Exonum-time is a time oracle service for Exonum blockchain framework. This service allows to determine time, import it from the external world to the blockchain and keep its current value in the blockchain.
Include exonum-time as a dependency in your Cargo.toml:
toml
[dependencies]
exonum-time = "0.5.0"
Add the time oracle service to the blockchain in the main project file:
```rust extern crate exonum; extern crate exonum_time;
use exonum::helpers::fabric::NodeBuilder; use exonum_time::TimeServiceFactory;
fn main() { exonum::helpers::initlogger().unwrap(); NodeBuilder::new() .withservice(Box::new(TimeServiceFactory)) .run(); } ```
Typical usage of the service boils down to importing the schema and calling its time() or validators_time() methods.
Below is an example of a method for processing a transaction, which must be executed no later than the specified time (this time is written in the transaction body in a separate field):
```rust message! { struct Tx { time: SystemTime, ... } }
impl Transaction for Tx { ... fn execute(&self, view: &mut Fork) { // Import schema. let timeschema = exonumtime::TimeSchema::new(&view); // The time in the transaction should be less than in the blockchain. match timeschema.time().get() { Some(ref currenttime) if current_time.time() <= self.time() => { // Execute transaction business logic. } _ => {} } } } ```
See the full implementation of the service, which uses the time oracle.
You can get the time of each validator node in the same manner the consolidated time of the system is obtained:
rust
let time_schema = exonum_time::TimeSchema::new(&view);
// Gets the times of all validators.
let validators_time = time_schema.validators_time();
// Gets the time of validator with a public key equal to `public_key`.
let validator_time = time_schema.validators_time().get(&public_key);
exonum-time is licensed under the Apache License (Version 2.0). See LICENSE for details.