redis/redis-py · error · NotImplementedError

LATENCY HISTOGRAM is intentionally not implemented in the cl

Error message

LATENCY HISTOGRAM is intentionally not implemented in the client.

What it means

latency_histogram is a stub that always raises NotImplementedError. Note: this is distinct from the TIMESERIES module's TS MRANGE aggregation or the Redis latency-event histogram. The method exists as a placeholder but does not invoke the server. Use execute_command if the underlying COMMAND LATENCY HISTOGRAM is available on your Redis version.

Source

Thrown at redis/commands/core.py:1964

    def memory_purge(self: SyncClientProtocol, **kwargs) -> bool: ...

    @overload
    def memory_purge(self: AsyncClientProtocol, **kwargs) -> Awaitable[bool]: ...

    def memory_purge(self, **kwargs) -> bool | Awaitable[bool]:
        """
        Attempts to purge dirty pages for reclamation by allocator

        For more information, see https://redis.io/commands/memory-purge
        """
        return self.execute_command("MEMORY PURGE", **kwargs)

    def latency_histogram(self, *args):
        """
        This function throws a NotImplementedError since it is intentionally
        not supported.
        """
        raise NotImplementedError(
            "LATENCY HISTOGRAM is intentionally not implemented in the client."
        )

    @overload
    def latency_history(self: SyncClientProtocol, event: str) -> list[list[int]]: ...

    @overload
    def latency_history(
        self: AsyncClientProtocol, event: str
    ) -> Awaitable[list[list[int]]]: ...

    def latency_history(
        self, event: str
    ) -> list[list[int]] | Awaitable[list[list[int]]]:
        """
        Returns the raw data of the ``event``'s latency spikes time series.

        For more information, see https://redis.io/commands/latency-history

View on GitHub (pinned to da03cdc7e8)

Solutions

Use r.execute_command('COMMAND', 'LATENCY') if your Redis version exposes command-latency stats.
For per-event latency spikes, use r.latency_history(event).
For aggregate command stats, parse r.info('commandstats').

Example fix

# before
r.latency_histogram('GET')
# after
r.execute_command('COMMAND', 'LATENCY')  # if supported by server

Defensive patterns

Strategy: fallback

Try / catch

try:
    r.latency_histogram()
except NotImplementedError:
    stats = r.execute_command('COMMAND', 'LATENCY')

Prevention

latency_histogram is an intentional stub — don't rely on it.
Distinguish command-latency stats from per-event latency history.

When it happens

Trigger: Calling r.latency_histogram() or r.latency_histogram('GET'). Confusing it with per-event latency history (latency_history).

Common situations: Developer expects command-latency percentile data. Confusing latency_histogram with the INFO commandstats output. Migrating from another client library that implemented it.

Related errors

AI-assisted analysis of redis/redis-py@da03cdc7e8 (2026-08-04). Data as JSON: /data/errors/ee8aae5533d9ed9e.json. Report an issue: GitHub.