[jira] [Assigned] (NIFI-4589) Allow multiple keys in FetchDistributedMapCache

["Matt Burgess (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/NIFI-4589?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Matt Burgess reassigned NIFI-4589:
----------------------------------

    Assignee: Matt Burgess

> Allow multiple keys in FetchDistributedMapCache
> -----------------------------------------------
>
>                 Key: NIFI-4589
>                 URL: https://issues.apache.org/jira/browse/NIFI-4589
>             Project: Apache NiFi
>          Issue Type: Improvement
>          Components: Extensions
>            Reporter: Matt Burgess
>            Assignee: Matt Burgess
>
> Currently (1.4.0) FetchDistributedMapCache will look up a single key and place the value (if present) in either the flow file content or a user-named attribute, depending on the value of the "Put Cache Value In Attribute" property. If the user wishes to look up more than one value, they need multiple FetchDistributedMapCache processors, and each would make one call to the server to get a single key.
> A useful improvement would be to allow multiple keys to be retrieved at once by FetchDistributedMapCache. This would likely involve the following:
> 1) Update documentation and code to accept a comma-separated list of Cache Key Identifiers
> 2) If a single Cache Key Identifier is specified, current behavior is retained (i.e. output to flow file content or a specified attribute)
> 3) If multiple Cache Key Identifiers are specified, then Put Cache Value In Attribute must be set, and the attributes will be prefixed by the value of said property, followed by a period, followed by the evaluated cache key. So if Cache Key Identifier is set to "field1, field2" and Put Cache Value In Attribute is set to "myattrs", then the value for field1 will be placed in the "myattrs.field1" attribute, and field2's value in "myattrs.field2" respectively.
> 4) Due to the possible presence of Expression Language in the Cache Key Identifier property, it may not be possible to determine whether multiple cache keys are present (i.e. a single EL function that generates a comma-separated list), so the requirement on Put Cache Value In Attribute being set must be checked at validation time (if possible) and also run-time
> 5) To make this fetch efficient, a method "subMap" can be created on the DistributedMapCache API, so multiple keys can be passed and multiple key/value pairs can be returned in a single call to the cache server.
> 6) #5 implies a new protocol version (would be 3 at the time of this writing) be added to the DistributedMapCache API
> 7) If protocol negotiation results in a lower version being used, then the client should gracefully degrade into using the "subMap" operation to make multiple calls to the "get" operation, and fill in the result map manually.



--
This message was sent by Atlassian JIRA
(v6.4.14#64029)