[GitHub] [jackrabbit-oak] stefan-egli commented on a change in pull request #241: OAK-9139: Log message on frozen node lookup by identifier

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stefan-egli commented on a change in pull request #241:
URL: https://github.com/apache/jackrabbit-oak/pull/241#discussion_r454268096



##########
File path: oak-jcr/src/main/java/org/apache/jackrabbit/oak/jcr/version/FrozenNodeLogger.java
##########
@@ -0,0 +1,95 @@
+/*
+ * 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.jackrabbit.oak.jcr.version;
+
+import java.io.Closeable;
+
+import org.apache.jackrabbit.oak.api.PropertyState;
+import org.apache.jackrabbit.oak.api.Tree;
+import org.apache.jackrabbit.oak.api.Type;
+import org.apache.jackrabbit.oak.spi.toggle.Feature;
+import org.apache.jackrabbit.oak.spi.whiteboard.Whiteboard;
+import org.apache.jackrabbit.oak.stats.Clock;
+import org.jetbrains.annotations.NotNull;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+import static org.apache.jackrabbit.JcrConstants.JCR_PRIMARYTYPE;
+import static org.apache.jackrabbit.JcrConstants.NT_FROZENNODE;
+import static org.apache.jackrabbit.oak.spi.toggle.Feature.newFeature;
+
+/**
+ * Logger facility for frozen node lookups by identifier. Calls to
+ * {@link #lookupById(Tree)} first check the feature toggle
+ * {@code oak.logFrozenNodeLookup} and then whether the given {@code Tree} is of
+ * type {@code nt:frozenNode} in which case the path of the tree is logged at
+ * INFO. Log messages are rate limited to one per second. If multiple frozen
+ * nodes are looked up by identifier with the period of one second, then only
+ * the first lookup is logged; the other lookups are not logged.
+ * Enabling DEBUG level for this class reveals the stack of the calling thread.
+ */
+public class FrozenNodeLogger implements Closeable {
+
+    private static final Logger log = LoggerFactory.getLogger(FrozenNodeLogger.class);
+
+    private static final long LOG_INTERVAL = 1000L;

Review comment:
       I was wondering if there might ever be a need for this to be adjusted? (eg convert this to a System Property? but might also be overkill)

##########
File path: oak-jcr/src/main/java/org/apache/jackrabbit/oak/jcr/version/FrozenNodeLogger.java
##########
@@ -0,0 +1,95 @@
+/*
+ * 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.jackrabbit.oak.jcr.version;
+
+import java.io.Closeable;
+
+import org.apache.jackrabbit.oak.api.PropertyState;
+import org.apache.jackrabbit.oak.api.Tree;
+import org.apache.jackrabbit.oak.api.Type;
+import org.apache.jackrabbit.oak.spi.toggle.Feature;
+import org.apache.jackrabbit.oak.spi.whiteboard.Whiteboard;
+import org.apache.jackrabbit.oak.stats.Clock;
+import org.jetbrains.annotations.NotNull;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+import static org.apache.jackrabbit.JcrConstants.JCR_PRIMARYTYPE;
+import static org.apache.jackrabbit.JcrConstants.NT_FROZENNODE;
+import static org.apache.jackrabbit.oak.spi.toggle.Feature.newFeature;
+
+/**
+ * Logger facility for frozen node lookups by identifier. Calls to
+ * {@link #lookupById(Tree)} first check the feature toggle
+ * {@code oak.logFrozenNodeLookup} and then whether the given {@code Tree} is of
+ * type {@code nt:frozenNode} in which case the path of the tree is logged at
+ * INFO. Log messages are rate limited to one per second. If multiple frozen
+ * nodes are looked up by identifier with the period of one second, then only
+ * the first lookup is logged; the other lookups are not logged.
+ * Enabling DEBUG level for this class reveals the stack of the calling thread.
+ */
+public class FrozenNodeLogger implements Closeable {
+
+    private static final Logger log = LoggerFactory.getLogger(FrozenNodeLogger.class);
+
+    private static final long LOG_INTERVAL = 1000L;
+
+    private static long NO_MESSAGE_UNTIL = 0;
+
+    private final Clock clock;
+
+    private final Feature feature;
+
+    public FrozenNodeLogger(@NotNull Clock clock,
+                            @NotNull Whiteboard whiteboard) {
+        this.clock = checkNotNull(clock);
+        this.feature = newFeature("OAK-9139_log_frozen_node_lookup", whiteboard);
+    }
+
+    public final void lookupById(@NotNull Tree tree) {
+        if (!feature.isEnabled()) {
+            return;
+        }
+        PropertyState primaryType = tree.getProperty(JCR_PRIMARYTYPE);
+        if (primaryType != null
+                && !primaryType.isArray()
+                && primaryType.getValue(Type.STRING).equals(NT_FROZENNODE)) {
+            long now = clock.getTime();
+            synchronized (FrozenNodeLogger.class) {
+                if (now >= NO_MESSAGE_UNTIL) {
+                    NO_MESSAGE_UNTIL = now + LOG_INTERVAL;
+                    logFrozenNode(tree);
+                }
+            }
+        }
+    }
+
+    @Override
+    public void close() {
+        feature.close();
+    }
+
+    protected void logFrozenNode(Tree tree) {
+        log.info("Frozen node {} looked up by id", tree.getPath());
+        if (log.isDebugEnabled()) {
+            log.debug("Call stack", new Exception());

Review comment:
       nitpicking: replace "Call stack" with sth more descriptive? (might potentially simplify future `grep` effort)




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