diff --git a/synapse/metrics/jemalloc.py b/synapse/metrics/jemalloc.py
index 6bc329f04a..1fc8a0e888 100644
--- a/synapse/metrics/jemalloc.py
+++ b/synapse/metrics/jemalloc.py
@@ -18,6 +18,7 @@ import os
import re
from typing import Iterable, Optional, overload
+import attr
from prometheus_client import REGISTRY, Metric
from typing_extensions import Literal
@@ -27,52 +28,24 @@ from synapse.metrics._types import Collector
logger = logging.getLogger(__name__)
-def _setup_jemalloc_stats() -> None:
- """Checks to see if jemalloc is loaded, and hooks up a collector to record
- statistics exposed by jemalloc.
- """
-
- # Try to find the loaded jemalloc shared library, if any. We need to
- # introspect into what is loaded, rather than loading whatever is on the
- # path, as if we load a *different* jemalloc version things will seg fault.
-
- # We look in `/proc/self/maps`, which only exists on linux.
- if not os.path.exists("/proc/self/maps"):
- logger.debug("Not looking for jemalloc as no /proc/self/maps exist")
- return
-
- # We're looking for a path at the end of the line that includes
- # "libjemalloc".
- regex = re.compile(r"/\S+/libjemalloc.*$")
-
- jemalloc_path = None
- with open("/proc/self/maps") as f:
- for line in f:
- match = regex.search(line.strip())
- if match:
- jemalloc_path = match.group()
-
- if not jemalloc_path:
- # No loaded jemalloc was found.
- logger.debug("jemalloc not found")
- return
-
- logger.debug("Found jemalloc at %s", jemalloc_path)
-
- jemalloc = ctypes.CDLL(jemalloc_path)
+@attr.s(slots=True, frozen=True, auto_attribs=True)
+class JemallocStats:
+ jemalloc: ctypes.CDLL
@overload
def _mallctl(
- name: str, read: Literal[True] = True, write: Optional[int] = None
+ self, name: str, read: Literal[True] = True, write: Optional[int] = None
) -> int:
...
@overload
- def _mallctl(name: str, read: Literal[False], write: Optional[int] = None) -> None:
+ def _mallctl(
+ self, name: str, read: Literal[False], write: Optional[int] = None
+ ) -> None:
...
def _mallctl(
- name: str, read: bool = True, write: Optional[int] = None
+ self, name: str, read: bool = True, write: Optional[int] = None
) -> Optional[int]:
"""Wrapper around `mallctl` for reading and writing integers to
jemalloc.
@@ -120,7 +93,7 @@ def _setup_jemalloc_stats() -> None:
# Where oldp/oldlenp is a buffer where the old value will be written to
# (if not null), and newp/newlen is the buffer with the new value to set
# (if not null). Note that they're all references *except* newlen.
- result = jemalloc.mallctl(
+ result = self.jemalloc.mallctl(
name.encode("ascii"),
input_var_ref,
input_len_ref,
@@ -136,21 +109,80 @@ def _setup_jemalloc_stats() -> None:
return input_var.value
- def _jemalloc_refresh_stats() -> None:
+ def refresh_stats(self) -> None:
"""Request that jemalloc updates its internal statistics. This needs to
be called before querying for stats, otherwise it will return stale
values.
"""
try:
- _mallctl("epoch", read=False, write=1)
+ self._mallctl("epoch", read=False, write=1)
except Exception as e:
logger.warning("Failed to reload jemalloc stats: %s", e)
+ def get_stat(self, name: str) -> int:
+ """Request the stat of the given name at the time of the last
+ `refresh_stats` call. This may throw if we fail to read
+ the stat.
+ """
+ return self._mallctl(f"stats.{name}")
+
+
+_JEMALLOC_STATS: Optional[JemallocStats] = None
+
+
+def get_jemalloc_stats() -> Optional[JemallocStats]:
+ """Returns an interface to jemalloc, if it is being used.
+
+ Note that this will always return None until `setup_jemalloc_stats` has been
+ called.
+ """
+ return _JEMALLOC_STATS
+
+
+def _setup_jemalloc_stats() -> None:
+ """Checks to see if jemalloc is loaded, and hooks up a collector to record
+ statistics exposed by jemalloc.
+ """
+
+ global _JEMALLOC_STATS
+
+ # Try to find the loaded jemalloc shared library, if any. We need to
+ # introspect into what is loaded, rather than loading whatever is on the
+ # path, as if we load a *different* jemalloc version things will seg fault.
+
+ # We look in `/proc/self/maps`, which only exists on linux.
+ if not os.path.exists("/proc/self/maps"):
+ logger.debug("Not looking for jemalloc as no /proc/self/maps exist")
+ return
+
+ # We're looking for a path at the end of the line that includes
+ # "libjemalloc".
+ regex = re.compile(r"/\S+/libjemalloc.*$")
+
+ jemalloc_path = None
+ with open("/proc/self/maps") as f:
+ for line in f:
+ match = regex.search(line.strip())
+ if match:
+ jemalloc_path = match.group()
+
+ if not jemalloc_path:
+ # No loaded jemalloc was found.
+ logger.debug("jemalloc not found")
+ return
+
+ logger.debug("Found jemalloc at %s", jemalloc_path)
+
+ jemalloc_dll = ctypes.CDLL(jemalloc_path)
+
+ stats = JemallocStats(jemalloc_dll)
+ _JEMALLOC_STATS = stats
+
class JemallocCollector(Collector):
"""Metrics for internal jemalloc stats."""
def collect(self) -> Iterable[Metric]:
- _jemalloc_refresh_stats()
+ stats.refresh_stats()
g = GaugeMetricFamily(
"jemalloc_stats_app_memory_bytes",
@@ -184,7 +216,7 @@ def _setup_jemalloc_stats() -> None:
"metadata",
):
try:
- value = _mallctl(f"stats.{t}")
+ value = stats.get_stat(t)
except Exception as e:
# There was an error fetching the value, skip.
logger.warning("Failed to read jemalloc stats.%s: %s", t, e)
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