Allow disabling logging by setting AUSTIN_NO_LOGGING in the environment

ChangeLog

@@ -2,6 +2,9 @@
 
   Added support for Python 3.11.
 
+  Allowed disabling logging by setting the environment variable
+  AUSTIN_NO_LOGGING.
+
   Improved permission error reporting on MacOS.
 
   Improved MacOS support.

README.md

@@ -355,6 +355,15 @@ where the structure of `[frame]` and the number and type of metrics on each line
 depend on the mode.
 
 
+## Environment variables
+
+Some behaviour of Austin can be configured via environment variables.
+
+| Variable             | Effect |
+| -------------------- | ------ |
+| `AUSTIN_NO_LOGGING=` | Disables all [log messages](#logging). |
+
+
 ## Normal Mode
 
 In normal mode, the `[frame]` part of each emitted sample has the structure
@@ -522,6 +531,8 @@ statistics. _Bad_ frames are output together with the other frames. In general,
 entries for bad frames will not be visible in a flame graph as all tests show
 error rates below 1% on average.
 
+Logging can be disabled using [environment variables](#environment-variables).
+
 
 ## Cheat sheet
 

src/logging.c

@@ -50,9 +50,11 @@ FILE * logfile = NULL;
 #include "austin.h"
 #include "logging.h"
 
+int logging = 0;
 
 void
 _log_writer(int prio, const char * fmt, va_list ap) {
+  if (!logging) return;
   #ifdef PL_UNIX
   vsyslog(prio, fmt, ap);
 
@@ -72,6 +74,8 @@ _log_writer(int prio, const char * fmt, va_list ap) {
 
 void
 logger_init(void) {
+  if (getenv("AUSTIN_NO_LOGGING") == NULL) logging = 1;
+  if (!logging) return;
   #ifdef PL_UNIX
   setlogmask (LOG_UPTO (LOG_DEBUG));
   openlog ("austin", LOG_CONS | LOG_PID | LOG_NDELAY, LOG_LOCAL1);
@@ -162,6 +166,7 @@ log_t(const char * fmt, ...) {
 
 void
 logger_close(void) {
+  if (!logging) return;
   #ifdef PL_UNIX
   closelog();
 

test/test_fork.py

@@ -235,3 +235,12 @@ def test_qualnames(py, austin):
 
     assert has_pattern(result.stdout, "qualnames.py:Foo.run"), compress(result.stdout)
     assert has_pattern(result.stdout, "qualnames.py:Bar.run"), compress(result.stdout)
+
+
+@allpythons()
+def test_no_logging(py):
+    datafile = tmp_path / "test_no_logging.austin"
+    env = {"AUSTIN_NO_LOGGING", ""}
+    script = "import time; time.sleep(.1)"
+    result = austin("-i", "1ms", "-o", datafile, *python(py), "-c", script, env=env)
+    assert result.returncode == 0, result.stderr or result.stdout

test/utils.py

@@ -27,7 +27,7 @@
 from pathlib import Path
 from subprocess import PIPE, CompletedProcess, Popen, check_output, run
 from test import PYTHON_VERSIONS
-from typing import Iterator, TypeVar
+from typing import Dict, Iterator, Optional, TypeVar
 
 import pytest
 
@@ -130,7 +130,9 @@ def __init__(self, name: str) -> None:
 
         self.ALL.append(self)
 
-    def __call__(self, *args: tuple[str], timeout: int = 60) -> CompletedProcess:
+    def __call__(
+        self, *args: tuple[str], timeout: int = 60, env: Optional[Dict[str, str]] = None
+    ) -> CompletedProcess:
         if not self.path.is_file():
             pytest.skip(f"Variant '{self}' not available")
 
@@ -140,6 +142,7 @@ def __call__(self, *args: tuple[str], timeout: int = 60) -> CompletedProcess:
             timeout=timeout,
             text=True,
             errors="ignore",
+            env=None if env is None else {**os.environ, **env},
         )
 
         if result.returncode in (-11, 139):  # SIGSEGV