[Slach]

Fixes #1671

Problem

download / restore / restore_remote / upload of an embedded backup required clickhouse.use_embedded_backup_restore: true (or --env CLICKHOUSE_USE_EMBEDDED_BACKUP_RESTORE=1 on every call), even though the backup metadata already carries the embedded tag. On Antalya CAS disks this failed in ~50ms with disk "cas" ... has no local files, set clickhouse.use_embedded_backup_restore: true.

Relaxing only the disk check (the fix suggested in the issue) is not enough: the local embedded backup path (EmbeddedBackupDataPath) was also resolved from the config flag only, so with the check relaxed restore failed with read backup metadata file: ... no such file or directory and download wrote into a relative path.

Fix

create keeps deciding by the config; read paths decide by the backup embedded tag:

• checkDisksConsistency(disks, isEmbeddedBackup) runs after the backup metadata is known in download / restore / upload (streaming restore_remote rejects embedded backups before the check, so it gets the specific error instead of the misleading CAS one)
• EmbeddedBackupDataPath is resolved by the tag (setEmbeddedBackupDataPathByTags), restore also looks for metadata.json on the embedded backup disk
• restore opens the remote destination for an embedded backup without embedded_backup_disk by the tag
• embedded ON CLUSTER: with use_embedded_backup_restore_cluster set, restore, restore_remote and delete local of an embedded backup drive the other nodes too (embeddedClusterInitiator(isEmbeddedBackup)), remote tags come from the listing remoteCloudBackupPrefix already does, worker commands get --env="CLICKHOUSE_USE_EMBEDDED_BACKUP_RESTORE=1" because a worker validates the flag before it reads the tags

Tests

• unit: TestCheckDisksConsistency (CAS + embedded tag without config flag), TestEmbeddedOnClusterWorkerValidation (fan-out by tag), TestEmbeddedClusterRestoreWorkerCommand (--env in worker command, shlex round trip); make test passes
• integration TestAntalyaCASDisk (altinity/clickhouse-server:26.6.8.20002.altinityantalya): download, restore, upload of the embedded backup with CLICKHOUSE_USE_EMBEDDED_BACKUP_RESTORE=false — passes locally (Antalya is not in the CI matrix)
• testflows embedded on cluster/restore remote on cluster by backup tags: two shards, restore_remote --env=CLICKHOUSE_USE_EMBEDDED_BACKUP_RESTORE=false via API, worker gets the --env, row counts match — /clickhouse backup/embedded* 7/7 ok locally

🤖 Generated with Claude Code

[coveralls]

Coverage Report for CI Build 42384833894

Coverage increased (+0.08%) to 70.745%

Details

• Coverage increased (+0.08%) from the base build.
• Patch coverage: 14 uncovered changes across 4 files (59 of 73 lines covered, 80.82%).
• 16 coverage regressions across 6 files.

Uncovered Changes

File	Changed	Covered	%
pkg/backup/restore_cloud.go	13	5	38.46%
pkg/backup/download.go	5	3	60.0%
pkg/backup/restore.go	10	8	80.0%
pkg/backup/restore_remote.go	9	7	77.78%
Total (10 files)	73	59	80.82%

Coverage Regressions

16 previously-covered lines in 6 files lost coverage.

File	Lines Losing Coverage	Coverage
pkg/backup/upload.go	5	74.35%
pkg/storage/general.go	3	70.27%
pkg/clickhouse/clickhouse.go	3	81.36%
pkg/backup/delete.go	2	74.44%
pkg/backup/create_remote.go	2	66.8%
pkg/status/status.go	1	90.91%

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Coverage Stats

Relevant Lines:	30060
Covered Lines:	21266
Line Coverage:	70.75%
Coverage Strength:	35926.32 hits per line

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💛 - Coveralls