Patch for FNV1A_CH support in graphite-web 0.9.15

graphite_0.9.15_epel_fnv1a.patch

diff -u -r graphite_old/render/datalib.py graphite/render/datalib.py
--- graphite_old/render/datalib.py	2016-10-19 18:22:37.000000000 +0200
+++ graphite/render/datalib.py	2016-10-19 18:12:00.000000000 +0200
@@ -106,7 +106,7 @@
     self.hosts = [ (server, instance) for (server, port, instance) in hosts ]
     self.ports = dict( ((server, instance), port) for (server, port, instance) in hosts )
     self.timeout = float(timeout)
-    self.hash_ring = ConsistentHashRing(self.hosts)
+    self.hash_ring = ConsistentHashRing(self.hosts, hash_type=settings.CARBONLINK_HASHING_TYPE)
     self.connections = {}
     self.last_failure = {}
     # Create a connection pool for each host
diff -u -r graphite_old/render/hashing.py graphite/render/hashing.py
--- graphite_old/render/hashing.py	2016-10-19 18:22:37.000000000 +0200
+++ graphite/render/hashing.py	2016-10-19 18:27:39.000000000 +0200
@@ -22,6 +22,24 @@
 from itertools import chain
 import bisect

+try:
+  import pyhash
+  hasher = pyhash.fnv1a_32()
+  def fnv32a(string, seed=0x811c9dc5):
+    return hasher(string, seed=seed)
+except ImportError:
+  def fnv32a(string, seed=0x811c9dc5):
+    """
+    FNV-1a Hash (http://isthe.com/chongo/tech/comp/fnv/) in Python.
+    Taken from https://gist.github.com/vaiorabbit/5670985
+    """
+    hval = seed
+    fnv_32_prime = 0x01000193
+    uint32_max = 2 ** 32
+    for s in string:
+      hval = hval ^ ord(s)
+      hval = (hval * fnv_32_prime) % uint32_max
+    return hval

 def hashRequest(request):
   # Normalize the request parameters so ensure we're deterministic
@@ -49,20 +67,28 @@


 class ConsistentHashRing:
-  def __init__(self, nodes, replica_count=100):
+  def __init__(self, nodes, replica_count=100, hash_type='carbon_ch'):
     self.ring = []
+    self.hash_type = hash_type
     self.replica_count = replica_count
     for node in nodes:
       self.add_node(node)

   def compute_ring_position(self, key):
-    big_hash = md5( str(key) ).hexdigest()
-    small_hash = int(big_hash[:4], 16)
+    if self.hash_type == 'fnv1a_ch':
+      big_hash = ('%X' % int(fnv32a(str(key)))).lower()
+      small_hash = int(big_hash[:4], 16) ^ int(big_hash[4:], 16)
+    else:
+      big_hash = md5( str(key) ).hexdigest()
+      small_hash = int(big_hash[:4], 16)
     return small_hash

   def add_node(self, key):
     for i in range(self.replica_count):
-      replica_key = "%s:%d" % (key, i)
+      if self.hash_type == 'fnv1a_ch':
+        replica_key = "%d-%s" % (i, key[1])
+      else:
+        replica_key = "%s:%d" % (key, i)
       position = self.compute_ring_position(replica_key)
       entry = (position, key)
       bisect.insort(self.ring, entry)
diff -u -r graphite_old/settings.py graphite/settings.py
--- graphite_old/settings.py	2016-10-19 18:22:37.000000000 +0200
+++ graphite/settings.py	2016-10-19 18:03:25.000000000 +0200
@@ -80,6 +80,7 @@
 CARBONLINK_HOSTS = ["127.0.0.1:7002"]
 CARBONLINK_TIMEOUT = 1.0
 CARBONLINK_QUERY_BULK = False
+CARBONLINK_HASHING_TYPE = 'fnv1a_ch'
 SMTP_SERVER = "localhost"
 DOCUMENTATION_URL = "http://graphite.readthedocs.org/"
 ALLOW_ANONYMOUS_CLI = True

Note: if you intend to use this patch to get fnv1a_ch in your graphite 0.9.15 installation, change the big_hash calculation in compute_ring_position to
big_hash = ('%08X' % int(fnv32a(str(key)))).lower()
otherwise you'll end up with some mismatches.