configurable thresholds for utxo merge policies

Author: adlai

joinmarket/configure.py

@@ -123,11 +123,10 @@ def jm_single():
 maker_timeout_sec = 30
 
 [POLICY]
-# for dust sweeping, try merge_algorithm = gradual
-# for more rapid dust sweeping, try merge_algorithm = greedy
-# for most rapid dust sweeping, try merge_algorithm = greediest
-# but don't forget to bump your miner fees!
-merge_algorithm = default
+# this knob is a list of ints, being each the amount of utxos in a mixdepth
+# sufficient for kicking in the next-mergiest utxo selection algorithm. the
+# default gives sane behavior; it is not clear what change improves privacy.
+merge_algorithm = [7, 14, 28]
 # the fee estimate is based on a projection of how many satoshis
 # per kB are needed to get in one of the next N blocks, N set here
 # as the value of 'tx_fees'. This estimate is high if you set N=1, 

joinmarket/support.py

@@ -17,6 +17,8 @@
 
 from math import exp
 
+import bitcoin                  # we only need bitcoin.select()
+
 # todo: this was the date format used in the original debug().  Use it?
 # logging.basicConfig(filename='logs/joinmarket.log',
 #                     stream=sys.stdout,
@@ -177,6 +179,20 @@ def select_greediest(unspent, value):
             end += 1
         return low[0:end]
 
+# ordered from most dusty (arguably, most private) to most mergiest (cheaper!)
+selectors = [bitcoin.select, select_gradual, select_greedy, select_greediest]
+
+def utxo_selector(configured_levels):
+    def select(unspent, value):
+        length = len(unspent)   # NB - counted only within each mixdepth
+        try:
+            for i in xrange(len(configured_levels)):
+                if length < configured_levels[i]:
+                    return selectors[i](unspent, value)
+        except IndexError:      # luser configured more levels than algos
+            log.debug("I'm sorry, Dave, but I can't let you merge that!")
+        return selectors[-1](unspent, value) # just use the greediest one
+    return select
 
 def calc_cj_fee(ordertype, cjfee, cj_amount):
     if ordertype == 'absorder':

joinmarket/wallet.py

@@ -3,6 +3,7 @@
 import os
 import pprint
 import sys
+import ast
 from decimal import Decimal
 
 from ConfigParser import NoSectionError
@@ -13,8 +14,7 @@
 from joinmarket.blockchaininterface import BitcoinCoreInterface
 from joinmarket.configure import jm_single, get_network, get_p2pk_vbyte
 
-from joinmarket.support import get_log, select_gradual, select_greedy, \
-    select_greediest
+from joinmarket.support import get_log, utxo_selector
 
 log = get_log()
 
@@ -38,19 +38,27 @@ class AbstractWallet(object):
 
     def __init__(self):
         self.max_mix_depth = 0
-        self.utxo_selector = btc.select  # default fallback: upstream
         try:
-            config = jm_single().config
-            if config.get("POLICY", "merge_algorithm") == "gradual":
-                self.utxo_selector = select_gradual
-            elif config.get("POLICY", "merge_algorithm") == "greedy":
-                self.utxo_selector = select_greedy
-            elif config.get("POLICY", "merge_algorithm") == "greediest":
-                self.utxo_selector = select_greediest
-            elif config.get("POLICY", "merge_algorithm") != "default":
-                raise Exception("Unknown merge algorithm")
+            policy = jm_single().config.get("POLICY", "merge_algorithm")
         except NoSectionError:
-            pass
+            policy = "default"  # maintain backwards compatibility!
+        if policy == "default":
+            self.merge_policy = [42] # well, almost (python lacks infinites)
+        elif policy == "gradual":
+            self.merge_policy = [6] # never goes beyond gradual
+        elif policy == "greedy":
+            self.merge_policy = [7, 7] # skip gradual, go greedy
+        elif policy == "greediest":
+            self.merge_policy = [8, 8, 8] # straight to greediest
+        else:
+            try:                # stop supporting word configs, someday...
+                self.merge_policy = ast.literal_eval(policy)
+                if ((type(self.merge_policy) is not list) or
+                    any(type(level) is not int for level in self.merge_policy)):
+                    raise Exception("Merge policy must be a list of ints")
+            except ValueError:
+                raise Exception("Unparseable merge policy: "+policy)
+        self.utxo_selector = utxo_selector(self.merge_policy)
 
     def get_key_from_addr(self, addr):
         return None