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async messaging nitric documentation foundations guides search search docs 1 9k search search docs introduction get started installation quick start guides foundations why nitric projects overview configuration infrastructure overview services resources security local development deployment architecture overview services apis schedules websockets websites storage key value stores async messaging queues topics sql databases secrets build apis batch ai ml hpc schedules websockets websites storage key value stores sql databases async messaging secrets deploy overview pulumi overview aws google cloud azure terraform overview aws google cloud azure service mappings aws apis batch schedules websockets websites storage key value stores sql databases topics queues secrets azure apis schedules websites storage key value stores sql databases topics queues secrets google cloud apis batch schedules websites storage key value stores sql databases topics queues secrets custom overview provider extension custom providers adding resource types install with docker languages overview node js overview apis api api get api post api put api delete api patch api route api route all api route get api route post api route put api route delete api route patch batch job job handler job submit http http key value stores kv kv get kv set kv delete kv keys topics topic topic publish topic subscribe queues queue queue enqueue queue dequeue secrets secret secret put secret version secret latest secret version access storage bucket bucket on bucket file bucket files file exists file read file write file delete file getdownloadurl file getuploadurl sql sql sql connectionstring schedules schedule schedule every schedule cron websockets websocket websocket on websocket send websocket close python overview apis api api get api post api put api delete api patch api methods api all batch job job handler job submit key value stores kv kv get kv set kv delete kv keys topics topic topic publish topic subscribe queues queue queue enqueue queue dequeue secrets secret secret put secret version secret latest secret version access storage bucket bucket on bucket file bucket files file read file write file delete file download_url file upload_url sql sql sql connection_string schedules schedule websockets websocket websocket on websocket send go overview resources newapi newjob newkv newqueue newsecret newsqldatabase newbucket newtopic newschedule newwebsocket apis api get api post api put api delete api patch api newroute api route all api route get api route post api route put api route delete api route patch batch job handler job submit key value stores kv get kv set kv delete kv keys topics topic publish topic subscribe queues queue enqueue queue dequeue secrets secret put secret accessversion secret access storage bucket on bucket listfiles bucket read bucket write bucket delete bucket downloadurl bucket uploadurl sql sqldatabase connectionstring schedules schedule every schedule cron websockets websocket on websocket send websocket close dart overview apis api api all api get api post api put api delete api patch api route api route all api route get api route post api route put api route delete api route patch batch job job handler job submit key value stores kv kv get kv set kv delete kv keys topics topic topic publish topic subscribe queues queue queue enqueue queue dequeue secrets secret secret put secret version secret latest secret version access storage bucket bucket on bucket file bucket files file exists file read file write file delete file getdownloadurl file getuploadurl sql sql sql connectionstring schedules schedule schedule every schedule cron websockets websocket websocket on websocket send websocket close reference cli preview features other config env vars custom service containers misc examples faq contributions support messaging nitric provides two common options for scalable decoupled asynchronous messaging between services topics for publish subscribe messaging where new messages are immediately pushed to subscribers and queues for pull messaging where new messages are put on a queue and must be requested in some circumstances messages sent to a topic may also be called events while messages sent to a queue may be called tasks the structures of these messages are very similar but the delivery and retry mechanisms are different it can be helpful to refer to these messages differently to assist in understanding the context in which they are used topics a topic is a named resource where events can be published they can be thought of as a subject that your services are communicating about topics are often the first choice for communication between services since they offer stateless scalable and highly decoupled communication if you re interested in the architecture provisioning or deployment steps they can be found here subscriptions a subscription is a binding between a topic and a service you can think of it as a channel that notifies your services when something new arrives on the topic creating a topic nitric allows you to define named topics when defining topics you can give the service permissions for publishing if permissions are not specified subscribers can be created here s an example of how to create a topic with permissions to publish messages javascript typescript python go dart copy copied import topic from nitric sdk const usercreatedtopic topic user created allow publish publishing a message to send a message to a topic and notify all subscribers use the publish method on the topic reference the service must have permissions to publish to the topic the below example publishes a message to a topic called user created javascript typescript python go dart copy copied import topic from nitric sdk const usercreatedtopic topic user created allow publish await usercreatedtopic publish email new user example com subscribing to a topic to execute a function when new messages are published you can create subscribers the delay between publishing a message and a subscriber being executed is usually only a few milliseconds this makes subscribers perfect for responding to messages as they happen the below code shows a subscription that responds to messages when new users are created javascript typescript python go dart copy copied import topic from nitric sdk import sendwelcomeemail from common const usercreatedtopic topic user created usercreatedtopic subscribe async ctx extract data from the event payload for processing const email ctx req json sendwelcomeemail email reliable subscribers if a subscriber encounters an error or is terminated before it finishes processing a message what happens is the event lost nitric deploys topics to cloud services that support at least once delivery messages are usually delivered exactly once in the same order that they re published however to prevent lost messages they re sometimes delivered more than once or out of order typically retries occur when a subscriber doesn t respond successfully like when unhandled exceptions occur you ll typically want to ensure messages aren t processed again by accident or partially processed leaving the system in an unexpected state building atomic publishers and idempotent subscribers can solve this atomic publishers your publishers need to update your database and publish associated events if a database update fails the events should never be sent if the database update succeeds the events should always publish the two shouldn t occur independently i e one shouldn t fail while the other succeeds one solution to this problem is the transactional outbox pattern idempotent subscribers messages from a topic can be delivered more than once but they should typically only be processed once to do this your subscribers need to identify and disregard duplicate events usually checking for duplicate payloads or ids is enough when you receive an event you ve seen before don t process it skip straight to returning a success response from your subscriber javascript typescript python go dart copy copied import topic from nitric sdk import isduplicate from common const updates topic updates updates subscribe ctx if isduplicate ctx req return ctx not a duplicate process the event if you re checking for duplicate ids ensure publishers can t resend failed events with new ids you can read more about idempotent subscribers and patterns to handle it here queues queues are another option for asynchronous messaging unlike topics messages sent to a queue won t automatically trigger services to process them instead services dequeue message by requesting them this makes queues ideal for batch workloads often paired with schedules if you re interested in the architecture provisioning or deployment steps they can be found here queue disambiguation some systems and cloud providers use the term queue to refer to a messaging broker with features akin to a topic i e they can push messages to subscribers in nitric a queue is a resource that messages are sent to and pulled from while a topic is a resource that messages are sent to and pushed from creating a queue nitric allows you to define named queues when defining queues you can give the service permissions for enqueueing and dequeueing messages here s an example of how to create a queue with permissions for enqueueing and dequeueing javascript typescript python go dart copy copied import queue from nitric sdk const transactionqueue queue transactions allow enqueue dequeue enqueue messages to send a message to a queue use the enqueue method on the queue reference the function must have permissions to enqueue to the queue the below example sends a message to a queue called transactions javascript typescript python go dart copy copied import queue from nitric sdk const transactionqueue queue transactions allow enqueue await transactionqueue enqueue message hello world messages can also be sent in batches by providing an array javascript typescript python go dart copy copied import queue from nitric sdk const transactionqueue queue transactions allow enqueue await transactionqueue enqueue message batch task 1 message batch task 2 dequeueing and acknowledging messages when you dequeue messages they are not immediately deleted from the queue instead they are leased which means they are temporarily hidden from other services until the lease expires to ensure proper handling your code should mark a dequeued message as complete after successfully processing it this action permanently removes the message from the queue if a lease expires before a dequeued message is marked as complete the message will reappear in the queue and can be dequeued again this mechanism prevents messages from getting lost in case of failures if your service encounters an error or is terminated before completing processing of a dequeued message it will automatically reappear in the queue ready to be processed again by following this approach you can ensure reliable message processing and minimize the chances of losing data in failure scenarios the below example dequeues 10 messages using the dequeue method then acknowledges them as complete using the complete method you ll note that the service has permissions to dequeue messages javascript typescript python go dart copy copied import queue from nitric sdk const transactionqueue queue transactions allow dequeue const tasks await transactionqueue dequeue 10 for let task of tasks process your task s data console log task message acknowledge when the task is complete await task complete choosing between queues and topics it s common to ask when to use a queue or a topic from a publisher s point of view both queues and topics are almost identical the difference is primarily on the receiver subscriber side topics push new messages to their subscribers immediately spinning up workers to process them while queues rely on the receiver to ask for new messages to process for these reasons we usually default to topics queues are more suitable for batch workloads or situations where there are occasional surges of requests that can be processed at a later time cloud service mapping each cloud provider comes with a set of default services used when deploying resources you can find the default services for each cloud provider below topics aws azure google cloud queues aws azure google cloud edit this page on github have feedback on this page open github issue last updated on jan 5 2026 on this page topics queues choosing between queues and topics cloud service mapping edit this page on github 2026 nitric inc contributions support foundations guides follow us on x follow us on github join our discord server youtube