Add runtime management of eligible server options via CONFIG GET/SET by vazois · Pull Request #1965 · microsoft/garnet

vazois · 2026-07-21T23:47:29Z

What

Adds runtime management of eligible GarnetServerOptions through the RESP CONFIG GET / CONFIG SET commands. These options can be viewed and adjusted at runtime because they are read live at their point of use and require no physical change to the running server (no restart, no reallocation).

How

ServerConfigType (libs/server/ServerConfigType.cs) is now a public enum augmented with a member per runtime-adjustable option, plus a COUNT sentinel. Time-based members carry an explicit unit suffix (_MS / _SECONDS / _MICROS) matching the underlying GarnetServerOptions property so the unit is unambiguous at every use site.
RuntimeServerConfig (libs/server/RuntimeServerConfig.cs, new public class) is a long[]-backed table indexed by ServerConfigType. It is allocation-free, contiguous, O(1) indexed, and read/written with Volatile (atomic on 64-bit). Each slot is a raw 8-byte cell whose interpretation (int / long / bool / enum / seconds-based timeout / string) is described by per-option metadata (ConfigKind). Values are seeded from GarnetServerOptions at startup (Init) and mutated at runtime via TrySet (with per-option range/type validation).
The table is held on StoreWrapper.runtimeConfig so the live value is reachable across both the server and cluster layers. GarnetServerOptions remains on StoreWrapper for options that are not runtime-adjustable.
ServerConfig.cs: CONFIG GET/CONFIG SET resolve parameter names (honoring aliases, e.g. cluster-timeout → cluster-node-timeout) via RuntimeServerConfig.TryGetType and read/write the table.
Read-only params (timeout, save, appendonly, databases) are exposed through CONFIG GET / GET * but reject CONFIG SET with a clear "read-only" error; their values are computed from live server state.
slave-read-only stays per-session, following Redis READWRITE/READONLY semantics, and is resolved by the CONFIG GET handler which has the session in scope.
Migrated the live read sites across libs/server and libs/cluster to read from the table.

Runtime-adjustable options included

cluster-node-timeout, replica-sync-delay, replica-offset-max-lag, aof-tail-witness-freq, aof-replay-max-drift, repl-diskless-sync-delay, repl-attach-timeout, cluster-replication-reestablishment-timeout, compaction-max-segments, compaction-force-delete, compaction-type, slowlog-log-slower-than, object-scan-count-limit, sg-get.

Tests

New tests in test/standalone/Garnet.test/RespConfigTests.cs:
- ConfigGetSetRuntimeOptionsTest — round-trips integer, long, boolean, enum, seconds-timeout, alias, and multi-option forms.
- ConfigSetRuntimeOptionValidationTest — rejects malformed / out-of-range values without mutating state.
- ConfigGetAllAndReadOnlyRejectionTest — read-only params reject SET; GET * includes read-only + per-session slave-read-only.
Existing RespAdminCommandsTests.SimpleConfigGet continues to pass (timeout/save/appendonly/slave-read-only/databases/cluster-node-timeout).
Server, cluster, and test projects build clean (0 warnings, TreatWarningsAsErrors on); dotnet format --verify-no-changes clean.

Copilot

Pull request overview

Adds a centralized RuntimeServerConfig table and wires CONFIG GET/CONFIG SET to manage a subset of server options at runtime, with call sites updated across server + cluster layers to read live values.

Changes:

Introduces RuntimeServerConfig (long[] + metadata) and expands ServerConfigType to cover runtime-adjustable and read-only CONFIG parameters.
Updates CONFIG GET/SET handling to resolve parameters via RuntimeServerConfig (including aliases) and formats responses via canonical names.
Migrates multiple option read sites (object scan, sg-get, compaction, replication timeouts/delays, etc.) to read from the runtime table; adds tests for round-tripping and validation.

Reviewed changes

Copilot reviewed 20 out of 20 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
test/standalone/Garnet.test/RespConfigTests.cs	Adds tests covering runtime CONFIG GET/SET round-trips, validation failures, and GET * contents.
libs/server/StoreWrapper.cs	Adds shared `runtimeConfig` to StoreWrapper and ensures clones share the same table.
libs/server/Storage/Session/StorageSession.cs	Plumbs `RuntimeServerConfig` into StorageSession and removes cached object-scan limit.
libs/server/Storage/Session/ObjectStore/Common.cs	Reads object scan count limit from `runtimeConfig` at use site.
libs/server/ServerConfigType.cs	Makes enum public and adds runtime-adjustable options with unit-suffixed members + COUNT sentinel.
libs/server/ServerConfig.cs	Routes CONFIG name parsing through `RuntimeServerConfig`; rewrites CONFIG GET/SET to use runtime table.
libs/server/RuntimeServerConfig.cs	New runtime-config table with metadata, parsing/validation, formatting, and alias resolution.
libs/server/Resp/RespServerSession.cs	Uses runtime config for slowlog threshold initialization; removes cached sg-get flag.
libs/server/Resp/Objects/SharedObjectCommands.cs	Uses runtime config for object scan count limit in RESP object commands.
libs/server/Resp/BasicCommands.cs	Uses runtime config for sg-get decision in GET dispatch path.
libs/server/Databases/DatabaseManagerBase.cs	Uses runtime config for compaction parameters.
libs/cluster/Server/Replication/ReplicationManager.cs	Uses runtime config for replication reestablishment timeout and AOF tail witness delay.
libs/cluster/Server/Replication/ReplicaOps/ReplicaDisklessSync.cs	Uses runtime config for replica attach timeout.
libs/cluster/Server/Replication/ReplicaOps/ReplicaDiskbasedSync.cs	Uses runtime config for replica attach timeout.
libs/cluster/Server/Replication/ReplicaOps/AOFReplay/ReplicaReplaySession.cs	Uses runtime config for replication offset max lag checks / sync replay decision.
libs/cluster/Server/Replication/ReplicaOps/AOFReplay/ReplicaReplayDriver.cs	Uses runtime config for replay max drift, sync delay, and max-lag throttling.
libs/cluster/Server/Replication/PrimaryOps/DisklessReplication/ReplicationSyncManager.cs	Uses runtime config for diskless sync delay.
libs/cluster/Server/Replication/PrimaryOps/AofOperations/AofSyncTask.cs	Uses runtime config for replica sync delay used by AOF sync consumption.
libs/cluster/Server/Replication/PrimaryOps/AofOperations/AofSyncDriver.cs	Uses runtime config for AOF tail witness frequency delay.
libs/cluster/Server/ClusterProvider.cs	Exposes replication_offset_max_lag from runtime config in replication info metrics.

Mathos1432 · 2026-07-30T14:51:09Z

If the configurations are still present in GarnetServerOptions, is there a risk that some code paths go through the "static" GarnetServerOptions instead of the runtime options, causing some paths to use the updated value and some to use the boot time value?

Is it possible to remove the runtime configs from the GarnetServerOptions, or make it hard to accidentally read their values?

Mathos1432 · 2026-07-30T14:31:03Z

+        Int64,
+        Bool,
+        Enum,
+        Seconds,


I wonder if it would be possible to instead have TimeSpan as a ConfigKind and use that instead of Seconds/Int32 for encoding/decoding?

It would avoid the need to encode the unit as a suffix which reduces the risk of incorrect storing/retrieval?

I added the appropriate Getter for this and also a collection of flags to indicate differents it can be retrieved as, i.e. TimeSpan, Int seconds, Int Milliseconds, etc.

kevin-montrose

Couple nits, and some potential bugs.

kevin-montrose · 2026-07-30T14:51:22Z

            this.serverOptions = serverOptions;
+            // Share the runtime config table across cloned wrappers (e.g. the AOF copy ctor) so that a
+            // CONFIG SET is observed consistently; otherwise seed a fresh table from the startup options.
+            this.runtimeConfig = runtimeConfig ?? new RuntimeServerConfig();


Rather than this if, pass this and serverOptions to RuntimeServerConfig constructor.

kevin-montrose · 2026-07-30T14:52:05Z

+            var db = redis.GetDatabase(0);
+
+            // Out-of-range integer (min is 0).
+            _ = Assert.Throws<RedisServerException>(() => db.Execute("CONFIG", "SET", "replica-sync-delay", "-5"));


We should check that the error messages are what we expect.

kevin-montrose · 2026-07-30T14:52:23Z

+            var db = redis.GetDatabase(0);
+
+            // CONFIG SET on read-only parameters is rejected.
+            _ = Assert.Throws<RedisServerException>(() => db.Execute("CONFIG", "SET", "appendonly", "yes"));


Similarly, we should check the error messages are correct.

vazois and others added 2 commits July 21, 2026 16:44

add support for runtime config management

027a4b8

Merge branch 'main' into vazois/runtime-config

35a2d46

vazois marked this pull request as ready for review July 23, 2026 18:43

Copilot AI review requested due to automatic review settings July 23, 2026 18:43

Merge branch 'main' into vazois/runtime-config

e6bf444

Copilot started reviewing on behalf of vazois July 23, 2026 18:43 View session

Copilot AI reviewed Jul 23, 2026

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Comment thread libs/server/ServerConfig.cs

Comment thread libs/server/RuntimeServerConfig.cs Outdated

Comment thread libs/server/Resp/RespServerSession.cs Outdated

vazois and others added 2 commits July 27, 2026 13:17

addressing comments

5d9fc1a

Merge branch 'main' into vazois/runtime-config

77cec68

kevin-montrose self-assigned this Jul 28, 2026

vazois assigned Mathos1432 Jul 28, 2026

Mathos1432 reviewed Jul 30, 2026

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kevin-montrose requested changes Jul 30, 2026

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vazois and others added 5 commits July 30, 2026 11:28

Merge branch 'main' into vazois/runtime-config

34b1cc6

add frozen dictionary and validate kind

aa97f87

add formal enum validation

e270fa0

canonical format check of enums for runtime config

42c222c

wip; readonly fall through for CONFIG GET off non-runtime options

270e0ec

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vazois commented Jul 21, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Runtime-adjustable options included

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Mathos1432 commented Jul 30, 2026

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vazois commented Jul 21, 2026 •

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