like cron, or specifying an exact date or countdown for when after the task should be executed. Performance Able to execute tasks while the user waits. Return Values Task return values can be saved to retrieve it later, or ignore it. Result Stores Database, MongoDB, Redis, Tokyo Tyrant, AMQP (high performance). Webhooks Your tasks can also be HTTP callbacks, enabling cross- language communication. Rate Logging Retrying a task if something fails Task options Example How it works Tips and Best Practices Performance and Strategies Executing Tasks Basics ETA and countdown Serializers Connections and connection

retrieve it later, or ignore it. Result Stores Database, MongoDB, Redis, Tokyo Tyrant, AMQP (high performance). Web- hooks Your tasks can also be HTTP callbacks, enabling cross-language communication. Rate don’t want – Disable rate limits if they’re not used – Avoid launching synchronous subtasks • Performance and Strategies – Granularity – Data locality – State – Database transactions 2.1.1 Basics A result.AsyncResult to check if the task is done, or get its return value. Only use if you need the performance and is able live without these features. Any exceptions raised will store the return value/status

like cron, or specifying an exact date or countdown for when after the task should be executed. Performance Able to execute tasks while the user waits. Return Values Task return values can be saved to retrieve it later, or ignore it. Result Stores Database, MongoDB, Redis, Tokyo Tyrant, AMQP (high performance). Webhooks Your tasks can also be HTTP callbacks, enabling cross- language communication. Rate Logging Retrying a task if something fails Task options Example How it works Tips and Best Practices Performance and Strategies Executing Tasks ETA and countdown Serializers Connections and connection timeouts

shown that adding more than twice the number of CPU’s is rarely effective, and likely to degrade performance instead. Including the default prefork pool, Celery also supports using Eventlet, Gevent, and @decorator1 def add(x, y): return x + y Custom task classes How it works Tips and Best Practices Performance and Strategies Example Basics You can easily create a task from any callable by using the task() subtask()‘s. You can read about chains and other powerful constructs at Canvas: Designing Workflows. Performance and Strategies Granularity The task granularity is the amount of computation needed by each subtask

shown that adding more than twice the number of CPU’s is rarely effective, and likely to degrade performance instead. Including the default prefork pool, Celery also supports using Eventlet, Gevent, and to the celery worker. See Prefork pool prefetch settings for more information, and for the best performance route long-running and short-running tasks to dedicated workers (Automatic routing). If your worker list): @app.task @decorator2 @decorator1 def add(x, y): return x + y Tips and Best Practices Performance and Strategies Example Basics You can easily create a task from any callable by using the task()

shown that adding more than twice the number of CPU’s is rarely effective, and likely to degrade performance instead. Including the default prefork pool, Celery also supports using Eventlet, Gevent, and to the celery worker. See Prefork pool prefetch settings for more information, and for the best performance route long-running and short-running tasks to dedicated workers (Automatic routing). If your worker list): @app.task @decorator2 @decorator1 def add(x, y): return x + y Tips and Best Practices Performance and Strategies Example Basics You can easily create a task from any callable by using the task()

shown that adding more than twice the number of CPU’s is rarely effective, and likely to degrade performance instead. Including the default prefork pool, Celery also supports using Eventlet, Gevent, and to the celery worker. See Prefork pool prefetch settings for more information, and for the best performance route long-running and short-running tasks to dedicated workers (Automatic routing). If your worker list): @app.task @decorator2 @decorator1 def add(x, y): return x + y Tips and Best Practices Performance and Strategies Example Basics You can easily create a task from any callable by using the task()

shown that adding more than twice the number of CPU’s is rarely effective, and likely to degrade performance instead. Including the default prefork pool, Celery also supports using Eventlet, Gevent, and to the celery worker. See Prefork pool prefetch settings for more information, and for the best performance route long-running and short-running tasks to dedicated workers (Automatic routing). If your worker list): @app.task @decorator2 @decorator1 def add(x, y): return x + y Tips and Best Practices Performance and Strategies Example Basics You can easily create a task from any callable by using the task()

don’t want – Disable rate limits if they’re not used – Avoid launching synchronous subtasks • Performance and Strategies – Granularity – Data locality – State – Database transactions • Example – blog/models server, with thousands of tasks the broker may be overloaded with queues and this will affect performance in negative ways. If you’re using RabbitMQ then each queue will be a separate Erlang process, so for more information about subtasks. 2.2. Tasks 27 Celery Documentation, Release 2.3.5 2.2.12 Performance and Strategies Granularity The task granularity is the amount of computation needed by each subtask

don’t want – Disable rate limits if they’re not used – Avoid launching synchronous subtasks • Performance and Strategies – Granularity – Data locality – State – Database transactions • Example – blog/models server, with thousands of tasks the broker may be overloaded with queues and this will affect performance in negative ways. If you’re using RabbitMQ then each queue will be a separate Erlang process, so for a single task invocation. See also: Subtasks for more information about subtasks. 2.2.12 Performance and Strategies Granularity The task granularity is the amount of computation needed by each subtask