Can I create a corda node basically I don't want to store any state. Purpose of this nodes is to handle communication between nodes in the same network and outside network.
I would not recommend you to do this. The whole idea of a Corda and having corda node's communication is to make sure that all parties have the same view of database, to make sure that "what you see is what I see".
If they aren't going to be any states, it doesn't make sense to put in the efforts to setup a node, you might simply have a simple database or a queue in between instead.
Related
My dev node is part of the Corda test network, and when I open the logs I see something like (node etc..sent you a flow which you don't have installed, you can kill it with kill flow). So I have 2 questions:
How do I reject these calls? I know the purpose of being part of the Corda network is to have the ability for CorDapps of different orgs to transact, and I don't want to go with the segregated network model (because it's more expensive for prod and pre-prod Corda nets).
Can a node on the network perform a DoS (Denial of Service) attack by sending me flows that I don't have installed and eventually bringing my node down?
I'm not sure if I'm right about my answer but as far as I know Corda Network is designed on a need to know basis and I know that you are aware of it and I was having the same doubt when I first started with Corda but I found out that one can simply block a node from sending you any undesired flows which could cost you unnecessary CPU runtime. The explanation to this is given in this link.
Apart from this I have gone through a Medium Post which explained about ResoponderFlow validating information passed through flows and one of the points mentioned over there was to verify the identity of the flow initiator(so as to find if we need that flow),which can't be done within a contract so it needs to be done inside a flow.
Also one can't keep flooding a node with a flow because it contains a timeout,maxRestartCount and backOffBase which really help in determining how the flow is getting propagated across the network.
I hope this helps you to construct a solution to your doubt.
Can there be just a single node (not even a notary) in the corda n/w?
If yes, can the single node execute corda flows that will have the single node both as sender and receiver?
Theoretically Yes, you could have a single node that serves both as a transacting party as well as a notary. For executing flows yes it can self-issue and consume states as well.
Practically, I do not see any implication of such a network, why use DLT for such use-case.
Looking through the documentation I can't find a way to get the current status of the nodes (online/offline) using the network map service.
Is this already implemented?
I can find this information using OS tools but I would like to know if there is a Corda way for this task.
Thanks in advance.
This feature is not implemented as of Corda V3. However, you can implement this functionality yourself. For example, see the Ping Pong sample here that allows you to ping other nodes.
In the future, it is expected that the network map will regularly poll each node on the network. Nodes that did not respond for a certain period of time (as defined by the network operator) would be evicted from the network map. However, this period of time is expected to be long (e.g. a month).
Please also note that:
In Corda, communication between nodes uses message acknowledgments. If a node is offline when you send it a message, no acknowledgment will be received, and the node will store the message to disk and retry delivery later. It will continue to retry until the counterparty acknowledges receipt of the message
Corda is designed with "always-on" nodes in mind. A node being offline will generally correspond to a disaster scenario, and the situation should not be long-lasting
If I know one the IP address of one Riak node, how do I use the Riak API to discover the other nodes?
Update 2013-10-22 5:37 PM CST: One of the reasons I want to do this is to detect network partitions. Being aware of them could be helpful. If my dev-ops infrastructure knows the list of Riak machines, then I could (as needed) contact each node and make sure that all are connected. If not, then it tells me that something in the dev-ops code isn't quite right or something else went wrong.
Connect to http://my-riak-node:8098/stats and inspect ring_members, which contains the "list of nodes which are members of the ring" according to the Riak HTTP API.
I am looking for a way to replicate a small and simple relational database (like SQLite) across peers. This should work in an environment with unstable network connections, hence the need for each peer to have a full copy of the database. This should allow a peer to continue working off-line in the event of network failure.
To keep things simple, replication should only have to support the replication of addition of data, i.e. only INSERTs, not DELETEs or UPDATEs.
Does anyone know of a good - and ideally cross-platform - technology or method of creating such a system? I am currently looking at JXTA and JXSE, but I am put off by its complexity and apparant lack of life in its community after the takeover of Sun by Oracle.
Thanks!
Frans
rqlite uses the raft consensus algorithm, so it should be fairly resilient to unstable network connection.
Also, it seems to be possible to configure rqlite to accept reads even in the case of a network failure.
A similar project, dqlite, exists as a library, available in various languages, but it seems less explicit about the event of a network failure.
You may want to explore JGroups for the communication layer if you don't like JXTA. For the replication, I think you will have to implement your own code.
I am working on something similar (though the code is far from ready). I'll describe a little about my intended approach, but whether that is suitable for you depends on some key design points you'd need to consider. I am not aware of any ready-built projects that will do this, unfortunately.
In particular we'd need to know what language you wish to use, or which languages you'd rather avoid.
Also, consider how you intend to do peer dicovery - can you set up trust between node pairs manually, or do you want them to auto-discover?
Presumably all peers may insert data?
If you are able to use PHP, and are happy manually peering node pairs, then my approach may be of interest. Set up an ORM such as Doctrine, Propel or NotORM, and get each node to regularly sync with an internet time source. For each new row in a db, grab the data (either in an array or ORM object), serialise it, and push it out to all nodes that you have a trust relationship with. Where a push fails, keep a note of this and retry at periodic intervals (potentially giving up after a remote node fails to answer a large number of retries).
Pushes can either be kicked off by your application that creates the row, or can be called by whatever scheduler is available on each machine. A push message can be XML, or for simplicity can be just a POST message containing the new row and whatever metadata (e.g. timestamp of save, so as to resolve INSERT order from several nodes).
If your nodes do not have static IP addresses, they could be registered with a dynamic DNS addressing service so as to allow each node to stay in touch with peers even if their IP changes. You might also consider adding a message signing system, to ensure that messages between nodes are genuine.