Blockchain, Rebuilt for Scale

Solana™ is a new blockchain architecture built from the ground up for scale. The architecture supports up to 710 thousand transactions per second on a gigabit network.

Disclaimer

All claims, content, designs, algorithms, estimates, roadmaps, specifications, and performance measurements described in this project are done with the author's best effort. It is up to the reader to check and validate their accuracy and truthfulness. Furthermore nothing in this project constitutes a solicitation for investment.

Introduction

It's possible for a centralized database to process 710,000 transactions per second on a standard gigabit network if the transactions are, on average, no more than 176 bytes. A centralized database can also replicate itself and maintain high availability without significantly compromising that transaction rate using the distributed system technique known as Optimistic Concurrency Control [H.T.Kung, J.T.Robinson (1981)]. At Solana, we're demonstrating that these same theoretical limits apply just as well to blockchain on an adversarial network. The key ingredient? Finding a way to share time when nodes can't trust one-another. Once nodes can trust time, suddenly ~40 years of distributed systems research becomes applicable to blockchain!

Perhaps the most striking difference between algorithms obtained by our method and ones based upon timeout is that using timeout produces a traditional distributed algorithm in which the processes operate asynchronously, while our method produces a globally synchronous one in which every process does the same thing at (approximately) the same time. Our method seems to contradict the whole purpose of distributed processing, which is to permit different processes to operate independently and perform different functions. However, if a distributed system is really a single system, then the processes must be synchronized in some way. Conceptually, the easiest way to synchronize processes is to get them all to do the same thing at the same time. Therefore, our method is used to implement a kernel that performs the necessary synchronization--for example, making sure that two different processes do not try to modify a file at the same time. Processes might spend only a small fraction of their time executing the synchronizing kernel; the rest of the time, they can operate independently--e.g., accessing different files. This is an approach we have advocated even when fault-tolerance is not required. The method's basic simplicity makes it easier to understand the precise properties of a system, which is crucial if one is to know just how fault-tolerant the system is. [L.Lamport (1984)]

Furthermore, and much to our surprise, it can be implemented using a mechanism that has existed in Bitcoin since day one. The Bitcoin feature is called nLocktime and it can be used to postdate transactions using block height instead of a timestamp. As a Bitcoin client, you'd use block height instead of a timestamp if you don't trust the network. Block height turns out to be an instance of what's being called a Verifiable Delay Function in cryptography circles. It's a cryptographically secure way to say time has passed. In Solana, we use a far more granular verifiable delay function, a SHA 256 hash chain, to checkpoint the ledger and coordinate consensus. With it, we implement Optimistic Concurrency Control and are now well en route towards that theoretical limit of 710,000 transactions per second.

Testnet Demos

The Solana repo contains all the scripts you might need to spin up your own local testnet. Depending on what you're looking to achieve, you may want to run a different variation, as the full-fledged, performance-enhanced multinode testnet is considerably more complex to set up than a Rust-only, singlenode testnode. If you are looking to develop high-level features, such as experimenting with smart contracts, save yourself some setup headaches and stick to the Rust-only singlenode demo. If you're doing performance optimization of the transaction pipeline, consider the enhanced singlenode demo. If you're doing consensus work, you'll need at least a Rust-only multinode demo. If you want to reproduce our TPS metrics, run the enhanced multinode demo.

For all four variations, you'd need the latest Rust toolchain and the Solana source code:

First, install Rust's package manager Cargo.

$ curl https://sh.rustup.rs -sSf | sh
$ source $HOME/.cargo/env

Now checkout the code from github:

$ git clone https://github.com/solana-labs/solana.git
$ cd solana

The demo code is sometimes broken between releases as we add new low-level features, so if this is your first time running the demo, you'll improve your odds of success if you check out the latest release before proceeding:

$ git checkout v0.8.0

Configuration Setup

The network is initialized with a genesis ledger and leader/validator configuration files. These files can be generated by running the following script.

$ ./multinode-demo/setup.sh

Drone

In order for the leader, client and validators to work, we'll need to spin up a drone to give out some test tokens. The drone delivers Milton Friedman-style "air drops" (free tokens to requesting clients) to be used in test transactions.

Start the drone on the leader node with:

$ ./multinode-demo/drone.sh

Singlenode Testnet

Before you start a fullnode, make sure you know the IP address of the machine you want to be the leader for the demo, and make sure that udp ports 8000-10000 are open on all the machines you want to test with.

Now start the server in a separate shell:

$ ./multinode-demo/leader.sh

Wait a few seconds for the server to initialize. It will print "leader ready..." when it's ready to receive transactions. The leader will request some tokens from the drone if it doesn't have any. The drone does not need to be running for subsequent leader starts.

Multinode Testnet

To run a multinode testnet, after starting a leader node, spin up some validator nodes in separate shells:

$ ./multinode-demo/validator.sh

To run a performance-enhanced leader or validator (on Linux), CUDA 9.2 must be installed on your system:

$ ./fetch-perf-libs.sh
$ SOLANA_CUDA=1 ./multinode-demo/leader.sh
$ SOLANA_CUDA=1 ./multinode-demo/validator.sh

Testnet Client Demo

Now that your singlenode or multinode testnet is up and running let's send it some transactions!

In a separate shell start the client:

$ ./multinode-demo/client.sh # runs against localhost by default

What just happened? The client demo spins up several threads to send 500,000 transactions to the testnet as quickly as it can. The client then pings the testnet periodically to see how many transactions it processed in that time. Take note that the demo intentionally floods the network with UDP packets, such that the network will almost certainly drop a bunch of them. This ensures the testnet has an opportunity to reach 710k TPS. The client demo completes after it has convinced itself the testnet won't process any additional transactions. You should see several TPS measurements printed to the screen. In the multinode variation, you'll see TPS measurements for each validator node as well.

Public Testnet

In this example the client connects to our public testnet. To run validators on the testnet you would need to open udp ports 8000-10000.

$ ./multinode-demo/client.sh --network $(dig +short testnet.solana.com):8001 --identity config-private/client-id.json --duration 60

You can observe the effects of your client's transactions on our dashboard

Linux Snap

A Linux Snap is available, which can be used to easily get Solana running on supported Linux systems without building anything from source. The edge Snap channel is updated daily with the latest development from the master branch. To install:

$ sudo snap install solana --edge --devmode

(--devmode flag is required only for solana.fullnode-cuda)

Once installed the usual Solana programs will be available as solona.* instead of solana-*. For example, solana.fullnode instead of solana-fullnode.

Update to the latest version at any time with:

$ snap info solana
$ sudo snap refresh solana --devmode

Daemon support

The snap supports running a leader, validator or leader+drone node as a system daemon.

Run sudo snap get solana to view the current daemon configuration. To view daemon logs:

1. Run sudo snap logs -n=all solana to view the daemon initialization log
2. Runtime logging can be found under /var/snap/solana/current/leader/, /var/snap/solana/current/validator/, or /var/snap/solana/current/drone/ depending on which mode= was selected. Within each log directory the file current contains the latest log, and the files *.s (if present) contain older rotated logs.

Disable the daemon at any time by running:

$ sudo snap set solana mode=

Runtime configuration files for the daemon can be found in /var/snap/solana/current/config.

Leader daemon

$ sudo snap set solana mode=leader

If CUDA is available:

$ sudo snap set solana mode=leader enable-cuda=1

rsync must be configured and running on the leader.

1. Ensure rsync is installed with sudo apt-get -y install rsync
2. Edit /etc/rsyncd.conf to include the following

[config]
path = /var/snap/solana/current/config
hosts allow = *
read only = true

3. Run sudo systemctl enable rsync; sudo systemctl start rsync
4. Test by running rsync -Pzravv rsync://<ip-address-of-leader>/config solana-config from another machine. If the leader is running on a cloud provider it may be necessary to configure the Firewall rules to permit ingress to port tcp:873, tcp:9900 and the port range udp:8000-udp:10000

To run both the Leader and Drone:

$ sudo snap set solana mode=leader+drone

Validator daemon

$ sudo snap set solana mode=validator

If CUDA is available:

$ sudo snap set solana mode=validator enable-cuda=1

By default the validator will connect to testnet.solana.com, override the leader IP address by running:

$ sudo snap set solana mode=validator leader-address=127.0.0.1 #<-- change IP address

It's assumed that the leader will be running rsync configured as described in the previous Leader daemon section.

Developing

Building

Install rustc, cargo and rustfmt:

$ curl https://sh.rustup.rs -sSf | sh
$ source $HOME/.cargo/env
$ rustup component add rustfmt-preview

If your rustc version is lower than 1.26.1, please update it:

$ rustup update

On Linux systems you may need to install libssl-dev, pkg-config, zlib1g-dev, etc. On Ubuntu:

$ sudo apt-get install libssl-dev pkg-config zlib1g-dev

Download the source code:

$ git clone https://github.com/solana-labs/solana.git
$ cd solana

Testing

Run the test suite:

$ cargo test

To emulate all the tests that will run on a Pull Request, run:

$ ./ci/run-local.sh

Debugging

There are some useful debug messages in the code, you can enable them on a per-module and per-level basis. Before running a leader or validator set the normal RUST_LOG environment variable.

For example, to enable info everywhere and debug only in the solana::banking_stage module:

$ export RUST_LOG=info,solana::banking_stage=debug

Generally we are using debug for infrequent debug messages, trace for potentially frequent messages and info for performance-related logging.

You can also attach to a running process with GDB. The leader's process is named solana-fullnode:

$ sudo gdb
attach <PID>
set logging on
thread apply all bt

This will dump all the threads stack traces into gdb.txt

Benchmarking

First install the nightly build of rustc. cargo bench requires unstable features:

$ rustup install nightly

Run the benchmarks:

$ cargo +nightly bench --features="unstable"

Release Process

The release process for this project is described here.

Code coverage

To generate code coverage statistics, install cargo-cov. Note: the tool currently only works in Rust nightly.

$ cargo +nightly install cargo-cov

Run cargo-cov and generate a report:

$ cargo +nightly cov test
$ cargo +nightly cov report --open

The coverage report will be written to ./target/cov/report/index.html

Why coverage? While most see coverage as a code quality metric, we see it primarily as a developer productivity metric. When a developer makes a change to the codebase, presumably it's a solution to some problem. Our unit-test suite is how we encode the set of problems the codebase solves. Running the test suite should indicate that your change didn't infringe on anyone else's solutions. Adding a test protects your solution from future changes. Say you don't understand why a line of code exists, try deleting it and running the unit-tests. The nearest test failure should tell you what problem was solved by that code. If no test fails, go ahead and submit a Pull Request that asks, "what problem is solved by this code?" On the other hand, if a test does fail and you can think of a better way to solve the same problem, a Pull Request with your solution would most certainly be welcome! Likewise, if rewriting a test can better communicate what code it's protecting, please send us that patch!