From fcd113cf7bf5587f8cac6d331ec1e427be0a830f Mon Sep 17 00:00:00 2001
From: "Richard W.M. Jones" <rjones@redhat.com>
Date: Thu, 29 Jul 2021 20:16:43 +0100
Subject: [PATCH] tests: cache: Test cache-on-read option really caches

By making use of the delay filter to add a penalty for hitting the
plugin we can check whether or not the cache-on-read option is
working.

(cherry picked from commit 3ae7aa533bb9322ab6dc6deecb687ded76634ab4)
---
 tests/Makefile.am                  |  2 +
 tests/test-cache-on-read-caches.sh | 87 ++++++++++++++++++++++++++++++
 tests/test-cache-on-read.sh        |  5 --
 3 files changed, 89 insertions(+), 5 deletions(-)
 create mode 100755 tests/test-cache-on-read-caches.sh

diff --git a/tests/Makefile.am b/tests/Makefile.am
index a038eabc..51ca913a 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -1373,6 +1373,7 @@ TESTS += \
 	test-cache.sh \
 	test-cache-block-size.sh \
 	test-cache-on-read.sh \
+	test-cache-on-read-caches.sh \
 	test-cache-max-size.sh \
 	test-cache-unaligned.sh \
 	$(NULL)
@@ -1380,6 +1381,7 @@ EXTRA_DIST += \
 	test-cache.sh \
 	test-cache-block-size.sh \
 	test-cache-on-read.sh \
+	test-cache-on-read-caches.sh \
 	test-cache-max-size.sh \
 	test-cache-unaligned.sh \
 	$(NULL)
diff --git a/tests/test-cache-on-read-caches.sh b/tests/test-cache-on-read-caches.sh
new file mode 100755
index 00000000..80b34159
--- /dev/null
+++ b/tests/test-cache-on-read-caches.sh
@@ -0,0 +1,87 @@
+#!/usr/bin/env bash
+# nbdkit
+# Copyright (C) 2018-2021 Red Hat Inc.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+# * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#
+# * Redistributions in binary form must reproduce the above copyright
+# notice, this list of conditions and the following disclaimer in the
+# documentation and/or other materials provided with the distribution.
+#
+# * Neither the name of Red Hat nor the names of its contributors may be
+# used to endorse or promote products derived from this software without
+# specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
+# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+# OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+
+source ./functions.sh
+set -e
+set -x
+
+requires_filter cache
+requires_filter delay
+requires_nbdsh_uri
+
+sock=$(mktemp -u /tmp/nbdkit-test-sock.XXXXXX)
+files="$sock cache-on-read-caches.pid"
+rm -f $files
+cleanup_fn rm -f $files
+
+# Run nbdkit with the cache filter, cache-on-read and a read delay.
+start_nbdkit -P cache-on-read-caches.pid -U $sock \
+             --filter=cache --filter=delay \
+             memory 64K cache-on-read=true rdelay=10
+
+nbdsh --connect "nbd+unix://?socket=$sock" \
+      -c '
+from time import time
+
+# First read should suffer a penalty.  Because we are reading
+# a single 64K block (same size as the cache block), we should
+# only suffer one penalty of approx. 10 seconds.
+st = time()
+zb = h.pread(65536, 0)
+et = time()
+el = et-st
+print("elapsed time: %g" % el)
+assert et-st >= 10
+assert zb == bytearray(65536)
+
+# Second read should not suffer a penalty.
+st = time()
+zb = h.pread(65536, 0)
+et = time()
+el = et-st
+print("elapsed time: %g" % el)
+assert el < 10
+assert zb == bytearray(65536)
+
+# Write something.
+buf = b"abcd" * 16384
+h.pwrite(buf, 0)
+
+# Reading back should be quick since it is stored in the overlay.
+st = time()
+buf2 = h.pread(65536, 0)
+et = time()
+el = et-st
+print("elapsed time: %g" % el)
+assert el < 10
+assert buf == buf2
+'
diff --git a/tests/test-cache-on-read.sh b/tests/test-cache-on-read.sh
index f8584dcd..85ca83d4 100755
--- a/tests/test-cache-on-read.sh
+++ b/tests/test-cache-on-read.sh
@@ -56,9 +56,4 @@ zero = h.pread(32768, 0)
 assert zero == bytearray(32768)
 buf2 = h.pread(65536, 32768)
 assert buf == buf2
-
-# XXX Suggestion to improve this test: Use the delay filter below the
-# cache filter, and time reads to prove that the second read is faster
-# because it is not going through the delay filter and plugin.
-# XXX second h.pread here ...
 '
-- 
2.31.1