v.util: make launch_tool more robust, when multiple v -b js file.v …

…commands are run at the same time (all trying to recompile the JS backend program) (#20631)

.cirrus.yml

@@ -2,7 +2,7 @@ env:
   LANG: en_US.UTF-8
 
 freebsd_instance:
-  image_family: freebsd-13-0
+  image_family: freebsd-13-2
 
 ## Note: all tasks should end with _script: here, otherwise they will not be picked up!
 freebsd_task:

vlib/os/filelock/lib.v

@@ -1,5 +1,7 @@
 module filelock
 
+import time
+
 pub struct FileLock {
 	name string
 mut:
@@ -12,3 +14,24 @@ pub fn new(fileName string) FileLock {
 		fd: -1
 	}
 }
+
+pub fn (mut l FileLock) wait_acquire(timeout time.Duration) bool {
+	fin := time.now().add(timeout)
+	for time.now() < fin {
+		if l.try_acquire() {
+			return true
+		}
+		time.sleep(1 * time.millisecond)
+	}
+	return false
+}
+
+pub fn (mut l FileLock) release() bool {
+	if l.fd != -1 {
+		unsafe {
+			l.unlink()
+		}
+		return true
+	}
+	return false
+}

vlib/os/filelock/lib_nix.c.v

@@ -1,7 +1,5 @@
 module filelock
 
-import time
-
 #include <sys/file.h>
 
 fn C.unlink(&char) int
@@ -32,27 +30,6 @@ pub fn (mut l FileLock) acquire() ! {
 	l.fd = fd
 }
 
-pub fn (mut l FileLock) release() bool {
-	if l.fd != -1 {
-		unsafe {
-			l.unlink()
-		}
-		return true
-	}
-	return false
-}
-
-pub fn (mut l FileLock) wait_acquire(s int) bool {
-	fin := time.now().add(s)
-	for time.now() < fin {
-		if l.try_acquire() {
-			return true
-		}
-		C.usleep(1000)
-	}
-	return false
-}
-
 fn open_lockfile(f string) int {
 	mut fd := C.open(&char(f.str), C.O_CREAT, 0o644)
 	if fd == -1 {

vlib/os/filelock/lib_windows.c.v

@@ -1,7 +1,5 @@
 module filelock
 
-import time
-
 fn C.DeleteFileW(&u16) bool
 fn C.CreateFileW(&u16, u32, u32, voidptr, u32, u32, voidptr) voidptr
 fn C.CloseHandle(voidptr) bool
@@ -26,28 +24,6 @@ pub fn (mut l FileLock) acquire() ! {
 	l.fd = fd
 }
 
-pub fn (mut l FileLock) release() bool {
-	if l.fd != -1 {
-		C.CloseHandle(l.fd)
-		l.fd = -1
-		t_wide := l.name.to_wide()
-		C.DeleteFileW(t_wide)
-		return true
-	}
-	return false
-}
-
-pub fn (mut l FileLock) wait_acquire(s int) bool {
-	fin := time.now().add(s)
-	for time.now() < fin {
-		if l.try_acquire() {
-			return true
-		}
-		time.sleep(1 * time.millisecond)
-	}
-	return false
-}
-
 fn open(f string) voidptr {
 	f_wide := f.to_wide()
 	// locking it

vlib/v/util/util.v

@@ -4,6 +4,8 @@
 module util
 
 import os
+import os.filelock
+import term
 import rand
 import time
 import v.pref
@@ -177,27 +179,48 @@ pub fn launch_tool(is_verbose bool, tool_name string, args []string) {
 		}
 
 		current_work_dir := os.getwd()
-		// The goal of the random sleep intervals below, is to reduce the chance of a thundering herd, on `v test` with VJOBS>10,
-		// when each compiled _test.c.v file could also need a recompilation of the js_builder in cmd/tools/builders/ .
-		// TODO: use the os.filelock's API for inter process coordination instead.
-		time.sleep((5 + rand.intn(15) or { 0 }) * time.millisecond)
-		tool_recompile_retry_max_count := 7
-		for i in 0 .. tool_recompile_retry_max_count {
-			// ensure a stable and known working folder, when compiling V's tools, to avoid module lookup problems:
-			os.chdir(vroot) or {}
-			tool_compilation := os.execute(compilation_command)
-			os.chdir(current_work_dir) or {}
-			if tool_compilation.exit_code == 0 {
-				break
-			} else {
-				if i == tool_recompile_retry_max_count - 1 {
-					eprintln('cannot compile `${tool_source}`: ${tool_compilation.exit_code}\n${tool_compilation.output}')
-					exit(1)
+		tlog('recompiling ${tool_source}')
+		lockfile := tool_exe + '.lock'
+		tlog('lockfile: ${lockfile}')
+		mut l := filelock.new(lockfile)
+		if l.try_acquire() {
+			tlog('lockfile acquired')
+			tool_recompile_retry_max_count := 7
+			for i in 0 .. tool_recompile_retry_max_count {
+				tlog('looping i: ${i} / ${tool_recompile_retry_max_count}')
+				// ensure a stable and known working folder, when compiling V's tools, to avoid module lookup problems:
+				os.chdir(vroot) or {}
+				tool_compilation := os.execute(compilation_command)
+				os.chdir(current_work_dir) or {}
+				tlog('tool_compilation.exit_code: ${tool_compilation.exit_code}')
+				if tool_compilation.exit_code == 0 {
+					break
+				} else {
+					if i == tool_recompile_retry_max_count - 1 {
+						eprintln('cannot compile `${tool_source}`: ${tool_compilation.exit_code}\n${tool_compilation.output}')
+						l.release()
+						exit(1)
+					}
 				}
+				time.sleep((20 + rand.intn(40) or { 0 }) * time.millisecond)
+			}
+			tlog('lockfile releasing')
+			l.release()
+			tlog('lockfile released')
+		} else {
+			tlog('another process got the lock')
+			// wait till the other V tool recompilation process finished:
+			if l.wait_acquire(10 * time.second) {
+				tlog('the other process finished')
+				l.release()
+			} else {
+				tlog('timeout...')
 			}
-			time.sleep((20 + rand.intn(40) or { 0 }) * time.millisecond)
+			time.sleep((50 + rand.intn(40) or { 0 }) * time.millisecond)
+			tlog('result of the other process compiling ${tool_exe}: ${os.exists(tool_exe)}')
 		}
 	}
+	tlog('executing: ${tool_exe} with ${tool_args}')
 	$if windows {
 		cmd_system('${os.quoted_path(tool_exe)} ${tool_args}')
 	} $else $if js {
@@ -212,11 +235,17 @@ pub fn launch_tool(is_verbose bool, tool_name string, args []string) {
 	exit(2)
 }
 
+@[if trace_launch_tool ?]
+fn tlog(s string) {
+	ts := time.now().format_ss_micro()
+	eprintln('${term.yellow(ts)} ${term.gray(s)}')
+}
+
 @[noreturn]
 fn cmd_system(cmd string) {
 	res := os.system(cmd)
 	if res != 0 {
-		eprintln('> error ${res}, while executing: ${cmd}')
+		tlog('> error ${res}, while executing: ${cmd}')
 	}
 	exit(res)
 }
@@ -485,7 +514,7 @@ pub fn prepare_tool_when_needed(source_name string) {
 	stool := os.join_path(vroot, 'cmd', 'tools', source_name)
 	tool_name, tool_exe := tool_source2name_and_exe(stool)
 	if should_recompile_tool(vexe, stool, tool_name, tool_exe) {
-		time.sleep(1001 * time.millisecond) // TODO: remove this when we can get mtime with a better resolution
+		time.sleep((1001 + rand.intn(20) or { 0 }) * time.millisecond) // TODO: remove this when we can get mtime with a better resolution
 		recompile_file(vexe, stool)
 	}
 }