Allow CouchDB-managed OS daemons to include information in _active_tasks
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Key: COUCHDB-1165
URL: https://issues.apache.org/jira/browse/COUCHDB-1165
Project: CouchDB
Issue Type: New Feature
Components: Database Core, HTTP Interface
Reporter: Gabor Ratky
Priority: Minor
The new Externals API coupled with the HTTP Proxying enables powerful
background data processing scenarios, similar to the replication and compaction
API's in the core CouchDB API. The Replication API returns a JSON structure
that includes information about the replication that has completed but progress
information is also available through _active_tasks and thus, Futon.
An OS daemon that handles proxied requests to perform data processing tasks can
also reply with information about a completed request but has no way other than
["log", DMESG] to communicate progress and append to the CouchDB log, similar
how view checkpointing is included in the CouchDB log.
The suggested JSON commands supported by the Externals API would allow a daemon
to register a long-running tasks, report completion progress and status and
signal when the long running task completes.
While I am not intimately familiar with the inner workings of _active_tasks and
{couch_httpd_misc_handlers, handle_task_status_req}, the following API would
work (suggestions welcome!):
Register a new active task:
["task", { "id":"import:foo.csv", "type": "File Import", "task":"foo.csv",
"status": "Imported 0 of 360,410 bytes (0%)" }]
Report progress (same structure as registering a new active task):
["task", { "id":"import:foo.csv", "type": "File Import", "task":"foo.csv",
"status": "Imported 150,428 of 360,410 bytes (41%)" }]
Register task completion:
["task", {"id":"import:foo.csv", complete: true}]
Of course, id could be a number id that uniquely identifies the process itself.
Currently, active tasks include the "pid" of the process that performs the
task.
It would be lovely to see this functionality in 1.2 and I will have time to
work on this in the 1.2 timeframe so if there are no objections and everyone
agrees on a meaningful command structure, I can work on the patch.
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