readyset: Infer default database_type from upstream_db_url

Make the database-type argument optional if the upstream_db_url is
present, and infer it from the upstream db url (by parsing it) if it's
not provided. If it *is* provided, check that it matches so we can
provide a nicer error message if it doesn't match.

Fixes: ENG-2935
Fixes: ENG-2897
Change-Id: Iae6e4e0beba0aa8eaff8c18befd60d53fe56da3f
Reviewed-on: https://gerrit.readyset.name/c/readyset/+/4781
Reviewed-by: Dan Wilbanks <dan@readyset.io>
Tested-by: Buildkite CI

readyset/src/lib.rs

@@ -162,9 +162,15 @@ pub struct Options {
     #[clap(long, env = "DEPLOYMENT", value_parser = NonEmptyStringValueParser::new())]
     deployment: String,
 
-    /// Database engine protocol to emulate
-    #[clap(long, env = "DATABASE_TYPE", value_enum)]
-    pub database_type: DatabaseType,
+    /// Database engine protocol to emulate. If omitted, will be inferred from the
+    /// `upstream-db-url`
+    #[clap(
+        long,
+        env = "DATABASE_TYPE",
+        value_enum,
+        required_unless_present("upstream_db_url")
+    )]
+    pub database_type: Option<DatabaseType>,
 
     /// Run ReadySet in standalone mode, running a readyset-server instance within this adapter.
     #[clap(long, env = "STANDALONE", conflicts_with = "embedded_readers")]
@@ -381,6 +387,33 @@ pub struct Options {
     cleanup: bool,
 }
 
+impl Options {
+    /// Return the configured database type, either explicitly set by the user or inferred from the
+    /// upstream DB URL
+    pub fn database_type(&self) -> anyhow::Result<DatabaseType> {
+        let infer_from_db_url = |db_url: &str| Ok(db_url.parse::<DatabaseURL>()?.database_type());
+
+        match (
+            self.database_type,
+            &self.server_worker_options.replicator_config.upstream_db_url,
+        ) {
+            (None, None) => bail!("One of either --database-type or --upstream-db-url is required"),
+            (None, Some(url)) => infer_from_db_url(url),
+            (Some(dt), None) => Ok(dt),
+            (Some(dt), Some(url)) => {
+                let inferred = infer_from_db_url(url)?;
+                if dt != inferred {
+                    bail!(
+                        "Provided --database-type {dt} does not match database type {inferred} for \
+                         --upstream-db-url"
+                    );
+                }
+                Ok(dt)
+            }
+        }
+    }
+}
+
 // Command-line options for running the experimental fallback_cache.
 //
 // This option struct is intended to be embedded inside of a larger option struct using
@@ -1363,4 +1396,55 @@ mod tests {
         assert_eq!(opts.max_processing_minutes, 15);
         assert_eq!(opts.migration_task_interval, 20000);
     }
+
+    #[test]
+    fn infer_database_type() {
+        let opts = Options::parse_from(vec![
+            "readyset",
+            "--deployment",
+            "test",
+            "--address",
+            "0.0.0.0:3306",
+            "--upstream-db-url",
+            "mysql://root:password@mysql:3306/readyset",
+        ]);
+        assert_eq!(opts.database_type().unwrap(), DatabaseType::MySQL);
+
+        let opts = Options::parse_from(vec![
+            "readyset",
+            "--deployment",
+            "test",
+            "--address",
+            "0.0.0.0:3306",
+            "--upstream-db-url",
+            "postgresql://root:password@db/readyset",
+        ]);
+        assert_eq!(opts.database_type().unwrap(), DatabaseType::PostgreSQL);
+
+        let opts = Options::parse_from(vec![
+            "readyset",
+            "--deployment",
+            "test",
+            "--address",
+            "0.0.0.0:3306",
+            "--upstream-db-url",
+            "postgresql://root:password@db/readyset",
+            "--database-type",
+            "postgresql",
+        ]);
+        assert_eq!(opts.database_type().unwrap(), DatabaseType::PostgreSQL);
+
+        let opts = Options::parse_from(vec![
+            "readyset",
+            "--deployment",
+            "test",
+            "--address",
+            "0.0.0.0:3306",
+            "--upstream-db-url",
+            "postgresql://root:password@db/readyset",
+            "--database-type",
+            "mysql",
+        ]);
+        opts.database_type().unwrap_err();
+    }
 }

readyset/src/main.rs

@@ -8,7 +8,8 @@ use readyset::{NoriaAdapter, Options};
 
 fn main() -> anyhow::Result<()> {
     let options = Options::parse();
-    match options.database_type {
+
+    match options.database_type()? {
         DatabaseType::MySQL => NoriaAdapter {
             description: "MySQL adapter for ReadySet.",
             default_address: SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 3306),