Added Bitcoin Core architecture diagram

ch03.asciidoc

@@ -11,9 +11,16 @@ When bitcoin was created by Satoshi Nakamoto, the software was actually complete
 Even though Bitcoin Core includes a reference implementation of a wallet, this is not intended to be used as a production wallet for users or for applications. Application developers are advised to build wallets using modern standards such as BIP39 and BIP32 (see <<mnemonic_code_words>> and <<hd_wallets>>). BIP stands for _Bitcoin Improvement Proposals_.
 ====
 
+<<bitcoin_core_architecture>> shows the architecture of Bitcoin Core:
+
+[[bitcoin_core_architecture]]
+.Bitcoin Core Architecture (Source: Eric Lombrozo)
+image::images/mbc2_0301["Bitcoin Core Architecture"]
+
+
 === Bitcoin Development Environment
 
-If you're a developer, you will want to set up a development environment with all the tools, libraries, and support software for writing bitcoin applications. In this highly technical chapter, we'll walk through that process step-by-step. If the material becomes too dense (and you're not actually setting up a development environment) feel free to skip to the next chapter, which is less technical. 
+If you're a developer, you will want to set up a development environment with all the tools, libraries, and support software for writing bitcoin applications. In this highly technical chapter, we'll walk through that process step-by-step. If the material becomes too dense (and you're not actually setting up a development environment) feel free to skip to the next chapter, which is less technical.
 
 [[compiling_core]]
 === Compiling Bitcoin Core from the Source Code
@@ -255,7 +262,7 @@ It is also recommended to set alertnotify so you are notified of problems;
 for example: alertnotify=echo %s | mail -s "Bitcoin Alert" admin@foo.com
 ----
 
-As you can see, the first time you run +bitcoind+ it tells you that you need to build a configuration file, with at least an +rpcuser+ and +rpcpassword+ entry. Additionally, it is recommended you set up the alerting mechanism. In the next section we will examine the various configuration options and set up a configuration file. 
+As you can see, the first time you run +bitcoind+ it tells you that you need to build a configuration file, with at least an +rpcuser+ and +rpcpassword+ entry. Additionally, it is recommended you set up the alerting mechanism. In the next section we will examine the various configuration options and set up a configuration file.
 
 ==== Configuring the Bitcoin Core Node
 
@@ -295,7 +302,7 @@ Options:
        Acceptable ciphers (default:
        TLSv1.2+HIGH:TLSv1+HIGH:!SSLv2:!aNULL:!eNULL:!3DES:@STRENGTH)
 ----
- 
+
 Here are some of the most important options that you can set in the configuration file, or as command-line parameters to +bitcoind+:
 
 alertnotify:: Run a specified command or script to send emergency alerts to the owner of this node, usually by sending email.
@@ -304,7 +311,7 @@ conf:: An alternative location for the configuration file. This only makes sense
 
 datadir:: Select the directory and filesystem in which to put all the blockchain data. By default this is the _.bitcoin_ subdirectory of your home directory. Make sure this filesystem has several gigabytes of free space.
 
-prune:: Reduce the disk space requirements to this many megabytes, by deleting old blocks. Use this on a resource-constrained node that can't fit the full blockchain. 
+prune:: Reduce the disk space requirements to this many megabytes, by deleting old blocks. Use this on a resource-constrained node that can't fit the full blockchain.
 
 txindex:: Maintain an index of all transactions. This means a complete copy of the blockchain and allows you to programmatically retrieve any transaction by ID.
 
@@ -385,9 +392,9 @@ Opened LevelDB successfully
 [... more startup messages ...]
 ----
 
-You can hit Ctrl+C to interrupt the process once you are satisfied that it is loading the correct settings and running as you expect it. 
+You can hit Ctrl+C to interrupt the process once you are satisfied that it is loading the correct settings and running as you expect it.
 
-To run Bitcoin Core in the background as a process, start it with the +daemon+ option, as +bitcoind -daemon+. 
+To run Bitcoin Core in the background as a process, start it with the +daemon+ option, as +bitcoind -daemon+.
 
 To monitor the progress and runtime status of your bitcoin node, use the command +bitcoin-cli getinfo+:
 ----
@@ -491,7 +498,7 @@ $ bitcoin-cli getinfo
 
 ----
 
-The data is returned in((("JavaScript Object Notation (JSON)"))) JavaScript Object Notation (JSON), a format that can easily be "consumed" by all programming languages but is also quite human-readable. Among this data we see the version numbers for the bitcoin software client (110200) and bitcoin protocol (70002).  We see the current block height, showing us how many blocks are known to this client (396367). We also see various statistics about the bitcoin network and the settings related to this client. 
+The data is returned in((("JavaScript Object Notation (JSON)"))) JavaScript Object Notation (JSON), a format that can easily be "consumed" by all programming languages but is also quite human-readable. Among this data we see the version numbers for the bitcoin software client (110200) and bitcoin protocol (70002).  We see the current block height, showing us how many blocks are known to this client (396367). We also see various statistics about the bitcoin network and the settings related to this client.
 
 [TIP]
 ====
@@ -575,7 +582,7 @@ d50f654e788acd0ef8000000000001976a9147f9b1a7fb68d60c536c2fd8aeaa53a8f3cc025a8&#x
           "1GdK9UzpHBzqzX2A9JFP3Di4weBwqgmoQA"
         ]
       }
-    }, 
+    },
     {
       "value": 0.08450000,
       "n": 1,
@@ -607,7 +614,7 @@ Commands: +getblock+, +getblockhash+
 
 ((("bitcoin-cli command line helper","getblock command")))((("bitcoin-cli command line helper","getblockhash command")))((("blocks","exploring")))((("getblock command (bitcoin-cli)")))((("getblockhash command (bitcoin-cli)")))
 
-Exploring blocks is similar to exploring transactions. However, blocks can be referenced either by the block _height_ or by the block _hash_. First, let's find a block by its height. In <<cup_of_coffee>>, we saw that Alice's transaction was included in block 277316. 
+Exploring blocks is similar to exploring transactions. However, blocks can be referenced either by the block _height_ or by the block _hash_. First, let's find a block by its height. In <<cup_of_coffee>>, we saw that Alice's transaction was included in block 277316.
 
 We use the +getblockhash+ command, which takes the block height as the parameter and returns the block hash for that block:
 
@@ -633,20 +640,20 @@ $ bitcoin-cli getblock 0000000000000001b6b9a13b095e96db41c4a928b97ef2d944a9b3&#x
   "version": 2,
   "merkleroot": "c91c008c26e50763e9f548bb8b2fc323735f73577effbc55502c51eb4cc7cf2e",
   "tx": [
-    "d5ada064c6417ca25c4308bd158c34b77e1c0eca2a73cda16c737e7424afba2f", 
+    "d5ada064c6417ca25c4308bd158c34b77e1c0eca2a73cda16c737e7424afba2f",
-    "b268b45c59b39d759614757718b9918caf0ba9d97c56f3b91956ff877c503fbe", 
+    "b268b45c59b39d759614757718b9918caf0ba9d97c56f3b91956ff877c503fbe",
-    "04905ff987ddd4cfe603b03cfb7ca50ee81d89d1f8f5f265c38f763eea4a21fd", 
+    "04905ff987ddd4cfe603b03cfb7ca50ee81d89d1f8f5f265c38f763eea4a21fd",
-    "32467aab5d04f51940075055c2f20bbd1195727c961431bf0aff8443f9710f81", 
+    "32467aab5d04f51940075055c2f20bbd1195727c961431bf0aff8443f9710f81",
-    "561c5216944e21fa29dd12aaa1a45e3397f9c0d888359cb05e1f79fe73da37bd", 
+    "561c5216944e21fa29dd12aaa1a45e3397f9c0d888359cb05e1f79fe73da37bd",
-[... hundreds of transactions ...] 
+[... hundreds of transactions ...]
-    "78b300b2a1d2d9449b58db7bc71c3884d6e0579617e0da4991b9734cef7ab23a", 
+    "78b300b2a1d2d9449b58db7bc71c3884d6e0579617e0da4991b9734cef7ab23a",
-    "6c87130ec283ab4c2c493b190c20de4b28ff3caf72d16ffa1ce3e96f2069aca9", 
+    "6c87130ec283ab4c2c493b190c20de4b28ff3caf72d16ffa1ce3e96f2069aca9",
-    "6f423dbc3636ef193fd8898dfdf7621dcade1bbe509e963ffbff91f696d81a62", 
+    "6f423dbc3636ef193fd8898dfdf7621dcade1bbe509e963ffbff91f696d81a62",
-    "802ba8b2adabc5796a9471f25b02ae6aeee2439c679a5c33c4bbcee97e081196", 
+    "802ba8b2adabc5796a9471f25b02ae6aeee2439c679a5c33c4bbcee97e081196",
-    "eaaf6a048588d9ad4d1c092539bd571dd8af30635c152a3b0e8b611e67d1a1af", 
+    "eaaf6a048588d9ad4d1c092539bd571dd8af30635c152a3b0e8b611e67d1a1af",
-    "e67abc6bd5e2cac169821afc51b207127f42b92a841e976f9b752157879ba8bd", 
+    "e67abc6bd5e2cac169821afc51b207127f42b92a841e976f9b752157879ba8bd",
-    "d38985a6a1bfd35037cb7776b2dc86797abbb7a06630f5d03df2785d50d5a2ac", 
+    "d38985a6a1bfd35037cb7776b2dc86797abbb7a06630f5d03df2785d50d5a2ac",
-    "45ea0a3f6016d2bb90ab92c34a7aac9767671a8a84b9bcce6c019e60197c134b", 
+    "45ea0a3f6016d2bb90ab92c34a7aac9767671a8a84b9bcce6c019e60197c134b",
     "c098445d748ced5f178ef2ff96f2758cbec9eb32cb0fc65db313bcac1d3bc98f"
   ],
   "time": 1388185914,
@@ -668,7 +675,7 @@ The block contains 419 transactions and the 64th transaction listed (+0627052b..
 
 The +bitcoin-cli+ helper is very useful for exploring the Bitcoin Core API and testing functions. But the whole point of an application programming interface is to access functions programmatically. In this section we will demonstrate accessing Bitcoin Core from another program.
 
-Bitcoin Core's API is a JSON-RPC interface. JSON stands for JavaScript Object Notation and it is a very convenient way to present data that both humans and programs can easily read. RPC stands for Remote Procedure Call, which means that we are calling procedures (functions) that are remote (on the Bitcoin Core node) via a network protocol. In this case, the network protocol is HTTP, or HTTPS (for encrypted connections). 
+Bitcoin Core's API is a JSON-RPC interface. JSON stands for JavaScript Object Notation and it is a very convenient way to present data that both humans and programs can easily read. RPC stands for Remote Procedure Call, which means that we are calling procedures (functions) that are remote (on the Bitcoin Core node) via a network protocol. In this case, the network protocol is HTTP, or HTTPS (for encrypted connections).
 
 When we used the +bitcoin-cli+ command to get help on a command, it showed us an example of using +curl+, the versatile command-line HTTP client to construct one of these JSON-RPC calls:
 
@@ -676,9 +683,9 @@ When we used the +bitcoin-cli+ command to get help on a command, it showed us an
 $ curl --user myusername --data-binary '{"jsonrpc": "1.0", "id":"curltest", "method": "getinfo", "params": [] }' -H 'content-type: text/plain;' http://127.0.0.1:8332/
 ----
 
-This command shows that +curl+ submits an HTTP request to the local host (127.0.0.1), connecting to the default bitcoin port (8332), and submitting a  +jsonrpc+ request for the +getinfo+ method, using a +text/plain+ encoding. 
+This command shows that +curl+ submits an HTTP request to the local host (127.0.0.1), connecting to the default bitcoin port (8332), and submitting a  +jsonrpc+ request for the +getinfo+ method, using a +text/plain+ encoding.
 
-If you're implementing a JSON-RPC call in your own program, you can use a generic HTTP library to construct the call, similar to what is shown in the preceding +curl+ example. 
+If you're implementing a JSON-RPC call in your own program, you can use a generic HTTP library to construct the call, similar to what is shown in the preceding +curl+ example.
 
 However, there are libraries in most every programming language that "wrap" the Bitcoin Core API in a way that makes this a lot simpler. We will use the +python-bitcoinlib+ library to simplify API access. Remember, this requires you to have a running Bitcoin Core instance, which will be used to make JSON-RPC calls.
 
@@ -696,13 +703,13 @@ include::code/rpc_example.py[]
 Running it gives us the following result:
 
 ----
-$ python rpc_example.py 
+$ python rpc_example.py
 394075
 ----
 
-It tells us that our local Bitcoin Core node has 394075 blocks in its blockchain. Not a spectacular result, but it demonstrates the basic use of the library as a simplified interface to Bitcoin Core's JSON-RPC API. 
+It tells us that our local Bitcoin Core node has 394075 blocks in its blockchain. Not a spectacular result, but it demonstrates the basic use of the library as a simplified interface to Bitcoin Core's JSON-RPC API.
 
-Next, let's use the +getrawtransaction+ and +decodetransaction+ calls to retrieve the details of Alice's coffee payment. In <<rpc_transaction>>, we retrieve Alice's transaction and list the transaction's outputs. For each output, we show the recipient address and value. As a reminder, Alice's transaction had one output paying Bob's Cafe and one output for change back to Alice. 
+Next, let's use the +getrawtransaction+ and +decodetransaction+ calls to retrieve the details of Alice's coffee payment. In <<rpc_transaction>>, we retrieve Alice's transaction and list the transaction's outputs. For each output, we show the recipient address and value. As a reminder, Alice's transaction had one output paying Bob's Cafe and one output for change back to Alice.
 
 [[rpc_transaction]]
 .Retrieving a transaction and iterating its outputs
@@ -716,14 +723,14 @@ include::code/rpc_transaction.py[]
 Running this code, we get:
 
 ----
-$ python rpc_transaction.py 
+$ python rpc_transaction.py
 ([u'1GdK9UzpHBzqzX2A9JFP3Di4weBwqgmoQA'], Decimal('0.01500000'))
 ([u'1Cdid9KFAaatwczBwBttQcwXYCpvK8h7FK'], Decimal('0.08450000'))
 ----
 
 Both of the preceding examples are rather simple. You don't really need a program to run them; you could just as easily use the +bitcoin-cli+ helper. The next example, however, requires several hundred RPC calls and more clearly demonstrates the use of a programmatic interface.
 
-In <<rpc_block>>, we first retrieve block 277316, then retrieve each of the 419 transactions within by reference to each transaction ID. Next, iterate through each of the transaction's outputs and add up the value. 
+In <<rpc_block>>, we first retrieve block 277316, then retrieve each of the 419 transactions within by reference to each transaction ID. Next, iterate through each of the transaction's outputs and add up the value.
 
 [[rpc_block]]
 .Retrieving a block and adding all the transaction outputs
@@ -737,7 +744,7 @@ include::code/rpc_block.py[]
 Running this code, we get:
 
 ----
-$ python rpc_block.py 
+$ python rpc_block.py
 
 ('Total value in block: ', Decimal('10322.07722534'))
 ----