Fix CmdModifierTest#testMemoryLimitModified in cgroup2 environment. (#4375)

* Fix `CmdModifierTest#testMemoryLimitModified` in cgroup2 environment.

The `testMemoryLimitModified` was failing in cgroup2 environment because of the missing
`/sys/fs/cgroup/memory/memory.limit_in_bytes` file.

In the cgroup2 environment a new file should be checked instead -- `/sys/fs/cgroup/memory.max`.

This commit intrdocues changes to `cat` both files:

1. `/sys/fs/cgroup/memory/memory.limit_in_bytes` from the first version of cgroup
2. `/sys/fs/cgroup/memory.max` from the second

Similar issues:

1. oracle/docker-images#1939
2. apify/crawlee#693

* Use `docker info` to distinguish cgroup version

* Use `DockerClientFactory.instance().client()` instead of `memoryLimitedRedis.getDockerClient()`

Author: cac03

docs/examples/junit4/generic/src/test/java/generic/CmdModifierTest.java

@@ -1,12 +1,16 @@
 package generic;
 
+import com.github.dockerjava.api.DockerClient;
+import com.github.dockerjava.api.model.Info;
 import org.junit.Rule;
 import org.junit.Test;
+import org.testcontainers.DockerClientFactory;
 import org.testcontainers.containers.Container;
 import org.testcontainers.containers.GenericContainer;
 import org.testcontainers.utility.DockerImageName;
 
 import java.io.IOException;
+import java.util.Objects;
 
 import static org.junit.Assert.assertEquals;
 
@@ -39,7 +43,18 @@ public void testHostnameModified() throws IOException, InterruptedException {
 
     @Test
     public void testMemoryLimitModified() throws IOException, InterruptedException {
-        final Container.ExecResult execResult = memoryLimitedRedis.execInContainer("cat", "/sys/fs/cgroup/memory/memory.limit_in_bytes");
+        final Container.ExecResult execResult = memoryLimitedRedis.execInContainer("cat", getMemoryLimitFilePath());
         assertEquals(String.valueOf(memoryInBytes), execResult.getStdout().trim());
     }
+
+    private String getMemoryLimitFilePath() {
+        DockerClient dockerClient = DockerClientFactory.instance().client();
+        Info info = dockerClient.infoCmd().exec();
+        Object cgroupVersion = info.getRawValues().get("CgroupVersion");
+        boolean cgroup2 = Objects.equals("2", cgroupVersion);
+        if (cgroup2) {
+            return "/sys/fs/cgroup/memory.max";
+        }
+        return "/sys/fs/cgroup/memory/memory.limit_in_bytes";
+    }
 }