Admission Control

Admission Control (AC) is the public API endpoint for Libra and it takes public gRPC requests from clients.

Overview

Admission Control (AC) serves two types of requests from clients:

1. SubmitTransaction - To submit a transaction to the associated validator.
2. UpdateToLatestLedger - To query storage, e.g., account state, transaction log, proofs, etc.

Implementation Details

Admission Control (AC) implements two public APIs:

1. SubmitTransaction(SubmitTransactionRequest)
   • Multiple validations will be performed against the request:
     • The Transaction signature is checked first. If this check fails, AdmissionControlStatus::Rejected is returned to client.
     • The Transaction is then validated by vm_validator. If this fails, the corresponding VMStatus is returned to the client.
   • Once the transaction passes all validations, AC queries the sender's account balance and the latest sequence number from storage and sends them to Mempool along with the client request.
   • If Mempool returns MempoolAddTransactionStatus::Valid, AdmissionControlStatus::Accepted is returned to the client indicating successful submission. Otherwise, corresponding AdmissionControlStatus is returned to the client.
2. UpdateToLatestLedger(UpdateToLatestLedgerRequest). No extra processing is performed in AC.

• The request is directly passed to storage for query.

Folder Structure

    .
    ├── README.md
    ├── admission_control_proto
    │   └── src
    │       └── proto                           # Protobuf definition files
    └── admission_control_service
        └── src                                 # gRPC service source files
            ├── admission_control_node.rs       # Wrapper to run AC in a separate thread
            ├── admission_control_service.rs    # gRPC service and main logic
            ├── main.rs                         # Main entry to run AC as a binary
            └── unit_tests                      # Tests

This module interacts with:

The Mempool component, to submit transactions from clients. The Storage component, to query validator storage.