COUNTERS_DB bare-table enumeration and BUFFER_POOL_WATERMARKS virtual path support

[Verma-Anukul]

Summary

Fix bare-path Get/Subscribe for keyed COUNTERS_DB tables (notably BUFFER_POOL_WATERMARKS) and strip SONiC NULL placeholders from JSON.

Before

gNMI Get on bare path /COUNTERS_DB/BUFFER_POOL_WATERMARKS returned empty or incomplete results (pools required an explicit wildcard).

gNMI JSON output for hashes carrying only a SONiC placeholder:

{"NULL": "NULL"}

Subscribe / ONCE mode (gnmic --mode once) on keyed COUNTERS_DB tables could hang or miss updates because PSUBSCRIBE patterns did not match keyed rows like BUFFER_POOL_WATERMARKS:<oid>.

gnmi.log (when key enumeration failed):

listBareTableKeys failed for {dbName:COUNTERS_DB tableName:BUFFER_POOL_WATERMARKS ...}: ...

After

gNMI Get on /COUNTERS_DB/BUFFER_POOL_WATERMARKS returns all buffer pools by name (via COUNTERS_BUFFER_POOL_NAME_MAP → COUNTERS:<oid>).

gNMI JSON output — NULL placeholder stripped:

{}

or with real fields:

{"ingress_lossless_pool": {"SAI_BUFFER_POOL_STAT_WATERMARK_BYTES": "1234"}}

Subscribe uses corrected keyspace patterns with delimSkipped for COUNTERS_DB non-COUNTERS tables; ONCE-mode subscriptions exit cleanly.

Test plan

• go test ./sonic_data_client/... -run TestMakeJSONRedisSkipsNull
• gNMI Get on /COUNTERS_DB/BUFFER_POOL_WATERMARKS → all pools
• gnmic --mode once subscribe on buffer pool watermarks → exits cleanly

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[mssonicbld]

Hi, there are workflow run(s) waiting for approval, you may be first-time contributor. I will notify maintainers to help approve once PR is approved. Thanks!

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• ✅ login: Verma-Anukul / name: Verma-Anukul (1b4164b, c9177b4, ceaaf6c)

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[Copilot]

Pull request overview

This PR improves gNMI behavior for COUNTERS_DB tables that use keyed Redis entries (notably BUFFER_POOL_WATERMARKS) by translating bare/wildcard paths into concrete COUNTERS:<oid> rows, fixes COUNTERS_DB keyspace subscription matching/extraction for ONCE/Subscribe workflows, and cleans up JSON output by stripping SONiC’s "NULL":"NULL" placeholder fields.

Changes:

• Add virtual-path translation for /COUNTERS_DB/BUFFER_POOL_WATERMARKS (bare and wildcard) via COUNTERS_BUFFER_POOL_NAME_MAP.
• Make bare-table reads enumerate both keyed (<table><delim>*) and flat-hash (<table>) Redis key layouts; adjust subscribe key extraction when delimiter is omitted in PSUBSCRIBE patterns.
• Strip "NULL" placeholder fields from Redis-hash JSON output and add a unit test for the behavior.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 5 comments.

File	Description
sonic_data_client/virtual_db.go	Adds BUFFER_POOL_WATERMARKS virtual-path translation and initializes pool-name→OID mappings per namespace; adjusts COUNTERS_DB subscribe pattern/key handling.
sonic_data_client/mixed_db_client.go	Uses shared bare-table key enumeration and fixes subscription key extraction when delimiter is omitted for COUNTERS_DB non-COUNTERS tables.
sonic_data_client/db_client.go	Introduces shared listBareTableKeys helper, updates bare-table reads to use it, and strips "NULL" fields in JSON rendering; aligns subscribe key extraction with delimiter-omission logic.
sonic_data_client/client_test.go	Adds unit test coverage for stripping "NULL":"NULL" placeholder fields from JSON output.

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Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.

Suppressed comments (4)

sonic_data_client/db_client.go:952

• The code comment/test describe skipping the SONiC placeholder pair {"NULL":"NULL"}, but this loop currently skips any field named "NULL" regardless of its value. Tighten the check to f == "NULL" && v == "NULL" to avoid dropping a legitimate "NULL" field if it ever appears with a real value.

	for f, v := range mfv {
		if f == "NULL" {
			continue
		}

sonic_data_client/db_client.go:1424

• Delete/hdel events do not update msi, so a later hset that recreates the same content can be incorrectly suppressed by reflect.DeepEqual(newMsi, msi) (because msi still holds the pre-delete state). Persist the delete state into msi so re-adds after deletes are always forwarded.

					key := keyFromChannel(subscr.Channel)
					newMsi[key] = fp

sonic_data_client/mixed_db_client.go:2143

• Delete/hdel events do not update msi, so a later hset that recreates the same content can be incorrectly suppressed by reflect.DeepEqual(newMsi, msi) (because msi still holds the pre-delete state). Persist the delete state into msi so re-adds after deletes are always forwarded.

					key := keyFromChannel(subscr.Channel)
					newMsi[key] = fp
					newMsi["delete"] = "null_value"

sonic_data_client/db_client.go:942

• The code comment/test describe skipping the SONiC placeholder pair {"NULL":"NULL"}, but this branch currently skips any field named "NULL" regardless of its value. Tighten the check to f == "NULL" && v == "NULL" to avoid dropping a legitimate "NULL" field if it ever appears with a real value.

This issue also appears on line 949 of the same file.

		for f, v := range mfv {
			if f == "NULL" {
				continue
			}

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[hdwhdw]

Two inline findings on API coverage and mapping lifecycle.

[hdwhdw]

Inline finding on buffer-pool mapping lifecycle.

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