Crate slog [−] [src]
Slog - Structured, extensible, composable logging for Rust
Features
- easy to use
- great performance; see: slog bench log
#![no_std]
support (with opt-outstd
cargo feature flag)- hierarchical loggers
- lazily evaluated values
- modular, lightweight and very extensible
- tiny core crate that does not pull any dependencies
- feature-crates for specific functionality
- backward compatibility for standard
log
crate (slog-stdlog
crate)- supports logging-scopes
- using slog in library does not force users of the library to use slog
(but gives benefits); see
crates/example-lib
- drains & output formatting
- filtering
- compile-time log level filter using cargo features (same as in
log
crate) - by level, msg, and any other meta-data
slog-envlogger
- port ofenv_logger
- compile-time log level filter using cargo features (same as in
- multiple outputs
- asynchronous IO writing
- terminal output, with color support (
slog-term
crate) - Json (
slog-json
crate)- Bunyan (
slog-bunyan
crate)
- Bunyan (
- syslog (
slog-syslog
crate) - first class custom drains
- filtering
Advantages over log
crate
- extensible -
slog
provides core functionality, and some standard feature-set. But using traits, anyone can easily implement as powerful fully-custom features, publish separately and growslog
feature-set for everyone. - composable - Wouldn't it be nice if you could use
env_logger
, but output authentication messages to syslog, while reporting errors over network in json format? Withslog
drains can reuse other drains! You can combine them together, chain, wrap - you name it. - context aware - It's not just one global logger. Hierarchical
loggers carry information about context of logging. When logging an error
condition, you want to know which resource was being handled, on which
instance of your service, using which source code build, talking with what
peer, etc. In standard
log
you would have to repeat this information in every log statement. Inslog
it will happen automatically. See slog-rs functional overview page to understand better logger and drain hierarchies and log record flow through them. - both human and machine readable - By keeping the key-value data format, meaning of logging data is preserved. Dump your logging to a JSON file, and send it to your data-mining system for further analysis. Don't parse it from lines of text anymore!
- lazy evaluation and asynchronous IO included. Waiting to
finish writing logging information to disk, or spending time calculating
data that will be thrown away at the current logging level, are sources of big
performance waste. Use
AsyncStreamer
drain, and closures to make your logging fast. - run-time configuration -
AtomicSwitch
drain allows changing logging behavior in the running program. You could use eg. signal handlers to change logging level or logging destinations. Seesignal
example.
Notable details
slog
by default removes at compile time trace and debug level statements
in release builds, and trace level records in debug builds. This makes
trace
and debug
level logging records practically free, which should
encourage using them freely. If you want to enable trace/debug messages
or raise the compile time logging level limit, use the following in your
Cargo.toml
:
slog = { version = "1.2", features = ["max_level_trace", "release_max_level_warn"] }
Due to the macro_rules
limitation log macros syntax comes in several
versions. See log!
macro, and pay attention to ;
and ,
details.
Root drain (passed to Logger::root
) must be one that does not ever
return errors, which forces user to pick error handing strategy. You
can use .fuse()
or .ignore_err()
methods from DrainExt
to do
it conveniently.
Examples & help
Look at slog-rs examples in slog-misc
repository
Read slog-rs wiki pages
Check sources of other software using slog-rs
Visit slog-rs gitter channel for immediate help.
Reexports
pub use ser::PushLazy; |
pub use ser::ValueSerializer; |
pub use ser::Serializer; |
pub use ser::Serialize; |
Modules
ser |
Serialization |
Macros
crit |
Log critical level record |
debug |
Log debug level record |
error |
Log error level record |
info |
Log info level record |
log |
Log message of a given level |
o |
Convenience macro for building |
slog_crit |
Log critical level record (alias) |
slog_debug |
Log debug level record (alias) |
slog_error |
Log error level record |
slog_info |
Log info level record (alias) |
slog_log |
Log message of a given level (alias) |
slog_o |
An alternative, longer-name version of |
slog_trace |
Log trace level record (alias) |
slog_warn |
Log warning level record (alias) |
trace |
Log trace level record |
warn |
Log warning level record |
Structs
Discard |
|
Duplicate |
|
Filter |
|
Fuse |
|
IgnoreErr |
|
LevelFilter |
|
Logger |
Logging handle used to execute logging statements |
MapError |
|
OwnedKeyValueList |
Chain of |
OwnedKeyValueListIterator |
Iterator over |
Record |
One logging record |
Enums
DuplicateError |
Logging error returned by |
FilterLevel |
Logging filtering level |
Level |
Logging level associated with a logging |
Statics
LOG_LEVEL_NAMES |
Official capitalized logging (and logging filtering) level names |
LOG_LEVEL_SHORT_NAMES |
Official capitalized logging (and logging filtering) short level names |
Traits
Drain |
Logging drain |
DrainExt |
Convenience methods for building drains |
Functions
duplicate |
Duplicate records to two drains |
filter |
Filter by |
level_filter |
Filter by log level |
Type Definitions
BorrowedKeyValue |
Key value pair that can be part of a logging record |
OwnedKeyValue |
Key value pair that can be owned by |