prometheus · brian-brazil · Jun 6, 2019 · Jun 4, 2019 · Jun 4, 2019 · Jun 4, 2019
diff --git a/prometheus_client/mmap_dict.py b/prometheus_client/mmap_dict.py
@@ -22,6 +22,29 @@ def _pack_integer(data, pos, value):
     data[pos:pos + 4] = _pack_integer_func(value)
 
 
+def _read_all_values(data, used=0):
+    """Yield (key, value, pos). No locking is performed."""
+
+    if used <= 0:
+        # If not valid `used` value is passed in, read it from the file.
+        used = _unpack_integer(data, 0)[0]
+
+    pos = 8
+
+    while pos < used:
+        encoded_len = _unpack_integer(data, pos)[0]
+        # check we are not reading beyond bounds
+        if encoded_len + pos > used:
+            raise RuntimeError('Read beyond file size detected, file is corrupted.')
+        pos += 4
+        encoded_key = data[pos : pos + encoded_len]
+        padded_len = encoded_len + (8 - (encoded_len + 4) % 8)
+        pos += padded_len
+        value = _unpack_double(data, pos)[0]
+        yield encoded_key.decode('utf-8'), value, pos
+        pos += 8
+
+
 class MmapedDict(object):
     """A dict of doubles, backed by an mmapped file.
 
@@ -37,9 +60,11 @@ class MmapedDict(object):
     def __init__(self, filename, read_mode=False):
         self._f = open(filename, 'rb' if read_mode else 'a+b')
         self._fname = filename
-        if os.fstat(self._f.fileno()).st_size == 0:
+        capacity = os.fstat(self._f.fileno()).st_size
+        if capacity == 0:
             self._f.truncate(_INITIAL_MMAP_SIZE)
-        self._capacity = os.fstat(self._f.fileno()).st_size
+            capacity = _INITIAL_MMAP_SIZE
+        self._capacity = capacity
         self._m = mmap.mmap(self._f.fileno(), self._capacity,
                             access=mmap.ACCESS_READ if read_mode else mmap.ACCESS_WRITE)
 
@@ -53,6 +78,17 @@ def __init__(self, filename, read_mode=False):
                 for key, _, pos in self._read_all_values():
                     self._positions[key] = pos
 
+    @staticmethod
+    def read_all_values_from_file(filename):
+        with open(filename, 'rb') as infp:
+            # Read the first block of data, including the first 4 bytes which tell us
+            # how much of the file (which is preallocated to _INITIAL_MMAP_SIZE bytes) is occupied.
+            data = infp.read(65535)
+            used = _unpack_integer(data, 0)[0]
+            if used > len(data):  # Then read in the rest, if needed.
+                data += infp.read(used - len(data))
+        return _read_all_values(data, used)
+
     def _init_value(self, key):
         """Initialize a value. Lock must be held by caller."""
         encoded = key.encode('utf-8')
@@ -72,31 +108,10 @@ def _init_value(self, key):
 
     def _read_all_values(self):
         """Yield (key, value, pos). No locking is performed."""
-
-        pos = 8
-
-        # cache variables to local ones and prevent attributes lookup
-        # on every loop iteration
-        used = self._used
-        data = self._m
-        unpack_from = struct.unpack_from
-
-        while pos < used:
-            encoded_len = _unpack_integer(data, pos)[0]
-            # check we are not reading beyond bounds
-            if encoded_len + pos > used:
-                msg = 'Read beyond file size detected, %s is corrupted.'
-                raise RuntimeError(msg % self._fname)
-            pos += 4
-            encoded = unpack_from(('%ss' % encoded_len).encode(), data, pos)[0]
-            padded_len = encoded_len + (8 - (encoded_len + 4) % 8)
-            pos += padded_len
-            value = _unpack_double(data, pos)[0]
-            yield encoded.decode('utf-8'), value, pos
-            pos += 8
+        return _read_all_values(data=self._m, used=self._used)
 
     def read_all_values(self):
-        """Yield (key, value, pos). No locking is performed."""
+        """Yield (key, value). No locking is performed."""
         for k, v, _ in self._read_all_values():
             yield k, v
 

diff --git a/prometheus_client/multiprocess.py b/prometheus_client/multiprocess.py
@@ -12,6 +12,8 @@
 from .samples import Sample
 from .utils import floatToGoString
 
+MP_METRIC_HELP = 'Multiprocess metric'
+
 
 class MultiProcessCollector(object):
     """Collector for files for multi-process mode."""
@@ -33,18 +35,31 @@ def merge(files, accumulate=True):
         But if writing the merged data back to mmap files, use
         accumulate=False to avoid compound accumulation.
         """
+        metrics = MultiProcessCollector._read_metrics(files)
+        return MultiProcessCollector._accumulate_metrics(metrics, accumulate)
+
+    @staticmethod
+    def _read_metrics(files):
         metrics = {}
+        key_cache = {}
+
+        def _parse_key(key):
+            val = key_cache.get(key)
+            if not val:
+                metric_name, name, labels = json.loads(key)
+                labels_key = tuple(sorted(labels.items()))
+                val = key_cache[key] = (metric_name, name, labels, labels_key)
+            return val
+
         for f in files:
             parts = os.path.basename(f).split('_')
             typ = parts[0]
-            d = MmapedDict(f, read_mode=True)
-            for key, value in d.read_all_values():
-                metric_name, name, labels = json.loads(key)
-                labels_key = tuple(sorted(labels.items()))
+            for key, value, pos in MmapedDict.read_all_values_from_file(f):
+                metric_name, name, labels, labels_key = _parse_key(key)
 
                 metric = metrics.get(metric_name)
                 if metric is None:
-                    metric = Metric(metric_name, 'Multiprocess metric', typ)
+                    metric = Metric(metric_name, MP_METRIC_HELP, typ)
                     metrics[metric_name] = metric
 
                 if typ == 'gauge':
@@ -54,43 +69,47 @@ def merge(files, accumulate=True):
                 else:
                     # The duplicates and labels are fixed in the next for.
                     metric.add_sample(name, labels_key, value)
-            d.close()
+        return metrics
 
+    @staticmethod
+    def _accumulate_metrics(metrics, accumulate):
         for metric in metrics.values():
             samples = defaultdict(float)
-            buckets = {}
+            buckets = defaultdict(lambda: defaultdict(float))
+            samples_setdefault = samples.setdefault
             for s in metric.samples:
-                name, labels, value = s.name, s.labels, s.value
+                name, labels, value, timestamp, exemplar = s
                 if metric.type == 'gauge':
-                    without_pid = tuple(l for l in labels if l[0] != 'pid')
+                    without_pid_key = (name, tuple([l for l in labels if l[0] != 'pid']))
                     if metric._multiprocess_mode == 'min':
-                        current = samples.setdefault((name, without_pid), value)
+                        current = samples_setdefault(without_pid_key, value)
                         if value < current:
-                            samples[(s.name, without_pid)] = value
+                            samples[without_pid_key] = value
                     elif metric._multiprocess_mode == 'max':
-                        current = samples.setdefault((name, without_pid), value)
+                        current = samples_setdefault(without_pid_key, value)
                         if value > current:
-                            samples[(s.name, without_pid)] = value
+                            samples[without_pid_key] = value
                     elif metric._multiprocess_mode == 'livesum':
-                        samples[(name, without_pid)] += value
+                        samples[without_pid_key] += value
                     else:  # all/liveall
                         samples[(name, labels)] = value
 
                 elif metric.type == 'histogram':
-                    bucket = tuple(float(l[1]) for l in labels if l[0] == 'le')
-                    if bucket:
-                        # _bucket
-                        without_le = tuple(l for l in labels if l[0] != 'le')
-                        buckets.setdefault(without_le, {})
-                        buckets[without_le].setdefault(bucket[0], 0.0)
-                        buckets[without_le][bucket[0]] += value
-                    else:
+                    # A for loop with early exit is faster than a genexpr
+                    # or a listcomp that ends up building unnecessary things
+                    for l in labels:
+                        if l[0] == 'le':
+                            bucket_value = float(l[1])
+                            # _bucket
+                            without_le = tuple(l for l in labels if l[0] != 'le')
+                            buckets[without_le][bucket_value] += value
+                            break
+                    else:  # did not find the `le` key
                         # _sum/_count
-                        samples[(s.name, labels)] += value
-
+                        samples[(name, labels)] += value
                 else:
                     # Counter and Summary.
-                    samples[(s.name, labels)] += value
+                    samples[(name, labels)] += value
 
             # Accumulate bucket values.
             if metric.type == 'histogram':