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Written by Neill Miller (neillm@altcoinlabs.com, neillm@thecodefactory.org)
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This is a PHP script to crawl an entire blockchain and store all
information in an easy to use/retrieve format in a MongoDB database
for inspection or analysis.  It can also be used to create and keep up
to date the backend datastore for a blockchain visualizer/explorer.

Since it can take time to crawl the entire blockchain and blockchains
are frequently updated, this script keeps track of where it left off
and starts scanning on later runs from that point on.  This makes it
suitable for repeated runs via cron and ensuring that the MongoDB is
always up to date.

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How to use:
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1) Copy localsite.inc.sample to localsite.inc
2) Update localsite.inc to point to the RPC port of your coin
   (i.e. bitcoin, litecoin, dogecoin, etc)
3) Run the script: php blockchain2mongodb.php
4) Profit!

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Troubleshooting:
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Problem #1: Program simply says "Starting run at block index -1" and exits
--
Solution: Create the mongo database using the command line as follows:

NOTE: DATABASE must match the coin name (e.g. "bitcoin")

use DATABASE
db.dropDatabase()
db.createCollection('blocks')
db.createCollection('transactions')
db.blocks.insert({"global":"last_block","last_block":0})
db.blocks.insert({"global":"last_connected_block","last_connected_block":0})

NOTE: be sure to add indices based on how you use it.  For example:

db.blocks.ensureIndex({'data.height': -1})
db.transactions.ensureIndex({'data.hash': -1})

Problem #2: Program cannot connect to the coin daemon
--
Starting run at block index 0 ...
PHP Warning:  fopen(http://...@localhost:9333/): failed to open
stream: HTTP request failed!  in jsonRPCClient.php on line 132
Failed to retrieve block info at index 0: exception 'Exception' with
message 'Unable to connect to http://rpcuser:rpcpass@localhost:9333/'
... snip ...

Solution:

- Be sure that your coin daemon is running.
- Be sure that your coin daemon will accept RPC commands.
- Ensure that your rpcuser and rpcpassword fields are set.
- Ensure that txindex is included in your config (if you just added
  it, restart the coin daemon with the -reindex command).  This is
  required because we need a full picture of the blockchain while
  crawling.

An example configuration is below:

txindex=1
server=1
rpcallowip=127.0.0.1
rpcuser=rpcuser
rpcpassword=rpcpass