What follows is a summary of the architecture and the components that are involved in running a Cartesi Compute Application, meaning some DApp that makes use of our SDK. It is convenient to start with the description of the typical ingredients involved in a decentralized application. Namely, the blockchain node and the client software.
Cartesi, is a layer-2 platform for the development and deployment of scalable decentralized applications. It offers a Linux operating system coupled with a blockchain infrastructure, which allows DApps to be developed in familiar programming languages like Python without the need to write Solidity code.
This section describes in detail the Drive _inputDrives parameter of the instantiate call.
At this point, an overview has been given of what constitutes a Cartesi computation, who are the parties involved, and what the software components of Cartesi Compute are. It is important to understand better what events happen during the execution of a Cartesi Machine.
How it works
Cartesi Compute SDK allows Cartesi DApps to specify and request verifiable computations to Cartesi Machines. Additionally, the SDK provides tools to facilitate and reduce the cost of inputting data into Cartesi Machines.
This section describes the main ingredient of the on-chain Cartesi Compute infrastructure.
This section describes the Cartesi Machine from the perspective of the blockchain.
The Cartesi Machine is Cartesi's solution for verifiable computation.
A relevant limitation of the Cartesi Machines as they have been described until now is the size of their input drives.
Although an extensive documentation of Cartesi Machines can be found here, one may choose to skip this reading and jump right away to their usage inside the blockchain through Cartesi Compute. For that, it is enough to regard a Cartesi Machine as a black box that executes computations.
Having discussed the concept of Cartesi Machines off-chain, capable of booting a Linux operating system and loading heavy-weight libraries, one naturally wonders how this will ever be stored or executed on the limited environment of a blockchain. The simple answer is that it won’t be.
Having informally discussed how Cartesi Compute represents Cartesi Machines on-chain, one can now describe in more details the API for requesting and retrieving computations in Cartesi Compute.
Cartesi Compute allows you to implement a function in which you receive a set of inputs and it provides an output. So you can think of a Compute DApp as a computational oracle that tells you the result of a computation.
Cartesi's reference off-chain implementation of Cartesi Machines is based on software emulation.
Platform Services is a new product developed and maintained by the Cartesi team that hosts Cartesi Node infrastructure for DApps. The service is elastic, making resources available to DApps upon demand. Developers deploy their Cartesi DApps on Platform Services and it automatically allocates resources according to user activity.
After going through the last section, the reader is already able to specify drives if the data was available to the caller at the time of instantiation.
Putting Things Together
To better understand how Cartesi Compute can be used, imagine the following simple Cartesi DApp with one claimer and one challenger. The DApp can be a skill-based game where players place their bets and challenge each other for the highest score over the blockchain. The winner takes the pot.
The scalability issue is one of the three parts of the Blockchain Trilemma, along with security and decentralization. Solving the scalability issue refers to any type of improvement within a blockchain system in terms of computational power, throughput, latency, bootstrap time, or cost per transaction. For example, high gas fees make it expensive for users to pay for their transactions within the Ethereum blockchain.
Broadly speaking, the Cartesi layer-2 platform architecture should be perceived as blockchain-agnostic, given that in principle any network could use Cartesi Machines to move complex computations off-chain without compromising on decentralization.
The off-chain API
After the call for instantiate, the blockchain may already have all information that is necessary to execute the machine. But in many cases it also needs to get input from other users. In a game for example, the user may need to insert their decisions on input drives for later processing.
When users interact with their blockchain DApps, they are free to manage and run their own blockchain nodes if so they wish. In a common scenario of the usage of the Ethereum network, DApps are accessed via browser and blockchain transaction requests are carried out by Metamask. The user signs the transaction which is typically sent to a remotely hosted node, such as Infura.
Cartesi is a second layer solution.