Crate std_logger[−][src]
Expand description
A crate that holds a logging implementation that logs to standard error and standard out. It uses standard error for all regular messages and standard out for requests.
This crate provides only a logging implementation. To do actual logging use
the log crate and it’s various macros.
Setting severity
You can use various environment variables to change the severity (log level) of the messages to actually log and which to ignore.
LOG and LOG_LEVEL can be used to set the severity to a specific value,
see the log’s package LevelFilter type for available values.
# In your shell of your choice:
# Set the log severity to only print log messages with info severity or
# higher, trace and debug messages won't be printed anymore.
$ LOG=info ./my_binary
# Set the log severity to only print log messages with warning severity or
# higher, informational (or lower severity) messages won't be printed
# anymore.
$ LOG=warn ./my_binaryAlternatively setting the TRACE variable (e.g. TRACE=1) sets the
severity to the trace, meaning it will log everything. Setting DEBUG will
set the severity to debug.
# In your shell of your choice:
# Enables trace logging.
$ TRACE=1 ./my_binary
# Enables debug logging.
$ DEBUG=1 ./my_binaryIf none of these environment variables are found it will default to an information severity.
In addition to these runtime filters the log crate provides compile time filters which allows you to filter log messages at compile time.
Logging requests
To log requests a special target is provided: REQUEST_TARGET and a
special macro: request. This will cause the message to be logged to
standard out, rather then standard error. This allows for separate
processing of error messages and request logs.
use std_logger::request;
request!("Got a request!");Limiting logging targets
Sometimes it’s useful to only log messages related to a specific target, for
example when debugging a single function you might want only see messages
from the module the function is in. This can be achieved by using the
LOG_TARGET environment variable.
# In your shell of choose:
# Only log messages from your crate.
$ LOG_TARGET=my_crate ./my_binary
# Only log messages from the `my_module` module in your crate.
$ LOG_TARGET=my_crate::my_module ./my_binary
# Multiple log targets are also supported by separating the values by a
# comma.
$ LOG_TARGET=my_crate::my_module,my_crate::my_other_module ./my_binary
# Very useful in combination with trace severity to get all messages you
# want, but filter out the message you don't need.
$ LOG_LEVEL=trace LOG_TARGET=my_crate::my_module ./my_binaryNote that requests and panics (with target=“panic”) are always logged.
Format
This crate supports two formats logfmt and gcloud. In the examples below we’ll use the logfmt format as the author believes its easier to read for humans.
For regular messages, printed to standard error, the following format is used:
ts="YYYY-MM-DDTHH:MM:SS.MICROSZ" lvl="$LOG_LEVEL" msg="$message" target="$target" module="$module"
For example:
ts="2018-03-24T13:48:28.820588Z" lvl="ERROR" msg="my error message" target="my_module" module="my_module"For requests, logged using the REQUEST_TARGET target or the request
macro and printed to standard out, the following format is used:
ts="YYYY-MM-DDTHH:MM:SS.MICROSZ" lvl="INFO" msg="$message" target="request" module="$module"
For example:
ts="2018-03-24T13:30:28.820588Z" lvl="INFO" msg="my request message" target="request" module="my_module"Note: the timestamp is not printed when the timestamp feature is not enabled, this feature is enabled by default, see Timestamp feature below.
Crate features
This crate has three features:
- timestamp, enabled by default.
- log-panic, enabled by default.
- nightly, disabled by default.
Timestamp feature
The timestamp feature adds a timestamp in front of every message. It uses
the format defined in RFC3339 with 6 digit microsecond precision, e.g.
2018-03-24T13:48:48.063934Z. The timestamp is always logged in UTC.
Notes
This feature uses SystemTime as time source, which is not monotonic.
This means that a log message created after an earlier log message can
have a timestamp before the earlier created log message.
Log-panic feature
The log-panic feature will log all panics using the error severity,
rather then using the default panic handler. It will log the panic message
as well as the location and a backtrace, see the log output below for an
example (this example doesn’t include a timestamp).
lvl="ERROR" msg="thread 'main' panicked at 'oops', examples/panic.rs:24" target="panic" module="" backtrace="
stack backtrace:
0: 0x106ba8f74 - backtrace::backtrace::trace<closure>
at backtrace-0.3.2/src/backtrace/mod.rs:42
1: 0x106ba49af - backtrace::capture::Backtrace::new::h54d7cfa8f40c5b43
at backtrace-0.3.2/src/capture.rs:64
2: 0x106b9f4e6 - log_panics::init::{{closure}}
at log-panics-1.2.0/src/lib.rs:52
3: 0x106bc6951 - std::panicking::rust_panic_with_hook::h6c19f9ba35264287
at src/libstd/panicking.rs:612
4: 0x106b93146 - std::panicking::begin_panic<&str>
at src/libstd/panicking.rs:572
5: 0x106b93bf1 - panic::main
at examples/panic.rs:24
6: 0x106bc751c - __rust_maybe_catch_panic
at src/libpanic_unwind/lib.rs:98
7: 0x106bc6c08 - std::rt::lang_start::h6f338c4ae2d58bbe
at src/libstd/rt.rs:61
8: 0x106b93c29 - main
"If the timestamp feature is enable the first line of the message will be prefixed with a timestamp as described in the Timestamp feature.
Nightly feature
Enabling this feature enables the crate to use unstable (i.e. nightly-only) features from the compiler and standard library.
Currently this is limited to using the std::backtrace for creating
backtraces, rather than an external library.
Examples
use log::info;
use std_logger::request;
fn main() {
// First thing we need to do is initialise the logger before anything
// else.
std_logger::init();
// Now we can start logging!
info!("Our application started!");
// Do useful stuff, like starting a HTTP server.
}
/// This our example request handler, just pretend it gets called with a
/// request.
fn log_handler(req: Request) {
// This will be logged to standard out, rather then standard error.
request!("url = {}, status = {}, response_time = {:?}",
req.url, req.status, req.response_time);
}Macros
Logs a request.
Structs
Configuration of the logger.
Constants
Target for logging requests.