structlog.nvim
Structured Logging for nvim, using Lua
Why using it
structlog
makes logging in Lua less painful and more powerful by adding structure to your log entries.
Instead of writting complex messages, you can start thinking in terms of an event that happens in the context of key/value pairs.
Each log entry is a meaningful dictionary instead of an opaque string!
Thanks to its flexible design, the structure of the final log output is up for you to decide.
Each log entry goes through a processor pipeline that is just a chain of functions that receive a dictionary and return a new dictionary that gets fed into the next function. That allows for simple but powerful data manipulation.
This dictionary is then formatted and sent out to the sink.
For more details, consider reading the documentation.
Installation
Using packer.nvim
use { "Tastyep/structlog.nvim" }
Using luarocks
luarocks install --local structlog.nvim
Design
As explained in the introduction, log messages go through a pipeline of functions to provide common information and to structure them into a comprehensible format. Internally, the log message is a dictionary built by the logger and is composed as follow:
local kwargs = {
level = Level.name(level), -- The log level represented as a string
msg = msg, -- The given message
events = events or {}, -- The dictionary containing the 'key=value' arguments
}
At the end of the processing pipeline, the message msg
field should contain the text to write to the sinks.
Processors
Processors are functions with the goal of enriching log messages. These functions accept one parameter, kwargs
which they edit by adding new key=value
pairs, such as the logger's name or the current timestamp, and return it on completion.
See the processors documentation.
Formatters
Formatters define the structure of the log. By default vim.inspect
is used to format the given arguments events
as key=value
pairs.
All formatters have the same interface. They expose a formatting function accepting a dictionary kwargs
and return that same dictionary, modified so that kwargs.msg
contains the log to write to the sink.
See the formatters documentation.
Sinks
Sinks specify where to write the log message. Like the other elements of the pipeline, sinks accept kwargs
as parameter.
See the sunks documentation.
Usage
Create and Use
local log = require("structlog")
local logger = log.Logger("name", {
log.sinks.Console(
log.level.INFO
{
processors = {
log.processors.Namer(),
log.processors.Timestamper("%H:%M:%S"),
},
formatter = log.formatters.Format( --
"%s [%s] %s: %-30s",
{ "timestamp", "level", "logger_name", "msg" }
),
}
),
})
logger:info("A log message")
logger:warn("A log message with keyword arguments", { warning = "something happened" })
10:32:40 [INFO] name: A log message
10:32:40 [WARN] name: A log message with keyword arguments warning="something happened"
Configure and Retrieve
local log = require("structlog")
log.configure({
name = {
sinks = {
log.sinks.Console(
log.level.INFO,
{
processors = {
log.processors.Namer(),
log.processors.Timestamper("%H:%M:%S"),
},
formatter = log.formatters.Format( --
"%s [%s] %s: %-30s",
{ "timestamp", "level", "logger_name", "msg" },
),
}
),
},
},
other_logger = {...},
})
local logger = log.get_logger("name")
Example
local log = require("structlog")
log.configure({
name = {
sinks = {
log.sinks.Console(
log.level.INFO,
{
processors = {
log.processors.Namer(),
log.processors.StackWriter({ "line", "file" }, { max_parents = 0, stack_level = 0 }),
log.processors.Timestamper("%H:%M:%S"),
},
formatter = log.formatters.FormatColorizer( --
"%s [%s] %s: %-30s",
{ "timestamp", "level", "logger_name", "msg" },
{ level = log.formatters.FormatColorizer.color_level() }
),
}
),
log.sinks.NvimNotify(
log.level.WARN,
{
processors = {
log.processors.Namer(),
},
formatter = log.formatters.Format( --
"%s",
{ "msg" },
{ blacklist = { "level", "logger_name" } }
),
params_map = { title = "logger_name" },
}),
log.sinks.File(
log.level.TRACE,
"./test.log",
{
processors = {
log.processors.Namer(),
log.processors.StackWriter({ "line", "file" }, { max_parents = 3 }),
log.processors.Timestamper("%H:%M:%S"),
},
formatter = log.formatters.Format( --
"%s [%s] %s: %-30s",
{ "timestamp", "level", "logger_name", "msg" }
),
}
),
},
},
-- other_logger = {...}
})
local logger = log.get_logger("name")
logger:info("A log message")
logger:warn("A log message with keyword arguments", { warning = "something happened" })
cat test.log:
10:43:23 [INFO] name: A log message file="lua/lsp/null-ls/formatters.lua", line=9
10:43:23 [WARN] name: A log message with keyword arguments file="lua/lsp/null-ls/formatters.lua", line=10, warning="something happened"