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https://github.com/jexp/neo4j-tx-participation

This is a Neo4j Server Extension to make Neo4j REST-API participate in transactions started by the transactional Cypher endpoint.
https://github.com/jexp/neo4j-tx-participation

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This is a Neo4j Server Extension to make Neo4j REST-API participate in transactions started by the transactional Cypher endpoint.

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== Transaction-Participation for Neo4j-REST-API



This is a Neo4j Server Extension to make http://neo4j.com/docs/stable/rest-api.html[Neo4j REST-API] participate in transactions started by the http://neo4j.com/docs/stable/rest-api-transactional.html#rest-api-begin-a-transaction[transactional Cypher endpoint].



=== Why do I need it?



There are a number of operations with Neo4j server that currently can't be done with Cypher but are exposed as REST-API endpoints.



Notably working with http://neo4j.com/docs/stable/rest-api-indexes.html[manual indexes], http://neo4j.com/docs/stable/rest-api-traverse.html[traversals] and http://neo4j.com/docs/stable/rest-api-graph-algos.html[graph algorithms].



As the Cypher endpoint starts it's own transactions, all the data created during those transactions *is not visible* to the outside until that transaction is committed.

So you can't create a node and add it to a manual fulltext or spatial index within the same transaction.



This extension makes it possible for other REST-operations to participate in transactions started by the cypher endpoint.



=== Installation



You can build it with `mvn package` and copy `target/transaction-participation-2.2.2-1.0-SNAPSHOT.jar` to your server's `plugins` directory.



A pre-built version is https://dl.dropboxusercontent.com/u/14493611/transaction-participation-2.2.2-1.0-SNAPSHOT.jar[here].



And edit `conf/neo4j-server.properties` to contain this registration for the extension:

----

org.neo4j.server.thirdparty_jaxrs_classes=org.neo4j.server.extension.tx=/tx

----



Then restart your server.



=== How does it work?



The extension installs a filter that intercepts the http request to the REST API takes the *transaction id from the `X-TxId` HTTP Header*

and resumes the transaction, so that the REST-API calls participates in that transaction.



After executing the request it suspends the transaction again, so that you can continue it with the Cypher endpoint and also committing it at the end.



Here is a sample session with explanations:

----

# open transaction, create node

curl -i -H accept:application/json -H content-type:application/json \

     -d '{"statements":[{"statement":"create (p:Person {name:\"Jack\"}) return id(p)"}]}' \

     http://localhost:7474/db/data/transaction



# response, see the transaction-id "6" and the returned node-id of "1" (nested in "data":[{"row":[1]}]}])

HTTP/1.1 201 Created

Location: http://localhost:7474/db/data/transaction/6

{"commit":"http://localhost:7474/db/data/transaction/6/commit",

 "results":[{"columns":["id(p)"],"data":[{"row":[1]}]}],

 "transaction":{"expires":"Sun, 24 May 2015 08:43:11 +0000"},

 "errors":[]}



curl -H X-TxId:6 \

     -i -H accept:application/json -H content-type:application/json \

     -d'{"key":"bio","value":"Jack was born in London in 1925","uri":"/db/data/node/1"}' \

     http://localhost:7474/db/data/index/node/people



# response, added to index



HTTP/1.1 201 Created

{  ...

   "indexed" : "http://localhost:7474/db/data/index/node/people/bio/Jack%20was%20born%20in%20London%20in%201925/1"

}



# commit transaction number 6

curl  -i -XPOST \

      http://localhost:7474/transaction/6

----