From: Zooko O'Whielacronx <zooko@zooko.com>
Date: Sat, 12 Jul 2008 21:26:22 +0000 (-0700)
Subject: add misc/simulate_load.py in an attempt to understand why permuting the peerlist... 
X-Git-Url: https://git.rkrishnan.org/components/com_hotproperty/%22doc.html/architecture.txt?a=commitdiff_plain;h=b483c4710dbd550dcc3ecb44adfb141eb71c6dda;p=tahoe-lafs%2Ftahoe-lafs.git

add misc/simulate_load.py in an attempt to understand why permuting the peerlist per each storage index matters
---

diff --git a/misc/simulate_load.py b/misc/simulate_load.py
new file mode 100644
index 00000000..6c03b244
--- /dev/null
+++ b/misc/simulate_load.py
@@ -0,0 +1,111 @@
+#!/usr/bin/env python
+
+
+import random
+
+class Server:
+    def __init__(self):
+        self.si = random.randrange(0, 2**31)
+        self.used = 0
+        self.max = 2**40
+        self.full_at_tick = None
+
+    def __repr__(self):
+        if self.full_at_tick is not None:
+            return "<%s %s full at %d>" % (self.__class__.__name__, self.si, self.full_at_tick)
+        else:
+            return "<%s %s>" % (self.__class__.__name__, self.si)
+
+SERVERS = 40
+K = 3
+N = 10
+
+MAXSHARESIZE = 2**34 / K
+
+def go(permutedpeerlist):
+    servers = [ Server() for x in range(SERVERS) ]
+    servers.sort(cmp=lambda x,y: cmp(x.si, y.si))
+
+    tick = 0
+    fullservers = 0
+    while True:
+        nextsharesize = random.randrange(40, MAXSHARESIZE)
+        if permutedpeerlist:
+            random.shuffle(servers)
+        else:
+            # rotate a random number
+            rot = random.randrange(0, len(servers))
+            servers = servers[rot:] + servers[:rot]
+
+        i = 0
+        sharestoput = K
+        while sharestoput:
+            server = servers[i]
+            if server.used + nextsharesize < server.max:
+                server.used += nextsharesize
+                sharestoput -= 1
+            else:
+                if server.full_at_tick is None:
+                    server.full_at_tick = tick
+                    fullservers += 1
+                    if fullservers == len(servers):
+                        # print "Couldn't place share -- all servers full.  Stopping."
+                        return servers
+
+            i = (i + 1) % len(servers)
+
+        tick += 1
+
+def test(permutedpeerlist, iters):
+    # the i'th element of the filledat list is how many servers got full on the tick numbered 4500 + i * 9
+    filledat = [0] * 77
+    for test in range(iters):
+        servers = go(permutedpeerlist)
+        for server in servers:
+            fidx = (server.full_at_tick - 4500) / 9
+            if fidx >= len(filledat):
+                filledat.extend([0]*(fidx-len(filledat)+1))
+            filledat[fidx] += 1
+
+    # the i'th element of the fullat list is how many servers were full by the tick numbered 4500 + i * 9 (on average)
+    fullat = [0] * 77
+    for idx, num in enumerate(filledat):
+        for fidx in range(idx, len(fullat)):
+            fullat[fidx] += num
+
+    for idx in range(len(fullat)):
+        fullat[idx]  = fullat[idx] / float(iters)
+
+    # Now print it out as an ascii art graph.
+    import sys
+    for serversfull in range(40, 0, -1):
+        sys.stdout.write("%2d" % serversfull)
+        for numfull in fullat:
+            if int(numfull) == serversfull:
+                sys.stdout.write("*")
+            else:
+                sys.stdout.write(" ")
+        sys.stdout.write("\n")
+
+    sys.stdout.write(" ^-- servers full\n")
+    idx = 0
+    while idx < len(fullat):
+        sys.stdout.write("%d--^ " % (4500 + idx * 9))
+        idx += 8
+
+    sys.stdout.write("\nfiles uploaded --> \n")
+
+
+
+if __name__ == "__main__":
+    import sys
+    iters = 16
+    for arg in sys.argv:
+        if arg.startswith("--iters="):
+            iters = int(arg[8:])
+    if "--permute" in sys.argv:
+        print "doing permuted peerlist, iterations: %d" % iters
+        test(True, iters)
+    else:
+        print "doing simple ring, iterations: %d" % iters
+        test(False, iters)