tracing: replace SimpleSpanProcessor with BatchSpanProcessor

This change make tokio could be use in vsock-exporter.

Signed-off-by: Tim Zhang <tim@hyper.sh>

src/agent/Cargo.lock

@@ -872,6 +872,8 @@ dependencies = [
  "rand",
  "serde",
  "thiserror",
+ "tokio",
+ "tokio-stream",
 ]
 
 [[package]]
@@ -1577,6 +1579,17 @@ dependencies = [
  "syn 1.0.72",
 ]
 
+[[package]]
+name = "tokio-stream"
+version = "0.1.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f8864d706fdb3cc0843a49647ac892720dac98a6eeb818b77190592cf4994066"
+dependencies = [
+ "futures-core",
+ "pin-project-lite",
+ "tokio",
+]
+
 [[package]]
 name = "tokio-util"
 version = "0.6.7"

src/agent/Cargo.toml

@@ -54,7 +54,7 @@ cgroups = { package = "cgroups-rs", version = "0.2.5" }
 tracing = "0.1.26"
 tracing-subscriber = "0.2.18"
 tracing-opentelemetry = "0.13.0"
-opentelemetry = "0.14.0"
+opentelemetry = { version = "0.14.0", features = ["rt-tokio-current-thread"]}
 vsock-exporter = { path = "vsock-exporter" }
 
 [dev-dependencies]

src/agent/src/tracer.rs

@@ -66,7 +66,7 @@ pub fn setup_tracing(name: &'static str, logger: &Logger, _agent_cfg: &AgentConf
     let config = Config::default();
 
     let builder = opentelemetry::sdk::trace::TracerProvider::builder()
-        .with_simple_exporter(exporter)
+        .with_batch_exporter(exporter, opentelemetry::runtime::TokioCurrentThread)
         .with_config(config);
 
     let provider = builder.build();