netudima commented on code in PR #4356: URL: https://github.com/apache/cassandra/pull/4356#discussion_r2369885197
########## src/java/org/apache/cassandra/db/virtual/ExceptionsTable.java: ########## @@ -0,0 +1,323 @@ +/* + * 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.db.virtual; + +import java.util.ArrayList; +import java.util.Collections; +import java.util.Date; +import java.util.LinkedHashMap; +import java.util.List; +import java.util.Map; + +import com.google.common.annotations.VisibleForTesting; + +import org.apache.cassandra.db.DecoratedKey; +import org.apache.cassandra.db.marshal.Int32Type; +import org.apache.cassandra.db.marshal.ListType; +import org.apache.cassandra.db.marshal.TimestampType; +import org.apache.cassandra.db.marshal.UTF8Type; +import org.apache.cassandra.dht.LocalPartitioner; +import org.apache.cassandra.schema.TableMetadata; +import org.apache.cassandra.utils.Clock; +import org.apache.cassandra.utils.logging.AbstractVirtualTableAppender; + +public class ExceptionsTable extends AbstractMutableVirtualTable +{ + public static final String EXCEPTIONS_TABLE_NAME = "uncaught_exceptions"; + public static final String EXCEPTION_CLASS_COLUMN_NAME = "exception_class"; + public static final String EXCEPTION_LOCATION_COLUMN_NAME = "exception_location"; + public static final String COUNT_COLUMN_NAME = "count"; + public static final String LAST_MESSAGE_COLUMN_NAME = "last_message"; + public static final String LAST_STACKTRACE_COLUMN_NAME = "last_stacktrace"; + public static final String LAST_OCCURRENCE_COLUMN_NAME = "last_occurrence"; + + /** + * Buffer of uncaught exceptions which happened while virtual table was not initialized. + */ + public static final List<ExceptionRow> preInitialisationBuffer = Collections.synchronizedList(new ArrayList<>()); + + @VisibleForTesting + public static volatile ExceptionsTable INSTANCE; + + // please be sure operations on this structure are thread-safe + @VisibleForTesting + final BoundedMap buffer; + + ExceptionsTable(String keyspace) + { + // for starters capped to 1k, I do not think we need to make this configurable (yet). + this(keyspace, 1000); + } + + ExceptionsTable(String keyspace, int maxSize) + { + super(TableMetadata.builder(keyspace, EXCEPTIONS_TABLE_NAME) + .comment("View into uncaught exceptions") + .kind(TableMetadata.Kind.VIRTUAL) + .partitioner(new LocalPartitioner(UTF8Type.instance)) + .addPartitionKeyColumn(EXCEPTION_CLASS_COLUMN_NAME, UTF8Type.instance) + .addClusteringColumn(EXCEPTION_LOCATION_COLUMN_NAME, UTF8Type.instance) + .addRegularColumn(COUNT_COLUMN_NAME, Int32Type.instance) + .addRegularColumn(LAST_MESSAGE_COLUMN_NAME, UTF8Type.instance) + .addRegularColumn(LAST_STACKTRACE_COLUMN_NAME, ListType.getInstance(UTF8Type.instance, false)) + .addRegularColumn(LAST_OCCURRENCE_COLUMN_NAME, TimestampType.instance) + .build()); + + this.buffer = new BoundedMap(maxSize); + } + + public void flush() + { + for (ExceptionRow row : preInitialisationBuffer) + add(row.exceptionClass, row.exceptionLocation, row.message, row.stackTrace, row.occurrence.getTime()); + + preInitialisationBuffer.clear(); + } + + @Override + public DataSet data() + { + SimpleDataSet result = new SimpleDataSet(metadata()); + + synchronized (buffer) + { + for (Map.Entry<String, LinkedHashMap<String, ExceptionRow>> partition : buffer.entrySet()) + { + for (Map.Entry<String, ExceptionRow> entry : partition.getValue().entrySet()) + populateRow(result, partition.getKey(), entry.getKey(), entry.getValue()); + } + } + + return result; + } + + @Override + public DataSet data(DecoratedKey partitionKey) + { + SimpleDataSet result = new SimpleDataSet(metadata()); + + synchronized (buffer) + { + String exceptionClass = UTF8Type.instance.getSerializer().deserialize(partitionKey.getKey()); + LinkedHashMap<String, ExceptionRow> partition = buffer.get(exceptionClass); + + if (partition != null) + { + for (Map.Entry<String, ExceptionRow> row : partition.entrySet()) + populateRow(result, exceptionClass, row.getKey(), row.getValue()); + } + } + + return result; + } + + private void populateRow(SimpleDataSet result, String exceptionClass, String exceptionLocation, ExceptionRow row) + { + result.row(exceptionClass, exceptionLocation) + .column(COUNT_COLUMN_NAME, row.count) + .column(LAST_MESSAGE_COLUMN_NAME, row.message) + .column(LAST_STACKTRACE_COLUMN_NAME, row.stackTrace) + .column(LAST_OCCURRENCE_COLUMN_NAME, row.occurrence); + } + + @Override + public void truncate() + { + synchronized (buffer) + { + buffer.clear(); + } + } + + public static void persist(Throwable t) + { + if (INSTANCE == null) + INSTANCE = AbstractVirtualTableAppender.getVirtualTable(ExceptionsTable.class, EXCEPTIONS_TABLE_NAME); + + Throwable toPersist = t; + + while (toPersist.getCause() != null) + toPersist = toPersist.getCause(); + + List<String> stackTrace = ExceptionRow.extractStacktrace(toPersist.getStackTrace()); + long now = Clock.Global.currentTimeMillis(); + + if (INSTANCE != null) + { + INSTANCE.add(toPersist.getClass().getName(), + stackTrace.get(0), + toPersist.getMessage(), + stackTrace, + now); + } + else + { + preInitialisationBuffer.add(new ExceptionRow(toPersist.getClass().getName(), + stackTrace.get(0), + 0, + toPersist.getMessage(), + stackTrace, + now)); + } + } + + + /** + * @param exceptionClass exception class of uncaught exception + * @param exceptionLocation location where that exception was thrown + * @param message message of given exception + * @param stackTrace whole stacktrace of given exception + * @param occurrenceTime time when given exception ocurred + */ + private void add(String exceptionClass, + String exceptionLocation, + String message, + List<String> stackTrace, + long occurrenceTime) + { + synchronized (buffer) + { + Map<String, ExceptionRow> exceptionRowWithLocation = buffer.computeIfAbsent(exceptionClass, (classToAdd) -> new LinkedHashMap<>()); + ExceptionRow exceptionRow = exceptionRowWithLocation.get(exceptionLocation); + if (exceptionRow == null) + { + // exception class and location can be null for value as we have it as part of keys already + exceptionRow = new ExceptionRow(null, null, 1, message, stackTrace, occurrenceTime); + exceptionRowWithLocation.put(exceptionLocation, exceptionRow); + // not important, can be null + // we need to do this, because if we add into a map which is + // a value of some buffer key, we might exceed the number + // of overall entries in the buffer + buffer.removeEldestEntry(null); + } + else + { + exceptionRow.count += 1; + exceptionRow.message = message; + exceptionRow.stackTrace = stackTrace; + exceptionRow.occurrence = new Date(occurrenceTime); + } + } + } + + // public to make warning go away about public preInitialisationBuffer exposing List<ExceptionRow> + // where ExceptionRow would have lower visibility than that. + public static final class ExceptionRow + { + final String exceptionClass; + final String exceptionLocation; + int count; + String message; + List<String> stackTrace; + Date occurrence; + + /** + * @param exceptionClass exception class of uncaught exception + * @param exceptionLocation location where that exception was thrown + * @param message message of given exception + * @param stackTrace whole stacktrace of given exception + * @param occurrenceTime time when given exception ocurred, in milliseconds from epoch + */ + ExceptionRow(String exceptionClass, + String exceptionLocation, + int count, + String message, + List<String> stackTrace, + long occurrenceTime) + { + this.exceptionClass = exceptionClass; + this.exceptionLocation = exceptionLocation; + this.count = count; + this.stackTrace = stackTrace; + this.message = message; + this.occurrence = new Date(occurrenceTime); + } + + public static List<String> extractStacktrace(StackTraceElement[] stackTraceArray) + { + List<String> result = new ArrayList<>(stackTraceArray.length); + + for (StackTraceElement element : stackTraceArray) + result.add(element.toString()); + + return result; + } + } + + @VisibleForTesting + static class BoundedMap extends LinkedHashMap<String, LinkedHashMap<String, ExceptionRow>> + { + private final int maxSize; + + public BoundedMap(int maxSize) + { + if (maxSize <= 0) + throw new IllegalArgumentException("maxSize has to be bigger than 0"); + + this.maxSize = maxSize; + } + + @Override + protected boolean removeEldestEntry(Map.Entry<String, LinkedHashMap<String, ExceptionRow>> eldest) + { + if (computeSize() > maxSize) + { + String oldestExceptionClass = null; + String oldestExceptionLocation = null; + long oldestLastOccurrence = Long.MAX_VALUE; + for (Map.Entry<String, LinkedHashMap<String, ExceptionRow>> entry : entrySet()) + { + for (Map.Entry<String, ExceptionRow> entryInEntry : entry.getValue().entrySet()) + { + long currentLastOccurrence = entryInEntry.getValue().occurrence.getTime(); + if (currentLastOccurrence < oldestLastOccurrence) + { + oldestExceptionLocation = entryInEntry.getKey(); + oldestExceptionClass = entry.getKey(); + oldestLastOccurrence = currentLastOccurrence; + } + } + } + + if (oldestLastOccurrence < Long.MAX_VALUE) + { + LinkedHashMap<String, ExceptionRow> aMap = get(oldestExceptionClass); + if (aMap.size() == 1) + remove(oldestExceptionClass); + else + aMap.remove(oldestExceptionLocation); + } + } + + // always returning false as per method's contract saying that + // overrides might modify the map directly but in that case it must return false + return false; + } + + private int computeSize() + { + int size = 0; + + for (Map.Entry<String, LinkedHashMap<String, ExceptionRow>> entry : entrySet()) Review Comment: nit: we can just iterate over values() -- This is an automated message from the Apache Git Service. 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