Re: [PATCH v2 00/11] More commit-graph/Bloom filter improvements

[Derrick Stolee <stolee@gmail.com>]

On 6/24/2020 8:38 PM, Junio C Hamano wrote:
> Derrick Stolee <stolee@gmail.com> writes:
> 
>> On 6/24/2020 7:11 PM, Junio C Hamano wrote:
>>> This does not seem to play well with what is in flight.  Tests seem
>>> to pass with topics up to es/config-hooks merged but not with this
>>> topic merged on top.
>>>
>>>     1b5d3d8260 Merge branch 'ds/commit-graph-bloom-updates' into seen
>>>     32169c595c Merge branch 'es/config-hooks' into seen
>>>     ...
>>>
>>> $ sh t4216-log-bloom.sh -i -v
>>>
>>> ends like so:
>>>
>>> ok 133 - Use Bloom filters if they exist in the latest but not all commit graphs in the chain.
>>>
>>> expecting success of 4216.134 'persist filter settings':
>>>         test_when_finished rm -rf .git/objects/info/commit-graph* &&
>>>         GIT_TRACE2_EVENT="$(pwd)/trace2.txt" git commit-graph write --reachable --changed-paths &&
>>>         grep "{\"hash_version\":1,\"num_hashes\":7,\"bits_per_entry\":10}" trace2.txt &&
>>>         cp .git/objects/info/commit-graph commit-graph-before &&
>>>         corrupt_graph $BASE_K_BYTE_OFFSET "\09" &&
>>>         corrupt_graph $BASE_LEN_BYTE_OFFSET "\0F" &&
>>>         cp .git/objects/info/commit-graph commit-graph-after &&
>>>         test_commit c18 A/corrupt &&
>>>         GIT_TRACE2_EVENT="$(pwd)/trace2.txt" git commit-graph write --reachable --changed-paths &&
>>>         grep "{\"hash_version\":1,\"num_hashes\":57,\"bits_per_entry\":70}" trace2.txt
>>>
>>> not ok 134 - persist filter settings
>>> # ...
>>>
>>> Thanks.
>>
>> Thanks for letting me know. I'll investigate carefully with the
>> rest of the 'seen' branch. This test is a bit fragile due to
>> computed values for which bytes to replace, so anything that
>> could have changed the length or order of chunks would lead to
>> a failure here.
>>
>> Sorry for the disruption.
> 
> Oh, not at all.  Thanks for helping
I'll squash the patch into my v3, but here it is now to make 'seen'
pass tests again.

The _real_ reason for the failure was that some changes in trace2
pushed the events out of the nesting limits. I also think it is a
good idea to make the test less brittle. Adding GIT_TEST_* variables
will also help anyone who wants to adjust the Bloom filter settings
for testing.

Question: Should these be GIT_BLOOM_SETTINGS_* instead of GIT_TEST_...?
I ask because this _could_ be a way to allow user customization,
without making it as public as a config option. Or, should I just do
the work and add config settings in this series?

Thanks,
-Stolee

-- >8 --
From 9245d31f0431eceec60f0b7a90900d2825787530 Mon Sep 17 00:00:00 2001
From: Derrick Stolee <dstolee@microsoft.com>
Date: Thu, 25 Jun 2020 09:19:13 -0400
Subject: [PATCH] fixup! commit-graph: persist existence of changed-paths

The previous version of this test was too fragile to subtle changes
in the commit-graph file size. This version now uses two environment
variables to customize the Bloom filter settings before rewriting
without those environment variables. This demonstrates that we
persist the settings correctly.

The issue with the 'seen' branch is due to es/trace-log-progress
adding trace2 regions in the progress indicators. This pushed the
trace2 data that the test was expecting outside the nesting limit.
Set GIT_TRACE2_EVENT_NESTING to ensure we still record those items.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 commit-graph.c       |  9 +++++++--
 t/t4216-log-bloom.sh | 34 +++++++++++-----------------------
 2 files changed, 18 insertions(+), 25 deletions(-)

diff --git a/commit-graph.c b/commit-graph.c
index 1de6800d74..026ec63d38 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -1576,10 +1576,15 @@ static int write_commit_graph_file(struct write_commit_graph_context *ctx)
 	int num_chunks = 3;
 	uint64_t chunk_offset;
 	struct object_id file_hash;
-	const struct bloom_filter_settings bloom_settings = DEFAULT_BLOOM_FILTER_SETTINGS;
+	struct bloom_filter_settings bloom_settings = DEFAULT_BLOOM_FILTER_SETTINGS;
 
-	if (!ctx->bloom_settings)
+	if (!ctx->bloom_settings) {
+		bloom_settings.bits_per_entry = git_env_ulong("GIT_TEST_BLOOM_SETTINGS_BITS_PER_ENTRY",
+							      bloom_settings.bits_per_entry);
+		bloom_settings.num_hashes = git_env_ulong("GIT_TEST_BLOOM_SETTINGS_NUM_HASHES",
+							  bloom_settings.num_hashes);
 		ctx->bloom_settings = &bloom_settings;
+	}
 
 	if (ctx->split) {
 		struct strbuf tmp_file = STRBUF_INIT;
diff --git a/t/t4216-log-bloom.sh b/t/t4216-log-bloom.sh
index 84f95972ca..d7dd717347 100755
--- a/t/t4216-log-bloom.sh
+++ b/t/t4216-log-bloom.sh
@@ -156,31 +156,19 @@ test_expect_success 'Use Bloom filters if they exist in the latest but not all c
 	test_bloom_filters_used_when_some_filters_are_missing "-- A/B"
 '
 
-BASE_BDAT_OFFSET=2240
-BASE_K_BYTE_OFFSET=$((BASE_BDAT_OFFSET + 10))
-BASE_LEN_BYTE_OFFSET=$((BASE_BDAT_OFFSET + 14))
-
-corrupt_graph() {
-	pos=$1
-	data="${2:-\0}"
-	grepstr=$3
-	orig_size=$(wc -c < .git/objects/info/commit-graph) &&
-	zero_pos=${4:-${orig_size}} &&
-	printf "$data" | dd of=".git/objects/info/commit-graph" bs=1 seek="$pos" conv=notrunc &&
-	dd of=".git/objects/info/commit-graph" bs=1 seek="$zero_pos" if=/dev/null
-}
-
 test_expect_success 'persist filter settings' '
 	test_when_finished rm -rf .git/objects/info/commit-graph* &&
-	GIT_TRACE2_EVENT="$(pwd)/trace2.txt" git commit-graph write --reachable --changed-paths &&
-	grep "{\"hash_version\":1,\"num_hashes\":7,\"bits_per_entry\":10}" trace2.txt &&
-	cp .git/objects/info/commit-graph commit-graph-before &&
-	corrupt_graph $BASE_K_BYTE_OFFSET "\09" &&
-	corrupt_graph $BASE_LEN_BYTE_OFFSET "\0F" &&
-	cp .git/objects/info/commit-graph commit-graph-after &&
-	test_commit c18 A/corrupt &&
-	GIT_TRACE2_EVENT="$(pwd)/trace2.txt" git commit-graph write --reachable --changed-paths &&
-	grep "{\"hash_version\":1,\"num_hashes\":57,\"bits_per_entry\":70}" trace2.txt
+	rm -rf .git/objects/info/commit-graph* &&
+	GIT_TRACE2_EVENT="$(pwd)/trace2.txt" \
+		GIT_TRACE2_EVENT_NESTING=5 \
+		GIT_TEST_BLOOM_SETTINGS_NUM_HASHES=9 \
+		GIT_TEST_BLOOM_SETTINGS_BITS_PER_ENTRY=15 \
+		git commit-graph write --reachable --changed-paths &&
+	grep "{\"hash_version\":1,\"num_hashes\":9,\"bits_per_entry\":15}" trace2.txt &&
+	GIT_TRACE2_EVENT="$(pwd)/trace2-auto.txt" \
+		GIT_TRACE2_EVENT_NESTING=5 \
+		git commit-graph write --reachable --changed-paths &&
+	grep "{\"hash_version\":1,\"num_hashes\":9,\"bits_per_entry\":15}" trace2-auto.txt
 '
 
 test_done
\ No newline at end of file
-- 
2.27.0