audio-knife: startup self-test for GOOGLE_APPLICATION_CREDENTIALS

Cargo.toml

@@ -25,7 +25,7 @@ members = [
 ]
 
 [workspace.package]
-version = "3.8.0"
+version = "3.8.1"
 edition = "2024"
 license = "MIT"
 repository = "https://github.com/pragmatrix/context-switch"

VERSIONING.md

@@ -0,0 +1,23 @@
+# Versioning
+
+The workspace uses a single shared version (`[workspace.package] version` in the
+root `Cargo.toml`); all member crates inherit it via `version.workspace = true`.
+
+## When to bump
+
+- **Every behavioral change** bumps the version by at least a patch increment,
+  in the commit that introduces the change. Behavioral changes include new or
+  altered runtime behavior, protocol changes, new configuration, and new
+  warnings or log outcomes that affect operation.
+- **Non-behavioral changes** (comment updates, doc rewording, formatting,
+  refactors without observable behavior change) do not require a bump.
+- Bump the minor version for new features or compatible protocol extensions,
+  and the major version for breaking protocol or interface changes, following
+  Semantic Versioning.
+
+## Release history
+
+| Version | Change |
+|---------|--------|
+| 3.8.0   | google-transcribe: numerals support via digit-sequence class token (#99) |
+| 3.8.1   | audio-knife: startup self-test warning for `GOOGLE_APPLICATION_CREDENTIALS` (#100) |

audio-knife/src/main.rs

@@ -3,6 +3,7 @@
 mod app_error;
 mod event_scheduler;
 mod mod_audio_fork;
+mod selftest;
 mod server_event_router;
 
 use std::env;
@@ -65,6 +66,8 @@ async fn main() -> Result<()> {
         info!("Environment variables loaded from {env_path:?}");
     }
 
+    selftest::run();
+
     let addr = {
         match env::var("AUDIO_KNIFE_ADDRESS") {
             Ok(addr) => addr.parse().expect("Failed to parse AUDIO_KNIFE_ADDRESS"),

audio-knife/src/selftest.rs

@@ -0,0 +1,33 @@
+//! Startup self-test: verifies deployment configuration that the server itself does not
+//! depend on, so problems are surfaced early without preventing startup.
+
+use std::env;
+use std::fs;
+use std::path::Path;
+
+use anyhow::{Context, Result};
+use tracing::warn;
+
+/// Runs the startup self-tests. Failures are logged as warnings with context about what will
+/// not work, but never prevent startup.
+pub fn run() {
+    if let Err(err) = google_credentials() {
+        warn!("The `google-transcribe` service will not work: {err:#}");
+    }
+}
+
+/// Checks `GOOGLE_APPLICATION_CREDENTIALS`: the variable must be set and point to a file
+/// containing valid JSON. Returns the first problem found as an error.
+fn google_credentials() -> Result<()> {
+    const VAR: &str = "GOOGLE_APPLICATION_CREDENTIALS";
+
+    let path = env::var(VAR).context(format!("{VAR} is not set"))?;
+
+    let json = fs::read_to_string(Path::new(&path))
+        .with_context(|| format!("{VAR}={path}: cannot read file"))?;
+
+    serde_json::from_str::<serde_json::Value>(&json)
+        .with_context(|| format!("{VAR}={path}: not valid JSON"))?;
+
+    Ok(())
+}