1 files changed, 111 insertions, 0 deletions
diff --git a/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/container/Cgroup.java b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/container/Cgroup.java
new file mode 100644
index 00000000000..3efadda183b
--- /dev/null
+++ b/node-admin/src/main/java/com/yahoo/vespa/hosted/node/admin/container/Cgroup.java
@@ -0,0 +1,111 @@
+// Copyright Verizon Media. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+//
+package com.yahoo.vespa.hosted.node.admin.container;
+
+import com.yahoo.vespa.hosted.node.admin.nodeagent.NodeAgentContext;
+import com.yahoo.vespa.hosted.node.admin.task.util.file.UnixPath;
+
+import java.io.IOException;
+import java.io.UncheckedIOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.FileSystem;
+import java.nio.file.Files;
+import java.nio.file.NoSuchFileException;
+import java.nio.file.Path;
+import java.util.OptionalInt;
+import java.util.logging.Logger;
+
+/**
+ * Read and write interface to the v1 cgroup of a podman container.
+ * See <a href="https://man7.org/linux/man-pages/man7/cgroups.7.html">cgroups(7)</a> for background.
+ *
+ * @author hakon
+ */
+public class Cgroup {
+
+    private static final Logger logger = Logger.getLogger(Cgroup.class.getName());
+
+    private final FileSystem fileSystem;
+    private final ContainerId containerId;
+
+    public Cgroup(FileSystem fileSystem, ContainerId containerId) {
+        this.fileSystem = fileSystem;
+        this.containerId = containerId;
+    }
+
+    public OptionalInt readCpuQuota() {
+        return readCgroupsCpuInt(cfsQuotaPath());
+    }
+
+    public OptionalInt readCpuPeriod() {
+        return readCgroupsCpuInt(cfsPeriodPath());
+    }
+
+    public OptionalInt readCpuShares() {
+        return readCgroupsCpuInt(sharesPath());
+    }
+
+    public boolean updateCpuQuota(NodeAgentContext context, int cpuQuotaUs) {
+        return writeCgroupsCpuInt(context, cfsQuotaPath(), cpuQuotaUs);
+    }
+
+    public boolean updateCpuPeriod(NodeAgentContext context, int periodUs) {
+        return writeCgroupsCpuInt(context, cfsPeriodPath(), periodUs);
+    }
+
+    public boolean updateCpuShares(NodeAgentContext context, int shares) {
+        return writeCgroupsCpuInt(context, sharesPath(), shares);
+    }
+
+    /** Returns the path to the podman container's scope directory for the cpuacct controller. */
+    public Path cpuacctPath() {
+        return fileSystem.getPath("/sys/fs/cgroup/cpuacct/machine.slice/libpod-" + containerId + ".scope");
+    }
+
+    /** Returns the path to the podman container's scope directory for the cpu controller. */
+    public Path cpuPath() {
+        return fileSystem.getPath("/sys/fs/cgroup/cpu/machine.slice/libpod-" + containerId + ".scope");
+    }
+
+    /** Returns the path to the podman container's scope directory for the memory controller. */
+    public Path memoryPath() {
+        return fileSystem.getPath("/sys/fs/cgroup/memory/machine.slice/libpod-" + containerId + ".scope");
+    }
+
+    private UnixPath cfsQuotaPath() {
+        return new UnixPath(cpuPath().resolve("cpu.cfs_quota_us"));
+    }
+
+    private UnixPath cfsPeriodPath() {
+        return new UnixPath(cpuPath().resolve("cpu.cfs_period_us"));
+    }
+
+    private UnixPath sharesPath() {
+        return new UnixPath(cpuPath().resolve("cpu.shares"));
+    }
+
+    private OptionalInt readCgroupsCpuInt(UnixPath unixPath) {
+        final byte[] currentContentBytes;
+        try {
+            currentContentBytes = Files.readAllBytes(unixPath.toPath());
+        } catch (NoSuchFileException e) {
+            return OptionalInt.empty();
+        } catch (IOException e) {
+            throw new UncheckedIOException(e);
+        }
+
+        String currentContent = new String(currentContentBytes, StandardCharsets.UTF_8).strip();
+        return OptionalInt.of(Integer.parseInt(currentContent));
+    }
+
+    private boolean writeCgroupsCpuInt(NodeAgentContext context, UnixPath unixPath, int value) {
+        int currentValue = readCgroupsCpuInt(unixPath).orElseThrow();
+        if (currentValue == value) {
+            return false;
+        }
+
+        context.recordSystemModification(logger, "Updating " + unixPath + " from " + currentValue + " to " + value);
+        unixPath.writeUtf8File(Integer.toString(value));
+        return true;
+    }
+}