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/**
* Copyright (C) 2015 MongoDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the GNU Affero General Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kCommand
#include "mongo/platform/basic.h"
#include <map>
#include <set>
#include <string>
#include <vector>
#include "mongo/client/connpool.h"
#include "mongo/db/catalog/document_validation.h"
#include "mongo/db/commands.h"
#include "mongo/db/commands/mr.h"
#include "mongo/db/query/collation/collation_spec.h"
#include "mongo/s/balancer/balancer_configuration.h"
#include "mongo/s/catalog/catalog_cache.h"
#include "mongo/s/catalog/dist_lock_manager.h"
#include "mongo/s/catalog/sharding_catalog_client.h"
#include "mongo/s/chunk_manager.h"
#include "mongo/s/client/shard_connection.h"
#include "mongo/s/client/shard_registry.h"
#include "mongo/s/commands/cluster_commands_common.h"
#include "mongo/s/commands/sharded_command_processing.h"
#include "mongo/s/commands/strategy.h"
#include "mongo/s/config.h"
#include "mongo/s/grid.h"
#include "mongo/s/sharding_raii.h"
#include "mongo/stdx/chrono.h"
#include "mongo/util/log.h"
namespace mongo {
using std::shared_ptr;
using std::map;
using std::set;
using std::string;
using std::vector;
namespace {
AtomicUInt32 JOB_NUMBER;
const Milliseconds kNoDistLockTimeout(-1);
/**
* Generates a unique name for the temporary M/R output collection.
*/
string getTmpName(StringData coll) {
return str::stream() << "tmp.mrs." << coll << "_" << time(0) << "_"
<< JOB_NUMBER.fetchAndAdd(1);
}
/**
* Given an input map/reduce command, this call generates the matching command which should
* be sent to the shards as part of the first phase of map/reduce.
*/
BSONObj fixForShards(const BSONObj& orig,
const string& output,
string& badShardedField,
int maxChunkSizeBytes) {
BSONObjBuilder b;
BSONObjIterator i(orig);
while (i.more()) {
BSONElement e = i.next();
const string fn = e.fieldName();
if (fn == bypassDocumentValidationCommandOption() || fn == "map" || fn == "mapreduce" ||
fn == "mapReduce" || fn == "mapparams" || fn == "reduce" || fn == "query" ||
fn == "sort" || fn == "collation" || fn == "scope" || fn == "verbose" ||
fn == "$queryOptions" || fn == "readConcern" ||
fn == QueryRequest::cmdOptionMaxTimeMS) {
b.append(e);
} else if (fn == "out" || fn == "finalize" || fn == "writeConcern") {
// We don't want to copy these
} else {
badShardedField = fn;
return BSONObj();
}
}
b.append("out", output);
b.append("shardedFirstPass", true);
if (maxChunkSizeBytes > 0) {
// Will need to figure out chunks, ask shards for points
b.append("splitInfo", maxChunkSizeBytes);
}
return b.obj();
}
/**
* Outline for sharded map reduce for sharded output, $out replace:
*
* ============= mongos =============
* 1. Send map reduce command to all relevant shards with some extra info like the value for
* the chunkSize and the name of the temporary output collection.
*
* ============= shard =============
* 2. Does normal map reduce.
*
* 3. Calls splitVector on itself against the output collection and puts the results into the
* response object.
*
* ============= mongos =============
* 4. If the output collection is *not* sharded, uses the information from splitVector to
* create a pre-split sharded collection.
*
* 5. Grabs the distributed lock for the final output collection.
*
* 6. Sends mapReduce.shardedfinish.
*
* ============= shard =============
* 7. Extracts the list of shards from the mapReduce.shardedfinish and performs a broadcast
* query against all of them to obtain all documents that this shard owns.
*
* 8. Performs the reduce operation against every document from step #7 and outputs them to
* another temporary collection. Also keeps track of the BSONObject size of every "reduced"
* document for each chunk range.
*
* 9. Atomically drops the old output collection and renames the temporary collection to the
* output collection.
*
* ============= mongos =============
* 10. Releases the distributed lock acquired at step #5.
*
* 11. Inspects the BSONObject size from step #8 and determines if it needs to split.
*/
class MRCmd : public Command {
public:
MRCmd() : Command("mapReduce", false, "mapreduce") {}
virtual bool slaveOk() const {
return true;
}
virtual bool adminOnly() const {
return false;
}
virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
return mr::mrSupportsWriteConcern(cmd);
}
virtual void help(std::stringstream& help) const {
help << "Runs the sharded map/reduce command";
}
virtual void addRequiredPrivileges(const std::string& dbname,
const BSONObj& cmdObj,
std::vector<Privilege>* out) {
mr::addPrivilegesRequiredForMapReduce(this, dbname, cmdObj, out);
}
virtual bool run(OperationContext* txn,
const std::string& dbname,
BSONObj& cmdObj,
int options,
std::string& errmsg,
BSONObjBuilder& result) {
Timer t;
const NamespaceString nss(parseNs(dbname, cmdObj));
uassert(ErrorCodes::InvalidNamespace, "Invalid namespace", nss.isValid());
const string shardResultCollection = getTmpName(nss.coll());
bool shardedOutput = false;
NamespaceString outputCollNss;
bool customOutDB = false;
bool inlineOutput = false;
string outDB = dbname;
BSONElement outElmt = cmdObj.getField("out");
if (outElmt.type() == Object) {
// Check if there is a custom output
BSONObj customOut = outElmt.embeddedObject();
shardedOutput = customOut.getBoolField("sharded");
if (customOut.hasField("inline")) {
inlineOutput = true;
uassert(ErrorCodes::InvalidOptions,
"cannot specify inline and sharded output at the same time",
!shardedOutput);
uassert(ErrorCodes::InvalidOptions,
"cannot specify inline and output database at the same time",
!customOut.hasField("db"));
} else {
// Mode must be 1st element
const string finalColShort = customOut.firstElement().str();
if (customOut.hasField("db")) {
customOutDB = true;
outDB = customOut.getField("db").str();
}
outputCollNss = NamespaceString(outDB, finalColShort);
uassert(ErrorCodes::InvalidNamespace,
"Invalid output namespace",
outputCollNss.isValid());
}
}
// Ensure the input database exists
auto status = grid.catalogCache()->getDatabase(txn, dbname);
if (!status.isOK()) {
return appendCommandStatus(result, status.getStatus());
}
shared_ptr<DBConfig> confIn = status.getValue();
shared_ptr<DBConfig> confOut;
if (customOutDB) {
// Create the output database implicitly, since we have a custom output requested
auto scopedDb = uassertStatusOK(ScopedShardDatabase::getOrCreate(txn, outDB));
confOut = scopedDb.getSharedDbReference();
} else {
confOut = confIn;
}
if (confOut->getPrimaryId() == "config" && !inlineOutput) {
return appendCommandStatus(
result,
Status(ErrorCodes::CommandNotSupported,
str::stream() << "Can not execute mapReduce with output database " << outDB
<< " which lives on config servers"));
}
const bool shardedInput =
confIn && confIn->isShardingEnabled() && confIn->isSharded(nss.ns());
if (!shardedOutput) {
uassert(15920,
"Cannot output to a non-sharded collection because "
"sharded collection exists already",
!confOut->isSharded(outputCollNss.ns()));
// TODO: Should we also prevent going from non-sharded to sharded? During the
// transition client may see partial data.
}
int64_t maxChunkSizeBytes = 0;
if (shardedOutput) {
// Will need to figure out chunks, ask shards for points
maxChunkSizeBytes = cmdObj["maxChunkSizeBytes"].numberLong();
if (maxChunkSizeBytes == 0) {
maxChunkSizeBytes =
Grid::get(txn)->getBalancerConfiguration()->getMaxChunkSizeBytes();
}
// maxChunkSizeBytes is sent as int BSON field
invariant(maxChunkSizeBytes < std::numeric_limits<int>::max());
}
// modify command to run on shards with output to tmp collection
string badShardedField;
BSONObj shardedCommand =
fixForShards(cmdObj, shardResultCollection, badShardedField, maxChunkSizeBytes);
if (!shardedInput && !shardedOutput && !customOutDB) {
LOG(1) << "simple MR, just passthrough";
const auto shard = grid.shardRegistry()->getShard(txn, confIn->getPrimaryId());
ShardConnection conn(shard->getConnString(), "");
BSONObj res;
bool ok = conn->runCommand(dbname, cmdObj, res);
conn.done();
if (auto wcErrorElem = res["writeConcernError"]) {
appendWriteConcernErrorToCmdResponse(shard->getId(), wcErrorElem, result);
}
result.appendElementsUnique(res);
return ok;
}
if (badShardedField.size()) {
errmsg = str::stream() << "unknown m/r field for sharding: " << badShardedField;
return false;
}
BSONObj q;
if (cmdObj["query"].type() == Object) {
q = cmdObj["query"].embeddedObjectUserCheck();
}
BSONObj collation;
if (cmdObj["collation"].type() == Object) {
collation = cmdObj["collation"].embeddedObjectUserCheck();
}
set<string> servers;
vector<Strategy::CommandResult> mrCommandResults;
BSONObjBuilder shardResultsB;
BSONObjBuilder shardCountsB;
map<string, int64_t> countsMap;
set<BSONObj> splitPts;
{
bool ok = true;
// TODO: take distributed lock to prevent split / migration?
try {
Strategy::commandOp(
txn, dbname, shardedCommand, 0, nss.ns(), q, collation, &mrCommandResults);
} catch (DBException& e) {
e.addContext(str::stream() << "could not run map command on all shards for ns "
<< nss.ns()
<< " and query "
<< q);
throw;
}
for (const auto& mrResult : mrCommandResults) {
// Need to gather list of all servers even if an error happened
string server;
{
const auto shard = grid.shardRegistry()->getShard(txn, mrResult.shardTargetId);
server = shard->getConnString().toString();
}
servers.insert(server);
if (!ok) {
continue;
}
BSONObj singleResult = mrResult.result;
ok = singleResult["ok"].trueValue();
if (!ok) {
// At this point we will return
errmsg = str::stream() << "MR parallel processing failed: "
<< singleResult.toString();
continue;
}
shardResultsB.append(server, singleResult);
BSONObj counts = singleResult["counts"].embeddedObjectUserCheck();
shardCountsB.append(server, counts);
// Add up the counts for each shard. Some of them will be fixed later like
// output and reduce.
BSONObjIterator j(counts);
while (j.more()) {
BSONElement temp = j.next();
countsMap[temp.fieldName()] += temp.numberLong();
}
if (singleResult.hasField("splitKeys")) {
BSONElement splitKeys = singleResult.getField("splitKeys");
vector<BSONElement> pts = splitKeys.Array();
for (vector<BSONElement>::iterator it = pts.begin(); it != pts.end(); ++it) {
splitPts.insert(it->Obj().getOwned());
}
}
}
if (!ok) {
_cleanUp(servers, dbname, shardResultCollection);
// Add "code" to the top-level response, if the failure of the sharded command
// can be accounted to a single error.
int code = getUniqueCodeFromCommandResults(mrCommandResults);
if (code != 0) {
result.append("code", code);
}
return false;
}
}
// Build the sharded finish command
BSONObjBuilder finalCmd;
finalCmd.append("mapreduce.shardedfinish", cmdObj);
finalCmd.append("inputDB", dbname);
finalCmd.append("shardedOutputCollection", shardResultCollection);
finalCmd.append("shards", shardResultsB.done());
finalCmd.append("writeConcern", txn->getWriteConcern().toBSON());
BSONObj shardCounts = shardCountsB.done();
finalCmd.append("shardCounts", shardCounts);
BSONObjBuilder timingBuilder;
timingBuilder.append("shardProcessing", t.millis());
BSONObjBuilder aggCountsB;
for (const auto& countEntry : countsMap) {
aggCountsB.append(countEntry.first, static_cast<long long>(countEntry.second));
}
BSONObj aggCounts = aggCountsB.done();
finalCmd.append("counts", aggCounts);
if (auto elem = cmdObj[QueryRequest::cmdOptionMaxTimeMS])
finalCmd.append(elem);
if (auto elem = cmdObj[bypassDocumentValidationCommandOption()])
finalCmd.append(elem);
Timer t2;
long long reduceCount = 0;
long long outputCount = 0;
BSONObjBuilder postCountsB;
bool ok = true;
BSONObj singleResult;
bool hasWCError = false;
if (!shardedOutput) {
const auto shard = grid.shardRegistry()->getShard(txn, confOut->getPrimaryId());
LOG(1) << "MR with single shard output, NS=" << outputCollNss.ns()
<< " primary=" << shard->toString();
ShardConnection conn(shard->getConnString(), outputCollNss.ns());
ok = conn->runCommand(outDB, finalCmd.obj(), singleResult);
BSONObj counts = singleResult.getObjectField("counts");
postCountsB.append(conn->getServerAddress(), counts);
reduceCount = counts.getIntField("reduce");
outputCount = counts.getIntField("output");
conn.done();
if (!hasWCError) {
if (auto wcErrorElem = singleResult["writeConcernError"]) {
appendWriteConcernErrorToCmdResponse(shard->getId(), wcErrorElem, result);
hasWCError = true;
}
}
} else {
LOG(1) << "MR with sharded output, NS=" << outputCollNss.ns();
// Create the sharded collection if needed
if (!confOut->isSharded(outputCollNss.ns())) {
// Enable sharding on db
confOut->enableSharding(txn);
// Shard collection according to split points
vector<BSONObj> sortedSplitPts;
// Points will be properly sorted using the set
for (const auto& splitPt : splitPts) {
sortedSplitPts.push_back(splitPt);
}
// Pre-split the collection onto all the shards for this database. Note that
// it's not completely safe to pre-split onto non-primary shards using the
// shardcollection method (a conflict may result if multiple map-reduces are
// writing to the same output collection, for instance).
//
// TODO: pre-split mapReduce output in a safer way.
set<ShardId> outShardIds;
confOut->getAllShardIds(&outShardIds);
BSONObj sortKey = BSON("_id" << 1);
ShardKeyPattern sortKeyPattern(sortKey);
// The collection default collation for the output collection. This is empty,
// representing the simple binary comparison collation.
BSONObj defaultCollation;
Status status = grid.catalogClient(txn)->shardCollection(txn,
outputCollNss.ns(),
sortKeyPattern,
defaultCollation,
true,
sortedSplitPts,
outShardIds);
if (!status.isOK()) {
return appendCommandStatus(result, status);
}
// Make sure the cached metadata for the collection knows that we are now sharded
confOut = uassertStatusOK(
grid.catalogCache()->getDatabase(txn, outputCollNss.db().toString()));
confOut->getChunkManager(txn, outputCollNss.ns(), true /* force */);
}
map<BSONObj, int> chunkSizes;
{
// Take distributed lock to prevent split / migration.
auto scopedDistLock = grid.catalogClient(txn)->distLock(
txn, outputCollNss.ns(), "mr-post-process", kNoDistLockTimeout);
if (!scopedDistLock.isOK()) {
return appendCommandStatus(result, scopedDistLock.getStatus());
}
BSONObj finalCmdObj = finalCmd.obj();
mrCommandResults.clear();
try {
const BSONObj query;
const BSONObj simpleCollation =
BSON(CollationSpec::kLocaleField << CollationSpec::kSimpleBinaryComparison);
Strategy::commandOp(txn,
outDB,
finalCmdObj,
0,
outputCollNss.ns(),
query,
simpleCollation,
&mrCommandResults);
ok = true;
} catch (DBException& e) {
e.addContext(str::stream() << "could not run final reduce on all shards for "
<< nss.ns()
<< ", output "
<< outputCollNss.ns());
throw;
}
for (const auto& mrResult : mrCommandResults) {
string server;
{
const auto shard =
grid.shardRegistry()->getShard(txn, mrResult.shardTargetId);
server = shard->getConnString().toString();
}
singleResult = mrResult.result;
if (!hasWCError) {
if (auto wcErrorElem = singleResult["writeConcernError"]) {
appendWriteConcernErrorToCmdResponse(
mrResult.shardTargetId, wcErrorElem, result);
hasWCError = true;
}
}
ok = singleResult["ok"].trueValue();
if (!ok) {
break;
}
BSONObj counts = singleResult.getObjectField("counts");
reduceCount += counts.getIntField("reduce");
outputCount += counts.getIntField("output");
postCountsB.append(server, counts);
// get the size inserted for each chunk
// split cannot be called here since we already have the distributed lock
if (singleResult.hasField("chunkSizes")) {
vector<BSONElement> sizes = singleResult.getField("chunkSizes").Array();
for (unsigned int i = 0; i < sizes.size(); i += 2) {
BSONObj key = sizes[i].Obj().getOwned();
const long long size = sizes[i + 1].numberLong();
invariant(size < std::numeric_limits<int>::max());
chunkSizes[key] = static_cast<int>(size);
}
}
}
}
// Do the splitting round
shared_ptr<ChunkManager> cm = confOut->getChunkManagerIfExists(txn, outputCollNss.ns());
uassert(34359,
str::stream() << "Failed to write mapreduce output to " << outputCollNss.ns()
<< "; expected that collection to be sharded, but it was not",
cm);
for (const auto& chunkSize : chunkSizes) {
BSONObj key = chunkSize.first;
const int size = chunkSize.second;
invariant(size < std::numeric_limits<int>::max());
// key reported should be the chunk's minimum
shared_ptr<Chunk> c = cm->findIntersectingChunkWithSimpleCollation(txn, key);
if (!c) {
warning() << "Mongod reported " << size << " bytes inserted for key " << key
<< " but can't find chunk";
} else {
c->splitIfShould(txn, size);
}
}
}
_cleanUp(servers, dbname, shardResultCollection);
if (!ok) {
errmsg = str::stream() << "MR post processing failed: " << singleResult.toString();
return 0;
}
// copy some elements from a single result
// annoying that we have to copy all results for inline, but no way around it
if (singleResult.hasField("result")) {
result.append(singleResult.getField("result"));
} else if (singleResult.hasField("results")) {
result.append(singleResult.getField("results"));
}
BSONObjBuilder countsB(32);
// input stat is determined by aggregate MR job
countsB.append("input", aggCounts.getField("input").numberLong());
countsB.append("emit", aggCounts.getField("emit").numberLong());
// reduce count is sum of all reduces that happened
countsB.append("reduce", aggCounts.getField("reduce").numberLong() + reduceCount);
// ouput is determined by post processing on each shard
countsB.append("output", outputCount);
result.append("counts", countsB.done());
timingBuilder.append("postProcessing", t2.millis());
result.append("timeMillis", t.millis());
result.append("timing", timingBuilder.done());
result.append("shardCounts", shardCounts);
result.append("postProcessCounts", postCountsB.done());
return true;
}
private:
/**
* Drops the temporary results collections from each shard.
*/
void _cleanUp(const set<string>& servers, string dbName, string shardResultCollection) {
try {
// drop collections with tmp results on each shard
for (const auto& server : servers) {
ScopedDbConnection conn(server);
conn->dropCollection(dbName + "." + shardResultCollection);
conn.done();
}
} catch (const DBException& e) {
warning() << "Cannot cleanup shard results" << redact(e);
} catch (const std::exception& e) {
severe() << "Cannot cleanup shard results" << causedBy(redact(e.what()));
}
}
} clusterMapReduceCmd;
} // namespace
} // namespace mongo
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