Validate chains are registered on startup

Previously chains were checked lazily at the time their pubkeys were
fetched or signing was requested.

This adds an eager check at the time clients start.

It would probably be better if this check mapped to some sort of
known-good handle (e.g. `Index` into a generational arena), but this
is enough to catch the error eagerly instead of lazily.

I encountered this personally during the `cosmoshub-3` upgrade.

src/client.rs

@@ -6,12 +6,13 @@
 //! as a "Key Management System".
 
 use crate::{
+    chain,
     config::ValidatorConfig,
     error::{Error, ErrorKind},
     prelude::*,
     session::Session,
 };
-use std::{panic, process, thread, time::Duration};
+use std::{panic, process::exit, thread, time::Duration};
 
 /// Join handle type used by our clients
 type JoinHandle = thread::JoinHandle<Result<(), Error>>;
@@ -36,14 +37,16 @@ pub struct Client {
 impl Client {
     /// Spawn a new client, returning a handle so it can be joined
     pub fn spawn(config: ValidatorConfig) -> Self {
+        register_chain(&config.chain_id);
+
         let name = format!("{}@{}", &config.chain_id, &config.addr);
 
         let handle = thread::Builder::new()
             .name(name.clone())
             .spawn(move || main_loop(config))
             .unwrap_or_else(|e| {
                 status_err!("error spawning thread: {}", e);
-                process::exit(1);
+                exit(1);
             });
 
         Self { name, handle }
@@ -82,6 +85,20 @@ fn main_loop(config: ValidatorConfig) -> Result<(), Error> {
     Ok(())
 }
 
+/// Ensure chain with given ID is properly registered
+pub fn register_chain(chain_id: &chain::Id) {
+    let registry = chain::REGISTRY.get();
+
+    debug!("registering chain: {}", chain_id);
+    registry.get_chain(chain_id).unwrap_or_else(|| {
+        status_err!(
+            "unregistered chain: {} (add it to tmkms.toml's [[chain]] section)",
+            chain_id
+        );
+        exit(1);
+    });
+}
+
 /// Open a new session and run the session loop
 pub fn run_client(config: ValidatorConfig) -> Result<(), Error> {
     panic::catch_unwind(move || Session::open(config)?.request_loop())

src/session.rs

@@ -127,7 +127,11 @@ impl Session {
         request.validate()?;
 
         let registry = chain::REGISTRY.get();
+
+        // unwrap is acceptable here as chain presence is validated in client.rs's
+        // `register_chain` function.
         let chain = registry.get_chain(&self.config.chain_id).unwrap();
+
         let (_, request_state) = parse_request(&request)?;
         let mut chain_state = chain.state.lock().unwrap();
 
@@ -178,6 +182,8 @@ impl Session {
 
     /// Get the public key for (the only) public key in the keyring
     fn get_public_key(&mut self, _request: &PubKeyRequest) -> Result<Response, Error> {
+        // unwrap is acceptable here as chain presence is validated in client.rs's
+        // `register_chain` function.
         let registry = chain::REGISTRY.get();
         let chain = registry.get_chain(&self.config.chain_id).unwrap();