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/*
 * (c) Copyright 2018 Palantir Technologies Inc. All rights reserved.
 *
 * Licensed 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 com.palantir.atlasdb.keyvalue.cassandra;

import com.google.common.base.Stopwatch;
import com.google.common.collect.ImmutableSet;
import com.palantir.atlasdb.cassandra.CassandraTracingConfig;
import com.palantir.atlasdb.keyvalue.api.TableReference;
import com.palantir.atlasdb.logging.LoggingArgs;
import com.palantir.atlasdb.logging.LoggingArgs.SafeAndUnsafeTableReferences;
import com.palantir.logsafe.SafeArg;
import com.palantir.logsafe.logger.SafeLogger;
import java.nio.ByteBuffer;
import java.util.Set;
import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.TimeUnit;
import java.util.function.Supplier;
import java.util.stream.Collectors;
import org.apache.thrift.TException;

public class TracingQueryRunner {
    private final SafeLogger log;
    private final Supplier tracingPrefs;

    public TracingQueryRunner(SafeLogger log, Supplier tracingPrefs) {
        this.log = log;
        this.tracingPrefs = tracingPrefs;
    }

    @FunctionalInterface
    public interface Action {
        V run() throws TException;
    }

    public  V run(CassandraClient client, Set tableRefs, Action action) throws TException {
        if (shouldTraceQuery(tableRefs)) {
            return trace(action, client, tableRefs);
        } else {
            try {
                return action.run();
            } catch (TException e) {
                logFailedCall(tableRefs);
                throw e;
            }
        }
    }

    public  V run(CassandraClient client, TableReference tableRef, Action action) throws TException {
        return run(client, ImmutableSet.of(tableRef), action);
    }

    public  V trace(Action action, CassandraClient client, Set tableRefs) throws TException {
        ByteBuffer traceId = client.trace_next_query();
        Stopwatch stopwatch = Stopwatch.createStarted();
        boolean failed = false;
        try {
            return action.run();
        } catch (TException e) {
            failed = true;
            logFailedCall(tableRefs);
            throw e;
        } finally {
            long duration = stopwatch.elapsed(TimeUnit.MILLISECONDS);
            logTraceResults(duration, tableRefs, traceId, failed);
        }
    }

    private boolean shouldTraceQuery(Set tableRefs) {
        CassandraTracingConfig prefs = tracingPrefs.get();
        if (!prefs.enabled()) {
            return false;
        }
        if (prefs.tablesToTrace().isEmpty()
                || tableRefs.stream().map(TableReference::getQualifiedName).anyMatch(prefs.tablesToTrace()::contains)) {
            if (prefs.traceProbability() >= 1.0) {
                return true;
            } else if (ThreadLocalRandom.current().nextDouble() <= prefs.traceProbability()) {
                return true;
            }
        }
        return false;
    }

    private void logFailedCall(Set tableRefs) {
        log.warn(
                "A call to table(s) {} failed with an exception.",
                tableRefs.stream().map(LoggingArgs::tableRef).collect(Collectors.toList()));
    }

    private void logTraceResults(long duration, Set tableRefs, ByteBuffer recvTrace, boolean failed) {
        if (failed || duration > tracingPrefs.get().minDurationToLog().toMilliseconds()) {
            SafeAndUnsafeTableReferences allTableArgs = LoggingArgs.tableRefs(tableRefs);
            log.info(
                    "Traced a call to {} that {}took {} ms. It will appear in system_traces with UUID={}",
                    allTableArgs.safeTableRefs(),
                    allTableArgs.unsafeTableRefs(),
                    SafeArg.of("failed", failed),
                    SafeArg.of("duration", duration),
                    // See
                    // https://github.com/palantir/cassandra/blob/af2a1aa70d0f39163aaa65531599fba0ce044509/src/java/org/apache/cassandra/thrift/CassandraServer.java#L234
                    // and CassandraKeyValueServices.convertCassandraByteBufferUuidToString docs.
                    // This is a random session id + cassandra node ids, which make this safe.
                    SafeArg.of(
                            "cassandraTraceId",
                            CassandraKeyValueServices.convertCassandraByteBufferUuidToString(recvTrace)));
        }
    }
}