3 files changed, 48 insertions, 6 deletions
diff --git a/synapse/metrics/__init__.py b/synapse/metrics/__init__.py
index 488280b4a6..bec3b13397 100644
--- a/synapse/metrics/__init__.py
+++ b/synapse/metrics/__init__.py
@@ -20,6 +20,7 @@ import os
 import platform
 import threading
 import time
+from typing import Dict, Union
 
 import six
 
@@ -29,20 +30,20 @@ from prometheus_client.core import REGISTRY, GaugeMetricFamily, HistogramMetricF
 
 from twisted.internet import reactor
 
+import synapse
 from synapse.metrics._exposition import (
     MetricsResource,
     generate_latest,
     start_http_server,
 )
+from synapse.util.versionstring import get_version_string
 
 logger = logging.getLogger(__name__)
 
 METRICS_PREFIX = "/_synapse/metrics"
 
 running_on_pypy = platform.python_implementation() == "PyPy"
-all_metrics = []
-all_collectors = []
-all_gauges = {}
+all_gauges = {}  # type: Dict[str, Union[LaterGauge, InFlightGauge, BucketCollector]]
 
 HAVE_PROC_SELF_STAT = os.path.exists("/proc/self/stat")
 
@@ -385,6 +386,16 @@ event_processing_last_ts = Gauge("synapse_event_processing_last_ts", "", ["name"
 # finished being processed.
 event_processing_lag = Gauge("synapse_event_processing_lag", "", ["name"])
 
+# Build info of the running server.
+build_info = Gauge(
+    "synapse_build_info", "Build information", ["pythonversion", "version", "osversion"]
+)
+build_info.labels(
+    " ".join([platform.python_implementation(), platform.python_version()]),
+    get_version_string(synapse),
+    " ".join([platform.system(), platform.release()]),
+).set(1)
+
 last_ticked = time.time()
 
 
diff --git a/synapse/metrics/_exposition.py b/synapse/metrics/_exposition.py
index 1933ecd3e3..74d9c3ecd3 100644
--- a/synapse/metrics/_exposition.py
+++ b/synapse/metrics/_exposition.py
@@ -36,7 +36,9 @@ from twisted.web.resource import Resource
 try:
     from prometheus_client.samples import Sample
 except ImportError:
-    Sample = namedtuple("Sample", ["name", "labels", "value", "timestamp", "exemplar"])
+    Sample = namedtuple(
+        "Sample", ["name", "labels", "value", "timestamp", "exemplar"]
+    )  # type: ignore
 
 
 CONTENT_TYPE_LATEST = str("text/plain; version=0.0.4; charset=utf-8")
diff --git a/synapse/metrics/background_process_metrics.py b/synapse/metrics/background_process_metrics.py
index edd6b42db3..c53d2a0d40 100644
--- a/synapse/metrics/background_process_metrics.py
+++ b/synapse/metrics/background_process_metrics.py
@@ -15,6 +15,8 @@
 
 import logging
 import threading
+from asyncio import iscoroutine
+from functools import wraps
 
 import six
 
@@ -173,7 +175,7 @@ def run_as_background_process(desc, func, *args, **kwargs):
 
     Args:
         desc (str): a description for this background process type
-        func: a function, which may return a Deferred
+        func: a function, which may return a Deferred or a coroutine
         args: positional args for func
         kwargs: keyword args for func
 
@@ -197,7 +199,17 @@ def run_as_background_process(desc, func, *args, **kwargs):
                 _background_processes.setdefault(desc, set()).add(proc)
 
             try:
-                yield func(*args, **kwargs)
+                result = func(*args, **kwargs)
+
+                # We probably don't have an ensureDeferred in our call stack to handle
+                # coroutine results, so we need to ensureDeferred here.
+                #
+                # But we need this check because ensureDeferred doesn't like being
+                # called on immediate values (as opposed to Deferreds or coroutines).
+                if iscoroutine(result):
+                    result = defer.ensureDeferred(result)
+
+                return (yield result)
             except Exception:
                 logger.exception("Background process '%s' threw an exception", desc)
             finally:
@@ -208,3 +220,20 @@ def run_as_background_process(desc, func, *args, **kwargs):
 
     with PreserveLoggingContext():
         return run()
+
+
+def wrap_as_background_process(desc):
+    """Decorator that wraps a function that gets called as a background
+    process.
+
+    Equivalent of calling the function with `run_as_background_process`
+    """
+
+    def wrap_as_background_process_inner(func):
+        @wraps(func)
+        def wrap_as_background_process_inner_2(*args, **kwargs):
+            return run_as_background_process(desc, func, *args, **kwargs)
+
+        return wrap_as_background_process_inner_2
+
+    return wrap_as_background_process_inner