Christopher KrahandXuanwo
b6d15558ec
`retry_with_exponential_backoff` retries every exception except an auth
error (`python/python/lancedb/embeddings/utils.py:298-318`). For Cohere,
Gemini, Jina and VoyageAI a missing API key raises from
`api_key_not_found_help`, and a missing provider package raises
`ImportError` everywhere. Neither can succeed on a retry, yet both sleep
through all seven rounds and then surface wrapped in `Exception("Maximum
number of retries...")`.
Before, on `142d032`, a VoyageAI function with no key set (script below,
`time.sleep` recorded, `random.seed(0)`):
```
$ python lance_retry_deterministic.py python/python
raised: Exception('Maximum number of retries (7) exceeded.', ValueError('Please set the VOYAGEAI_API_KEY environment v
attempts: 8 sleeps: [4, 13, 37, 93, 280, 788, 2811]
slept 4026 s before a missing-API-key error surfaced
```
After:
```
$ python lance_retry_deterministic.py python/python
raised: MissingApiKeyError('Please set the VOYAGEAI_API_KEY environment variable.')
attempts: 1 sleeps: []
```
<details><summary>lance_retry_deterministic.py</summary>
```python
# loads the pure-Python embeddings package from the tree, native extension stubbed
import os, random, sys, time, types
TREE = sys.argv[1]
pkg = types.ModuleType("lancedb"); pkg.__path__ = [TREE + "/lancedb"]; sys.modules["lancedb"] = pkg
native = types.ModuleType("lancedb._lancedb"); native.__getattr__ = lambda name: None
sys.modules["lancedb._lancedb"] = native
import pyarrow as pa
from lancedb.embeddings import get_registry
random.seed(0)
os.environ.pop("VOYAGE_API_KEY", None)
slept = []
time.sleep = slept.append
func = get_registry().get("voyageai").create(name="voyage-3")
try:
func.compute_source_embeddings_with_retry(pa.array(["hello"]))
except Exception as e:
print("raised:", repr(e)[:110])
print("attempts:", len(slept) + 1, "sleeps:", [round(s) for s in slept])
print("slept %.0f s before a missing-API-key error surfaced" % sum(slept))
```
</details>
The message names the wrong variable: `voyageai.py:501` reads
`VOYAGE_API_KEY`. I left that for a separate fix.
`api_key_not_found_help` now raises `MissingApiKeyError`, a `ValueError`
subclass, so existing `except ValueError` callers still catch it. That
error and `ImportError` join the 401 exemption from #2995. A plain
`ValueError` is still retried, because `bedrock.py:171` wraps boto3
throttling in one. No issue exists for this. OpenAI is not covered: with
no key, `openai.OpenAI()` raises `OpenAIError`, which has no status
code, so it still retries. I can follow up on that.
### Verification
```
# lance_stub: an empty stand-in for lancedb._lancedb, loaded from the source tree
$ pytest -p lance_stub --noconftest python/tests/test_embeddings.py -k "retry or 401 or deterministic" -q
5 passed, 23 deselected in 0.59s
# utils.py from 142d032, tests kept:
2 failed, 3 passed, 23 deselected in 0.74s
$ pytest -p lance_stub --noconftest python/tests/test_voyageai_embeddings.py -q
18 passed in 0.18s
# not run: the full suite or pyright; the native extension did not build here
```
Baseline on `142d032` has 2 of these tests. The new ones cover a missing
key, a missing package, and a wrapped throttling error that must still
retry. ruff 0.16.10 check and format are clean.
@wjones127 you merged the 401 change. Is a `ValueError` subclass the way
you want to mark this?
Co-authored-by: Xuanwo <github@xuanwo.io>
LanceDB Python SDK
A Python library for LanceDB.
Installation
pip install lancedb
If no wheel is published for your platform, pip builds lancedb from the source distribution. That build needs a Rust toolchain and protoc (the Protocol Buffers compiler) on your PATH, and can take a while.
Pre-Haswell x86_64 hosts: lancedb-compat
The default lancedb wheel targets x86-64-haswell (AVX2 + FMA + F16C) for full performance on modern hardware. Pre-Haswell hosts — Intel Sandy Bridge / Ivy Bridge / Westmere; AMD Bulldozer / Piledriver / Steamroller — don't have AVX2 and crash with Illegal instruction at import lancedb.
For those hosts, install the lancedb-compat package instead:
pip install lancedb-compat
Same Python API (import lancedb works as usual). The compat wheel is compiled at the x86-64-v2 baseline (Nehalem-class) and uses runtime SIMD dispatch in the embedded lance crate to pick the right kernel tier (scalar / AVX / AVX+FMA / AVX2+FMA / AVX-512) at load time, so it still goes fast on modern hardware while running cleanly on the pre-Haswell silicon. Use lance.simd_info() from Python to verify which tier was selected.
lancedb and lancedb-compat install to the same lancedb/ namespace and conflict at install time. Pick one. To switch, pip uninstall lancedb first, then pip install lancedb-compat (or vice-versa).
If you need a custom baseline (or lancedb-compat isn't yet published for your platform), build from source with the override:
RUSTFLAGS="-C target-cpu=x86-64-v2" maturin build --release
pip install ./target/wheels/lancedb-*.whl
Preview Releases
Stable releases are created about every 2 weeks. For the latest features and bug fixes, you can install the preview release. These releases receive the same level of testing as stable releases, but are not guaranteed to be available for more than 6 months after they are released. Once your application is stable, we recommend switching to stable releases.
pip install --pre --extra-index-url https://pypi.fury.io/lancedb/ lancedb
Threading in CPU-limited containers
LanceDB uses separate pools for compute work and storage I/O. On a container with two visible CPUs, current releases intentionally use one compute worker by default; no manual configuration is needed. If every query logs an I/O core reservation warning on a two-CPU container, upgrade from LanceDB 0.21.1 or earlier.
The two commonly tuned environment variables control different resources:
LANCE_CPU_THREADSoverrides the number of compute workers. One worker is the appropriate setting for a two-CPU container when an explicit override is needed.LANCE_IO_THREADScontrols concurrent storage operations, not reserved CPU cores. Its default can be greater than the number of CPUs because I/O workers spend much of their time waiting for storage.
Keep the defaults unless measurements show that the workload benefits from an override. See the Lance threading model for the current defaults and tuning guidance.
Usage
Basic Example
import lancedb
db = lancedb.connect('<PATH_TO_LANCEDB_DATASET>')
table = db.open_table('my_table')
results = table.search([0.1, 0.3]).limit(20).to_list()
print(results)
Development
See CONTRIBUTING.md for information on how to contribute to LanceDB.