Neo4j returns HTTP 400

Question

I'm a co-founder of a service called Endorphin that uses neo4j to store social graph data. We have an issue with it.

We thought that improving the query will resolve the issue but as it turns out this is not the reason of DB failure because sometimes it returns successfully and sometimes fails with SyntaxException. We cant see the reason that makes this happen. Sending queries through API results in unsystematic failure of queries whereas when we send same queries using console they work perfectly well.

Details:

The Neo4j version is 1.9.2

We're using Windows Azure, OS Ubuntu 12.04LTS, running in JDK7

System configuration is AMD Opteron(tm) Processor 4171 HE 8 core cpu, memory 14GB, HDD 250 GB + 1TB, the database size is 1GB.

Cache config is the following:

cache_type=gcr 
use_memory_mapped_buffers=true 
neostore.nodestore.db.mapped_memory=1024M 
neostore.relationshipstore.db.mapped_memory=1024M
neostore.propertystore.db.mapped_memory=2048M
neostore.propertystore.db.strings.mapped_memory=1024M
neostore.propertystore.db.arrays.mapped_memory=1024M

I've attached an example of the query and error:

The query was:

start n=node(1341474), oldFriend0 = node(21103), 
      oldFriend1 = node(21103), oldFriend2 = node(302) 
create unique n<-[:Comment{CreatedTime:635082180250000000}]-oldFriend0 
create unique n<-[:Comment{CreatedTime:635082713870000000}]-oldFriend1 
create unique n<-[:Comment{CreatedTime:635082527270000000}]-oldFriend2 
return 1.0 as Val

The response status was: 400 Bad Request

The response from Neo4j (which might include useful detail!) was:

{"message" : "Can't create UNNAMED1 with properties here. 
It already exists in this context", "exception" : "SyntaxException", "fullname" : "org.neo4j.cypher.SyntaxException", "stacktrace" : 
[ "org.neo4j.cypher.internal.pipes.ExecuteUpdateCommandsPipe$$anonfun$assertNothingIsCreatedWhenItShouldNot$1.apply(ExecuteUpdateCommandsPipe.scala:83)", 
"org.neo4j.cypher.internal.pipes.ExecuteUpdateCommandsPipe$$anonfun$assertNothingIsCreatedWhenItShouldNot$1.apply(ExecuteUpdateCommandsPipe.scala:82)", 
"scala.collection.immutable.Stream.foreach(Stream.scala:547)", 
"org.neo4j.cypher.internal.pipes.ExecuteUpdateCommandsPipe.assertNothingIsCreatedWhenItShouldNot(ExecuteUpdateCommandsPipe.scala

One more example:

The query was:

start n=node(1398749), oldFriend0 = node(6856), oldFriend1 = node(6856), 
oldFriend2 = node(6848), oldFriend3 = node(6848), oldFriend4 = node(6848), 
oldFriend5 = node(5600), oldFriend6 = node(7245), oldFriend7 = node(223), 
oldFriend8 = node(223), oldFriend9 = node(223), oldFriend10 = node(223), 
oldFriend11 = node(223), oldFriend12 = node(223), oldFriend13 = node(223), 
oldFriend14 = node(223), oldFriend15 = node(7821), oldFriend16 = node(126899), 
oldFriend17 = node(7133), oldFriend18 = node(7133), oldFriend19 = node(6844), 
oldFriend20 = node(6915) create unique n<-[:Comment{CreatedTime:635094700950000000}]-oldFriend0 create unique n<-[:Comment{CreatedTime:635094783870000000}]-oldFriend1 
create unique n<-[:Comment{CreatedTime:635094735780000000}]-oldFriend2 
create unique n<-[:Comment{CreatedTime:635094744040000000}]-oldFriend3 
create unique n<-[:Comment{CreatedTime:635094744310000000}]-oldFriend4 
create unique n<-[:Comment{CreatedTime:635094776820000000}]-oldFriend5 
create unique n<-[:Comment{CreatedTime:635094730830000000}]-oldFriend6 
create unique n<-[:Comment{CreatedTime:635094731200000000}]-oldFriend7 
create unique n<-[:Comment{CreatedTime:635094742500000000}]-oldFriend8 
create unique n<-[:Comment{CreatedTime:635094742990000000}]-oldFriend9 
create unique n<-[:Comment{CreatedTime:635094743440000000}]-oldFriend10 
create unique n<-[:Comment{CreatedTime:635094743840000000}]-oldFriend11 
create unique n<-[:Comment{CreatedTime:635094744640000000}]-oldFriend12 
create unique n<-[:Comment{CreatedTime:635094749740000000}]-oldFriend13 
create unique n<-[:Comment{CreatedTime:635094826130000000}]-oldFriend14 
create unique n<-[:Comment{CreatedTime:635094748250000000}]-oldFriend15 
create unique n<-[:Comment{CreatedTime:635094708340000000}]-oldFriend16 
create unique n<-[:Comment{CreatedTime:635094742320000000}]-oldFriend17 
create unique n<-[:Comment{CreatedTime:635094742770000000}]-oldFriend18 
create unique n<-[:Comment{CreatedTime:635094692580000000}]-oldFriend19 
create unique n<-[:Comment{CreatedTime:635094743430000000}]-oldFriend20 
return 1.0 as Val

The response status was: 400 Bad Request

The response from Neo4j (which might include useful detail!) was: 
{ "message" : "Can't create UNNAMED1 with properties here. 
It already exists in this context", "exception" : "SyntaxException", 
"fullname" : "org.neo4j.cypher.SyntaxException", 
"stacktrace" : [ "org.neo4j.cypher.internal.pipes.ExecuteUpdateCommandsPipe$$anonfun$assertNothingIsCreatedWhenItShouldNot$1.apply(ExecuteUpdateCommandsPipe.scala:83)",
 "org.neo4j.cypher.internal.pipes.ExecuteUpdateCommandsPipe$$anonfun$assertNothingIsCreatedWhenItShouldNot$1.apply(ExecuteUpdateCommandsPipe.scala:82)", 
"scala.collection.immutable.Stream.foreach(Stream.scala:547)"

Any help is appreciated. Thanks in advance.

UPD: We're using Neo4jClient for C# to execute the queries. They don't fail via console, but they randomly fail when executed with this driver.

Answer 1

For reference there's this issue that will track progress/findings for this issue: https://github.com/neo4j/neo4j/issues/1040

Answer 2

I'll take a stab at something that might help.

Have you tried sending as a batch of separate statements? See: http://docs.neo4j.org/chunked/stable/rest-api-batch-ops.html

This way you could parameterize it and just send them all at once:

start n=node({destId}), oldFriend=node({oldFriend})
create unique n<-[:Comment {relProps}]-oldFriend

And in the params use:

{CreatedTime:635094700950000000}