Manila as a runtime data source

Manila as a runtime data source

https://blueprints.launchpad.net/sahara/+spec/manila-as-a-data-source

Using manila nfs shares and the mounting features developed for use with job binaries, it should be feasible to use nfs shares to host input and output data. This will allow data to be referenced through local filesystem paths as a another simple alternative to hdfs or swift storage.

Problem description

The work has already been done to support mounting of manila nfs shares at cluster provisioning time or automounting shares for EDP job binaries with a url of the form manila://<share-id>/path. Additionally, the Hadoop filesystem APIs already support file:///path urls for referencing the local filesystem.

Sahara can build on these existing features by allowing manila://<share-id>/path urls for data sources, automounting shares referenced by data sources when necessary, and generating the correct local filesystem urls for EDP jobs at runtime.

Some of the benefits of this approach are:

  • parity for job binaries and data sources in regards to manila shares
  • the ability to store job binaries and data sources in the same share
  • the flexibility to add a new data share to a cluster at any time
  • the ability to operate on data from a cluster node using native OS tools
  • works on any node where mount -t nfs … is supported
  • lays the groundwork for other manila share types in the future

The problem can be divided into three high-level items:

  • Add a manila data source type with validation of manila:// urls
  • Translate manila:// urls to file:// urls for use at job runtime
  • Call the existing automounting methods when a data source references a new share

Note, automounting and url translation will only work for manila shares referenced by data source objects. A manila:// url embedded as a literal in a job config, param, or arg will be ignored. It will not be translated to a file:// url by Sahara and it will not cause automounting. However, there is a precedent for this – Sahara currently has other features that are only supported on data source objects, not on literal urls. (It may be possible to remove these limitations in the future through greater use of the unified job mapping interface recently introduced).

Proposed change

A manila data source type will be added to the JSON schema for data sources, with appropriate validation of manilla:// urls.

The existing code in sahara/service/edp/binary_retrievers/manila_share.py that supports path name generation and automounting of manila nfs shares for job binaries will be refactored and broken up between sahara/service/edp/job_utils.py and sahara/service/shares.py. The essential implementation is complete, but this logic needs to be callable from multiple places and in different combinations to support data sources.

Currently, all data source urls are returned to the EDP engines from get_data_sources() and resolve_data_source_references() in job_utils.py. The returned urls are recorded in the job_execution object and used by the EDP engine to generate the job on the cluster. These two routines will be extended to handle manila data sources in the following ways:

  • Mount a referenced nfs share on the cluster when necessary. Since an EDP job runs on multiple nodes, the share must be mounted to the whole cluster instead of to an individual instance
  • Translate the manila:// url to a file:// url and return both urls Since the submission time url and the runtime url for these data sources will be different, both must be returned. Sahara will record the submission time url in the job_execution but use the runtime url for job generation

Alternatives

Do not support manila:// urls for data sources but support data hosted on nfs as described in

https://review.openstack.org/#/c/210839/

However, these features are complementary, not mutually exclusive, and most of the appartus necessary to make this proposal work already exists.

Data model impact

None

REST API impact

None (only “manila” as a valid data source type in the JSON schema)

Other end user impact

None

Deployer impact

Obviously, if this feature is desired then the manila service should be running

Developer impact

None

Sahara-image-elements impact

None (nfs-utils element is already underway)

Sahara-dashboard / Horizon impact

Sahara needs a manila data source type on the data source creation form

Implementation

Assignee(s)

Primary assignee:
tmckay
Other contributors:
croberts, egafford

Work Items

  • Add manila data source type to the JSON schema
  • Allow submission time and runtime urls to differ (https://review.openstack.org/#/c/209634/3)
  • Refactor binary_retrievers/manila_share.py
  • Extend job_utils get_data_sources() and resolve_data_source_references() to handle manila:// urls
  • Add manila data source creation to Horizon
  • Modify/extend unit tests
  • Documentation

Testing

Unit tests.

Eventually, as with job binaries, this can be tested with integration tests if/when we have manila support in the gate

Documentation Impact

Discussion of the manila data source type should be added to any sections we currently have that talk about data being hosted in swift of hdfs.

Additionally, we should consider adding information to the Sahara section of the security guide on the implications of using manila data shares.

If the security guide or the manila documentation contains a section on security, this probably can be a short discussion from a Sahara perspective with a link to the security info. If there isn’t such a section currently, then probably there should be a separate CR against the security guide to create a section for Manila.

References

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