transactions in Arangodb - node.js

Question

I have some problem with transactions in ArangoDB+nodejs. I need to do something like this:
transaction
{
insertedId=insertItemOneInDB();
insertItemTwoInDB();
}
but when the second insert failed, the first one didn't rollback!
please help me with an example!
here is my code:
var transaction = function (collections,params,callback)
{
try
{
db.transaction.submit("user_merchant_tbl",params,
function ()
{
console.log("_collections:",collections);
console.log("params:");
console.log(params);
console.log("---");
console.log("+==========+");
//
var insertedDataId;
var relationsArrayIds=[];
db.document.create(collections,params.data).then(function(_insertedId)
{
insertedDataId=_insertedId;
}
,function(err)
{
console.log("ERROR: Arango--insert-->err: %j", err);
//throw "Error: "+err;
return false;
});
/////
var relations=params.relations;
for(var i=0;i<relations.length;i++)
{
db.document.create(relations[i].edge,relations[i].data).then(
function(_id)
{
relationsArrayIds.push(_id);
next(true);
}
,function(err)
{
console.log("ERROR: Arango--insert.edge-->err:23232 %j", err);
console.log("after return");
next(false);
return false
});
}
console.log("transaction before true");
function next(result)
{
if(result==true)
{
console.log("transaction is ok:",result);
callback(insertedDataId,result);
}
else
{
console.log("transaction is not OK:",result);
callback(insertedDataId,false);
}
}
}
);
}
catch(e)
{
console.log("catch->error in -->Arango.transaction: ",e);
}
}

Answer 1

first of all there seems to be a misunderstanding in how to write the action that is supposed to be executed. This action is executed directly on the Database Server , hence you cant use any functionality provided by the Arango Javascript api.
If you want to design your action it has to run in the arango shell or on the server console (bin/arangod data --console)
I took a look into your code and assume you want to store relations between users and merchants. As Arango comes with a nice graph module you could follow the following approach :
// First we define a graph, containing of 2 document collections ("users" and "merchants") and 2 edge collections (one per relation type, in this example "contactRequested" and "boughtSomethingFrom".
// Note that in this definition the relation "boughtSomethingFrom" is only allowed from a user to a merchant. Of course this is just one way to design it, you have to do it the way it suits you the best.
var edgeDefinitions = [{
collection: "contactRequested",
from: ["users", "merchants"],
to: ["users", "merchants"]
}, {
collection: "boughtSomethingFrom",
from: ["users"],
to: ["merchants"]
}];
// Now we create a graph called "user_merchant_graph" and in the callback function execute a transaction
db.graph.create("user_merchant_graph", edgeDefinitions, function(err, ret, message) {
// Lets define the action for the transaction, again this will be executed directly on the server ......
var action = function (params) {
// We have to require the database module ....
var db = require("internal").db;
var relationsArrayIds = [];
// now we store the user provided to the function
var insertedUserId = db["users"].insert(params.data)._id;
var relations = params.relations;
// Now we loop over through the relations object, store each merchant and it's relations to the user
Object.keys(relations).forEach(function (relation) {
// store merchant
var insertedMerchantId = db["merchants"].insert({merchantName : relation})._id;
// store relation as edge from "insertedUserId" to "insertedMerchantId".
var edgeId = db[relations[relation].relation].insert(insertedUserId, insertedMerchantId, relations[relation].additionalData)._id;
relationsArrayIds.push(edgeId);
});
};
// End of action
var options = {};
options.params = {
data: {
userName : "someUserName",
userSurname : "someUserSurname"
},
relations : {
merchantA : {relation : "contactRequested", additionalData : {data :"someData"}},
merchantB : {relation : "boughtSomethingFrom", additionalData : {data :"someData"}},
merchantC : {relation : "contactRequested", additionalData : {data :"someData"}}
}
};
// Now we call the transaction module ... a note to the collections parameter, it has to be an object containing the keys "write" and "read" which have a list of all collections as value into which the action is writing /reading from
// This collections object is NOT available within your action, the only thing passed as argument to your action is "options.params" !!
db.transaction.submit({write : ["users", "merchants", "contactRequested", "boughtSomethingFrom"]}, action, options, function(err, ret, message) {
//some callback
});
});
With regards to transactions they are working, you can give this code a shot and if you f.e. mess up the storing of the edges (change it to "var edgeId = db[relations[relation].relation].insert(relations[relation].additionalData)._id;")
you will see that your user and merchant have not been stored
I hope this helps