chore: merge master, release 0.43.8-dc.2, document releasing

.github/workflows/dectris-release.yml

@@ -8,10 +8,12 @@ on:
   workflow_dispatch:
     inputs:
       version:
-        description: "Release version (e.g. 0.43.8-dc.1). A 'v' prefix will be added for the tag/release."
+        # Deliberately has no default: it must match GEESEFS_VERSION in
+        # core/cfg/flags.go, and a default here goes stale the moment that
+        # constant moves. Pass it explicitly at dispatch time.
+        description: "Release version, must match GEESEFS_VERSION in core/cfg/flags.go (e.g. 0.43.8-dc.2). A 'v' prefix is added for the tag/release."
         required: true
         type: string
-        default: '0.43.8-dc.1'
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}

CLAUDE.md

@@ -80,6 +80,42 @@ cd docker && just test-multipart-boundary
 
 **Virtual symlinks**: Symlinks stored in `.geesefs_symlinks` (no S3 object) are distinguished from S3-backed symlinks via `Inode.isVirtualSymlink` bool field. Always use this field for detection, not `userMetadata[SymlinkAttr] != nil`.
 
+## Branches
+
+**`dev` is the main branch.** All dectris development on geesefs lives here, every PR targets it, and releases are cut from it. Treat it as the trunk.
+
+**`master` is a read-only mirror of `yandex-cloud/geesefs`.** It must always point at the exact upstream commit the fork is based on, and must never carry a dectris change. Verify with:
+
+```bash
+git fetch upstream
+git rev-list --count upstream/master..origin/master   # must be 0
+```
+
+Upstream syncs go `master` → `dev`: fast-forward `master` to the new upstream commit, then merge `master` into `dev` and resolve there.
+
+Opening a PR against `master` is always wrong. Its content will be absent from `dev`, and a release cut afterwards silently ships without it, with nothing failing to warn you. If it happens, merge `master` into `dev` to recover the work, then reset `master` back to the upstream commit.
+
+Older branches on the remote (`symlinks`, `fix/utf-8`, `ci/dev_releases`, `dectris-master`, `perf-fio-sync-master`, …) predate this layout and are superseded. Their content is already in `dev`; do not branch from them.
+
+## Releasing
+
+The version lives in one place: `GEESEFS_VERSION` in `core/cfg/flags.go`. Bump it, merge to `dev`, then dispatch:
+
+```bash
+gh workflow run dectris-release.yml -f version=<version> --ref dev
+gh release edit v<version> --prerelease=false --latest
+```
+
+The version is a dispatch parameter, so do not edit the workflow to change it. It has no default on purpose: a default duplicates `GEESEFS_VERSION` and goes stale the moment that constant moves.
+
+A dispatched run is marked prerelease, hence the `release edit`. Pushing a `v*` tag instead publishes a full release directly, but only the dispatch path is exercised regularly.
+
+Tag scheme: `v<upstream-version>-dc.<n>`, e.g. `v0.43.8-dc.2`.
+
 ## Go Module
 
 Module: `github.com/yandex-cloud/geesefs` (Go 1.25). Uses the stock `github.com/aws/aws-sdk-go` with no `replace` directive. Yandex-only S3 extensions (`PatchObject`, `ListObjectsV1Ext`) live in `core/ycs3ext/`, built on the SDK's `request.Request` rather than a forked SDK.
+
+## Downstream
+
+`compute-amis` pins the version in `terraform/infrastructure/main.tf` (`geesefs_version`) and its AMI recipe downloads the release asset. A new release needs a matching bump there.

core/cfg/flags.go

@@ -30,7 +30,7 @@ import (
 	"github.com/urfave/cli"
 )
 
-const GEESEFS_VERSION = "0.43.8-dc.1"
+const GEESEFS_VERSION = "0.43.8-dc.2"
 
 var flagCategories map[string]string
 

main.go

@@ -152,6 +152,10 @@ func main() {
 			log.Println("File system has been successfully mounted.")
 			if !flags.Foreground {
 				daemonizer.NotifySuccess(true)
+				// Runtime panics write to fd 2, which the two Close calls
+				// below discard, so a crashed daemon leaves no trace anywhere.
+				// Route crash output to a file first (Go keeps a dup of it).
+				setupCrashLog(bucketName, flags.MountPoint)
 				os.Stderr.Close()
 				os.Stdout.Close()
 			}

main_nowindows.go

@@ -22,16 +22,46 @@ import (
 	"fmt"
 	"os"
 	"os/signal"
+	"runtime/debug"
 	"strings"
 	"sync"
 	"syscall"
+	"time"
 
 	daemon "github.com/sevlyar/go-daemon"
 
 	"github.com/yandex-cloud/geesefs/core"
 	"github.com/yandex-cloud/geesefs/core/cfg"
 )
 
+// Where Go runtime crash output goes once the daemon has closed its stderr.
+// Overridable for non-root mounts via GEESEFS_CRASH_LOG.
+const defaultCrashLogPath = "/var/log/geesefs-crash.log"
+
+// setupCrashLog routes runtime crash output (panics, fatal errors, deadlock
+// dumps) to a shared append-only file. These bypass the logger and write to
+// fd 2, which the daemon closes right after mounting, so without this a
+// crashed daemon leaves no trace anywhere. The header line ties the pid to
+// its mount so a following dump can be attributed.
+func setupCrashLog(bucketName string, mountPoint string) {
+	path := os.Getenv("GEESEFS_CRASH_LOG")
+	if path == "" {
+		path = defaultCrashLogPath
+	}
+	f, err := os.OpenFile(path, os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0600)
+	if err != nil {
+		log.Warnf("Cannot open crash log %v: %v; runtime panics will be lost", path, err)
+		return
+	}
+	fmt.Fprintf(f, "--- %s geesefs pid %d serving %s at %s: crash output armed ---\n",
+		time.Now().UTC().Format(time.RFC3339), os.Getpid(), bucketName, mountPoint)
+	if err = debug.SetCrashOutput(f, debug.CrashOptions{}); err != nil {
+		log.Warnf("Cannot set crash output to %v: %v", path, err)
+	}
+	// SetCrashOutput keeps its own duplicate of the descriptor.
+	f.Close()
+}
+
 var signalsToHandle = []os.Signal{os.Interrupt, syscall.SIGTERM, syscall.SIGUSR1}
 
 func isSigUsr1(s os.Signal) bool {

main_windows.go

@@ -25,6 +25,11 @@ import (
 
 var signalsToHandle = []os.Signal{os.Interrupt, syscall.SIGTERM}
 
+// Unreachable on Windows: canDaemonize is false, so the daemon-only branch
+// that calls this never runs. Present only to keep the build compiling.
+func setupCrashLog(bucketName string, mountPoint string) {
+}
+
 func isSigUsr1(s os.Signal) bool {
 	return false
 }