add CLI tool to test migration

sled-agent/src/bin/services-ledger-check-migrate.rs

@@ -0,0 +1,53 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+//! Test-migrates one or more old-format services ledger files to new-format
+//! Omicron zones ledgers
+
+use anyhow::Context;
+use camino::Utf8PathBuf;
+use clap::Parser;
+use omicron_common::cmd::fatal;
+use omicron_common::cmd::CmdError;
+use omicron_sled_agent::services::ZonesConfig;
+use omicron_sled_agent::services_migration::AllServiceRequests;
+
+#[tokio::main]
+async fn main() {
+    if let Err(message) = do_run().await {
+        fatal(CmdError::Failure(format!("{:#}", message)));
+    }
+}
+
+// XXX-dap make this two subcommands:
+// - `check` does what this does now
+// - `show` takes one argument and pretty-prints the converted form
+
+#[derive(Debug, Parser)]
+struct Args {
+    #[clap(action)]
+    files: Vec<Utf8PathBuf>,
+}
+
+async fn do_run() -> Result<(), anyhow::Error> {
+    let args = Args::parse();
+    for file_path in &args.files {
+        let contents = tokio::fs::read_to_string(file_path)
+            .await
+            .with_context(|| format!("read {:?}", &file_path))?;
+        let parsed: AllServiceRequests = serde_json::from_str(&contents)
+            .with_context(|| format!("parse {:?}", &file_path))?;
+        let converted = ZonesConfig::try_from(parsed)
+            .with_context(|| format!("migrate contents of {:?}", &file_path))?;
+        // XXX-dap what sanity-checks on the result?
+        println!(
+            "{}: converted okay (zones: {})",
+            file_path,
+            converted.zones.len()
+        );
+    }
+
+    println!("all files converted okay (files: {})", args.files.len());
+    Ok(())
+}

sled-agent/src/lib.rs

@@ -28,8 +28,8 @@ pub mod params;
 mod profile;
 pub mod rack_setup;
 pub mod server;
-mod services;
-mod services_migration;
+pub mod services;
+pub mod services_migration;
 mod sled_agent;
 mod smf_helper;
 pub(crate) mod storage;

sled-agent/src/services.rs

@@ -672,6 +672,49 @@ impl ServiceManager {
                 );
 
                 ledger.commit().await?;
+
+                // We could consider removing the old ledger here.  That would
+                // not guarantee that it would be gone, though, because we could
+                // crash during `ledger.commit()` above having written at least
+                // one of the new ledgers.  In that case, we won't go through
+                // this code path again on restart.  If we wanted to ensure the
+                // old-format ledger was gone after the migration, we could
+                // consider unconditionally removing the old ledger paths in the
+                // caller, after we've got a copy of the new-format ledger.
+                //
+                // Should we?  In principle, it shouldn't matter either way
+                // because we will never look at the old-format ledger unless we
+                // don't have a new-format one, and we should now have a
+                // new-format one forever now.
+                //
+                // When might it matter?  Two cases:
+                //
+                // (1) If the sled agent is downgraded to a previous version
+                //     that doesn't know about the new-format ledger.  Do we
+                //     want that sled agent to use the old-format one?  It
+                //     depends.  If that downgrade happens immediately because
+                //     the upgrade to the first new-format version was a
+                //     disaster, then we'd probably rather the downgraded sled
+                //     agent _did_ start its zones.  If the downgrade happens
+                //     months later, potentially after various additional
+                //     reconfigurations, then that old-format ledger is probably
+                //     out of date and shouldn't be used.  There's no way to
+                //     really know which case we're in, but the latter seems
+                //     quite unlikely (why would we downgrade so far back after
+                //     so long?).  So that's a reason to keep the old-format
+                //     ledger.
+                //
+                // (2) Suppose a developer or Oxide support engineer removes the
+                //     new ledger for some reason, maybe thinking sled agent
+                //     would come up with no zones running.  They'll be
+                //     surprised to discover that it actually starts running a
+                //     potentially old set of zones.  This probably only matters
+                //     on a production system, and even then, it probably
+                //     shouldn't happen.
+                //
+                // Given these cases, we're left ambivalent.  We choose to keep
+                // the old ledger around.  If nothing else, if something goes
+                // wrong, we'll have a copy of its last contents!
                 Ok(Some(ledger))
             }
         }

sled-agent/src/services_migration.rs

@@ -177,12 +177,6 @@ impl std::fmt::Display for ServiceType {
     }
 }
 
-/// Used to request that the Sled initialize multiple services.
-#[derive(Clone, Debug, Deserialize, Serialize, JsonSchema, PartialEq)]
-pub struct ServiceEnsureBody {
-    pub services: Vec<ServiceZoneRequest>,
-}
-
 /// Describes a request to provision a specific dataset
 #[derive(
     Clone, Debug, Deserialize, Serialize, JsonSchema, PartialEq, Eq, Hash,