From 63ef6eb66bfde84361a41532ceb4e2c092123798 Mon Sep 17 00:00:00 2001
From: Kim Altintop <kim@eagain.io>
Date: Tue, 17 Oct 2023 13:13:27 +0200
Subject: [PATCH] db: Swap order of fsync and provide error context

---
 crates/core/src/db/commit_log.rs | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/crates/core/src/db/commit_log.rs b/crates/core/src/db/commit_log.rs
index db5e416923..209ae93304 100644
--- a/crates/core/src/db/commit_log.rs
+++ b/crates/core/src/db/commit_log.rs
@@ -15,6 +15,7 @@ use crate::{
     error::DBError,
 };
 
+use anyhow::Context;
 use spacetimedb_lib::{
     hash::{hash_bytes, Hash},
     DataKey,
@@ -69,9 +70,15 @@ impl CommitLog {
             let mut mlog = mlog.lock().unwrap();
             mlog.append(commit)?;
             if self.fsync {
-                mlog.sync_all()?;
+                let offset = mlog.open_segment_max_offset;
+                // Sync the odb first, as the mlog depends on its data. This is
+                // not an atomicity guarantee, but the error context may help
+                // with forensics.
                 let mut odb = self.odb.lock().unwrap();
-                odb.sync_all()?;
+                odb.sync_all()
+                    .with_context(|| format!("Error syncing odb to disk. Log offset: {offset}"))?;
+                mlog.sync_all()
+                    .with_context(|| format!("Error syncing mlog to disk. Log offset: {offset}"))?;
                 log::trace!("DATABASE: FSYNC");
             } else {
                 mlog.flush()?;