# Percentile speculative execution

This policy has access to `Metrics` shared with session, and triggers
speculative execution when the request to the current host is above a
given percentile.

This policy requires enabling crate feature `"metrics"` to be available.

## Example

To use this policy in `Session`:

```rust
use std::{sync::Arc, time::Duration};
use scylla::client::session::Session;
use scylla::client::session_builder::SessionBuilder;
use scylla::{
    policies::speculative_execution::PercentileSpeculativeExecutionPolicy,
    client::execution_profile::ExecutionProfile,
};

let policy = PercentileSpeculativeExecutionPolicy  {
    max_retry_count: 3,
    percentile: 99.0,
};

let handle = ExecutionProfile::builder()
    .speculative_execution_policy(Some(Arc::new(policy)))
    .build()
    .into_handle();

let session: Session = SessionBuilder::new()
    .known_node("127.0.0.1:9042")
    .default_execution_profile_handle(handle)
    .build()
    .await?;
```