Aptos Indexer SDK

Generally, an indexer processor follow this flow:

1. Receive a stream of Aptos transactions
2. Extract data from the transactions
3. Transform and merge the parsed data into a coherent, standardized schema
4. Store the transformed data into a database

The Aptos Indexer SDK works by modeling each processor as a graph of independent steps. Each of the steps in the flow above is written as a Step in the SDK, and the output of each Step is connected to the input of the next Step by a channel.

How to use

To your Cargo.toml , add

aptos-indexer-processor-sdk = { git = "https://github.com/aptos-labs/aptos-indexer-processor-sdk.git", rev = "{COMMIT_HASH}" }
aptos-indexer-processor-sdk-server-framework = { git = "https://github.com/aptos-labs/aptos-indexer-processor-sdk.git", rev = "{COMMIT_HASH}" }

Get started

We’ve created a Quickstart Guide to Aptos Indexer SDK which gets you setup and running an events processor that indexes events on the Aptos blockchain.

Documentation

Creating a step

To create a step in the SDK, implement these traits:

1. Processable

   #[async_trait]
   impl Processable for MyExtractorStep {
       type Input = Transaction;
       type Output = ExtractedDataModel;
       type RunType = AsyncRunType;
   
   		// Processes a batch of input items and returns a batch of output items.
       async fn process(
           &mut self,
           input: TransactionContext<Transaction>,
       ) -> Result<Option<TransactionContext<ExtractedDataModel>>, ProcessorError> {
           let extracted_data = ...
           // Extract data from items.data
           
           Ok(Some(TransactionContext {
               data: extracted_data,
               start_version: input.start_version,
               end_version: input.end_version,
               start_transaction_timestamp: input.start_transaction_timestamp,
               end_transaction_timestamp: input.end_transaction_timestamp,
               total_size_in_bytes: input.total_size_in_bytes,
           }))
       }
   }

2. NamedStep

   impl NamedStep for MyExtractorStep {
       fn name(&self) -> String {
           "MyExtractorStep".to_string()
       }
   }

3. Either AsyncStep or PollableAsyncStep, which defines how the step will be run in the processor.

   1. The most basic step is an AsyncStep, which processes a batch of input items and returns a batch of output items.

      #[async_trait]
      impl Processable for MyExtractorStep {
          ...
          type RunType = AsyncRunType;
      		...
      }
      
      impl AsyncStep for MyExtractorStep {}

   2. A PollableAsyncStep does the same as AsyncStep, but it also periodically polls its internal state and returns a batch of output items if available.

      #[async_trait]
      impl<T> Processable for MyPollStep<T>
      where
          Self: Sized + Send + 'static,
          T: Send + 'static,
      {
          ...
          type RunType = PollableAsyncRunType;
      		...
      }
      
      #[async_trait]
      impl<T: Send + 'static> PollableAsyncStep for MyPollStep<T>
      where
          Self: Sized + Send + Sync + 'static,
          T: Send + 'static,
      {
      		/// Returns the duration between polls
          fn poll_interval(&self) -> std::time::Duration {
              // Define duration
          }
      
      		/// Polls the internal state and returns a batch of output items if available.
          async fn poll(&mut self) -> Result<Option<Vec<TransactionContext<T>>>, ProcessorError> {
              // Define polling logic
          }
      }

Common steps

The SDK provides several common steps to use in your processor.

1. TransactionStreamStep provides a stream of Aptos transactions to the processor
2. TimedBufferStep buffers a batch of items and periodically polls to release the items to the next step

Connecting steps

When ProcessorBuilder connects two steps, a channel is created linking the two steps and the output of the first step becomes the input of the next step.

let (pb, buffer_receiver) = ProcessorBuilder::new_with_inputless_first_step(
      first_step.into_runnable_step(),
  )
  .connect_to(second_step.into_runnable_step(), channel_size)
  .connect_to(third_step.into_runnable_step(), channel_size)
  .end_and_return_output_receiver(channel_size);

Adding a new processor

1. Use aptos-indexer-processor-example as a starting point
2. Add the new processor to ProcessorConfig and Processor
3. Add the processor to RunnableConfig

Running a processor

To run the processor, we recommend using the example in aptos-indexer-processor-example and following this configuration guide.

Advanced features (experimental)

1. Fanout + ArcifyStep
2. Fan in