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Upgrading to Containers API » History » Version 4

Peter Amstutz, 10/17/2018 07:00 PM

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h1. Upgrading to Containers API
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The "containers" API is the recommended way to submit compute work to Arvados.  It supersedes the "jobs" API, which is deprecated.
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h2. Benefits over the "jobs" API
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* Simpler and more robust execution with fewer points of failure
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* Automatic retry for containers that fail to run to completion due to infrastructure errors
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* Scales to thousands of simultaneous containers
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* Able to support alternate schedulers/dispatchers in addition to slurm
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* Improved logging, different streams logs/metrics stored in different files in the log collection
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* Records more upfront detail about the compute node, and additional metrics (such as available disk space over the course of the container run)
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* Better behavior when deciding whether to reuse past work -- pick the oldest container that matches the criteria
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* Can reuse running containers between workflows, cancelling a workflow will not cancel containers that are shared with other workflows
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* Supports setting time-to-live on intermediate output collections for automatic cleanup
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* Supports "secret" inputs, suitable for passwords or access tokens, which are hidden from the API responses and logs, and forgotten after use
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* Does not require "git" for dispatching work
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h2. Differences from the "jobs" API
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Containers cannot reuse jobs (but can reuse other containers)
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Uses the service "crunch-dispatch-slurm":https://doc.arvados.org/install/crunch2-slurm/install-dispatch.html instead of @crunch-dispatch.rb@
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Non-CWL Arvados "pipeline templates" are not supported with containers.  Pipeline templates should be rewritten in CWL and registered as "Workflows".
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The containers APIs is incompatible with the jobs API, code which integrates with the "jobs" API must be updated to work with containers
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Containers have network access disabled by default
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The keep mount only exposes collections which are explicitly listed as inputs
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h2. Migrating to "containers" API
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Run your workflows using @arvados-cwl-runner --api=containers@ (only necessary if both the jobs and containers APIs are enabled, if the jobs API is disabled, it will use the containers API automatically)
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Register your workflows so they can be run from workbench using @arvados-cwl-runner --api=containers --create-workflow@
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Read "Migrating running CWL on jobs API to containers API":https://doc.arvados.org/user/cwl/cwl-style.html#migrate
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Use @arv:APIRequirement: {}@ in the @requirements@ section of your CWL file to enable network access for the container (see "Arvados CWL Extensions":https://doc.arvados.org/user/cwl/cwl-extensions.html)
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For examples on how to manage container requests with the Python SDK, see https://doc.arvados.org/sdk/python/cookbook.html