## Introduction This document walks through the steps to setup a side chain running on your local machine and make your first cross chain transfers. ## Get Ready This section describes how to install the python dependencies, create the environment variables, and create the configuration files that scripts need to run correctly. ### Build rippled Checkout the `sidechain` branch from the rippled repository, and follow the usual process to build rippled. ### Create a Python virtual environment and install dependencies 1. Check the current python version. The python scripts require python 3.8 or greater: ``` python3 --version ``` 2. Choose a directory to put the virtual environment. For example, `~/envs`. 3. Create this directory and cd to it: ``` $ mkdir ~/env $ cd ~/env ``` 4. Create a new python virtual environment and activate it. Here the new envrionment is called `sidechain`. Of course, you can choose whatever name you'd like: ``` $ python3 -m venv sidechain $ source ./sidechain/bin/activate ``` 5. Install the required python modules. Change directories to where the side chain branch is located and use pip3 to install the modules: Assuming the code is located in `~/projs/sidechain`, the following commands will do it: ``` cd ~/projs/sidechain $ pip3 install -r bin/sidechain/python/requirements.txt ``` ### Activate the python virtual environment ``` $ cd ~/env $ source ./sidechain/bin/activate ``` There's no harm if it was already active. ### Environment variables The python scripts need to know the locations of two files and one directory. These can be specified either through command line arguments or by setting environment variables. 1. The location of the rippled executable used for main chain servers. Either set the environment variable `RIPPLED_MAINCHAIN_EXE` or use the command line switch `--exe_mainchain`. Until a new RPC is integrated into the main branch (this will happen very soon), use the code built from the sidechain branch as the main chain exe. 2. The location of the rippled executable used for side chain servers. Either set the environment variable `RIPPLED_SIDECHAIN_EXE` or use the command line switch `--exe_sidechain`. This should be the rippled executable built from the sidechain branch. 3. The location of the directory that has the rippled configuration files. Either set the environment variable `RIPPLED_SIDECHAIN_CFG_DIR` or use the command line switch `--cfgs_dir`. The configuration files do not exist yet. There is a script to create these for you. For now, just choose a location where the files should live and make sure that directory exists. Setting environment variables can be very convient. For example, a small script can be sourced to set these environment variables when working with side chains. ### Creating configuration files Assuming rippled is built, the three environment variables are set, and the python environment is activated, run the following script: ``` bin/sidechain/python/create_config_files.py --usd ``` There should now be many configuration files in the directory specified by the `RIPPLED_SIDECHAIN_CFG_DIR` environment variable. The `--usd` creates a sample cross chain assert for USD -> USD transfers. ## Running the interactive shell There is an interactive shell called `RiplRepl` that can be used to explore side chains. It will use the configuration files built above to spin up test rippled main chain running in standalone mode as well as 5 side chain federators running in regular consensus mode. To start the shell, run the following script: ``` bin/sidechain/python/riplrepl.py ``` The shell will not start until the servers have synced. It may take a minute or two until they do sync. The script should give feedback while it is syncing. Once the shell has started, the following message should appear: ``` Welcome to the sidechain test shell. Type help or ? to list commands. RiplRepl> ``` Type the command `server_info` to make sure the servers are running. An example output would be: ``` RiplRepl> server_info pid config running server_state ledger_seq complete_ledgers main 0 136206 main.no_shards.mainchain_0/rippled.cfg True proposing 75 2-75 side 0 136230 sidechain_0/rippled.cfg True proposing 92 1-92 1 136231 sidechain_1/rippled.cfg True proposing 92 1-92 2 136232 sidechain_2/rippled.cfg True proposing 92 1-92 3 136233 sidechain_3/rippled.cfg True proposing 92 1-92 4 136234 sidechain_4/rippled.cfg True proposing 92 1-92 ``` Of course, you'll see slightly different output on your machine. The important thing to notice is there are two categories, one called `main` for the main chain and one called `side` for the side chain. There should be a single server for the main chain and five servers for the side chain. Next, type the `balance` command, to see the balances of the accounts in the address book: ``` RiplRepl> balance balance currency peer limit account main root 99,999,989,999.999985 XRP door 9,999.999940 XRP side door 99,999,999,999.999954 XRP ``` There are two accounts on the main chain: `root` and `door`; and one account on the side chain: `door`. These are not user accounts. Let's add two user accounts, one on the main chain called `alice` and one on the side chain called `bob`. The `new_account` command does this for us. ``` RiplRepl> new_account mainchain alice RiplRepl> new_account sidechain bob ``` This just added the accounts to the address book, but they don't exist on the ledger yet. To do that, we need to fund the accounts with a payment. For now, let's just fund the `alice` account and check the balances. The `pay` command makes a payment on one of the chains: ``` RiplRepl> pay mainchain root alice 5000 RiplRepl> balance balance currency peer limit account main root 99,999,984,999.999969 XRP door 9,999.999940 XRP alice 5,000.000000 XRP side door 99,999,999,999.999954 XRP bob 0.000000 XRP ``` Finally, let's do something specific to side chains: make a cross chain payment. The `xchain` command makes a payment between chains: ``` RiplRepl> xchain mainchain alice bob 4000 RiplRepl> balance balance currency peer limit account main root 99,999,984,999.999969 XRP door 13,999.999940 XRP alice 999.999990 XRP side door 99,999,995,999.999863 XRP bob 4,000.000000 XRP ``` Note: the account reserve on the side chain is 100 XRP. The cross chain amount must be greater than 100 XRP or the payment will fail. Making a cross chain transaction from the side chain to the main chain is similar: ``` RiplRepl> xchain sidechain bob alice 2000 RiplRepl> balance balance currency peer limit account main root 99,999,984,999.999969 XRP door 11,999.999840 XRP alice 2,999.999990 XRP side door 99,999,997,999.999863 XRP bob 1,999.999990 XRP ``` If you typed `balance` very quickly, you may catch a cross chain payment in progress and the XRP may be deducted from bob's account before it is added to alice's. If this happens just wait a couple seconds and retry the command. Also note that accounts pay a ten drop fee when submitting transactions. Finally, exit the program with the `quit` command: ``` RiplRepl> quit Thank you for using RiplRepl. Goodbye. WARNING: Server 0 is being stopped. RPC commands cannot be sent until this is restarted. ``` Ignore the warning about the server being stopped. ## Conclusion Those two cross chain payments are a "hello world" for side chains. It makes sure you're environment is set up correctly.