In beam sdk, pubusbIO read provides an option to deduplicate messages by using message id: https://beam.apache.org/releases/javadoc/2.23.0/org/apache/beam/sdk/io/gcp/pubsub/PubsubIO.Read.html#withIdAttribute-java.lang.String-
When I checkout Pubsub client libs (for java and python), I don't see there is a similar option for using message id to deduplicate messages.
So my questions are:
Do pubsub client libs (python and java) have similar functionality? Perhaps I missed it because of different naming.
If they don't, how are you handling this situation? I'm just curious how it is solved as an inspiration. Cause I'm thinking about using a cache to store most recent message ids for deduplication purpose in my client application.
Thank you.
There isn't the same feature in the PubSub client library. Cloud Dataflow, that run Beam pipeline, keep a cache of the latest messageIds (I don't know how many and how many time, but it's only few minutes). It's a Beam feature.
When you use PubSub, and because PubSub guaranty only at-least-one-delivery, it's recommended to have your process idempotent
In general, accommodating more-than-once delivery requires your subscriber to be idempotent when processing messages.
Related
I have a scenario where I need to call an api to the notification service which will send an email to the user.
Based on the message that appears to the topic I need to consume and call an api.
But if the consumer fails in between due to the nature of the at-least once configuration of the consumer its hard to avoid duplicate processing.
Sorry for newbie question. I Tried to find the many blogs but most of them are using newer version of Kafka but in our infra they are still using older version.
Wondering how can we achieve this behavior?
Links that I referred earlier :
If exactly-once semantics are impossible, what theoretical constraint is Kafka relaxing?
I also saw there documentation where they mention to store the processing result and offset to the same storage. But my scenario is api call lets imagine if the consumer call api and dies in between before committing offset then next poll will get that message and call api. In this way email will be sent twice.
Any help is appreciated.
I need to create a solution that receives events from web/desktop application that runs on kiosks. There are hundreds of kiosks spread across the country and each one generate time to time automatic events and events when something happens.
Despite this application is a locked desktop application it is built in Angular v8. I mean, it runs in a webview.
I was researching for scalable but reliable solutions and found Apache Kafka seems to be a great solution. I know there are clients for NodeJS but couldn't find any option for Angular. Angular runs on browser, for this reason, it must communicate to backend through HTTP/S.
In the end, I realized the best way to send events from Angular is to create a API that just gets message from a HTTP/S endpoint and publishes to Kafka topic. Or, is there any adapter for Kafka that exposes topics as REST?
I suppose this approach is way faster than store message in database. Is this statement correct?
Thanks in advance.
this approach is way faster than store message in database. Is this statement correct?
It can be slower. Kafka is asynchronous, so don't expect to get a response in the same time-period you could perform a database read/write. (Again, would require some API, and also, largely depends on the database used)
is there any adapter for Kafka that exposes topics as REST?
Yes, the Confluent REST Proxy is an Apache2 licensed product.
There is also a project divolte/divolte-collector for collecting click-data and other browser-driven events.
Otherwise, as you've discovered, create your own API in any language you are comfortable with, and have it use a Kafka producer client.
I am new to Apache Kafka and its stream services related to API's, but was wondering if there was any formal documentation on where to obtain the initial raw data required for ingestion?
In essence, I want to try my hand at building a rudimentary crypto trading bot, but was under the impression that http APIs may have more latency than APIs that integrate with Kafka Streams. For example, I know RapidAPI has a library of http APIs that can be accessed that would help pull data, but was unsure if there was something similar if I wanted the data to be ingested through Kafka Streams. I guess I am under the impression that the two data sources will not be similar and will be different in some way, but am also unsure if this is not the case.
I tried digging around on Google, but it's not very clear on what APIs or source data is taken for Kafka Streams, or if they are the same/similar just handled differently.
If you have any insight or documentation that would be greatly appreciated. Also feel free to let me know if my understanding is completely false.
any formal documentation on where to obtain the initial raw data required for ingestion?
Kafka accepts binary data. You can feed in serialized data from anywhere (although, you are restricted by (configurable) message size limits).
APIs that integrate with Kafka Streams
Kafka Streams is an intra-cluster library, it doesn't integrate with anything but Kafka.
If you want to periodically, poll/fetch an HTTP/1 API, then you would use a regular HTTP client, and a Kafka Producer.
Probably a similar answer with streaming HTTP/2 or websocket, although, still not able to use Kafka Streams, and you'd have to deal with batching records into a Kafka Producer request
You instead should look for Kafka Connect projects on the web that operate with HTTP, or opt for something like Apache NiFi as a broader project with lots of different "processors" like GetHTTP and ProduceKafka.
Once the data is in Kafka, you are welcome to use Kafka Streams/KSQL to do some processing
We have developed modular web app with very powerful API and now we need queuing tool for delayed|time consuming jobs. We are looking at RabbitMQ or AWS SQS. But these two just store messages, and you have to manually get messages from them or I misunderstood it?
We would like to channel all messages through our API, so when message is published to Queue in should be POST-ed (after some delay) to to our Interface.
So my question:
Is there any tool for queuing that support http post (with oauth2)?
If not, is this approach somehow valid:
Create worker that poll messages from queue
and POST them to API with some client?
(we have to maintain cli tool, and we want to avoid that).
Are there any alternatives?
When using SQS polling is the only way out.
To make things easier you can write this polling logic in AWS Lambda because lambda functions do not have the overhead of maintaining infrastructure and servers
I need to fetch messages from Kafka topics and notify other systems via HTTP based APIs. That is, get message from topic, map to the 3rd party APIs and invoke them. I intend to write a Kafka Sink Connector for this.
For this use case, is Kafka Connect the right choice or I should go with Kafka Client.
Kafka clients when you have full control on your code and you are expert developer, you want to connect an application to Kafka and can modify the code of the application.
push data into Kafka
pull data from Kafka.
https://cwiki.apache.org/confluence/display/KAFKA/Clients
Kafka Connect when you don’t have control on third party code new in Kafka and to you have to connect Kafka to datastores that you can’t modify code.
Kafka Connect’s scope is narrow: it focuses only on copying streaming data to and from Kafka and does not handle other tasks.
http://docs.confluent.io/2.0.0/connect/
I am adding few lines form other blogs to explain differences
Companies that want to adopt Kafka write a bunch of code to publish their data streams. What we’ve learned from experience is that doing this correctly is more involved than it seems. In particular, there are a set of problems that every connector has to solve:
• Schema management: The ability of the data pipeline to carry schema information where it is available. In the absence of this capability, you end up having to recreate it downstream. Furthermore, if there are multiple consumers for the same data, then each consumer has to recreate it. We will cover the various nuances of schema management for data pipelines in a future blog post.
• Fault tolerance: Run several instances of a process and be resilient to failures
• Parallelism: Horizontally scale to handle large scale datasets
• Latency: Ingest, transport and process data in real-time, thereby moving away from once-a-day data dumps.
• Delivery semantics: Provide strong guarantees when machines fail or processes crash
• Operations and monitoring: Monitor the health and progress of every data integration process in a consistent manner
These are really hard problems in their own right, it just isn’t feasible to solve them separately in each connector. Instead you want a single infrastructure platform connectors can build on that solves these problems in a consistent way.
Until recently, adopting Kafka for data integration required significant developer expertise; developing a Kafka connector required building on the client APIs.
https://www.confluent.io/blog/announcing-kafka-connect-building-large-scale-low-latency-data-pipelines/
Kafka Connect will work well for this purpose, but this would also be a pretty straightforward consumer application as well because consumers also have the benefits of fault tolerance/scalability and in this case you're probably just doing simple message-at-a-time processing within each consumer instance. You can also easily use enable.auto.commit for this application, so you will not encounter the tricky parts of using the consumer directly. The main thing using Kafka Connect would give you compared to using the consumer in this case would be that the connector could be made generic for different input formats, but that may not be important to you for a custom connector.
you should use kafka connect sink when you are using kafka connect source for producing messages to a specific topic.
for e.g. when you are using file-source then you should use file-sink to consume what source have been produced. or when you are using jdbc-source you should use jdbc-sink to consume what you have produced.
because the schema of the producer and sink consumer should be compatible then you should use compatible source and sink in both sides.
if in some cases the schemas are not compatible you can use SMT (Simple message transform) capability that is added since version 10.2 of kafka onward and you will be able to write message transformers to transfer message between incompatible producers and consumers.
Note: if you want to transfer messages faster I suggest that you use avro and schema registry to transfer message more efficiently.
If you can code with java you can use java kafka stream, Spring-Kafka project or stream processing to achieve what you desire.
In the book that is called Kafka In Actionis explained like following:
The purpose of Kafka Connect is to help move data in or out of Kafka without having to deal with writing our own producers and clients. Connect is a framework that is already part of Kafka that really can make it simple to use pieces that have been already been built to start your streaming journey.
As for your problem, Firstly, one of the simpliest questions that one should ask is if you can modify the application code of the systems from which you need data interaction.
Secondly, If you would write custom connector which have the in-depth knowledge the ability and this connector will be used by others, it worth it. Because it may help others that may not be the experts in those systems. Otherwise, this kafka connector is used only by yourself, I think you should write Kafka connector. So you can get more flexibility and can write more easily implementing.