Server diagnostics

redis.Server exposes latency reports and histories, cumulative command latency histograms, memory reports and allocator purging, and the current slow-log length. Each ordinary method executes on one node. Event and command names remain literal; WithKeyPrefix never changes them. These methods are immediate and have no deferred batch or transaction counterparts.

string latencyReport = await redis.Server.LatencyDoctorAsync();
RespireLatencyHistorySample[] history = await redis.Server.LatencyHistoryAsync("command");
RespireLatencyHistogram[] histograms = await redis.Server.LatencyHistogramsAsync(["get", "set"]);
string memoryReport = await redis.Server.MemoryDoctorAsync();
long slowLogLength = await redis.Server.SlowLogLengthAsync();

The existing LatestLatencyAsync, MemoryStatsAsync, and SlowLogAsync methods keep their existing contracts. SlowLogLengthAsync counts retained entries, not all commands that have ever exceeded the configured slow-log threshold.

Histories and histograms

Event history requires a nonzero latency-monitor-threshold configuration, measured in milliseconds. Each event retains at most 160 samples. Unknown events return an empty array. Timestamp converts Unix seconds to DateTimeOffset; Latency converts the server's integer milliseconds to TimeSpan. Event names cannot be null or whitespace.

Histograms require latency-tracking, enabled by default on supported servers. Calls is the number of sampled calls, and every bucket contains an upper bound in microseconds with a cumulative count. Subtract the previous bucket's count to obtain an individual bucket's count. These distributions accumulate across calls; CONFIG RESETSTAT clears them. They are separate from the event monitor and its LATENCY RESET command. These inspection methods do not change either configuration.

Omit command names to request every available histogram. Unknown names and commands without samples are omitted by the server. Names are copied before asynchronous work and sent as individual arguments without tokenization. Null names are rejected. The server may expand a parent command to its subcommands and returns its own command names, including names such as config|get. Repeated or overlapping requested names can produce duplicate results; the returned array preserves them.

Results own their strings, arrays, and nested unknown fields and survive reply or client disposal. Arrays are mutable; record equality compares array references. Histogram AdditionalFields preserves future fields as recursively copied RespireResult values backed by GC-owned storage. Disposal of those values is optional; explicit disposal invalidates their nested views. Required malformed fields, impossible time values, and invalid cumulative bucket sequences produce RespireProtocolException.

Memory purging

PurgeMemoryAsync requires RespireOptions.AllowAdmin = true, checked before network I/O. Server ACL checks still apply to every diagnostic command.

await using var admin = RespireClient.Create(new RespireOptions
{
    Endpoints = [new RespireEndpoint("localhost", 6379)],
    AllowAdmin = true,
});
await admin.Server.PurgeMemoryAsync();

MEMORY PURGE asks jemalloc to release reclaimable pages and can block the server. Other allocators may acknowledge it as a no-op. Success does not promise a reduction in resident memory. It does not delete keys or flush Respire's client-side cache; the read-only diagnostics also preserve cached values and in-flight cache reads. Cancellation cannot undo a purge already accepted by the server.

Both doctor methods return the server's human-readable text, including RESP3 verbatim strings. Wording depends on server version and current configuration; do not parse it as a stable structured format. Prefer the typed measurements for automated monitoring. History and histogram results allocate owned snapshots. Request specific commands and avoid overlapping polls when inspecting large command catalogs or many nodes.

Explicit per-node results

All six methods have OnAllNodesAsync counterparts returning RespireServerResult<T>[]. They follow the server fan-out contract: fresh Cluster discovery includes replicas, execution uses temporary connections with bounded concurrency, and each endpoint retains its own value or failure. Standalone clients produce one endpoint result. Discovery failure or cancellation throws; after discovery, cancellation is recorded in affected results. Inspect IsSuccess or Error before Value.

var nodes = await redis.Server.LatencyHistogramsOnAllNodesAsync(["get"]);
foreach (var node in nodes)
{
    if (node.IsSuccess)
        Console.WriteLine($"{node.Endpoint}: {node.Value.Length} histogram(s)");
    else
        Console.WriteLine($"{node.Endpoint}: {node.Error}");
}

Snapshots are not atomic or aggregated across nodes. Different observation windows and resets can make cumulative counts incomparable. Fan-out never changes Cluster slot ownership or retries a command against another endpoint. PurgeMemoryOnAllNodesAsync also requires AllowAdmin, returns true for each successful endpoint, and can partly succeed. No rollback is possible for an allocator purge.

Compatibility

API pair (ordinary and OnAllNodesAsync)	Command	Minimum Redis version
LatencyDoctorAsync	LATENCY DOCTOR	2.8.13
LatencyHistoryAsync	LATENCY HISTORY	2.8.13
LatencyHistogramsAsync	LATENCY HISTOGRAM	7.0
MemoryDoctorAsync	MEMORY DOCTOR	4.0
PurgeMemoryAsync	MEMORY PURGE	4.0
SlowLogLengthAsync	SLOWLOG LEN	2.2.12

Valkey 7.2.5+ supports all six inherited commands, verified against its tagged command metadata. The integration matrix covers Redis 6.2, Redis 7.0, and Valkey 8.1 with both RESP2 and RESP3, including the older Redis error for unsupported histograms. Unsupported commands and ACL denials remain server errors; there is no fallback or emulation. The command minimum versions do not imply every Respire connection or fan-out configuration works on those historical server versions.

This prerelease adds twelve required IServerCommands members: the six methods above and their six OnAllNodesAsync counterparts. Custom implementations, decorators, and mocks must implement or forward them.

References: Redis LATENCY DOCTOR, LATENCY HISTORY, LATENCY HISTOGRAM, MEMORY DOCTOR, MEMORY PURGE, and SLOWLOG LEN; Valkey histograms, history, and memory purging.