_048_576 ): AsyncFileLogger =

proc newThreadFileLogger*( filename_tpl = "$app.$y$MM$dd.log", fmtStr = "$datetime $levelname ", level_threshold = lvlAll, mode: FileMode = fmAppend, writeout_interval_ms = 100, ): ThreadFileLogger =

proc newThreadRotatingFileLogger*( compress = false, filename_tpl = "$app.$y$MM$dd.log", fmtStr = "$datetime $levelname ", level_threshold = lvlAll, mode: FileMode = fmAppend, rotate_interval = "1d", writeout_interval_ms = 100, ): ThreadRotatingFileLogger

==== Generating log file names dynamically

Filenames are generated from filename_tpl Default value: "$app.$y$MM$dd.log" The following formatters are supported:

$y year $MM month $dd day $hh hour $mm minute $ss second $hostname hostname $appname application name

=== Systemd's Journald logger (recommended)

Journald supports logging user-defined key-value pairs and provides fast indexing.

Enable with -d:systemd

.Usage: [source,nim]

let log = newJournaldLogger() log.info("hello world", {"key_1": "value_1"})

Keys are converted to uppercase. They can contain underscores but not as the first character.

JournaldLogger will automatically add CODE_FILE, CODE_FUNC, CODE_LINE keys to show the filename, function and line number that generated the log message.

Note: '--stackTrace:on' and '--lineTrace:on' are required when building in release mode to enable this feature.

You can override them by passing the keys in uppercase with your own values.

.Output example: [source,bash]

sudo journalctl -e -o json-pretty KEY_1=value_1 -n1 --no-pager { "PRIORITY" : "5", "_TRANSPORT" : "journal", "_UID" : "1000", "_GID" : "1000", "MESSAGE" : "hello world", "KEY_1" : "value_1", "CODE_FUNC" : "myfunction", "CODE_FILE" : "mytest.nim", "CODE_LINE" : "24", < other lines redacted > < ... > }

=== Stdout logger

Useful mostly for debugging.

.Usage: [source,nim]

import morelogging let log = newStdoutLogger(fmtStr="$time ") log.info("hello world")