update README to match new configuration through environment variables

Author: philenius

README.md

@@ -4,50 +4,111 @@ This application extracts transactions from the Ethereum blockchain and exports
 
 ## Run
 * You'll need an Ethereum node in order to execute API requests. If you don't have your own net yet, then you can start a local Ethereum node as a Docker container with this command:
-  ```bash
-  docker run -d --name ethereum-node -v /home/user/ethereum:/root -p 8545:8545 -p 30303:30303 \
-         ethereum/client-go --rpc --rpcapi "eth,net,web3" --rpcaddr 0.0.0.0 --syncmode "fast"
-  ```
+   ```bash
+   docker run \
+       --name ethereum-node \
+       -v /home/user/ethereum:/root \
+       -p 8545:8545 \
+       -p 30303:30303 \
+       ethereum/client-go \
+       --rpc \
+       --rpcapi "eth,net,web3" \
+       --rpcaddr 0.0.0.0 \
+       --syncmode "fast"
+   ```
 
-* You'll also need a local installation of Golang to run this application:
-  ```bash
-  go get ./...
-  go build
-  LOGXI=* ./ethereum-blockchain-transaction-csv-export -start 46147 -count 10
-  ```
-  This demo should fetch the blocks 46147 through 46157 including the first ever made transaction on the Ethereum blockchain.  
+* This application is dockerized. Use these commands to build and run the application:
+   ```bash
+   docker build -t ethereum-blockchain-transaction-csv-export .
 
-:warning: It might take some time, until your Ethereum node synchronized enough blocks to respond to API requests for those blocks. You can also set the flag `--start` to `0`. But, keep in mind that about the first 46.000 blocks of the Ethereum blockchain contain any transactions.
+   # create directory for log and CSV files
+   mkdir ./output/
+
+   docker run \
+      --network host \
+      -v $(pwd)/output:/output \
+      -e LOGXI="*" \
+      -e START_BLOCK_HEIGHT="46147" \
+      -e BLOCK_COUNT="10" \
+      ethereum-blockchain-transaction-csv-export
+   ```
+
+   This demo should fetch the blocks 46147 through 46157. These blocks contain only one transaction, the first transaction that was ever made on the Ethereum blockchain.
+
+* The resulting CSV export is stored in the file `./output/geth_tx_export_<yyyy-MM-dd-HH-mm-ss>.csv`. The CSV file contains the following columns:
+  
+  | Column            | Description                                                  |
+  | ----------------- | ------------------------------------------------------------ |
+  | tx_hash           | 32 Bytes hash of the transaction.     |
+  | tx_nonce          | The number of transactions made by the sender prior to this one. |
+  | tx_block_hash     | 32 Bytes hash of the block where this transaction was in. |
+  | tx_block_number   | Block number where this transaction was in. `null` when its pending. |
+  | tx_index          | Integer of the transaction's index position in the block. `null` when its pending. |
+  | tx_from           | 20 Bytes address of the sender |
+  | tx_to             | 20 Bytes address of the receiver. `null` when its a contract creation transaction. |
+  | tx_value          | Value transferred in Wei. |
+  | tx_gas            | Gas provided by the sender. |
+  | tx_gas_price      | Gas price provided by the sender in Wei. |
+  | tx_input          | The data send along with the transaction. |
+  | tx_timestamp      | Integer of the unix timestamp when the transaction was sent. |
+
+
+:warning: It might take some time, until your Ethereum node synchronized enough blocks to respond to API requests for those blocks. You can also set the environment variable `START_BLOCK_HEIGHT` to `0`. But, keep in mind that about the first 46.000 blocks of the Ethereum blockchain don't contain any transactions.
 
 **Another example:**  
 
-This command exports all transactions contained in the first 4 million blocks (estimated time to completion: 11 hours):
+This command exports all transactions contained in the first 4 million blocks (this process might take several hours):
 
 ```bash
-LOGXI=WRN nohup ./ethereum-blockchain-transaction-csv-export \
-    -count 4000000 \
-    -blockConcurr 20 \
-    -txConcurr 30 \
-    &
+docker run \
+  --network host \
+  -v $(pwd)/output:/output \
+  -e LOGXI="*=INF" \
+  -e START_BLOCK_HEIGHT="0" \
+  -e BLOCK_COUNT="4000000" \
+  -e WORKER_COUNT_FOR_BLOCKS="20" \
+  -e WORKER_COUNT_FOR_TRANSACTIONS="30" \
+  ethereum-blockchain-transaction-csv-export
 ```
 
 ## Configuration
-This application can be configured using command line flags. Type `--help` to find out more about the available configurations:
-```bash
-./ethereum-blockchain-transaction-csv-export --help
-Usage of ./ethereum-blockchain-transaction-csv-export:
-  -blockConcurr int
-        The count of concurrent workers for fetching block. (default 10)
-  -count int
-        The total amount of blocks to fetch. (default 1000)
-  -host string
-        The hostname / IP address of the Ethereum node. (default "127.0.0.1")
-  -port int
-        The port number of the Ethereum node. (default 8545)
-  -start int
-        The height / number of the block where to start.
-  -statsIntervalSec int
-        The invertal in seconds to display stats. (default 5)
-  -txConcurr int
-        The count of concurrent workers for fetching transactions. (default 20)
+
+This application is configured via the environment. The following environment variables can be used:
+
+```
+BLOCK_COUNT
+  [description] The total amount of blocks to fetch.
+  [type]        Integer
+  [default]     1000
+  [required]    
+HOSTNAME
+  [description] The hostname / IP address of the Ethereum node.
+  [type]        String
+  [default]     127.0.0.1
+  [required]    
+PORT
+  [description] The port number of the Ethereum node.
+  [type]        Integer
+  [default]     8545
+  [required]    
+START_BLOCK_HEIGHT
+  [description] The height / number of the first block to fetch.
+  [type]        Integer
+  [default]     0
+  [required]    
+STATS_INTERVAL_IN_SECONDS
+  [description] The invertal in seconds to display stats.
+  [type]        Integer
+  [default]     5
+  [required]    
+WORKER_COUNT_FOR_BLOCKS
+  [description] The count of concurrent workers for fetching blocks.
+  [type]        Integer
+  [default]     10
+  [required]    
+WORKER_COUNT_FOR_TRANSACTIONS
+  [description] The count of concurrent workers for fetching transactions.
+  [type]        Integer
+  [default]     20
+  [required]
 ```