Backup & Restore

Authagonal provides two CLI tools for backing up and restoring Azure Table Storage data. Both are .NET console applications in the tools/ directory, and both are thin wrappers over the Authagonal.Backup NuGet package. Hosts that need scheduled, multi-tenant, or non-filesystem backups can use the library directly (see Using the library).

Backup

dotnet run --project tools/Authagonal.Backup -- \
  --connection-string "DefaultEndpointsProtocol=https;..." \
  --output ./backups

Options

Output format

Each backup creates a timestamped directory:

backups/
  20260329-120000/          (full backup)
    Users.jsonl
    Clients.jsonl
    Grants.jsonl
    ...
    _manifest.json
  20260329-180000-incr/     (incremental, compressed)
    Users.jsonl.gz
    _tombstones.jsonl.gz
    _manifest.json

Each .jsonl file contains one JSON object per line (one per table entity). With --gzip, files are compressed as .jsonl.gz. The _manifest.json records the backup id, timestamp, mode (full or incremental), compression, the incremental watermark, per-table entity counts, the tombstone count, which tables (if any) were read via the change-log (ChangeLogTables, null means full scan coverage), and SHA-256 file hashes for integrity verification.

Incremental backups also write a _tombstones.jsonl(.gz) file recording deletes since the watermark: one line per deleted row with Table, PartitionKey, RowKey, and DeletedAt. Restore replays these so deleted rows are not resurrected (see Tombstone replay).

Entity values round-trip exactly: each backed-up row carries a "@v" format marker and an explicit "{column}@odata.type" annotation (Edm.Guid, Edm.DateTime, Edm.Binary, Edm.Int64, Edm.Double) for every column JSON can’t represent unambiguously, so restore writes back the original types rather than stringified or re-inferred values.

Integrity verification

Each backup manifest includes a FileHashes dictionary mapping filenames to their SHA-256 hashes. During restore, each file’s integrity is verified against these hashes before any of its data is written; a file that fails the check, or a data file absent from the manifest, aborts the restore with an error. Backups written before integrity hashing existed (no FileHashes in the manifest) cannot be verified and are restored with a loud warning instead. Verification can be disabled programmatically via RestoreOptions.VerifyIntegrity (default true).

Incremental backups

Pass --incremental to only back up entities modified since the last successful backup. The tool uses Azure Table Storage’s built-in Timestamp property for filtering and tracks the high-water mark in a .lastbackup file in the output directory.

If no .lastbackup file exists, the first incremental run performs a full backup.

Every incremental Timestamp filter subtracts a small safety margin (BackupDefaults.WatermarkSkewMargin, 5 minutes) before filtering. The watermark comes from the caller’s clock while row timestamps are stamped by the storage service, so a mutation committing inside the clock skew would otherwise be missed by this run and every later one. Re-reading the margin costs a few duplicate rows per run, which restore’s upsert semantics dedupe.

Default tables

The backup tool includes all Authagonal tables by default (BackupDefaults.Tables):

Users, UserEmails, UserFirstNames, UserLastNames, UserLogins, UserExternalIds, UserEmailDomains, UserEmailLocalPrefixes, Clients, Grants, GrantsBySubject, GrantsByExpiry, SigningKeys, SsoDomains, SamlProviders, OidcProviders, UserProvisions, MfaCredentials, MfaChallenges, MfaWebAuthnIndex, ScimTokens, ScimGroups, ScimGroupExternalIds, ScimGroupRoleMappings, Roles, Scopes, ProvisioningApps

Transient tables (SamlReplayCache, OidcStateStore, RevokedTokens) are excluded by default since their entries are bounded by token lifetimes; include them explicitly with --tables if needed. The Tombstones change-log table is handled separately by the backup engine and should not be listed.

Signing keys are excluded by default

The SigningKeys table is in the default table list but filtered out of backups by default (BackupOptions.IncludeSigningKeys, default false; the CLI never enables it). For hosts using the local (table-stored) key source, this table holds the JWT signing private key, and writing it to a plaintext backup file would let anyone who reads the backup forge tokens. (Hosts that sign via HashiCorp Vault Transit keep no private key in the table, so this concern doesn’t apply to them.)

⚠️ Only opt in via BackupOptions.IncludeSigningKeys when the backup target is itself encrypted at rest and access-controlled. The same applies to the rest of the backup: with the default plaintext secret provider, backups also contain upstream OIDC client secrets and TOTP / MFA seeds in cleartext. See Configuration → Secret Provider.

Restore

dotnet run --project tools/Authagonal.Restore -- \
  --connection-string "DefaultEndpointsProtocol=https;..." \
  --input ./backups/20260329-120000

Options

Restore modes

Gzip-compressed backup files (.jsonl.gz) are detected and decompressed automatically; no extra flags needed.

Tombstone replay

After the data files, restore applies the backup’s _tombstones file: each recorded key is deleted from the restored tables (RestoreOptions.ApplyTombstones, default true). An incremental’s deletes are as much a part of its state as its upserts; skipping them would resurrect deleted rows, including GDPR-erased ones, when restoring a full plus incrementals sequence. Full backups carry no tombstone file. When restoring a full backup followed by incrementals, apply them oldest first so a later recreate lands after an earlier delete. The tombstone file’s hash is verified against the manifest like the data files.

Exact type round-trip

Rows written with the "@v" format marker carry explicit EDM type annotations, so restore reconstructs the exact original column types (Int64, Guid, Binary, DateTime, Double); an unannotated string is restored as a string. Legacy backup files without the marker fall back to shape-based inference, kept only so old backups remain restorable (inference can mis-type GUID-shaped or date-shaped string columns).

Exit codes

Using the library

The Authagonal.Backup NuGet package exposes the same operations programmatically, for background services or custom orchestration:

var serviceClient = new TableServiceClient(connectionString);
var target = new FileSystemBackupTarget("./backups");
var options = new BackupOptions { Incremental = true, Gzip = true };
var manifest = await new BackupService(serviceClient, target, options).RunAsync(ct);

Change-log-driven incrementals

Azure Table Storage only indexes PartitionKey and RowKey, so an incremental backup filtered on Timestamp is still a full scan of each table. To avoid that, Authagonal’s stores record every mutation in a change-log via the IChangeWriter seam (Authagonal.Core), implemented for Azure by TableChangeWriter (Authagonal.AzureProvider). It is one physical table, still named Tombstones: PK = the logical table name, RK = "{pk}|{rk}", an Op column of "U" (upsert) or "D" (delete), and authoritative OrigPK/OrigRK columns (a | inside the original PartitionKey makes splitting the composite RowKey ambiguous, so the backup reader trusts the columns and only falls back to the split for legacy rows). Each key holds one row (upsert-replace), so the last operation in a backup window wins.

With the change-log path enabled, an incremental backup enumerates a table’s Op = "U" change-log entries since the watermark and point-reads each live row instead of scanning the table. The feature is opt-in and off by default: BackupOptions.ChangeLoggedTables null or empty means every table stays on the scan path, so the mechanism ships inert until a deliberate flip (a deploy can’t silently miss rows changed by pre-capture code). Two presets:

The manifest’s ChangeLogTables property lists which tables a run read via the change-log; null or empty means the run had full scan coverage (a full backup, a plain scan incremental, or a backstop scan).

Full-scan backstop

Because change-log capture can miss writes (login-state fields, non-store writers, pods running pre-capture code during a deploy), pair change-log incrementals with a periodic full re-scan. Set BackupOptions.WatermarkOverride to the timestamp of the last full-coverage scan and leave ChangeLoggedTables unset for that run: the incremental then filters on Timestamp across the whole window since that scan, picking up anything the change-log never captured. A daily backstop alongside hourly change-log incrementals is a reasonable cadence. Deletes are the one mutation class with no self-heal (a live-row scan cannot see a row that is gone), which is why stores write the delete tombstone before deleting the data row.

All incremental filters, backstop included, subtract BackupDefaults.WatermarkSkewMargin (5 minutes) from the watermark; callers that purge the change-log after a backup must bound the purge by the same margin or they delete rows the next run still needs.

Rollups

RollupService.RollupAsync merges a full backup and its incrementals into a new full backup; RollupAndCleanAsync additionally deletes the inputs afterwards. The optional newBackupId parameter names the result (null derives a timestamp id); a specially retained snapshot (for example a weekly rollup) must pass its id here, since id-based retention lists physical backup ids, not manifests.

During a merge, tombstones apply with timestamp ordering: a delete removes a captured row only when the row’s Timestamp does not postdate the tombstone’s DeletedAt. A key deleted early in the window and recreated later has both a tombstone and a live capture, and the recreated row survives the rollup. Legacy tombstones without DeletedAt remove unconditionally.

Docker

The backup tool ships a Dockerfile (tools/Authagonal.Backup/Dockerfile) for running in CI or without installing the .NET SDK:

docker build -f tools/Authagonal.Backup/Dockerfile -t authagonal-backup .

docker run --rm -v $(pwd)/backups:/backups \
  -e STORAGE_CONNECTION_STRING="..." \
  authagonal-backup --output /backups

The restore tool has no image; run it with the .NET SDK (dotnet run --project tools/Authagonal.Restore).

Scheduling backups

For production use, run the backup tool on a schedule (e.g. daily full + hourly incremental):

# Daily full backup (compressed)
0 2 * * * authagonal-backup --connection-string "$CONN" --output /backups --gzip

# Hourly incremental (compressed)
0 * * * * authagonal-backup --connection-string "$CONN" --output /backups --incremental --gzip

Hosts embedding the library typically run hourly incrementals with the change-log path on, a daily full-scan backstop, and periodic rollups to bound the incremental chain.