[Compatibility] Added LCS command #843

Vijay-Nirmal · 2024-11-30T20:16:20Z

Adding the LCS commands to garnet

Add LCS commands
Add Integration Test cases, ACL Test and Slot Verification Test
Add documentation

badrishc · 2024-12-05T03:13:04Z

Nicely done!!

TalZaccai

Great contribution! This is a gnarly one to implement 👍
A few initial comments... Let me know if you need any further guidance.

libs/server/API/IGarnetApi.cs

TalZaccai · 2024-12-06T01:09:14Z

libs/server/Resp/ArrayCommands.cs

+                }
+                else if (option.EqualsUpperCaseSpanIgnoringCase(CmdStrings.MINMATCHLEN))
+                {
+                    if (!parseState.TryGetInt(tokenIdx++, out var minLen) || minLen < 0)


Doesn't look like there's an issue with setting minLen to a non-positive number, it just doesn't do anything

It might be a miss from Redis side. Personally, I don't think we should inherit their flaws (Provided this is a flaw from Redis). Do you want to remove this check?

I agree with you 100%, I'm just wondering if this might break any existing clients that rely on this logic for some reason...

libs/server/Resp/ArrayCommands.cs

libs/server/Storage/Session/MainStore/MainStoreOps.cs

TalZaccai · 2024-12-06T01:21:09Z

libs/server/Storage/Session/MainStore/MainStoreOps.cs

+        {
+            var m = str1.Length;
+            var n = str2.Length;
+            var dp = new int[m + 1, n + 1];


As you're only using the current and previous row, it's sufficient to hold 2 1D arrays.
In general, it is not a good idea to use multidimensional arrays, see: https://stackoverflow.com/questions/597720/differences-between-a-multidimensional-array-and-an-array-of-arrays

I tried with 2D array first, but when using 2 1D arrays I am getting wrong results compared to Redis because it can't maintain the direction when backtracking. This implementation is inspired from https://www.geeksforgeeks.org/longest-common-subsequence-dp-4/. What I can do is that if we just need length (lenOnly option) then I can use 2D array, for others we need multidimensional arrays. I tried a lot with 2 1D arrays, I am pretty sure we can't use it when we need actual LCS back or its indices.

Also, modern .Net has comparable performance between multidimensional and array of arrays. Source: https://stackoverflow.com/a/63031036/7331395 (Will run it locally and test)

Verified the valkey code that also uses multi-dimensional array with regressive calls, I think that might be less performant than our implementation. The space complexity of LCS is O(m * n), unless we come up with a new algorithm to find LCS, I don't think we can have lower space complexity.

Link to the code?

Here: They have 1D array with m * n items using regressive calls to populate it

https://github.com/valkey-io/valkey/blob/f20d629dbe31d31eb82e360f9da4ef94ba9aabdc/src/t_string.c#L806-L849

Let's perf test this as Badrish suggested, we can compare with valkey for funsies

I tested by adding BDN benchmark, [m,n], [m][n], [m*n] doesn't make any noticeable difference

Any update on this?

libs/server/Storage/Session/MainStore/MainStoreOps.cs

Vijay-Nirmal · 2024-12-08T08:18:23Z

@TalZaccai Fixed review command with an open question

badrishc · 2024-12-08T20:50:53Z

Might be a good idea to perf test these commands, varying #threads:

time memtier_benchmark -s <host> -p<port> -Predis --hide-histogram --command="<insert command here>" -c 1 -t 1

another example:

memtier_benchmark -s 10.3.0.54 -p 12002 -c 50 -t 14 \ --command="hset __key__ f1 v1 f2 v2 f3 v3 f4 v4 f5 v5 f6 v6 f7 v7" \ --hide-histogram --test-time 180 --run-count 3

Vijay-Nirmal · 2024-12-14T16:58:04Z

I don't think I have proper setup to run memtier_benchmark, certainly I don't have proper setup to run benchmark to compare again Redis/Valkey. I am running Garnet in windows and running memtier_benchmark in WSL with mirrored networking. I have lot of run to run variants. If you see the below 2 benchmark (one is LCS and another is simple GET) then you can see looks like GET is slower than LCS, also the performance of GET is not consistent. If I rerun the test then I am getting different results

Data Load

MSET key1 ohmytext key2 mynewtext

LCS

nirmal@Nirmal-Omen:~$ memtier_benchmark -c 50 -t 14 --command="LCS key1 key2" --hide-histogram --test-time 120 --run-count 3
Writing results to stdout
[RUN #1] Preparing benchmark client...
[RUN #1] Launching threads now...
[RUN #1 100%, 120 secs]  0 threads:    14981678 ops,  114772 (avg:  124825) ops/sec, 4.93MB/sec (avg: 5.36MB/sec),  6.09 (avg:  5.60) msec latency

[RUN #2] Preparing benchmark client...
[RUN #2] Launching threads now...
[RUN #2 100%, 120 secs]  0 threads:    14388754 ops,  121305 (avg:  119886) ops/sec, 5.21MB/sec (avg: 5.14MB/sec),  5.76 (avg:  5.83) msec latency

[RUN #3] Preparing benchmark client...
[RUN #3] Launching threads now...
[RUN #3 100%, 120 secs]  0 threads:    15949146 ops,  140447 (avg:  132892) ops/sec, 6.03MB/sec (avg: 5.70MB/sec),  4.98 (avg:  5.26) msec latency

14        Threads
50        Connections per thread
120       Seconds


BEST RUN RESULTS
==================================================================================================
Type         Ops/sec    Avg. Latency     p50 Latency     p99 Latency   p99.9 Latency       KB/sec
--------------------------------------------------------------------------------------------------
Lcss       132892.98         5.26037         5.05500        11.51900        23.93500      5840.02
Totals     132892.98         5.26037         5.05500        11.51900        23.93500     11680.05


WORST RUN RESULTS
==================================================================================================
Type         Ops/sec    Avg. Latency     p50 Latency     p99 Latency   p99.9 Latency       KB/sec
--------------------------------------------------------------------------------------------------
Lcss       119889.36         5.83048         5.56700        12.92700        29.05500      5268.58
Totals     119889.36         5.83048         5.56700        12.92700        29.05500     10537.15


AGGREGATED AVERAGE RESULTS (3 runs)
==================================================================================================
Type         Ops/sec    Avg. Latency     p50 Latency     p99 Latency   p99.9 Latency       KB/sec
--------------------------------------------------------------------------------------------------
Lcss       126120.02         5.55366         5.31100        12.09500        26.11100      5542.38
Totals     126120.02         5.55366         5.31100        12.09500        26.11100     11084.77

GET

nirmal@Nirmal-Omen:~$ memtier_benchmark -c 50 -t 14 --command="GET key1" --hide-histogram --test-time 120 --run-count 3
Writing results to stdout
[RUN #1] Preparing benchmark client...
[RUN #1] Launching threads now...
[RUN #1 100%, 120 secs]  0 threads:    16169842 ops,  113057 (avg:  134725) ops/sec, 3.99MB/sec (avg: 4.75MB/sec),  6.18 (avg:  5.19) msec latency

[RUN #2] Preparing benchmark client...
[RUN #2] Launching threads now...
[RUN #2 100%, 120 secs]  0 threads:    10675355 ops,   76615 (avg:   88939) ops/sec, 2.70MB/sec (avg: 3.14MB/sec),  9.11 (avg:  7.86) msec latency

[RUN #3] Preparing benchmark client...
[RUN #3] Launching threads now...
[RUN #3 100%, 120 secs]  0 threads:    10032443 ops,   90045 (avg:   83583) ops/sec, 3.18MB/sec (avg: 2.95MB/sec),  7.77 (avg:  8.36) msec latency

14        Threads
50        Connections per thread
120       Seconds


BEST RUN RESULTS
==================================================================================================
Type         Ops/sec    Avg. Latency     p50 Latency     p99 Latency   p99.9 Latency       KB/sec
--------------------------------------------------------------------------------------------------
Gets       134726.19         5.18910         4.95900        10.30300        19.19900      4868.04
Totals     134726.19         5.18910         4.95900        10.30300        19.19900      9736.07


WORST RUN RESULTS
==================================================================================================
Type         Ops/sec    Avg. Latency     p50 Latency     p99 Latency   p99.9 Latency       KB/sec
--------------------------------------------------------------------------------------------------
Gets        83565.60         8.36044         8.15900        22.52700        46.07900      3019.46
Totals      83565.60         8.36044         8.15900        22.52700        46.07900      6038.92


AGGREGATED AVERAGE RESULTS (3 runs)
==================================================================================================
Type         Ops/sec    Avg. Latency     p50 Latency     p99 Latency   p99.9 Latency       KB/sec
--------------------------------------------------------------------------------------------------
Gets       102476.23         6.82447         6.49500        15.99900        39.67900      3702.75
Totals     102476.23         6.82447         6.49500        15.99900        39.67900      7405.51

@badrishc @TalZaccai Provided the inconsistency with my setup of memtier_benchmark, I am not going to use that for my performance testing of LCS command. I will use BDN.Benchmark of Garnet to perf test the LCS command and check I can do something to optimize.

Feel free to guide me in the right direction if I am doing something wrong with memtier_benchmark. I haven't used memtier_benchmark before, so most definitely I am doing something wrong.

Vijay-Nirmal added 6 commits December 1, 2024 01:45

Added LCS command

694db58

Format fix

2f6b1ea

Reverted CommandDocsUpdater.cs

bdcf91b

Fix cluster test

e31a46b

Fixed wrong change

b67d932

Moved to constant

a2514ce

TalZaccai self-requested a review December 3, 2024 19:26

TalZaccai requested changes Dec 6, 2024

View reviewed changes

microsoft deleted a comment from TalZaccai Dec 8, 2024

Vijay-Nirmal added 2 commits December 8, 2024 13:38

Review command fixes

f9cedf8

Merged latest

78c06c4

vazois and others added 3 commits December 9, 2024 09:08

Merge branch 'main' into new/LCS-command-support

939e281

Merged latest

0d31c3f

Fixed review comment

426c36b

Vijay-Nirmal added 2 commits December 14, 2024 22:30

Fixed test issue

ba4d216

Merged latest

437b4e3

Vijay-Nirmal requested a review from TalZaccai December 17, 2024 07:21

Merged latest

03ea9b8

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[Compatibility] Added LCS command #843

[Compatibility] Added LCS command #843

Vijay-Nirmal commented Nov 30, 2024

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[Compatibility] Added LCS command #843

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[Compatibility] Added LCS command #843

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