[BUG] MemGraph+neo4j-go-driver is stuck if cypher contains any path and does not have RETURN

[inv2004]

Memgraph version
2.4.1 (mage)

Environment
docker on WSL2

Describe the bug
memgraph+neo4j-go-driver is stuck on sess.Close or res.Consume if cypher contains any path and does not have RETURN. neo4j works ok

To Reproduce

package main

import (
	"context"
	"fmt"
	"time"

	"github.com/neo4j/neo4j-go-driver/v5/neo4j"
)

const url = "bolt://localhost:7687"

func query(driver neo4j.DriverWithContext, cypher string) error {
	ctx := context.Background()
	ctx, cancel := context.WithTimeout(ctx, 2*time.Second)
	defer cancel()
	sess := driver.NewSession(ctx, neo4j.SessionConfig{})
	defer sess.Close(ctx) // stuck here is no res.Consume

	res, err := sess.Run(ctx, cypher, nil)
	if err != nil {
		return err
	}

	for res.Next(ctx) {
		fmt.Println(res.Record().Values...)
	}

	err = res.Err()
	if err != nil {
		return err
	}

	if res.IsOpen() {
		fmt.Println("trying to consume")
		_, err := res.Consume(ctx)
		if err != nil {
			return err
		}
		fmt.Println("ok")
	}

	return nil
}

func example() error {
	driver, err := neo4j.NewDriverWithContext(url, neo4j.BasicAuth("", "", ""))
	if err != nil {
		return err
	}

	if err := query(driver, "RETURN 1+1"); err != nil {
		return err
	}
	if err := query(driver, "MATCH ()-[r]->() SET r.test = 123 RETURN DISTINCT 1"); err != nil {
		fmt.Println(err)
	}
	if err := query(driver, "MATCH ()-[r]->() SET r.test = 123"); err != nil {
		fmt.Println(err)
	}
	if err := query(driver, "MATCH (r)-[]->() SET r.test = 123"); err != nil {
		fmt.Println(err)
	}

	return nil
}

func main() {
	if err := example(); err != nil {
		panic(err)
	}
}

Expected behavior
No timeout errors

Logs

2
1
trying to consume
ConnectivityError: Timeout while reading from connection [server-side timeout hint: -1ns, user-provided context deadline: 2022-11-15 16:09:01.720096798 +0300 MSK m=+2.011375250]: context deadline exceeded
trying to consume
ConnectivityError: Timeout while reading from connection [server-side timeout hint: -1ns, user-provided context deadline: 2022-11-15 16:09:03.722075187 +0300 MSK m=+4.013353634]: context deadline exceeded

[gitbuda]

@inv2004 thanks for reporting, we'll take a look at what is happening 😄

[as51340]

Hi @inv2004 I wasn't able to reproduce the error, at my local environment it doesn't hang, can you maybe include more details like the content you filled database with?

[inv2004]

@as51340 I can confirm that I cannot reproduce with empty neo4j or simple relations. Let me think how to reproduce it with filled graph

[inv2004]

@as51340 Please find json file attached: 3.json.gz

 CALL import_util.json('3.json');

[as51340]

@inv2004 when the database is filled, I am able to reproduce the error. The error occurs after trying to consume the stream of results, here:

_, err := res.Consume(ctx)
if err != nil {
  return err
}

and it happens because private field summary from result_with_context struct isn't set to nil. You can check here for more details: https://github.com/neo4j/neo4j-go-driver/blob/5.0/neo4j/result_with_context.go
Unfortunately, at the moment, the only advice I can give you is to use some kind of return statement in each query and then you don't need to consume stream so you can delete this part of the code:

if res.IsOpen() {
  fmt.Println("trying to consume")
  _, err := res.Consume(ctx)
  if err != nil {
    return err
  }
  fmt.Println("ok")
}

because even if the res.isOpen() is true, stream consumation will not succeed and logically, the stream should have already been consumed when looping over the res.Next. We don't know if the issue comes from the Bolt implementation part or driver's side, my best guess it is some weird combination of both but we will get back to you when we find out.

Btw. there are also other methods, e.g Collect but it seems that they all rely on the same underling mechanism and the issue persists with them too.

[inv2004]

@as51340 Thank you for investigation,

About the if res.IsOpen() { branch - I can delete it, but the code appeared for the reason: if it does not exists then the code hangs anyway on defer sess.Close(ctx)