High CPU overhead on LettuceArgSplitter

[123liuziming]

Describe the bug

package com.alibaba;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public final class A {
    public static void main(String[] args) {
        long stime = System.nanoTime();
        for (int i = 0; i < 100; ++i) {
            System.out.println(splitArgs("key<XGJT:FLIGHT_DEMAND_FLOWDETAILFD_SUB113759198792552> 1800 value<WATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATD{jUiAPb1rz8gj9oGQL}cBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuB{l}InORGXM>"));
        }
        long etime = System.nanoTime();
        System.out.printf("Executing split args for %d ns.", (etime - stime));
    }
}

We can use the sample above to do a simple benchmark, if we add an additional > character in the args, for example:

package com.alibaba;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public final class A {
    public static void main(String[] args) {
        long stime = System.nanoTime();
        for (int i = 0; i < 100; ++i) {
            System.out.println(splitArgs("key<XGJT:FLIGHT_DEMAND_FLOWDETAILFD_SUB113759198792552> 1800 value<WATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBl>InORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATD{jUiAPb1rz8gj9oGQL}cBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuB{l}InORGXM>"));
        }
        long etime = System.nanoTime();
        System.out.printf("Executing split args for %d ns.", (etime - stime));
    }
}

Due to the mismatch of < and >, the performance of regex is significantly degraded due to backtracking.

Steps to reproduce

JFR file：

lettuce-1744556713-arms.jfr.zip

Expected behavior

Normal CPU overhead while splitting args.

Actual behavior

High CPU overhead while splitting args.

Javaagent or library instrumentation version

main

Environment

JDK:
OS:

Additional context

No response

[laurit]

Due to the mismatch of < and >, the performance of regex is significantly degraded due to backtracking.

Is that still a valid redis query? Is this a synthetic sample on how to make the regex slow or based on some real world observation?

[123liuziming]

Due to the mismatch of < and >, the performance of regex is significantly degraded due to backtracking.

Is that still a valid redis query? Is this a synthetic sample on how to make the regex slow or based on some real world observation?

It is a valid redis query based on the real world observation, you can do the query using lettuce like:

LettuceApplication.syncCommands.setex("XGJT:FLIGHT_DEMAND_FLOWDETAILFD_SUB113759198792552", 1800, "WATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBl>InORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuBlInORGXMWATD{jUiAPb1rz8gj9oGQL}cBBAGkhT4NYNj9CiA6UMuBlInORGXMWATDjUiAPb1rz8gj9oGQLcBBAGkhT4NYNj9CiA6UMuB{l}InORGXM");

We use JMH to benchmark the command above and generate the JFR file above.

[laurit]

@123liuziming can you test whether Pattern.compile("((key|value)<(?<wrapped>.*?)>|(?<plain>\\S++))(?:\\s+|$)"); works better?

[laurit]

Note that instrumentation for lettuce 6.0+ does not use this method.

[123liuziming]

Pattern.compile("((key|value)<(?.*?)>|(?\S++))(?:\s+|$)");

It works far more better, 100 times faster than before.

// 1701465167 ns # original regex
// 12900417 ns # current regex