HaloDB | A fast , log structured key-value store | Key Value Database library
kandi X-RAY | HaloDB Summary
kandi X-RAY | HaloDB Summary
HaloDB is a fast and simple embedded key-value store written in Java. HaloDB is suitable for IO bound workloads, and is capable of handling high throughput reads and writes at submillisecond latencies. HaloDB was written for a high-throughput, low latency distributed key-value database that powers multiple ad platforms at Yahoo, therefore all its design choices and optimizations were primarily for this use case. Basic design principles employed in HaloDB are not new. Refer to this document for more details about the motivation for HaloDB and its inspirations. HaloDB comprises of two main components: an index in memory which stores all the keys, and append-only log files on the persistent layer which stores all the data. To reduce Java garbage collection pressure the index is allocated in native memory, outside the Java heap.
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Top functions reviewed by kandi - BETA
- Puts an entry into the map
- Increment the hash table
- Write to the next available slot
- Writes a new entry into the memory pool
- Create a map of string values as a string
- Convert stale data map to string
- Gets unit
- Starts the benchmark
- Updates a thread with random data
- Opens the configuration
- Deserializes an indexFileEntry from a byte buffer
- Returns the average histogram value
- Generate new offsets
- Rebuilds the index file
- Opens the database
- Write the histogram to the logger
- Clears the hash table
- Returns an estimated histogram of buckets
- Generate a string representation of the histogram
- Returns a snapshot of the total and free capacity statistics
- Reads a record
- Deserializes the indexFileEntry from the buffer
- Deserializes a tombstone entry
- Computes the estimated value at the given percentile
- Removes a key from this pool
- Returns true if the specified object is equals false otherwise
HaloDB Key Features
HaloDB Examples and Code Snippets
Community Discussions
Trending Discussions on Key Value Database
QUESTION
I'm developing a Laravel application & started using Redis as a caching system. I'm thinking of caching the data of all of a specific model I have, as a user may make an API request that this model is involved in quite often. Would a valid solution be storing each model in a hash, where the field is that record's unique ID, and the values are just the unique model's data, or is this use case too complicated for a simple key value database like Redis? I"m also curious as to how I would create model instances from the hash, when I retrieve all the data from it. Replies are appreciated!
...ANSWER
Answered 2021-Jul-08 at 17:02Short answer: Yes, you can store a model, or collections, or basically anything in the key-value caching of Redis. As long as the key provided is unique and can be retraced. Redis could even be used as a primary database.
Long answer
Ultimately, I think it depends on the implementation. There is a lot of optimization that can be done before someone can/should consider caching all models. For "simple" records that involve large datasets, I would advise to first optimize your queries and code and check the results. Examples:
- Select only data you need, not entire models.
- Use the Database Query Builder for interacting with the database when targeting large records, rather than Eloquent (Eloquent is significantly slower due to the Active Record pattern).
- Consider using the
toBase()method. This retrieves all data but does not create the Eloquent model, saving precious resources. - Use tools like the Laravel debugbar to analyze and discover potential long query loads.
For large datasets that do not change often or optimization is not possible anymore: caching is the way to go!
There is no right answer here, but maybe this helps you on your way! There are plenty of packages that implement similar behaviour.
QUESTION
In many articles, I've read that compacted Kafka topics can be used as a database. However, when looking at the Kafka API, I cannot find methods that allow me to query a topic for a value based on a key.
So, can a compacted Kafka topic be used as a (high performance, read-only) key-value database?
In my architecture I want to feed a component with a compacted topic. And I'm wondering whether that component needs to have a replica of that topic in its local database, or whether it can use that compacted topic as a key value database instead.
...ANSWER
Answered 2020-Nov-25 at 01:12Compacted kafka topics themselves and basic Consumer/Producer kafka APIs are not suitable for a key-value database. They are, however, widely used as a backstore to persist KV Database/Cache data, i.e: in a write-through approach for instance. If you need to re-warmup your Cache for some reason, just replay the entire topic to repopulate.
In the Kafka world you have the Kafka Streams API which allows you to expose the state of your application, i.e: for your KV use case it could be the latest state of an order, by the means of queriable state stores. A state store is an abstraction of a KV Database and are actually implemented using a fast KV database called RocksDB which, in case of disaster, are fully recoverable because it's full data is persisted in a kafka topic, so it's quite resilient as to be a source of the data for your use case.
Imagine that this is your Kafka Streams Application architecture:
To be able to query these Kafka Streams state stores you need to bundle an HTTP Server and REST API in your Kafka Streams applications to query its local or remote state store (Kafka distributes/shards data across multiple partitions in a topic to enable parallel processing and high availability, and so does Kafka Streams). Because Kafka Streams API provides the metadata for you to know in which instance the key resides, you can surely query any instance and, if the key exists, a response can be returned regardless of the instance where the key lives.
With this approach, you can kill two birds in a shot:
- Do stateful stream processing at scale with Kafka Streams
- Expose its state to external clients in a KV Database query pattern style
All in a real-time, highly performant, distributed and resilient architecture.
The images were sourced from a wider article by Robert Schmid where you can find additional details and a prototype to implement queriable state stores with Kafka Streams.
Notable mention:
If you are not in the mood to implement all of this using the Kafka Streams API, take a look at ksqlDB from Confluent which provides an even higher level abstraction on top of Kafka Streams just using a cool and simple SQL dialect to achieve the same sort of use case using pull queries. If you want to prototype something really quickly, take a look at this answer by Robin Moffatt or even this blog post to get a grip on its simplicity.
While ksqlDB is not part of the Apache Kafka project, it's open-source, free and is built on top of the Kafka Streams API.
Community Discussions, Code Snippets contain sources that include Stack Exchange Network
Vulnerabilities
No vulnerabilities reported
Install HaloDB
You can use HaloDB like any standard Java library. Please include the the jar files in your classpath. You can also use any IDE and you can run and debug the HaloDB component as you would do with any other Java program. Best practice is to use a build tool that supports dependency management such as Maven or Gradle. For Maven installation, please refer maven.apache.org. For Gradle installation, please refer gradle.org .
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