Add block pruning functionality

This adds a -prune=N option to bitcoind, which if set to N>0 will enable block
file pruning. When pruning is enabled, block and undo files will be deleted to
try to keep total space used by those files to below the prune target (N, in
MB) specified by the user, subject to some constraints:

- The last 288 blocks on the main chain are always kept (MIN_BLOCKS_TO_KEEP),
- N must be at least 550MB (chosen as a value for the target that could
  reasonably be met, with some assumptions about block sizes, orphan rates,
  etc; see comment in main.h),
- No blocks are pruned until chainActive is at least 100,000 blocks long (on
  mainnet; defined separately for mainnet, testnet, and regtest in chainparams
  as nPruneAfterHeight).

This unsets NODE_NETWORK if pruning is enabled.

Also included is an RPC test for pruning (pruning.py).

Thanks to @rdponticelli for earlier work on this feature; this is based in
part off that work.

2 files changed, 361 insertions, 2 deletions

diff --git a/qa/rpc-tests/pruning.py b/qa/rpc-tests/pruning.py
new file mode 100755
index 0000000000..f26cbee1e2
--- /dev/null
+++ b/qa/rpc-tests/pruning.py
@@ -0,0 +1,356 @@
+#!/usr/bin/env python2
+# Copyright (c) 2014 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#
+# Test pruning code
+# ********
+# WARNING:
+# This test uses 4GB of disk space and takes in excess of 30 mins to run
+# ********
+
+from test_framework import BitcoinTestFramework
+from bitcoinrpc.authproxy import AuthServiceProxy, JSONRPCException
+from util import *
+import os.path
+
+def calc_usage(blockdir):
+    return sum(os.path.getsize(blockdir+f) for f in os.listdir(blockdir) if os.path.isfile(blockdir+f))/(1024*1024)
+
+class PruneTest(BitcoinTestFramework):
+
+    def __init__(self):
+        self.utxo = []
+        self.address = ["",""]
+
+        # Some pre-processing to create a bunch of OP_RETURN txouts to insert into transactions we create
+        # So we have big transactions and full blocks to fill up our block files
+
+        # create one script_pubkey
+        script_pubkey = "6a4d0200" #OP_RETURN OP_PUSH2 512 bytes
+        for i in xrange (512):
+            script_pubkey = script_pubkey + "01"
+        # concatenate 128 txouts of above script_pubkey which we'll insert before the txout for change
+        self.txouts = "81"
+        for k in xrange(128):
+            # add txout value
+            self.txouts = self.txouts + "0000000000000000"
+            # add length of script_pubkey
+            self.txouts = self.txouts + "fd0402"
+            # add script_pubkey
+            self.txouts = self.txouts + script_pubkey
+
+
+    def setup_chain(self):
+        print("Initializing test directory "+self.options.tmpdir)
+        initialize_chain_clean(self.options.tmpdir, 3)
+
+    def setup_network(self):
+        self.nodes = []
+        self.is_network_split = False
+
+        # Create nodes 0 and 1 to mine
+        self.nodes.append(start_node(0, self.options.tmpdir, ["-debug","-maxreceivebuffer=20000","-blockmaxsize=999000", "-checkblocks=5"], timewait=300))
+        self.nodes.append(start_node(1, self.options.tmpdir, ["-debug","-maxreceivebuffer=20000","-blockmaxsize=999000", "-checkblocks=5"], timewait=300))
+
+        # Create node 2 to test pruning
+        self.nodes.append(start_node(2, self.options.tmpdir, ["-debug","-maxreceivebuffer=20000","-prune=550"], timewait=300))
+        self.prunedir = self.options.tmpdir+"/node2/regtest/blocks/"
+
+        self.address[0] = self.nodes[0].getnewaddress()
+        self.address[1] = self.nodes[1].getnewaddress()
+
+        connect_nodes(self.nodes[0], 1)
+        connect_nodes(self.nodes[1], 2)
+        connect_nodes(self.nodes[2], 0)
+        sync_blocks(self.nodes[0:3])
+
+    def create_big_chain(self):
+        # Start by creating some coinbases we can spend later
+        self.nodes[1].generate(200)
+        sync_blocks(self.nodes[0:2])
+        self.nodes[0].generate(150)
+        # Then mine enough full blocks to create more than 550MB of data
+        for i in xrange(645):
+            self.mine_full_block(self.nodes[0], self.address[0])
+
+        sync_blocks(self.nodes[0:3])
+
+    def test_height_min(self):
+        if not os.path.isfile(self.prunedir+"blk00000.dat"):
+            raise AssertionError("blk00000.dat is missing, pruning too early")
+        print "Success"
+        print "Though we're already using more than 550MB, current usage:", calc_usage(self.prunedir)
+        print "Mining 25 more blocks should cause the first block file to be pruned"
+        # Pruning doesn't run until we're allocating another chunk, 20 full blocks past the height cutoff will ensure this
+        for i in xrange(25):
+            self.mine_full_block(self.nodes[0],self.address[0])
+
+        waitstart = time.time()
+        while os.path.isfile(self.prunedir+"blk00000.dat"):
+            time.sleep(0.1)
+            if time.time() - waitstart > 10:
+                raise AssertionError("blk00000.dat not pruned when it should be")
+
+        print "Success"
+        usage = calc_usage(self.prunedir)
+        print "Usage should be below target:", usage
+        if (usage > 550):
+            raise AssertionError("Pruning target not being met")
+
+    def create_chain_with_staleblocks(self):
+        # Create stale blocks in manageable sized chunks
+        print "Mine 24 (stale) blocks on Node 1, followed by 25 (main chain) block reorg from Node 0, for 12 rounds"
+
+        for j in xrange(12):
+            # Disconnect node 0 so it can mine a longer reorg chain without knowing about node 1's soon-to-be-stale chain
+            # Node 2 stays connected, so it hears about the stale blocks and then reorg's when node0 reconnects
+            # Stopping node 0 also clears its mempool, so it doesn't have node1's transactions to accidentally mine
+            stop_node(self.nodes[0],0)
+            self.nodes[0]=start_node(0, self.options.tmpdir, ["-debug","-maxreceivebuffer=20000","-blockmaxsize=999000", "-checkblocks=5"], timewait=300)
+            # Mine 24 blocks in node 1
+            self.utxo = self.nodes[1].listunspent()
+            for i in xrange(24):
+                if j == 0:
+                    self.mine_full_block(self.nodes[1],self.address[1])
+                else:
+                    self.nodes[1].generate(1) #tx's already in mempool from previous disconnects
+
+            # Reorg back with 25 block chain from node 0
+            self.utxo = self.nodes[0].listunspent()
+            for i in xrange(25): 
+                self.mine_full_block(self.nodes[0],self.address[0])
+
+            # Create connections in the order so both nodes can see the reorg at the same time
+            connect_nodes(self.nodes[1], 0)
+            connect_nodes(self.nodes[2], 0)
+            sync_blocks(self.nodes[0:3])
+
+        print "Usage can be over target because of high stale rate:", calc_usage(self.prunedir)
+
+    def reorg_test(self):
+        # Node 1 will mine a 300 block chain starting 287 blocks back from Node 0 and Node 2's tip
+        # This will cause Node 2 to do a reorg requiring 288 blocks of undo data to the reorg_test chain
+        # Reboot node 1 to clear its mempool (hopefully make the invalidate faster)
+        # Lower the block max size so we don't keep mining all our big mempool transactions (from disconnected blocks)
+        stop_node(self.nodes[1],1)
+        self.nodes[1]=start_node(1, self.options.tmpdir, ["-debug","-maxreceivebuffer=20000","-blockmaxsize=5000", "-checkblocks=5", "-disablesafemode"], timewait=300)
+
+        height = self.nodes[1].getblockcount()
+        print "Current block height:", height
+
+        invalidheight = height-287
+        badhash = self.nodes[1].getblockhash(invalidheight)
+        print "Invalidating block at height:",invalidheight,badhash
+        self.nodes[1].invalidateblock(badhash)
+
+        # We've now switched to our previously mined-24 block fork on node 1, but thats not what we want
+        # So invalidate that fork as well, until we're on the same chain as node 0/2 (but at an ancestor 288 blocks ago)
+        mainchainhash = self.nodes[0].getblockhash(invalidheight - 1)
+        curhash = self.nodes[1].getblockhash(invalidheight - 1)
+        while curhash != mainchainhash:
+            self.nodes[1].invalidateblock(curhash)
+            curhash = self.nodes[1].getblockhash(invalidheight - 1)
+
+        assert(self.nodes[1].getblockcount() == invalidheight - 1)
+        print "New best height", self.nodes[1].getblockcount()
+
+        # Reboot node1 to clear those giant tx's from mempool
+        stop_node(self.nodes[1],1)
+        self.nodes[1]=start_node(1, self.options.tmpdir, ["-debug","-maxreceivebuffer=20000","-blockmaxsize=5000", "-checkblocks=5", "-disablesafemode"], timewait=300)
+
+        print "Generating new longer chain of 300 more blocks"
+        self.nodes[1].generate(300)
+
+        print "Reconnect nodes"
+        connect_nodes(self.nodes[0], 1)
+        connect_nodes(self.nodes[2], 1)
+        sync_blocks(self.nodes[0:3])
+
+        print "Verify height on node 2:",self.nodes[2].getblockcount()
+        print "Usage possibly still high bc of stale blocks in block files:", calc_usage(self.prunedir)
+
+        print "Mine 220 more blocks so we have requisite history (some blocks will be big and cause pruning of previous chain)"
+        self.nodes[0].generate(220) #node 0 has many large tx's in its mempool from the disconnects
+        sync_blocks(self.nodes[0:3])
+
+        usage = calc_usage(self.prunedir)
+        print "Usage should be below target:", usage
+        if (usage > 550):
+            raise AssertionError("Pruning target not being met")
+
+        return invalidheight,badhash
+
+    def reorg_back(self):
+        # Verify that a block on the old main chain fork has been pruned away
+        try:
+            self.nodes[2].getblock(self.forkhash)
+            raise AssertionError("Old block wasn't pruned so can't test redownload")
+        except JSONRPCException as e:
+            print "Will need to redownload block",self.forkheight
+
+        # Verify that we have enough history to reorg back to the fork point
+        # Although this is more than 288 blocks, because this chain was written more recently
+        # and only its other 299 small and 220 large block are in the block files after it,
+        # its expected to still be retained
+        self.nodes[2].getblock(self.nodes[2].getblockhash(self.forkheight))
+
+        first_reorg_height = self.nodes[2].getblockcount()
+        curchainhash = self.nodes[2].getblockhash(self.mainchainheight)
+        self.nodes[2].invalidateblock(curchainhash)
+        goalbestheight = self.mainchainheight
+        goalbesthash = self.mainchainhash2
+
+        # As of 0.10 the current block download logic is not able to reorg to the original chain created in
+        # create_chain_with_stale_blocks because it doesn't know of any peer thats on that chain from which to
+        # redownload its missing blocks.
+        # Invalidate the reorg_test chain in node 0 as well, it can successfully switch to the original chain
+        # because it has all the block data.
+        # However it must mine enough blocks to have a more work chain than the reorg_test chain in order
+        # to trigger node 2's block download logic.
+        # At this point node 2 is within 288 blocks of the fork point so it will preserve its ability to reorg
+        if self.nodes[2].getblockcount() < self.mainchainheight:
+            blocks_to_mine = first_reorg_height + 1 - self.mainchainheight
+            print "Rewind node 0 to prev main chain to mine longer chain to trigger redownload. Blocks needed:", blocks_to_mine
+            self.nodes[0].invalidateblock(curchainhash)
+            assert(self.nodes[0].getblockcount() == self.mainchainheight)
+            assert(self.nodes[0].getbestblockhash() == self.mainchainhash2)
+            goalbesthash = self.nodes[0].generate(blocks_to_mine)[-1]
+            goalbestheight = first_reorg_height + 1
+
+        print "Verify node 2 reorged back to the main chain, some blocks of which it had to redownload"
+        waitstart = time.time()
+        while self.nodes[2].getblockcount() < goalbestheight:
+            time.sleep(0.1)
+            if time.time() - waitstart > 300:
+                raise AssertionError("Node 2 didn't reorg to proper height")
+        assert(self.nodes[2].getbestblockhash() == goalbesthash)
+        # Verify we can now have the data for a block previously pruned
+        assert(self.nodes[2].getblock(self.forkhash)["height"] == self.forkheight)
+
+    def mine_full_block(self, node, address):
+        # Want to create a full block
+        # We'll generate a 66k transaction below, and 14 of them is close to the 1MB block limit
+        for j in xrange(14):
+            if len(self.utxo) < 14:
+                self.utxo = node.listunspent()
+            inputs=[]
+            outputs = {}
+            t = self.utxo.pop()
+            inputs.append({ "txid" : t["txid"], "vout" : t["vout"]})
+            remchange = t["amount"] - Decimal("0.001000")
+            outputs[address]=remchange
+            # Create a basic transaction that will send change back to ourself after account for a fee
+            # And then insert the 128 generated transaction outs in the middle rawtx[92] is where the #
+            # of txouts is stored and is the only thing we overwrite from the original transaction
+            rawtx = node.createrawtransaction(inputs, outputs)
+            newtx = rawtx[0:92]
+            newtx = newtx + self.txouts
+            newtx = newtx + rawtx[94:]
+            # Appears to be ever so slightly faster to sign with SIGHASH_NONE
+            signresult = node.signrawtransaction(newtx,None,None,"NONE")
+            txid = node.sendrawtransaction(signresult["hex"], True)
+        # Mine a full sized block which will be these transactions we just created
+        node.generate(1)
+
+
+    def run_test(self):
+        print "Warning! This test requires 4GB of disk space and takes over 30 mins"
+        print "Mining a big blockchain of 995 blocks"
+        self.create_big_chain()
+        # Chain diagram key:
+        # *   blocks on main chain
+        # +,&,$,@ blocks on other forks
+        # X   invalidated block
+        # N1  Node 1
+        #
+        # Start by mining a simple chain that all nodes have
+        # N0=N1=N2 **...*(995)
+
+        print "Check that we haven't started pruning yet because we're below PruneAfterHeight"
+        self.test_height_min()
+        # Extend this chain past the PruneAfterHeight
+        # N0=N1=N2 **...*(1020)
+
+        print "Check that we'll exceed disk space target if we have a very high stale block rate"
+        self.create_chain_with_staleblocks()
+        # Disconnect N0
+        # And mine a 24 block chain on N1 and a separate 25 block chain on N0
+        # N1=N2 **...*+...+(1044)
+        # N0    **...**...**(1045)
+        #
+        # reconnect nodes causing reorg on N1 and N2
+        # N1=N2 **...*(1020) *...**(1045)
+        #                   \
+        #                    +...+(1044)
+        #
+        # repeat this process until you have 12 stale forks hanging off the
+        # main chain on N1 and N2
+        # N0    *************************...***************************(1320)
+        #
+        # N1=N2 **...*(1020) *...**(1045) *..         ..**(1295) *...**(1320)
+        #                   \            \                      \
+        #                    +...+(1044)  &..                    $...$(1319)
+
+        # Save some current chain state for later use
+        self.mainchainheight = self.nodes[2].getblockcount()   #1320
+        self.mainchainhash2 = self.nodes[2].getblockhash(self.mainchainheight)
+
+        print "Check that we can survive a 288 block reorg still"
+        (self.forkheight,self.forkhash) = self.reorg_test() #(1033, )
+        # Now create a 288 block reorg by mining a longer chain on N1
+        # First disconnect N1
+        # Then invalidate 1033 on main chain and 1032 on fork so height is 1032 on main chain
+        # N1   **...*(1020) **...**(1032)X..
+        #                  \
+        #                   ++...+(1031)X..
+        #
+        # Now mine 300 more blocks on N1
+        # N1    **...*(1020) **...**(1032) @@...@(1332)
+        #                 \               \
+        #                  \               X...
+        #                   \                 \
+        #                    ++...+(1031)X..   ..
+        #
+        # Reconnect nodes and mine 220 more blocks on N1
+        # N1    **...*(1020) **...**(1032) @@...@@@(1552)
+        #                 \               \
+        #                  \               X...
+        #                   \                 \
+        #                    ++...+(1031)X..   ..
+        #
+        # N2    **...*(1020) **...**(1032) @@...@@@(1552)
+        #                 \               \
+        #                  \               *...**(1320)
+        #                   \                 \
+        #                    ++...++(1044)     ..
+        #
+        # N0    ********************(1032) @@...@@@(1552) 
+        #                                 \
+        #                                  *...**(1320)
+
+        print "Test that we can rerequest a block we previously pruned if needed for a reorg"
+        self.reorg_back()
+        # Verify that N2 still has block 1033 on current chain (@), but not on main chain (*)
+        # Invalidate 1033 on current chain (@) on N2 and we should be able to reorg to
+        # original main chain (*), but will require redownload of some blocks
+        # In order to have a peer we think we can download from, must also perform this invalidation
+        # on N0 and mine a new longest chain to trigger.
+        # Final result:
+        # N0    ********************(1032) **...****(1553)
+        #                                 \
+        #                                  X@...@@@(1552)
+        #
+        # N2    **...*(1020) **...**(1032) **...****(1553)
+        #                 \               \
+        #                  \               X@...@@@(1552)
+        #                   \
+        #                    +..
+        #
+        # N1 doesn't change because 1033 on main chain (*) is invalid
+
+        print "Done"
+
+if __name__ == '__main__':
+    PruneTest().main()
diff --git a/qa/rpc-tests/util.py b/qa/rpc-tests/util.py
index 9ecee31959..cf789f48e2 100644
--- a/qa/rpc-tests/util.py
+++ b/qa/rpc-tests/util.py
@@ -158,7 +158,7 @@ def _rpchost_to_args(rpchost):
         rv += ['-rpcport=' + rpcport]
     return rv
 
-def start_node(i, dirname, extra_args=None, rpchost=None):
+def start_node(i, dirname, extra_args=None, rpchost=None, timewait=None):
     """
     Start a bitcoind and return RPC connection to it
     """
@@ -172,7 +172,10 @@ def start_node(i, dirname, extra_args=None, rpchost=None):
                           ["-rpcwait", "getblockcount"], stdout=devnull)
     devnull.close()
     url = "http://rt:rt@%s:%d" % (rpchost or '127.0.0.1', rpc_port(i))
-    proxy = AuthServiceProxy(url)
+    if timewait is not None:
+        proxy = AuthServiceProxy(url, timeout=timewait)
+    else:
+        proxy = AuthServiceProxy(url)
     proxy.url = url # store URL on proxy for info
     return proxy