You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: trigger_initial_size_calculation.rs
    path of file: ./repos/neon/pageserver/pagebench/src/cmd
    
    the code of the file until where you have to start completion: use std::sync::Arc;

use humantime::Duration;
use tokio::task::JoinSet;
use utils::id::TenantTimelineId;

use pageserver_client::mgmt_api::ForceAwaitLogicalSize;

#[derive(clap::Parser)]
pub(crate) struct Args {
    #[clap(long, default_value = "http://localhost:9898")]
    mgmt_api_endpoint: String,
    #[clap(long, default_value = "localhost:64000")]
    page_service_host_port: String,
    #[clap(long)]
    pageserver_jwt: Option<String>,
    #[clap(
        long,
        help = "if specified, poll mgmt api to check whether init logical size calculation has completed"
    )]
    poll_for_completion: Option<Duration>,
    #[clap(long)]
    limit_to_first_n_targets: Option<usize>,
    targets: Option<Vec<TenantTimelineId>>,
}

pub(crate) fn main(args: Args) -> anyhow::Result<()> {
    let rt
    
async fn main_impl(args: Args) -> anyhow::Result<()> {
    let args: &'static Args = Box::leak(Box::new(args));

    let mgmt_api_client = Arc::new(pageserver_client::mgmt_api::Client::new(
        args.mgmt_api_endpoint.clone(),
        args.pageserver_jwt.as_deref(),
    ));

    // discover targets
    let timelines: Vec<TenantTimelineId> = crate::util::cli::targets::discover(
        &mgmt_api_client,
        crate::util::cli::targets::Spec {
            limit_to_first_n_targets: args.limit_to_first_n_targets,
            targets: args.targets.clone(),
        },
    )
    .await?;

    // kick it off

    let mut js = JoinSet::new();
    for tl in timelines {
        let mgmt_api_client = Arc::clone(&mgmt_api_client);
        js.spawn(async move {
            let info = mgmt_api_client
                .timeline_info(tl.tenant_id, tl.timeline_id, ForceAwaitLogicalSize::Yes)
                .await
                .unwrap();

            // Polling should not be strictly required here since we await
            // for the initial logical size, however it's possible for the request
            // to land before the timeline is initialised. This results in an approximate
            // logical size.
            if let Some(period) = args.poll_for_completion {
                let mut ticker = tokio::time::interval(period.into());
                ticker.set_missed_tick_behavior(tokio::time::MissedTickBehavior::Delay);
                let mut info = info;
                while !info.current_logical_size_is_accurate {
                    ticker.tick().await;
                    info = mgmt_api_client
                        .timeline_info(tl.tenant_id, tl.timeline_id, ForceAwaitLogicalSize::Yes)
                        .await
                        .unwrap();
                }
            }
        });
    }
    while let Some(res) = js.join_next().await {
        let _: () = res.unwrap();
    }
    Ok(())
}