xtr

What is it?

XTR is a C++ logging library aimed at applications with low-latency or real-time requirements. The cost of log statements is minimised by delegating as much work as possible to a background thread.

It is designed so that the cost of a log statement is consistently fast---i.e. every call is fast, not just the average case. No allocations or system calls are made when a log statement is made.

Features

• Fast (please see benchmark results).
• No allocations when logging, even when logging strings.
• Formatting, I/O etc are all delegated to a background thread. Work done at the log statement call-site is minimized---for example a no argument log statement only involves writing a single pointer to a ring buffer.
• Safe: No references taken to arguments unless explicitly requested.
• Comprehensive suite of unit tests which run cleanly under AddressSanitizer, UndefinedBehaviourSanitizer, ThreadSanitizer and LeakSanitizer.
• Log sinks with independent log levels (so that levels for different subsystems may be modified independently).
• Ability to modify log levels via an external command.
• Non-printable characters are sanitized for safety (to prevent terminal escape sequence injection attacks).
• Type-safe---formatting is done via fmtlib.
• io_uring support.
• Support for custom I/O back-ends (e.g. to log to the network, write compressed files, etc).
• Support for logrotate integration.
• Support for systemd journal integration.
• CMake and Conan integration supported.
• Fully documented.

Supported platforms

• Linux (x86-64)
• FreeBSD (x86-64)

Documentation

https://choll.github.io/xtr

Benchmarks

Below is the output of PRODUCER_CPU=2 CONSUMER_CPU=1 make benchmark_cpu on a stock Ryzen 5950X with SMT disabled, isolated cores and g++ version 11.2.0

sudo cpupower --cpu 2,1 frequency-set --governor performance
Setting cpu: 1
Setting cpu: 2
build/g++-lto-release/benchmark/benchmark
2022-04-26T22:54:43+01:00
Running build/g++-lto-release/benchmark/benchmark
Run on (16 X 5084 MHz CPU s)
CPU Caches:
  L1 Data 32 KiB (x16)
  L1 Instruction 32 KiB (x16)
  L2 Unified 512 KiB (x16)
  L3 Unified 32768 KiB (x2)
Load Average: 3.32, 2.74, 1.99
***WARNING*** CPU scaling is enabled, the benchmark real time measurements may be noisy and will incur extra overhead.
---------------------------------------------------------------------------------
Benchmark                                       Time             CPU   Iterations
---------------------------------------------------------------------------------
logger_benchmark                             2.19 ns         2.19 ns    318972090
logger_benchmark_tsc                         7.81 ns         7.81 ns     89307646
logger_benchmark_clock_realtime_coarse       8.05 ns         8.05 ns     87732373
logger_benchmark_int                         3.31 ns         3.31 ns    210259973
logger_benchmark_long                        3.33 ns         3.33 ns    209935480
logger_benchmark_double                      3.26 ns         3.26 ns    212240698
logger_benchmark_c_str                       4.86 ns         4.86 ns    146577914
logger_benchmark_str_view                    3.12 ns         3.12 ns    224958501
logger_benchmark_str                         4.36 ns         4.36 ns    158750720
logger_benchmark_non_blocking                2.01 ns         2.01 ns    349312408

Benchmarks Comparing Against Other loggers

Integer Benchmark, One Thread

Library	50	75	90	95	99	99.9	Max	Version
xtr	11	12	12.5	13	14	41	55.5	2.0.1
platformlab_nanolog	11.5	11.5	12	12	12.5	14.5	33	85b71b6
quill	12	13	13.5	14	14.5	16	530.5	v2.0.2
reckless	17	17	17.5	17.5	19.5	21.5	38	v3.0.3
ms_binlog	29.5	31	32	32.5	68	105.5	384	2020-04-26-82-g2de2fa0
iyengar_nanolog	142	158	173.5	192.5	421	484	41490	3ffc74a
spdlog	284.5	317	346	363.5	399.5	501.5	572.5	v1.10.0
g3log	2543	2637	2724	2779	2879	3015	3354	1.3.4

Integer Benchmark, Four Threads

Library	50	75	90	95	99	99.9	Max	Version
xtr	11	12	12.5	13.5	14.5	41.5	73	2.0.1
platformlab_nanolog	11.5	12	12.5	12.5	13	17	33.5	85b71b6
quill	13	14.5	15.5	16.5	18	21.5	23	v2.0.2
reckless	18	19.5	20.5	20.5	21.5	28	65	v3.0.3
ms_binlog	29.5	31	32	33	70.5	107.5	412	2020-04-26-82-g2de2fa0
iyengar_nanolog	135	152.5	172	184	227	507.5	63290	3ffc74a
spdlog	280.5	314.5	342.5	361.5	403.5	540.5	669.5	v1.10.0
g3log	2530	2624	2710	2767	2878	3017	7146	1.3.4

String Benchmark, One Thread

Library	50	75	90	95	99	99.9	Max	Version
xtr	12.5	13.5	14	14.5	16	41.5	51	2.0.1
platformlab_nanolog	13.5	14	14.5	14.5	15.5	19	35.5	85b71b6
quill	14.5	15.5	18	18.5	20	21.5	22.5	v2.0.2
ms_binlog	34	35.5	36.5	38	75	109.5	389.5	2020-04-26-82-g2de2fa0
reckless	44	47.5	49.5	50.5	52.5	79.5	134.5	v3.0.3
iyengar_nanolog	120	150	166.5	181	379.5	492.5	41680	3ffc74a
spdlog	255	299	344	373.5	484.5	1123	1602	v1.10.0
g3log	1975	2214	2340	2416	2536	2693	2888	1.3.4

String Benchmark, Four Threads

Library	50	75	90	95	99	99.9	Max	Version
xtr	13	13.5	14.5	15	16.5	46	66	2.0.1
platformlab_nanolog	13.5	14	14.5	15	16.5	22	39	85b71b6
quill	14.5	15.5	17	18	20	21.5	23.5	v2.0.2
ms_binlog	34.5	36	37.5	38.5	75.5	115.5	408.5	2020-04-26-82-g2de2fa0
reckless	44	48	50	51	52.5	68.5	216.5	v3.0.3
iyengar_nanolog	96.5	132.5	161.5	174.5	229.5	487	8354	3ffc74a
spdlog	256	301.5	349.5	379	495.5	1177	2071	v1.10.0
g3log	1911	2245	2380	2451	2582	2738	6578	1.3.4

See logger_benchmarks for more details.

Installation notes

See INSTALL.md