From ecb97c9a61e81465fa748b4324da0ddd12872fdc Mon Sep 17 00:00:00 2001
From: Sergey Matveev <stargrave@stargrave.org>
Date: Thu, 28 Jan 2021 21:14:00 +0300
Subject: [PATCH] Reduce number of opened files while waiting for job slot

---
 doc/news.texi |  3 +++
 run.go        | 46 +++++++++++++++++++++++++++++++++-------------
 2 files changed, 36 insertions(+), 13 deletions(-)

diff --git a/doc/news.texi b/doc/news.texi
index 7f67ba9..56b537d 100644
--- a/doc/news.texi
+++ b/doc/news.texi
@@ -8,6 +8,9 @@
     Dependency files @file{.dep} extension changed to @file{.rec}, to
     reflect its recfile format nature and editors file type better
     determination.
+@item
+    Reduce number of file descriptors kept open (1 instead of 4) while
+    waiting for job slot token.
 @end itemize
 
 @anchor{Release 1.1.0}
diff --git a/run.go b/run.go
index 25e8bac..af17eaa 100644
--- a/run.go
+++ b/run.go
@@ -246,6 +246,7 @@ func runScript(tgtOrig string, errs chan error, traced bool) error {
 		lockRelease()
 		return TgtErr{tgtOrig, err}
 	}
+	fdDepPath := fdDep.Name()
 	cleanup := func() {
 		lockRelease()
 		fdDep.Close()
@@ -292,6 +293,7 @@ func runScript(tgtOrig string, errs chan error, traced bool) error {
 		cleanup()
 		return TgtErr{tgtOrig, err}
 	}
+	fdDep.Close()
 	trace(CWait, "%s", runErr.Name())
 
 	// Prepare command line
@@ -316,7 +318,9 @@ func runScript(tgtOrig string, errs chan error, traced bool) error {
 		cleanup()
 		return TgtErr{tgtOrig, err}
 	}
-	tmpPath := fdStdout.Name() + ".3" // and for $3
+	stdoutPath := fdStdout.Name()
+	fdStdout.Close()
+	tmpPath := stdoutPath + ".3" // and for $3
 	tmpPathRel, err := filepath.Rel(cwd, tmpPath)
 	if err != nil {
 		panic(err)
@@ -330,7 +334,6 @@ func runScript(tgtOrig string, errs chan error, traced bool) error {
 
 	cmd := exec.Command(cmdName, args...)
 	cmd.Dir = cwd
-	cmd.Stdout = fdStdout
 	// cmd.Stdin reads from /dev/null by default
 	cmd.Env = append(os.Environ(), fmt.Sprintf("%s=%d", EnvLevel, Level+1))
 	cmd.Env = append(cmd.Env, fmt.Sprintf("%s=%s", EnvDirPrefix, dirPrefix))
@@ -342,10 +345,6 @@ func runScript(tgtOrig string, errs chan error, traced bool) error {
 	))
 
 	fdNum := 0
-	cmd.ExtraFiles = append(cmd.ExtraFiles, fdDep)
-	cmd.Env = append(cmd.Env, fmt.Sprintf("%s=%d", EnvDepFd, 3+fdNum))
-	fdNum++
-
 	if FdStatus == nil {
 		cmd.Env = append(cmd.Env, fmt.Sprintf("%s=NO", EnvStatusFd))
 	} else {
@@ -367,10 +366,6 @@ func runScript(tgtOrig string, errs chan error, traced bool) error {
 	}
 
 	// Preparing stderr
-	stderr, err := cmd.StderrPipe()
-	if err != nil {
-		panic(err)
-	}
 	var fdStderr *os.File
 	if StderrKeep {
 		fdStderr, err = os.OpenFile(
@@ -396,6 +391,26 @@ func runScript(tgtOrig string, errs chan error, traced bool) error {
 		if FdStatus != nil {
 			FdStatus.Write([]byte{StatusRun})
 		}
+
+		started := time.Now()
+		runErr.Started = &started
+		fdStdout, err = os.OpenFile(stdoutPath, os.O_RDWR, os.FileMode(0666))
+		if err != nil {
+			runErr.Err = err
+			errs <- runErr
+			return
+		}
+		cmd.Stdout = fdStdout
+		fdDep, err = os.OpenFile(fdDepPath, os.O_WRONLY|os.O_APPEND, os.FileMode(0666))
+		if err != nil {
+			runErr.Err = err
+			errs <- runErr
+			return
+		}
+		cmd.ExtraFiles = append(cmd.ExtraFiles, fdDep)
+		cmd.Env = append(cmd.Env, fmt.Sprintf("%s=%d", EnvDepFd, 3+fdNum))
+		fdNum++
+
 		defer func() {
 			jsRelease(shCtx)
 			lockRelease()
@@ -413,9 +428,14 @@ func runScript(tgtOrig string, errs chan error, traced bool) error {
 			}
 			Jobs.Done()
 		}()
-		started := time.Now()
-		runErr.Started = &started
-		err := cmd.Start()
+		stderr, err := cmd.StderrPipe()
+		if err != nil {
+			runErr.Err = err
+			errs <- runErr
+			return
+		}
+		started = time.Now()
+		err = cmd.Start()
 		if err != nil {
 			runErr.Err = err
 			errs <- runErr
-- 
2.44.0