SimpleExporter is not useable with OTLP/Http

[cijothomas]

SimpleExporter is not useable with OTLP/HTTP (Reqwest client and Hyper client both fails), as export just hangs forever.

Minimal repro when using Reqwest

use tracing::info;
use tracing_subscriber::layer::SubscriberExt;
use tracing_subscriber::Registry;
use tracing_subscriber::util::SubscriberInitExt;
use opentelemetry_appender_tracing::layer::OpenTelemetryTracingBridge;
use opentelemetry_otlp::WithExportConfig;

fn main() {
     let exporter = opentelemetry_otlp::new_exporter().http();
    let logger_provider = opentelemetry_otlp::new_pipeline()
        .logging()
        .with_exporter(
            exporter
                .with_protocol(Protocol::HttpBinary)
                .with_endpoint("http://localhost:4318/v1/logs"),
        )
        .install_simple()
        .unwrap();

    // Create a new OpenTelemetryTracingBridge using the above LoggerProvider.
    let layer = OpenTelemetryTracingBridge::new(&logger_provider);
    tracing_subscriber::registry()
        .with(layer)
        .init();

    info!(name: "my-event", target: "my-target", "hello from {}. My price is {}", "apple", 1.99);

    let _ = logger_provider.shutdown();
}

Minimal repro when using Hyper

let exporter = opentelemetry_otlp::new_exporter().http();
    let exporter = exporter.with_http_client(hyper::HyperClient::default());
    let logger_provider = opentelemetry_otlp::new_pipeline()
        .logging()
        .with_exporter(
            exporter
                .with_protocol(Protocol::HttpBinary)
                .with_endpoint("http://localhost:4318/v1/logs"),
        )
        .install_simple()
        .unwrap();
``

[lalitb]

Just to be clear - it doesn't work with reqwest client (both blocking and async) ?

[cijothomas]

Just to be clear - it doesn't work with reqwest client (both blocking and async) ?

"reqwest-blocking-client" works fine in this case. (only as long as it is not called from a tokio managed thread)

[lalitb]

Also to add, async-compat crate under smol-rs org, provides the compatibility between futures and tokio runtimes. This means we can use the reqwest client in the non-blocking mode under SimpleExporter. Eg. with:

use async_compat::{Compat, CompatExt};
futures_executor::block_on(Compat::new((exporter.export(LogBatch::new(log_tuple)))))

This is as documented here - https://docs.rs/async-compat/latest/async_compat/#

fn main() -> std::io::Result<()> {
    futures::executor::block_on(Compat::new(async {
        let stdin = tokio::io::stdin();
        let mut stdout = tokio::io::stdout();

        futures::io::copy(stdin.compat(), &mut stdout.compat_mut()).await?;
        Ok(())
    }))
}

As per the docs, this adapter internally creates the tokio runtime if not already running, and then allows using types and traits from the futures crate in this tokio runtime.

If a runtime is already available via tokio
//!       thread-locals, then it will be used. Otherwise, a new single-threaded runtime will be
//!       created on demand.

Have tested this with OTLP + reqwest and it works. Will validate if it works for tonic and hyper.