Add reader.next_check().

README.rst

@@ -117,6 +117,15 @@ recently checked.
 
 XXX ...
 
+.. _xreader.next_check():
+
+DURATION xreader.next_check()
+-----------------------------
+
+Returns the time remaining until the next check will be performed.
+
+XXX ...
+
 .. _file.version():
 
 STRING version()

src/tests/info.vtc

@@ -16,6 +16,7 @@ varnish v1 -vcl {
 		set req.http.Size = rdr.size();
 		set req.http.Mtime = rdr.mtime();
 		set req.http.Delta-Mtime = now - rdr.mtime();
+		set req.http.Next-Check = rdr.next_check();
 		return (synth(200));
 	}
 
@@ -23,6 +24,7 @@ varnish v1 -vcl {
 		set resp.http.Size = req.http.Size;
 		set resp.http.Mtime = req.http.Mtime;
 		set resp.http.Delta-Mtime = req.http.Delta-Mtime;
+		set resp.http.Next-Check = req.http.Next-Check;
 		return (deliver);
 	}
 } -start
@@ -36,6 +38,8 @@ client c1 {
 	expect resp.http.Mtime ~ "GMT$"
 	expect resp.http.Delta-Mtime > 0
 	expect resp.http.Delta-Mtime < 1
+	expect resp.http.Next-Check >= 0
+	expect resp.http.Next-Check <= 0.1
 } -run
 
 shell {echo -n "foo" > ${tmpdir}/sz}
@@ -49,6 +53,8 @@ client c1 {
 	expect resp.http.Mtime ~ "GMT$"
 	expect resp.http.Delta-Mtime > 0
 	expect resp.http.Delta-Mtime < 1
+	expect resp.http.Next-Check >= 0
+	expect resp.http.Next-Check <= 0.1
 } -run
 
 shell {rm -f ${tmpdir}/sz}
@@ -100,3 +106,36 @@ logexpect l1 -v v1 -d 0 -g vxid -q "VCL_Error" {
 client c1 -run
 
 logexpect l1 -wait
+
+shell {touch ${tmpdir}/nxtchk}
+
+varnish v1 -vcl {
+	import ${vmod_file};
+	backend b { .host = "${bad_ip}"; }
+
+	sub vcl_init {
+		new rdr = file.reader("${tmpdir}/nxtchk", ttl=0.1s);
+	}
+
+	sub vcl_recv {
+		set req.http.Next-Check = rdr.next_check();
+		return (synth(200));
+	}
+
+	sub vcl_synth {
+		set resp.http.Next-Check = req.http.Next-Check;
+		return (deliver);
+	}
+}
+
+shell {rm -f ${tmpdir}/nxtchk}
+delay .1
+
+# next_check() is not affected by errors.
+client c1 {
+	txreq
+	rxresp
+	expect resp.status == 200
+	expect resp.http.Next-Check >= 0
+	expect resp.http.Next-Check <= 0.1
+} -run

src/vmod_file.c

@@ -560,6 +560,23 @@ vmod_reader_mtime(VRT_CTX, struct VPFX(file_reader) *rdr)
 	return (secs + nsecs * 1e-9);
 }
 
+VCL_DURATION
+vmod_reader_next_check(VRT_CTX, struct VPFX(file_reader) *rdr)
+{
+	struct itimerspec t;
+
+	CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
+	CHECK_OBJ_NOTNULL(rdr, FILE_READER_MAGIC);
+
+	errno = 0;
+	if (timer_gettime(rdr->timerid, &t) != 0) {
+		VRT_fail(ctx, "%s.next_check(): timer read failed: %s",
+			rdr->vcl_name, vstrerror(errno));
+		return (0.);
+	}
+	return (t.it_value.tv_sec + 1e-9 * t.it_value.tv_nsec);
+}
+
 VCL_STRING
 vmod_version(VRT_CTX)
 {

src/vmod_file.vcc

@@ -85,6 +85,12 @@ recently checked.
 
 XXX ...
 
+$Method DURATION .next_check()
+
+Returns the time remaining until the next check will be performed.
+
+XXX ...
+
 $Function STRING version()
 
 Return the version string for this VMOD.