I need to get the current server time/timestamp from AWS dynamodb to my ios swift application.
In firebase db we can write the current timestamp to db and after that we can read it from the app. Any suggestion about this is appreciated.
DynamoDB does not provide any sort of server time—any timestamps must be added by the client. That being said, you can emulate a server time behavior by setting up a Lambda function or an EC2 instance as a write proxy for DynamoDB and have it add a timestamp to anything being written to DynamoDB. But it’s actually even easier than that.
AWS allows you to use API Gateway to act as a proxy to many AWS services. The process is a little long to explain in detail here, but there is an in-depth AWS blog post you can follow for setting up a proxy for DynamoDB. The short version is that you can create a rest endpoint, choose “AWS Service Proxy” as the integration type, and apply a transformation to the request that inserts the time of the request (as seen by API Gateway). The exact request mapping you set up will depend on how you want to define the REST resources and on the tables you are writing to. There is a request context variable that you can use to get the API Gateway server time. It is $context.requestTimeEpoch.
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I have an external service that provides weather data via Restfull API with authentication.
What would be the best option to able to consume the services and send/insert the data to a Context broker.
I was thinking to develop a custom IoT Agent with json file to provide the external Restfull service endpoint and configuration for the Context broker.
Is any other option to achieve the same functionality?
The big question here is whether you need to inject the data into the context broker, or just inform the context broker that such data exists. If you want to consider the weather station as a device, then indeed, your proposed architecture makes sense:
Create a chron job to fire periodically
Generate a file in a known format (e.g. JSON) and pass the file to a custom micro-service
The micro-service interprets the file and runs a batch upsert to send all the data as measures into the context broker
An example of this with a code walkthrough is discussed in the following webinar
The alternative would be to create a micro-service which listens to the registration endpoint(s) - for NGSI-v2 uses the /v2/op/query batch endpoint for this, for NGSI-LD it is a direct forwarding of a request. In this scenario, the weather-station data remains outside of the context broker itself and can be used to augment existing entities. A working example can be found within the FIWARE Tutorials
Obviously the route you choose will depend upon what you need to do with the data, if you need to subscribe to temperature changes for example, then it is better to treat the weather station as a device providing context data in the form of measures and go for Option 1.
I am setting up a read only GraphQL instance using Java. GraphQL as I understand it needs to be told when to re-query its data sources. We are using GCP, and Cloud SQL for our primary data source. Our monolithic system is what is responsible for updating the data.
Is there a way to trigger a web request or pub/sub message from cloud sql without sys_eval(sys_eval('curl https://example.com'));?
or is there a way to turn on sys_eval in cloud sql?
After some brainstorming around sys_eval alternatives such as binary logs and so on, I think the course of action I'd recommend is to move the MySQL client to the GCE instance, and establish the connection to the Cloud SQL instance through a Private IP.
Such connection will be guaranteed a much lower latency, and an a lot higher network security, since, the service does not use Public IPs and it would be protected from the "outside" Internet; all compared to your current architecture.
You can find connection examples using VPC networks in the documentation provided.
I need to create a API where the Vendors will push the data to the server using REST calls and this data needs to further pushed to a user on mobile app(using Websocket guessing as of now) to whom the data belongs.
For Vendors to use REST API : I need to check the Vendor credential and Write that data to DB.
I am keen to know what approach should I use ? Should I use AWS API Gateway which can help for security and scalability.
and while using AWS API Gateway - what would be a better approach to have EC2 Endpoint or Lambda Endpoint.
Using EC2 vs Lambda depends on how you want to design your services and specific use cases. Going serverless is a trend these days, but you do not need to go serverless, just for the sake of being serverless.
For your use case, If the REST API you will expose updates a Database, let's say RDS, Lambda function probably is not an ideal choice. As you will need to open a connection every time the lambda function is invoked. Moreover, if you are running the lambda in a NO VPC config, You will need to publicly expose your RDS port. If its DynamoDB, it works out well.
But again, you want to push out the update to Mobile apps over say web sockets. You definitely need a WebSocket Server somewhere, and I guess its EC2.
You may design your application in way such that all your business logic resides in the lambda functions, updates the DB, posts a message to an SQS queue. The WebSocket server can then pick up messages from the SQS queue and post updates. This decouples your application architecture. This is just one approach and wont scale horizontally out of the box.
OR - You may choose to put everything in one EC2 instance, expose a REST API that updates the DB and also posts updates to the WebSocket connection.
We have different database as per client but all SP's and tables schema are same for all.
How to connect azure mobile service base on client?
Option:
publish service as per client, so number of client is equal to services.
put all connection string in config file. Read header value and pick connection accordingly.
any other option, do you know.
1st option is not feasible for us. because need publish code on all site for single change.
Please suggest me.
You cannot really use Azure Mobile Services for this. Azure Mobile Services is pretty much designed around a single database per service. I'd suggest switching over to Azure App Service. If you just need database access, you can set up a REST endpoint that provides the necessary access but looking up your connection strings on a per-authenticated user. You might want to use a schema per client instead to reduce the number of connection strings you have.
Short version: Look at the design of your service to reduce the number of SQL connection strings you are using. An ideal number is 1.
I have a RESTful web-service application that I developed using the Netbeans IDE. The application uses MySQL server as its back end server. What I am wondering now is how often a client application that uses my RESTful application would refresh to reflect the data change in the server.
Are there any default pull intervals that clients get from the RESTful application? Does the framework(JAX-RS) do something about it Or is that my business to take care of.
Thanks in advance
#Abraham
There are no such rules. Only thing you can use for properly implementing this is HTTP's caching capabilities. Service must include control information how long representation of a particular resource can be cached, revalidated, never cached etc...
On client application side of things each client may decide it's own path how it will keep itself in sync with a service. It can be done by locally storing data and serve end user from local cache etc... Service can not(and shouldn't know) how clients are implemented, only thing service can do is to include caching information in response messages as i already mentioned above.
It is your responsibility to schedule the service to execute again and again. We can set time out interval but there is no pull interval.