[GitHub] [cassandra] adelapena commented on a diff in pull request #1546: CASSANDRA-17150 trunk: Guardrails for disk usage

[GitBox <gi...@apache.org>]

adelapena commented on code in PR #1546:
URL: https://github.com/apache/cassandra/pull/1546#discussion_r841663000


##########
src/java/org/apache/cassandra/service/disk/usage/DiskUsageMonitor.java:
##########
@@ -0,0 +1,174 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.cassandra.service.disk.usage;
+
+import java.math.BigDecimal;
+import java.util.Set;
+import java.util.concurrent.TimeUnit;
+import java.util.function.Consumer;
+import java.util.function.Supplier;
+
+import com.google.common.annotations.VisibleForTesting;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import org.apache.cassandra.concurrent.ScheduledExecutors;
+import org.apache.cassandra.config.Config;
+import org.apache.cassandra.db.ColumnFamilyStore;
+import org.apache.cassandra.db.Directories;
+import org.apache.cassandra.db.Memtable;
+import org.apache.cassandra.db.guardrails.Guardrails;
+import org.apache.cassandra.db.guardrails.GuardrailsConfig;
+import org.apache.cassandra.io.util.FileUtils;
+
+/**
+ * Schedule periodic task to monitor local disk usage and notify {@link DiskUsageBroadcaster} if local state changed.
+ */
+public class DiskUsageMonitor
+{
+    private static final Logger logger = LoggerFactory.getLogger(DiskUsageMonitor.class);
+
+    private static final int MONITOR_INTERVAL_MS = Integer.parseInt(System.getProperty(Config.PROPERTY_PREFIX + "disk_usage.monitor_interval_ms",
+                                                                                       Integer.toString(30 * 1000)));
+
+    public static DiskUsageMonitor instance = new DiskUsageMonitor();
+
+    private final GuardrailsConfig config = Guardrails.CONFIG_PROVIDER.getOrCreate(null);
+    private final Supplier<Set<Directories.DataDirectory>> dataDirectoriesSupplier;
+
+    private volatile DiskUsageState localState = DiskUsageState.NOT_AVAILABLE;
+
+    @VisibleForTesting
+    public DiskUsageMonitor()
+    {
+        this.dataDirectoriesSupplier = Directories.dataDirectories::getAllDirectories;
+    }
+
+    @VisibleForTesting
+    public DiskUsageMonitor(Supplier<Set<Directories.DataDirectory>> dataDirectoriesSupplier)
+    {
+        this.dataDirectoriesSupplier = dataDirectoriesSupplier;
+    }
+
+    /**
+     * Start monitoring local disk usage and call notifier when local disk usage state changed.
+     */
+    public void start(Consumer<DiskUsageState> notifier)
+    {
+        // start the scheduler regardless guardrail is enabled, so we can enable it later without a restart
+        ScheduledExecutors.scheduledTasks.scheduleAtFixedRate(() -> {
+
+            if (!Guardrails.localDiskUsage.enabled(null))

Review Comment:
   I've added that utility method.



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