Add network state to system.interval telemetry (#1959)

* add network state to system.interval telemetry

* use serde_json

* use unwrap_or_default

substrate/Cargo.lock

@@ -3644,6 +3644,7 @@ dependencies = [
  "log 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "names 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "regex 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde_json 1.0.38 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-primitives 0.1.0",
  "structopt 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "substrate-client 0.1.0",

substrate/core/cli/Cargo.toml

@@ -20,6 +20,7 @@ tokio = "0.1.7"
 futures = "0.1.17"
 fdlimit = "0.1"
 exit-future = "0.1"
+serde_json = "1.0"
 sysinfo = "0.8.0"
 panic-handler = { package = "substrate-panic-handler", path = "../../core/panic-handler" }
 client = { package = "substrate-client", path = "../../core/client" }

substrate/core/cli/src/informant.rs

@@ -82,9 +82,12 @@ pub fn start<C>(service: &Service<C>, exit: ::exit_future::Exit, handle: TaskExe
 				(proc.cpu_usage(), proc.memory())
 			} else { (0.0, 0) };
 
+			let network_state = serde_json::to_string(&network.network_state()).unwrap_or_default();
+
 			telemetry!(
 				SUBSTRATE_INFO;
 				"system.interval";
+				"network_state" => network_state,
 				"status" => format!("{}{}", status, target),
 				"peers" => num_peers,
 				"height" => best_number,