[chore] Exit on misconfigured journal mode

Adds documentation and a configuration validation check to ensure that
when folks run with the WASM SQLite build on anything other than Linux
we don't allow them to run with journaling set to WAL. That will result
in abysmal performance until ncruces/go-sqlite3#85 is resolved.

Fixes #2962

docs/configuration/database.md

@@ -12,6 +12,9 @@ To configure GoToSocial to use SQLite, change `db-type` to `sqlite`. The `addres
 
 Note that the `:memory:` setting will use an *in-memory database* which will be wiped when your GoToSocial instance stops running. This is for testing only and is absolutely not suitable for running a proper instance, so *don't do this*.
 
+!!! warning "WASM SQLite build"
+    When running the experimental WASM SQLite build on anything other than Linux, you have to set `db-sqlite-journal-mode` to `TRUNCATE` instead of `WAL`. You'll experience abysmal performance otherwise.
+
 ## Postgres
 
 Postgres is a heavier database format, which is useful for larger instances where you need to scale performance, or where you need to run your database on a dedicated machine separate from your GoToSocial instance (or do funky stuff like run a database cluster).
@@ -143,6 +146,11 @@ db-max-open-conns-multiplier: 8
 # SQLite only -- unused otherwise.
 # If set to empty string, the sqlite default will be used.
 # See: https://www.sqlite.org/pragma.html#pragma_journal_mode
+#
+# WARNING: when running the experimental WASM SQLite build on
+# anything other than Linux, set this to "TRUNCATE" instead.
+# The server will complain about this on startup.
+#
 # Examples: ["DELETE", "TRUNCATE", "PERSIST", "MEMORY", "WAL", "OFF"]
 # Default: "WAL"
 db-sqlite-journal-mode: "WAL"

example/config.yaml

@@ -214,6 +214,11 @@ db-max-open-conns-multiplier: 8
 # SQLite only -- unused otherwise.
 # If set to empty string, the sqlite default will be used.
 # See: https://www.sqlite.org/pragma.html#pragma_journal_mode
+#
+# WARNING: when running the experimental WASM SQLite build on
+# anything other than Linux, set this to "TRUNCATE" instead.
+# The server will complain about this on startup.
+#
 # Examples: ["DELETE", "TRUNCATE", "PERSIST", "MEMORY", "WAL", "OFF"]
 # Default: "WAL"
 db-sqlite-journal-mode: "WAL"

internal/config/validate.go

@@ -19,6 +19,10 @@ package config
 
 import (
 	"fmt"
+	"runtime"
+	"runtime/debug"
+	"slices"
+	"strings"
 
 	"github.com/miekg/dns"
 	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
@@ -144,5 +148,42 @@ func Validate() error {
 		)
 	}
 
+	if err := checkSQLiteJournalMode(); err != nil {
+		errf("%s", err)
+	}
+
 	return errs.Combine()
 }
+
+func checkSQLiteJournalMode() error {
+	// check if we're running SQLite
+	if GetDbDatabase() != "sqlite" {
+		return nil
+	}
+
+	// check if this uses the WASM build
+	info, _ := debug.ReadBuildInfo()
+	isWasm := false
+	for _, s := range info.Settings {
+		// check the build tags
+		if s.Key == "-tags" {
+			vals := strings.Split(s.Value, ",")
+			if slices.Contains(vals, "wasmsqlite3") {
+				isWasm = true
+				break
+			}
+			// we don't need to process other build setting keys
+			break
+		}
+	}
+
+	if !isWasm {
+		return nil
+	}
+
+	if runtime.GOOS != "linux" && GetDbSqliteJournalMode() == "WAL" {
+		return fmt.Errorf("when using the WASM SQLite build on a non-Linux platform the %s configuration value must be set to TRUNCATE", DbSqliteJournalModeFlag())
+	}
+
+	return nil
+}