From 217b0dfd683cda0a082fb33636b38f0172a4af31 Mon Sep 17 00:00:00 2001
From: Alex Auvolat <alex@adnab.me>
Date: Sun, 21 Feb 2021 14:30:26 +0100
Subject: Add script to simulate different kinds of rings

---
 script/simulate_ring.py | 120 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 120 insertions(+)
 create mode 100644 script/simulate_ring.py

diff --git a/script/simulate_ring.py b/script/simulate_ring.py
new file mode 100644
index 00000000..fa875d4e
--- /dev/null
+++ b/script/simulate_ring.py
@@ -0,0 +1,120 @@
+import hashlib
+import bisect
+import xxhash
+
+
+def walk_ring_from_pos(tokens, dcs, start, rep):
+    ret = []
+    ret_dcs = set()
+    delta = 0
+    while len(ret) < rep:
+        i = (start + delta) % len(tokens)
+        delta = delta + 1
+
+        (token_k, token_dc, token_node) = tokens[i]
+        if token_dc not in ret_dcs:
+            ret_dcs |= set([token_dc])
+            ret.append(token_node)
+        elif len(ret_dcs) == len(dcs) and token_node not in ret:
+            ret.append(token_node)
+    return ret
+
+def count_tokens_per_node(tokens):
+    tokens_of_node = {}
+    for _, _, token_node in tokens:
+        if token_node not in tokens_of_node:
+            tokens_of_node[token_node] = 0
+        tokens_of_node[token_node] += 1
+    print("#tokens per node:")
+    for node, ntok in sorted(list(tokens_of_node.items())):
+        print(node, ": ", ntok)
+
+def method1(nodes):
+    tokens = []
+    dcs = set()
+    for (node_id, dc, n_tokens) in nodes:
+        dcs |= set([dc])
+        for i in range(n_tokens):
+            token = hashlib.sha256(f"{node_id} {i}".encode('ascii')).hexdigest()
+            tokens.append((token, dc, node_id))
+    tokens.sort(key=lambda tok: tok[0])
+
+    count_tokens_per_node(tokens)
+
+    space_of_node = {}
+
+    def walk_ring(v, rep):
+        i = bisect.bisect_left([tok for tok, _, _ in tokens], hashlib.sha256(v).hexdigest())
+        return walk_ring_from_pos(tokens, dcs, i, rep)
+
+    return walk_ring
+
+
+def method2(nodes):
+    partition_bits = 10
+    partitions = list(range(2**partition_bits))
+    def partition_node(i):
+        h, hn, hndc = None, None, None
+        for (node_id, node_dc, n_tokens) in nodes:
+            for tok in range(n_tokens):
+                #hnode = hashlib.sha256(f"{i} {node_id} {tok}".encode('ascii')).hexdigest()
+                xxh = xxhash.xxh64()
+                xxh.update(f"partition {i} node {node_id} token {tok}".encode('ascii'))
+                hnode = xxh.digest()
+                if h is None or hnode < h:
+                    h = hnode
+                    hn = node_id
+                    hndc = node_dc
+        return (i, hndc, hn)
+
+    partition_nodes = [partition_node(i) for i in partitions]
+    count_tokens_per_node(partition_nodes)
+
+    dcs = list(set(node_dc for _, node_dc, _ in nodes))
+
+        
+    def walk_ring(v, rep):
+        vh = hashlib.sha256(v).digest()
+        i = (vh[0]<<8 | vh[1]) % (2**partition_bits)
+        return walk_ring_from_pos(partition_nodes, dcs, i, rep)
+
+    return walk_ring
+
+
+
+def evaluate_method(walk_ring):
+    node_data_counts = {}
+    for i in range(100000):
+        nodes = walk_ring(f"{i}".encode('ascii'), 3)
+        for n in nodes:
+            if n not in node_data_counts:
+                node_data_counts[n] = 0
+            node_data_counts[n] += 1
+    print("Number of data items per node:")
+    for n, v in sorted(list(node_data_counts.items())):
+        print(n, ": ", v)
+
+
+if __name__ == "__main__":
+
+    nodes = [('digitale', 'atuin', 10),
+             ('drosera', 'atuin', 10),
+             ('datura', 'atuin', 10),
+             ('io', 'jupiter', 20),
+             ('meta', 'pipo', 10),
+             ('mega', 'pipo', 10),
+             ('mina', 'pipo', 10),
+             #('moni', 'pipo', 10),
+             #('mimi', 'pipo', 10),
+             #('mesi', 'pipo', 10),
+             ]
+
+    print("------")
+    print("method 1")
+    method1_walk_ring = method1(nodes)
+    evaluate_method(method1_walk_ring)
+
+    print("------")
+    print("method 2")
+    method2_walk_ring = method2(nodes)
+    evaluate_method(method2_walk_ring)
-- 
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