Slow BsonDocumentCodec instantiation while decoding

[hborchardt]

Version 4.8.3
Hi, while profiling my application I saw that 50% of the time spent in JacksonCodec.decode() is actually spent constructing an instance of BsonDocumentCodec.

It is constructed here:

mongojack/src/main/java/org/mongojack/internal/stream/JsonParserAdapter.java

Line 37 in c24369f

protected final BsonJavaScriptWithScopeCodec withScopeCodec = new BsonJavaScriptWithScopeCodec(new BsonDocumentCodec(MongoClientSettings.getDefaultCodecRegistry()));

Having one JsonParserAdapter instance per decode() call makes sense, because it holds parsing state. But I think the withScopeCodec property and its parameters have no state and just static arguments, so withScopeCodec could also be a static variable.

It would be cool to significantly speed up decoding by reusing this instance.

[rlodge]

You might be completely right, but I'm reluctant to risk statically holding all that state. I published 5.0.2-SNAPSHOT and 4.8.4-SNAPSHOT to https://oss.sonatype.org/content/repositories/snapshots with a change to instantiate that json scope codec only when actually used, which I guess is in less than 1% of cases. Test it out and let me know if that addresses your concerns.

[hborchardt]

Hello, thanks for looking into this so quickly!

I tested the snapshot, and my requests are now faster by the amount that I hoped for - success! 🏆

I wanted to also test the (new to me) feature of decoding a js function with scope, to make sure that it is not broken, but I got the following:
Inserted a mongodb object into

db.tmp.insert({
    name: "incrementX",
    f: (function() { x++; })
})

queried like this:

var a = mongoDB.getTmpCollection().find(Filters.eq(new ObjectId("66fa7024fae13f3bf1dd58a2")), Document.class).first();
System.out.println(a);

and got this:

Exception

"Caused by com.fasterxml.jackson.databind.exc.InvalidFormatException: Cannot deserialize value of type `org.bson.types.Code` from native value (`JsonToken.VALUE_EMBEDDED_OBJECT`) of type `org.bson.BsonJavaScript`: incompatible types\n at [Source: UNKNOWN; byte offset: #UNKNOWN]", "com.fasterxml.jackson.databind.exc.InvalidFormatException.from(InvalidFormatException.java:67)", "com.fasterxml.jackson.databind.DeserializationContext.weirdNativeValueException(DeserializationContext.java:1988)", "com.fasterxml.jackson.databind.DeserializationContext.handleWeirdNativeValue(DeserializationContext.java:1314)", "com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromEmbedded(BeanDeserializerBase.java:1694)", "com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeOther(BeanDeserializer.java:203)", "com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:187)", "com.fasterxml.jackson.databind.deser.DefaultDeserializationContext.readRootValue(DefaultDeserializationContext.java:342)", "com.fasterxml.jackson.databind.ObjectReader._bind(ObjectReader.java:2099)", "com.fasterxml.jackson.databind.ObjectReader.readValue(ObjectReader.java:1249)", "org.mongojack.internal.stream.JacksonDecoder.decode(JacksonDecoder.java:43)", "org.mongojack.internal.stream.JacksonCodec.decode(JacksonCodec.java:71)", "org.bson.codecs.ContainerCodecHelper.readValue(ContainerCodecHelper.java:65)", "org.bson.codecs.DocumentCodec.decode(DocumentCodec.java:182)", "org.bson.codecs.DocumentCodec.decode(DocumentCodec.java:44)", "com.mongodb.internal.operation.CommandResultArrayCodec.decode(CommandResultArrayCodec.java:52)", "com.mongodb.internal.operation.CommandResultDocumentCodec.readValue(CommandResultDocumentCodec.java:60)", "org.bson.codecs.BsonDocumentCodec.decode(BsonDocumentCodec.java:87)", "org.bson.codecs.BsonDocumentCodec.decode(BsonDocumentCodec.java:42)", "org.bson.internal.LazyCodec.decode(LazyCodec.java:53)", "org.bson.codecs.BsonDocumentCodec.readValue(BsonDocumentCodec.java:104)", "com.mongodb.internal.operation.CommandResultDocumentCodec.readValue(CommandResultDocumentCodec.java:63)", "org.bson.codecs.BsonDocumentCodec.decode(BsonDocumentCodec.java:87)", "org.bson.codecs.BsonDocumentCodec.decode(BsonDocumentCodec.java:42)", "com.mongodb.internal.connection.ReplyMessage.(ReplyMessage.java:50)", "com.mongodb.internal.connection.InternalStreamConnection.getCommandResult(InternalStreamConnection.java:538)", "com.mongodb.internal.connection.InternalStreamConnection.receiveCommandMessageResponse(InternalStreamConnection.java:423)", "com.mongodb.internal.connection.InternalStreamConnection.sendAndReceive(InternalStreamConnection.java:340)", "com.mongodb.internal.connection.UsageTrackingInternalConnection.sendAndReceive(UsageTrackingInternalConnection.java:116)", "com.mongodb.internal.connection.DefaultConnectionPool$PooledConnection.sendAndReceive(DefaultConnectionPool.java:643)", "com.mongodb.internal.connection.CommandProtocolImpl.execute(CommandProtocolImpl.java:71)", "com.mongodb.internal.connection.DefaultServer$DefaultServerProtocolExecutor.execute(DefaultServer.java:206)", "com.mongodb.internal.connection.DefaultServerConnection.executeProtocol(DefaultServerConnection.java:119)", "com.mongodb.internal.connection.DefaultServerConnection.command(DefaultServerConnection.java:85)", "com.mongodb.internal.connection.DefaultServerConnection.command(DefaultServerConnection.java:75)", "com.mongodb.internal.connection.DefaultServer$OperationCountTrackingConnection.command(DefaultServer.java:293)", "com.mongodb.internal.operation.CommandOperationHelper.createReadCommandAndExecute(CommandOperationHelper.java:233)", "com.mongodb.internal.operation.FindOperation.lambda$execute$1(FindOperation.java:332)", "com.mongodb.internal.operation.OperationHelper.lambda$withSourceAndConnection$0(OperationHelper.java:356)", "com.mongodb.internal.operation.OperationHelper.withSuppliedResource(OperationHelper.java:381)", "com.mongodb.internal.operation.OperationHelper.lambda$withSourceAndConnection$1(OperationHelper.java:355)", "com.mongodb.internal.operation.OperationHelper.withSuppliedResource(OperationHelper.java:381)", "com.mongodb.internal.operation.OperationHelper.withSourceAndConnection(OperationHelper.java:354)", "com.mongodb.internal.operation.FindOperation.lambda$execute$2(FindOperation.java:329)", "com.mongodb.internal.async.function.RetryingSyncSupplier.get(RetryingSyncSupplier.java:67)", "com.mongodb.internal.operation.FindOperation.execute(FindOperation.java:340)", "com.mongodb.internal.operation.FindOperation.execute(FindOperation.java:79)", "com.mongodb.client.internal.MongoClientDelegate$DelegateOperationExecutor.execute(MongoClientDelegate.java:191)", "com.mongodb.client.internal.FindIterableImpl.first(FindIterableImpl.java:213)",

It seems that the Document codec expects to get a org.bson.types.Code object instead of org.bson.BsonJavaScript. The other cases in the JsonParserAdapter.toJsonToken function also produce e.g. ObjectId instead of BsonObjectId.

Deserializing a Document that contains Code is an intended usecase, right?

Apparently the CodeWithScope bson type is actually deprecated since mongodb 4.4 and removed since mongodb 6, so I can't test the CodeWithScope code path myself, as I use mongodb 7.

[rlodge]

Since it's been deprecated that long, and the last operational version is 5.x, and that EOLs this month, and the 5.x images won't run on my apple silicon mac, I think we're justified in not testing the deprecated feature.

Otherwise, you're good with the change? I can cut a release if you are.

[hborchardt]

Yes, I am happy with the change and would appreciate it being released. For the Code deserialization I can also open another issue, it seems unrelated to this one as well as your changes.

[rlodge]

Released 5.0.2. If the Code deserialization problem can be reproduced usefully in 6.x or 7.x, then file an issue. Otherwise, I'm not concerned about it.