redis/redis-py · critical · NoValidDatabaseException

Initial connection failed - no active database found

Error message

Initial connection failed - no active database found

What it means

Raised by MultiDBClient.initialize() (redis/asyncio/multidb/client.py:140) after the initial health check completes but no database has a CLOSED circuit breaker. The client iterates `self._databases` looking for the first CLOSED database to promote as active; if every database is OPEN (unhealthy), it cannot establish an active connection and aborts startup with NoValidDatabaseException.

Source

Thrown at redis/asyncio/multidb/client.py:140

                self._check_databases_health,
            )
        )

        is_active_db_found = False

        for database, weight in self._databases:
            # Set on state changed callback for each circuit.
            database.circuit.on_state_changed(self._on_circuit_state_change_callback)

            # Set states according to a weights and circuit state
            if database.circuit.state == CBState.CLOSED and not is_active_db_found:
                # Directly set the active database during initialization
                # without recording a geo failover metric
                self.command_executor._active_database = database
                is_active_db_found = True

        if not is_active_db_found:
            raise NoValidDatabaseException(
                "Initial connection failed - no active database found"
            )

        self.initialized = True

    def get_databases(self) -> Databases:
        """
        Returns a sorted (by weight) list of all databases.
        """
        return self._databases

    async def set_active_database(self, database: AsyncDatabase) -> None:
        """
        Promote one of the existing databases to become an active.
        """
        exists = None

        for existing_db, _ in self._databases:

View on GitHub (pinned to da03cdc7e8)

Solutions

1. Verify each `DatabaseConfig` URL/credentials with a direct `redis-py` PING before constructing MultiDBClient.
2. Bring up at least one Redis instance the client can reach (e.g. `invoke devenv`).
3. Check network/TLS: ensure host/port reachable, certificates valid, firewall rules allow egress.
4. If some DBs are expected to be down at startup, confirm `initial_health_check_policy` is set to `ONE_AVAILABLE` or `MAJORITY_AVAILABLE` in `MultiDbConfig`.

Example fix

# before
client = MultiDBClient(MultiDbConfig(databases_config=[
    DatabaseConfig(from_url='redis://wrong-host:6379/0'),
]))
await client.initialize()  # NoValidDatabaseException

# after
# verify endpoint first
import redis.asyncio as redis
r = redis.from_url('redis://correct-host:6379/0')
await r.ping()
client = MultiDBClient(MultiDbConfig(databases_config=[
    DatabaseConfig(from_url='redis://correct-host:6379/0'),
]))
await client.initialize()

import redis.asyncio as redis

async def all_endpoints_reachable(urls: list[str]) -> bool:
    for u in urls:
        r = redis.from_url(u)
        try:
            await r.ping()
        except Exception:
            await r.aclose()
            return False
        finally:
            await r.aclose()
    return True

# call before MultiDBClient(...).initialize()

from redis.asyncio.multidb.client import MultiDBClient

def is_multidb(obj) -> bool:
    return isinstance(obj, MultiDBClient)

from redis.multidb.exception import NoValidDatabaseException

try:
    await client.initialize()
except NoValidDatabaseException:
    # startup cannot proceed: log, alert, abort or fall back to single-client mode
    raise

When it happens

Trigger: Constructing a `MultiDBClient` and calling `await client.initialize()` (or issuing the first command which auto-initializes) when all configured databases are unreachable, misconfigured, or failed their initial health checks. Also reached if the initial health check policy is lenient (ONE_AVAILABLE) but even one healthy DB could not be found.

Common situations: All Redis endpoints down or wrong host/port in `DatabaseConfig`; network partition isolating the client from every DB; TLS/auth misconfiguration causing every PING probe to fail; Redis Enterprise cluster not yet bootstrapped; CI running without the docker-compose stack up.

Related errors

• Cannot set active database, database is unhealthy
• Initial health check failed. Initial health check policy: {s
• No valid database available for communication
• No database connections currently available. This is a tempo
• Unhealthy database

AI-assisted analysis of redis/redis-py@da03cdc7e8 (2026-08-04). Data as JSON: /data/errors/0d1569121f845421.json. Report an issue: GitHub.