From 8f351ae4d14fc2abcc83716a192dfacff6dc65ef Mon Sep 17 00:00:00 2001
From: Craig Jennings <c@cjennings.net>
Date: Thu, 25 Jun 2026 01:37:41 -0400
Subject: feat: lock backups internally so cron needs no flock wrapper

rsyncshot now acquires an exclusive, non-blocking lock (fd 200) before the backup phase, so a slow backup can't overlap the next cron tick. Only real backups lock. Help, list, status, and dryrun don't, so they're never blocked.

The lock file defaults to /run/lock/rsyncshot.lock, a root-only directory that avoids the symlink-truncation risk of a predictable name in world-writable /tmp. It falls back to /var/lock then /tmp, and is configurable via LOCKFILE. It's deliberately a different file from the old /tmp/rsyncshot.lock cron wrappers, so existing wrapped crontabs keep working until the wrapper is removed.

setup() no longer wraps cron entries in flock, since the script locks itself.
---
 tests/cases/test_cron.sh | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

(limited to 'tests/cases/test_cron.sh')

diff --git a/tests/cases/test_cron.sh b/tests/cases/test_cron.sh
index 5c9bbfa..7e38060 100755
--- a/tests/cases/test_cron.sh
+++ b/tests/cases/test_cron.sh
@@ -118,6 +118,35 @@ EOF
     assert_contains "$crontab_content" "rsyncshot" "should also have rsyncshot jobs" || return 1
 }
 
+# ------------------------------------------------------------------------------
+# Test: Cron entries no longer wrap rsyncshot in an external flock
+# ------------------------------------------------------------------------------
+# rsyncshot locks internally now, so setup should write bare cron commands.
+test_cron_no_flock_wrapper() {
+    setup_test_env
+    save_crontab
+
+    crontab -r 2>/dev/null || true
+
+    cat > "$TEST_CONFIG_DIR/config" << EOF
+REMOTE_HOST=""
+MOUNTDIR="$TEST_BACKUP_DIR"
+EOF
+    create_test_includes
+    create_test_excludes
+
+    sudo INSTALLHOME="$TEST_CONFIG_DIR" SCRIPTLOC="/tmp/rsyncshot-test" RSYNCSHOT_SKIP_MOUNT_CHECK=1 "$SCRIPT_PATH" setup >/dev/null 2>&1 || true
+
+    local crontab_content
+    crontab_content=$(crontab -l 2>/dev/null)
+
+    restore_crontab
+    teardown_test_env
+
+    assert_not_contains "$crontab_content" "flock" "cron entries should not wrap rsyncshot in flock (internal locking)" || return 1
+    assert_contains "$crontab_content" "rsyncshot" "cron should still contain rsyncshot entries" || return 1
+}
+
 # ------------------------------------------------------------------------------
 # Run tests
 # ------------------------------------------------------------------------------
@@ -129,6 +158,7 @@ run_cron_tests() {
     run_test "setup adds cron jobs" test_setup_adds_cron_jobs
     run_test "repeated setup doesn't duplicate entries" test_no_duplicate_cron_entries
     run_test "setup preserves existing cron jobs" test_preserves_existing_cron
+    run_test "cron entries have no flock wrapper" test_cron_no_flock_wrapper
 }
 
 # Run if executed directly
-- 
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