SAVE

Synchronously write a point-in-time native Goblin Core snapshot.

SAVE [path [ACCEL | NOACCEL]]

SAVE does not return until the snapshot has been written, fsynced, and atomically renamed into place. A successful OK reply therefore means the final file is ready to load or copy. The default path is dump.gcsn, relative to the server's working directory.

The server executes commands atomically on one serving thread. While SAVE serializes and installs the snapshot, no other command is interleaved and the server does not serve other clients. Use BGSAVE when the process can safely fork and continuing to serve during a large snapshot matters.

Snapshot contents

The native GCSN image contains every persistent key type, TTLs, the replication lineage and logical offset, and the exact acknowledged Kafka offset when one is known. Restart with --load path, or load the image explicitly with GOBLIN.LOAD path.

ACCEL is the default. It adds same-build index accelerators so routine restarts can copy compatible packed structures instead of rebuilding them. NOACCEL emits the smaller canonical image intended for movement between Goblin Core versions, architectures, or C++ standard-library builds. Both forms contain the same logical database.

Why choose SAVE

Use SAVE when the caller must know that the file is durable before proceeding, for example:

immediately before a planned process replacement;
before copying a snapshot to another host;
from a deployment script that must fail if the snapshot cannot be installed;
when --arena-hugetlb is active;
when an active native transport runtime cannot safely survive fork().

Unlike BGSAVE, SAVE does not create a copy-on-write child and does not temporarily increase memory through fork-time page copies. The tradeoff is that snapshot serialization blocks the serving thread.

SAVE returns an error instead of racing an active BGSAVE or GOBLIN.DUMPWORLD child. Retry after the background snapshot has completed.

Reply

OK means the final snapshot path has been fsynced and atomically installed.
ERR background snapshot already in progress means another fork-time snapshot owns the snapshot slot.
ERR snapshot save failed means the file could not be written, synced, or installed.

Examples

Use the default accelerated format and path:

redis-cli SAVE

Install a known file before replacing the process:

redis-cli SAVE /var/lib/goblin/state.gcsn ACCEL
systemctl restart goblin-core

Create a canonical migration image:

redis-cli SAVE /var/lib/goblin/portable.gcsn NOACCEL

Compatibility and aliases

The synchronous command name and completion semantics match Redis. Goblin Core extends the syntax with an optional server-side path and ACCEL / NOACCEL format selection.

GOBLIN.SAVE is an exact alias retained for existing Goblin Core clients. New documentation and deployments should use SAVE. Typed SBE clients expose the same operation through save(); SBE clients and servers must be exactly the same version. Use RESP when version compatibility is required.