Add the log_checks parameter to the reader constructor.

src/tests/get.vtc

@@ -56,7 +56,8 @@ varnish v1 -vcl {
 	backend b { .host = "${bad_ip}"; }
 
 	sub vcl_init {
-		new rdr = file.reader("${tmpdir}/file", ttl=0.1s);
+		new rdr = file.reader("${tmpdir}/file", ttl=0.1s,
+		                      log_checks=true);
 	}
 
 	sub vcl_recv {
@@ -85,6 +86,12 @@ client c1 {
 	expect resp.http.Get == "quux baz bar foo"
 } -run
 
+logexpect l1 -v v1 -d 1 -g raw -q "Debug" {
+	expect * * Debug	{^vmod file: rdr: check for \S+ running at}
+	expect * * Debug	{^vmod file: rdr: updating \S+ at}
+	expect * * Debug	{^vmod file: rdr: check for \S+ finished successfully at}
+} -run
+
 shell {rm -f ${tmpdir}/file}
 delay .1
 

src/vmod_file.c

@@ -67,6 +67,7 @@ struct file_info {
 	size_t		len;
 	dev_t		dev;
 	ino_t		ino;
+	VCL_BOOL	log_checks;
 };
 
 #define RDR_INITIALIZED	(1 << 0)
@@ -95,6 +96,7 @@ check(union sigval val)
 	struct stat st;
 	int fd;
 	void *addr;
+	char timbuf[VTIM_FORMAT_SIZE];
 
 	CAST_OBJ_NOTNULL(rdr, val.sival_ptr, FILE_READER_MAGIC);
 	CHECK_OBJ_NOTNULL(rdr->info, FILE_INFO_MAGIC);
@@ -103,6 +105,12 @@ check(union sigval val)
 	AN(rdr->errbuf);
 	AN(info->path);
 
+	if (info->log_checks) {
+		VTIM_format(VTIM_real(), timbuf);
+		VSL(SLT_Debug, 0, "vmod file: %s: check for %s running at %s",
+		    rdr->vcl_name, info->path, timbuf);
+	}
+
 	AZ(pthread_rwlock_wrlock(&rdr->lock));
 
 	errno = 0;
@@ -130,6 +138,12 @@ check(union sigval val)
 		goto out;
 	}
 
+	if (info->log_checks) {
+		VTIM_format(VTIM_real(), timbuf);
+		VSL(SLT_Debug, 0, "vmod file: %s: updating %s at %s",
+		    rdr->vcl_name, info->path, timbuf);
+	}
+
 	if (rdr->flags & RDR_MAPPED) {
 		AN(rdr->addr);
 		if (munmap(rdr->addr, info->len) != 0) {
@@ -186,13 +200,21 @@ check(union sigval val)
 
  out:
 	AZ(pthread_rwlock_unlock(&rdr->lock));
+
+	if (info->log_checks) {
+		VTIM_format(VTIM_real(), timbuf);
+		VSL(SLT_Debug, 0,
+		    "vmod file: %s: check for %s finished successfully at %s",
+		    rdr->vcl_name, info->path, timbuf);
+	}
 	return;
 }
 
 VCL_VOID
 vmod_reader__init(VRT_CTX, struct VPFX(file_reader) **rdrp,
 		  const char *vcl_name, struct vmod_priv *priv,
-		  VCL_STRING name, VCL_STRING path, VCL_DURATION ttl)
+		  VCL_STRING name, VCL_STRING path, VCL_DURATION ttl,
+		  VCL_BOOL log_checks)
 {
 	struct VPFX(file_reader) *rdr;
 	struct file_info *info;
@@ -233,6 +255,7 @@ vmod_reader__init(VRT_CTX, struct VPFX(file_reader) **rdrp,
 
 	rdr->info = info;
 	rdr->vcl_name = strdup(vcl_name);
+	info->log_checks = log_checks;
 
 	if (*name == '/')
 		info->path = strdup(name);

src/vmod_file.vcc

@@ -36,7 +36,7 @@ XXX ...
 
 $Object reader(PRIV_VCL, STRING name,
  STRING path="/usr/local/etc/varnish:/usr/local/share/varnish/vcl:/usr/etc/varnish:/usr/share/varnish/vcl",
-               DURATION ttl=120)
+               DURATION ttl=120, BOOL log_checks=0)
 
 XXX ...