A Vector Store node is now considered down if it returns an HTTP 5xx status.
This can happen, for example, if the node fails to
connect to the database or has not completed its initial full scan.
The logic for marking a node as 'up' is also enhanced. A node is now
only considered up when its status is 'SERVING'.
The maximum backoff delay for status checking now depends on the
`read_request_timeout_in_ms` configuration option. The delay is set
to twice the value of this parameter.
This exception should only occur due to internal errors, not client or external issues.
If triggered, it indicates an internal problem. Therefore, we notify about this exception
using on_internal_error_noexcept.
Introduces logic to mark clients that fail to answer an ANN request as
"down". Down clients are omitted from further requests until they
successfully respond to a health check.
Health checks for down clients are performed in the background using the
`status` endpoint, with an exponential backoff retry policy ranging
from 100ms to 20s.
To unify error handling, the low-level client methods now return
`std::expected` instead of throwing exceptions. This allows for
consistent and explicit error propagation from the client up to the
caller.
The relevant error types have been moved to a new `vector_search/error.hh`
header to centralize their definitions.
This refactoring extracts low-level client logic into a new, dedicated
`client` class. The new class is responsible for connecting to the
server and serializing requests.
This change prepares for extending the `vector_store_client` to check
node status via the `api/v1/status` endpoint.
`/ann` Response deserialization remains in the `vector_store_client` as it
is schema-dependent.
