Implement timeout for force_flush and shutdown.

Note that the spec only has configuration for maximum time to export data. So the timeout is based on the export time.

opentelemetry/Cargo.toml

@@ -21,17 +21,17 @@ all-features = true
 rustdoc-args = ["--cfg", "docsrs"]
 
 [dependencies]
-async-std = { version = "1.6", features = ["unstable"], default-features = false, optional = true  }
+async-std = { version = "1.6", features = ["unstable"], default-features = false, optional = true }
 async-trait = { version = "0.1", optional = true }
 bincode = { version = "1.2", optional = true }
 dashmap = { version = "4.0.0-rc6", optional = true }
 fnv = { version = "1.0", optional = true }
-futures = "0.3"
+futures = { version = "0.3", features = ["std"] }
 lazy_static = "1.4"
 percent-encoding = { version = "2.0", optional = true }
 pin-project = { version = "0.4", optional = true }
 rand = { version = "0.7", default-features = false, features = ["std"], optional = true }
-regex = { version = "1.3", default-features = false, features = ["std", "perf"], optional = true}
+regex = { version = "1.3", default-features = false, features = ["std", "perf"], optional = true }
 serde = { version = "1.0", features = ["derive", "rc"], optional = true }
 http = { version = "0.2", optional = true }
 thiserror = { version = "1.0", optional = true }
@@ -44,6 +44,7 @@ surf = { version = "2.0", default-features = false, optional = true }
 criterion = "0.3.1"
 rand_distr = "0.3.0"
 tokio = { version = "0.2", features = ["full"] }
+async-std = { version = "1.6", features = ["unstable"] }
 
 [features]
 default = ["trace"]

opentelemetry/src/sdk/trace/provider.rs

@@ -116,7 +116,12 @@ impl Builder {
         // drop. We cannot assume we are in a multi-threaded tokio runtime here, so use
         // `spawn_blocking` to avoid blocking the main thread.
         let spawn = |fut| tokio::task::spawn_blocking(|| futures::executor::block_on(fut));
-        let batch = sdk::trace::BatchSpanProcessor::builder(exporter, spawn, tokio::time::interval);
+        let batch = sdk::trace::BatchSpanProcessor::builder(
+            exporter,
+            spawn,
+            tokio::time::delay_for,
+            tokio::time::interval,
+        );
         self.with_batch_exporter(batch.build())
     }
 
@@ -127,6 +132,7 @@ impl Builder {
         let batch = sdk::trace::BatchSpanProcessor::builder(
             exporter,
             async_std::task::spawn,
+            async_std::task::sleep,
             async_std::stream::interval,
         );
         self.with_batch_exporter(batch.build())