Dynamo | A lightweight state-based controller for Android | Reactive Programming library
kandi X-RAY | Dynamo Summary
kandi X-RAY | Dynamo Summary
An extremely lightweight collection of classes for implementing a state based decoupled controller architecture for Android applications. A major benefit of this is that it also keeps asynchronous code away from the Android lifecycle.
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Top functions reviewed by kandi - BETA
- Called when the activity is created
- Gets the ComputationDynamo instance
- Visit the current state machine
- Get the singleton instance
- Get the dynamo instance for the given meta factory
- Called when aGo button is pressed
- Get the state machine
- Get the current state
- Invoked when the current state machine has been processed
- Sets the text of the computation
- Sets the button to be displayed
- This method is called when the DynamoState instance is ready
- Handle a new state change event
- Moves the current state to the next state
- Removes a object from the cache
- Removes all objects
- Terminates the state machine
- Observe the state of the observer
- Deletes the observer
- Removes the oldest entry from the map
Dynamo Key Features
Dynamo Examples and Code Snippets
Community Discussions
Trending Discussions on Dynamo
QUESTION
I read this answer, which clarified a lot of things, but I'm still confused about how I should go about designing my primary key.
First off I want to clarify the idea of WCUs. I get that WCU is the write capacity of max 1kb per second. Does it mean that if writing a piece of data takes 0.25 seconds, I would need 4 of those to be billed 1 WCU? Or each time I write something it consumes 1 WCU, but I could also write X times within 1 second and still be billed 1 WCU?
Usage
I want to create a table that stores the form data for a set of gyms (95% will be waivers, the rest will be incidents reports). Most of the time, each forms will be accessed directly via its unique ID. I also want to query the forms by date, form, userId, etc..
We can assume an average of 50k forms per gym
Options
First option is straight forward: having the formId be the partition key. What I don't like about this option is that scan operations will always filter out 90% of the data (i.e. the forms from other gyms), which isn't good for RCUs.
Second option is that I would make the gymId the partition key, and add a sort key for the date, formId, userId. To implement this option I would need to know more about the implications of having 50k records on one partition key.
Third option is to have one table per gyms and have the formId as partition key. This seems to be like the best option for now, but I don't really like the idea of having a a large number of tables doing the same thing in my account.
Is there another option? Which one of the three is better?
Edit: I'm assuming another option would be SimpleDB?
...ANSWER
Answered 2021-May-21 at 20:26For your PK design. What data does the app have when a user is going to look for a form? Does it have the GymID, userID, and formID? If so, make a compound key out of that for the PK perhaps? So your PK might look like:
QUESTION
I have written terraform code which:
- Creates IAM Role
- Creates lambda functions and attaches the above created role
- Dynamo DB table creation
- Creates API gateway, resources and adds POST method with lambda integration.
The first 3 steps works well. However while creating and configuring the API gateway, I am encountering below error in resource aws_api_gateway_integration & aws_lambda_permission, where I am trying to attach the lambda function "save_course" to the POST method under "courses" resource
...ANSWER
Answered 2021-Jun-12 at 22:21Change your locals from
QUESTION
I have a method in an AWS Lambda which receives a completed list of items. It processes those items and then inserts them into a Dynamo DB table. Order of processing or inserting into the DB does not matter.
I'm looking for the most thread-safe, yet easy to understand manner in which to make this run faster; Either by using async await or something other (likely parallel?) operations.
I was thinking Parallel.ForEach() but that seems a bit heavy. Is there a simpler, more obvious way?
ANSWER
Answered 2021-Jun-10 at 20:22Here are some basic changes I would make to start off with. There may be other improvements you can make from there.
- Avoid
Thread.Sleepin async code.Task.Delayis the async equivalent. - Create many tasks before awaiting any. The runtime will try to run some concurrently if it can.
QUESTION
This might be a very silly question when it comes to dynamo DB.
Well,to summarize the issue I have a dynamoDB set up in my project.
(FYI, I have not setup a local dynamodb, I'm trying to connect to my remote db in lab environment)
The configuration for which is as follows:
ANSWER
Answered 2021-Jun-08 at 16:52The problem is that your local machine doesn't have an instance profile.
If you're looking to consume AWS services from your local machine, you will have to use a credentials provider that retrieves the information locally. I recommend using DefaultAWSCredentialsProviderChain, which looks for local configuration (either in $HOME/.aws or via environment variables or system properties), and also supports instance profiles (in case you're running on an EC2 instance).
That's why removing amazonDynamoDB.setCredentials(new InstanceProfileCredentialsProvider(false)); worked
QUESTION
ANSWER
Answered 2021-Jun-07 at 12:45There are a couple of problems in your code:
- you need to parse the event body if it's JSON using
Item=json.loads(event['body']) - you need to stringify the returned dict using
'body': json.dumps(response)
QUESTION
When I used enhanced client to put but it throws class cast exception.
...ANSWER
Answered 2021-Jun-04 at 15:28This worked for me SpringBoot - Java AWS SDK 2 DynamoDB Enhanced Client and devtools problem
So basically the issue was with spring dev tools and its class loader(2 in number), so you can either remove it or move dynamo to the same class loader.
QUESTION
ANSWER
Answered 2021-Apr-24 at 18:15Like was discussed in the comments, you need to create an expression attribute value map with the value of the filter and use this.
Try something like this:
QUESTION
I'm trying to setup a lambda to receive a dynamo dB stream and publish these database changes to an sns topic. I'm not sure how I would publish a message from the lambda to my topic using the cdk. Are there any examples of this?
...ANSWER
Answered 2021-May-29 at 12:38aws-cdk is used to create AWS resources. In other words you use it to create AWS Labmda, Dynamo DB table, SNS Topic. However, once those resources are created one rarely uses CDK to operate on them.
In order to send messages to SNS inside your Lambda refer to documentation of AWS SDK for the runtime you choose. For instance, if you decided to write your lambda in node.js you would refer to AWS SDK for node.js.
This is how your lambda code could look like:
QUESTION
I have a DynamoDB table where I'm aggregating CDN access logs. Specifically I want to track:
For a given customer (all of whose requests can be identified from the URL being downloaded), how many bytes were delivered on their behalf each day?
I have a primary partition key on customer and a primary sort key on time_bucket (day). This way given a customer I can say "find all records from March 1st, 2021 to March 31st, 2021" for instance. So far, so good
The issue arose when I wanted to start deleting old data. Anything older than 5 years should be dropped from the database.
Because the partition key isn't on time_bucket, there's no easy way to say "retrieve all records for May 25th, 2016". Doing so requires a scan instead of a query, and scans are out of the question (unusably slow given how much data I'm handling)
I don't want to swap the partition key and sort key for two reasons:
- When processing new data to add to the Dynamo table, all new CDN logs will be for the same day. This means that my table will be unbalanced: every write operation made during a single day will hit the same partition key
- If I wanted to pull a month's worth of data for a single customer I would have to make 30 queries -- one for each day of the month. This gets even worse when pulling a year of data, or 3 years of data
My first thought was "just add an index on the time_bucket column", but when I tried this I got an error:
Attribute Name is duplicated: time_bucket (Service: AmazonDynamoDBv2; Status Code: 400; Error Code: ValidationException; Request ID: PAN9FVSEMBBJT412NCV013VURNVV4KQNSO5AEMVJF66Q9ASUAAJG; Proxy: null)
It seems like DynamoDB does not allow you to create an index on the sort key. So what's the proper solution here?
...ANSWER
Answered 2021-May-26 at 15:37The right way to handle this is to simply set a 5yr TTL on the records when you put them in DDB.
Not only will the records be removed automatically, but the removal is free. No WCU is consumed.
You could add TTL now, but you're going to have to put together a little utility to add a expiration time attribute to the existing records.
If you want to do it manually, you'll need add Global Secondary Index (GSI). You could do so with the existing timebucket as the GSI hash key. Then you'd
Query(GSI, hk='2016-05-01') to find the records and DeleteItem() for each one.
Note that a GSI has it's own costs, and you'll pay to read the GSI and delete from the table.
QUESTION
As per DynamoDB's documentation it supports both key-value and document-oriented properties of NoSQL even though other NoSQL databases fall only under only one type either Key-Value or Document or Graph or Column-oriented
Also it says
Amazon DynamoDB is "built on the principles of Dynamo"[3] and is a hosted service within the AWS infrastructure. However, while Dynamo is based on leaderless replication, DynamoDB uses single-leader replication.
And Dynamo is
A set of techniques that together can form a highly available key-value structured storage system[1] or a distributed data store
So when DynamoDB is built on the principles of Dynamo which is not related to Document-oriented storage system and since it is mandatory for a developer to create a primary key and the table requires key for every item how and in what sense DynamoDB is called a Document-oriented database ?
Can a DB fall under two types of NoSQL databases in the first place ?
...ANSWER
Answered 2021-May-25 at 16:01First, it is important to realize that "Dynamo" was an earlier nosql database designed by Amazon, and its design was made public in 2007 (e.g., see https://www.allthingsdistributed.com/2007/10/amazons_dynamo.html). Other people later took this design, and other contemporary designs (like Google's BigTable) and improved on them, resulting in projects such as Cassandra (2008). Amazon's DynamoDB was only released in 2012, based on many ideas from those other systems (and especially Cassandra) and had very little in common with the original "Dynamo". So almost anything you can say about the original "Dynamo" would not be relevant when you discuss the modern DynamoDB.
Now regarding your main question:
A key-value store holds for each key a single value. Arguably, if the value can be an entire document, you can call this database a "document store". In this sense, DynamoDB is a document store. The DynamoDB API lets you conveniently store a JSON document as the value, and also read or writes part of this document directly instead of reading or writing the entire document (although, you actually pay for reading and writing the entire document).
You should note that DynamoDB, like Cassandra and BigTable (and unlike the original "Dynamo") actually gives you more than that: Each so-called "partition key" can hold not just one value (or document), but a sorted list of such values. I mentioned this interesting feature, which I don't know how to call, in my question How do you call the data model of DynamoDB and Cassandra?
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