What would be the most reliable way of checking if a given TX on different network has been confirmed k times using Chainlink?
I know I can make an API call to Etherscan, for instance, but since this is a common use-case I wonder if there are more reliable well-known methods for doing it.
Chainlink itself advertises Cross-Chain solutions (https://chain.link/solutions/cross-chain) but I could not find any technical documentation about those. Pointers are welcome.
Chainlink CCIP (Cross-Chain Interoperability Protocol) is still in development.
In the meantime, you can make an API call to another blockchain with the Chainlink API feature. You'll have to do some work to make sure that you have enough nodes making the API calls to make sure it's decentralized, but that's essentially it!
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I have a requirement to persist some data in a table (single table). The data is coming from UI. Do i need to write just the system API and persist the data OR i need to write process and system API both? I don't see a use of process API in this case. Please suggest. Is it always necessary to access system API through process API or system API can be invoked without process API as well.
I would recommend a fine-grained approach to this. We should be following it through the experience layer even though we do not have must customization to the data.
In short, an experience layer API and directly calling System layer API (if there is no orchestration/data conversion/formatting needed)
Why we need a system API & experience API? A couple of points.
System API should be more attached to the underlying system. And if
in case, in the future, it changes then it should not impact any of
the clients.
Secondly, giving an upper layer gives us the feasibility to add
different SLAs, policies, logging and lots more, to different
clients. Even if you have a single client right now it's better to
architect for the future. Reusing is the key advantage of these APIs.
Please check Pattern 2 in this document
That is a question for the enterprise architect in your organisation. In this case, the process API would probably be a simple proxy for the system API, but that might not always be the case in future. Also, it is sometimes useful to follow a standard architectural pattern even if it creates some spurious complexity in the implementation. As always, there are design trade-offs and the answer will depend on factors that cannot be known by people outside of your organisation.
I saw in articles that OpenStreet map provides an API that, given a route with an origin and destination and multiple (unlimited?) waypoints it sorts the waypoints according to the best route.
I couldn't tell which endpoint it was. Could someone point me to the part of the documentation that explains how to achieve this? Is there a ruby gem that wraps up this endpoint request?
Thank you very much
This is the traveling salesman problem. There is more than one OSM-based router for solving this problem. According to a similar question at help.openstreetmap.org:
All major OSM routing engines support this:
Mapzen's Valhalla
("Valhalla also includes tools like time+distance matrix computation,
isochrones, elevation sampling, map matching and tour optimization
(Travelling Salesman)."),
Mapbox's
OSRM ("The
trip plugin solves the Traveling Salesman Problem using a greedy
heuristic...")
Graphhopper uses the JSPrit
library
for route optimization ("TSP problem can be modelled by defining a
vehicle routing problem...")
None of these services have a free and unlimited online offering (it
would quickly be abused by people trying to save on their own AWS
cost). Mapzen has an offer where you register a free API key and use
that. OSRM doesn't need an API key, you can just use it. Graphhopper
requires registration and while they have a free trial, I don't think
they have a free tier.
All three are Open Source and you can install and use them without
limits locally.
For GraphHopper take a look at the Route Optimization API. For OSRM see the trip plugin.
Set up your own OpenStreetMap server - this way you won't be incurring data access fees every time your app needs to run maps queries.
Specifically, install the Valhalla maps server. It's a free application. Best to install it on a Linux box:
https://github.com/valhalla/valhalla
Or download and run the docker image in Docker instead:
https://hub.docker.com/r/abihf/valhalla/
https://github.com/interline-io/valhalla-docker
The server provides an API specifically for ordering waypoints:
https://valhalla.readthedocs.io/en/latest/api/optimized/api-reference/
I am working with geocoder gem and like to process more number of requests from an IP. By default Google API provides only 2500 requests per day.
Please share your thoughts on how I can do more requests than the limit?
As stated before: Using only Google API the only way around the limitation is to pay for it. Or in a more shady way make the requests form more than one IP/API-Key which i would not recommend.
But to stay on the save side i would suggest mixing the services up since there a few more Geocoding APIs out there - for free.
With the right gem mixing them is also not a big issue:
http://www.rubygeocoder.com/
Supports a couple of them with a nice interface. You would pretty much only have to add some rate-limiting counters making sure you stay within the limits of each provider.
Or go the heavy way of implementing your own geocoding. With for example your own running Openstreetmaps database. The Database can be downloaded here: http://wiki.openstreetmap.org/wiki/Planet.osm#Worldwide_data
Which is the best way depends on what your actual requirements are and what ressources you have available.
before I start I realise there are a few SNMP related questions here already but not many seem to have been answered - that could mean I'm asking in the wrong place but I don't know where else to go at the moment.
I've been reading up as best I can on SNMP for a couple of days but am finding it difficult to get my head around what is meant to be happening. The idea is eventually we will integrate SNMP into our Java application server which will allow the end users to incorporate it into their pre-existing Network Management Systems(NMS).
Unfortunately I'm feeling entirely confused by what is meant to be going on. From what I understood from talking to the end users (which was unfortunately before any research) was that the monitoring allows their existing NMS to give their admin guys a view of the vital statistics in a tree type display, giving them feedback regarding different parts of the system at a high level and allowing them to dig down into specific subsystems.
From reading around we would implement an 'Agent' which has several defined interfaces allowing for GET requests etc to be processed and responded to. That makes sense but I am at a loss to work out what the format of the communication is - there don't seem to be any specific examples of what any of the messages look like, how the information is encoded.
More of my confusion though is regarding Management Information Base(MIB). I had, wrongly, assumed that the interface of the agent would allow for the monitored attributes to be requested and then in turn the values for those attributes requested. Allowing any new Agent to be started and detected without any configuration on the NMS end (with the exception of authentication in v3). This, if I understand correctly, is not the case and the Agent must instead define MIBs which can be used by the NMS to determine those attributes. My confusion is increased when people start referring to thousands of existing MIBs and that they can be reused which I don't understand. Is the intention that a single MIB definition can be used to say describe how a particular attribute of a network device (something simple like internet connected on a router:yes/no) for many different devices? If so I don't believe that our software would allow the monitoring of anything common to any other device/system but should we be looking for already exising MIBs? At the moment I don't really see any good rational for such a system, surely it would be easier for the Agent to export that information - so I'd appreciate it if someone could enlighten me!
I think it would help if I was able to setup a simple SNMP agent and some sort of client, I could begin to see the process and eventually inspect the communication between the two but am finding it difficult to find anywhere that provides any information on doing such a thing. Nagios has been recommended to us as a test 'client'/NMS but their 'get started quick' section recommends downloading a 600Mb virtual machine - surely there is a quicker way to get started?
Any help or suggestions will be appreciated, I have been through the Wiki page but it doesn't seem to go into much detail about the MIBs and the having not had to deal with anything like the referenced RFCs before, while they may contain all of the information they seem completely impenetrable to me at the moment. Or if there are any books that can be recommended for an overview and implementation of v3?
Thanks for reading and even more thanks if you think you can help!
It seems to me that you read all SNMP information piece by piece in an disorganized way. This is highly not recommended and of course lead you to confusion.
What about forgetting what you have learnt so far and dive into a good book such as Essential SNMP?
http://shop.oreilly.com/product/9780596008406.do
Click the Google Preview icon to preview it please.
You could not depend on a network forum to tell you the ABCs, as that's impractical I find out.
The communications interface is SNMP. That's the protocol used for transmission (usually on top of UDP). The thing that services information requests is an SNMP Agent. The thing that sends information requests is an SNMP Manager.
The definition of what information should be made available by the Agent, and requested by the Manager, goes in a MIB. A MIB is the "glue", a directory of what sort of things any particular system can/should offer. It maps numeric codes to names and types that allow us to make sense of the data, much like how a phone directory maps phone numbers to people's names and addresses.
Generally you would create and ship and use your own MIBs that can describe aspects specific to your own product, but you are supposed to service some standard information requests as well, which are defined in existing MIBs. Yes there are thousands of other pre-existing MIBs and the likelihood that you need more than one or two of these is remote. They are typically published versions of MIBs for existing products.
The conventional way to "toy around" is to install Net-SNMP (a software suite that includes an agent implementation and allows you to "bolt on" your own logic and your own MIBs fairly easily) then examine the results using a packet capturer like Wireshark.
For a fuller implementation in production you may stick with Net-SNMP, or write your own Agent software, or do what I did and create a hybrid of the two that's a little more flexible and performant but uses Net-SNMP's backend for handling all the low-level SNMP stuff.
Your first step, though, is to read a book or some other teaching material that can clear all your misconceptions, because guesswork won't cut it.
I had success using the samples from this page. Both the shell and Perl NetSNMP code was very straightforward to implement and query.
I'm interested in how you would approach implementing a BitTorrent-like social network. It might have a central server, but it must be able to run in a peer-to-peer manner, without communication to it:
If a whole region's network is disconnected from the internet, it should be able to pass updates from users inside the region to each other
However, if some computer gets the posts from the central server, it should be able to pass them around.
There is some reasonable level of identification; some computers might be dissipating incomplete/incorrect posts or performing DOS attacks. It should be able to describe some information as coming from more trusted computers and some from less trusted.
It should be able to theoretically use any computer as a server, however, optimizing dynamically the network so that typically only fast computers with ample internet work as seeders.
The network should be able to scale to hundreds of millions of users; however, each particular person is interested in less than a thousand feeds.
It should include some Tor-like privacy features.
Purely theoretical question, though inspired by recent events :) I do hope somebody implements it.
Interesting question. With the use of already existing tor, p2p, darknet features and by using some public/private key infrastructure, you possibly could come up with some great things. It would be nice to see something like this in action. However I see a major problem. Not by some people using it for file sharing, BUT by flooding the network with useless information. I therefore would suggest using a twitter like approach where you can ban and subscribe to certain people and start with a very reduced set of functions at the beginning.
Incidentally we programmers could make a good start to accomplish that goal by NOT saving and analyzing to much information about the users and use safe ways for storing and accessing user related data!
Interesting, the rendezvous protocol does something similar to this (it grabs "buddies" in the local network)
Bittorrent is a mean of transfering static information, its not intended to have everyone become producers of new content. Also, bittorrent requires that the producer is a dedicated server until all of the clients are able to grab the information.
Diaspora claims to be such one thing.