ZSS / ZLUX Editor: Write support for datasets

[NolanRogers]

Members and non-vsam datasets need the ability to be saved like files in the editor. Locking is required.

ZSS handles dataset read/write locks improperly (not the same way ISPF 3.4 does).
E.g. a PDS member can't be saved if the PDS member list is viewed in ISPF.

Expected:
ZSS repeats ISPF 3.4 behaviour.

End user behavior is supposed to look closely to the file writing behavior

Some more research done in this regard:

• optimistic locking approach

An optimistic locking approach:

• fetch content, and calculate content hash
• append content hash to response headers as e-tag
• let user modify content
• fetch and calculate content hash again, and compare it with e-tag of modified file
• if same, grab lock , else throw error
• replace content with modified content, and save
• and free, lock

Need foundational **locking service ** to implement writing:

• to lock a resource
• to free/unlock a resource
• to check if lock exists
• to calculate or get content hash

RSE Dataset locking mechanism:
https://www.ibm.com/support/knowledgecenter/en/SSBDYH_3.2/com.ibm.zexpl.config.hostconfigref.doc/topics/dataset_lock_owner.html

[NakulManchanda]

hi, we are going to revive this epic
Adding more stories

[NakulManchanda]

GAP Analysis ZSS - ZOSMF - Explorer API:
https://docs.google.com/spreadsheets/d/1tOT5yZVX2THhFBAaVzJLb_x-duhJljLXocyuZxRjJPk/edit#gid=0

[NakulManchanda]

ZSS Swagger:
https://raw.githubusercontent.com/zowe/zlux-app-server/master/doc/swagger/fileapi.yaml

try this swagger on:
https://editor.swagger.io/

Dataset:

Unix:

[NakulManchanda]

Explorer API Swagger:
Point to your zowe installation
https://mainframe.ibm.com:8547/swagger-ui.html -

Datasets API

Unix Files API

[NakulManchanda]

ZOSMF Files API:
https://www.ibm.com/support/knowledgecenter/en/SSLTBW_2.1.0/com.ibm.zos.v2r1.izua700/IZUHPINFO_API_RESTFILES.htm

[NakulManchanda]

We can start with following missing APIs

- Create
create pds - #498
create sequential - #498

• create member

- Update
update member
update sequential

- Delete
Delete pds
Delete Sequential
Delete member

[1000TurquoisePogs]

I think delete already exists, but probably doesn't do locking currently so it can be made better.
https://github.com/zowe/zss/blob/master/c/datasetService.c#L118

Write code does exist but is not exposed due to lack of locking, and I think there are some limitations in how we did it (dynalloc + LE's fread)... we may need to swap out LE file i/o libraries for lower-level functions.
https://github.com/zowe/zowe-common-c/blob/64577d0f01c0bf5472d89c3e24776688f8f8e0ac/c/datasetjson.c#L692

[1000TurquoisePogs]

Status as we enter 21 PI2:

• Can lock/unlock/write dataset, with a heartbeat

• Semaphore logic has issues with being leftover when zss crashes, area of the code that uses semaphores might be able to be swapped for pthread_lock, otherwise a bigger refactor is needed

• The number of threads = the number of datasets locked, but we could optimize by changing this to number of threads = number of users, which should be a lower number (refactor needed due to how sleep is factored - hard to add additional lock management to existing thread if it's sleeping)

• automated test coverage does not track issues like left behind finite OS object like semaphores