hdfs-s3-gateway (Python)

Python bindings for the HDFS → S3 read-only gateway. This package wraps the Rust gateway so it can be driven from Python either as a foreground blocking call or as an in-process background server.

Usage

from hdfs_s3_gateway import Gateway

# Background server (no subprocess — runs on its own native thread + tokio runtime).
gw = Gateway(namenode_uri="hdfs://localhost:8020", hdfs_root="/data", bucket_name="hdfs")
gw.start()
print(gw.address)   # e.g. "127.0.0.1:8080"
# ... point any S3 client at the endpoint ...
gw.stop()           # graceful shutdown

# Or as a context manager:
with Gateway(config_path="gateway.toml") as gw:
    print(gw.address)
    # ... use the endpoint ...

Caches (metadata, block maps, directory listings and negative lookups) are off by default. Enable them for read-heavy workloads with Gateway(..., cache_enabled=True) (or [cache] enabled = true / HDFS_S3_CACHE_ENABLED=1). The same argument is the incident kill switch: pass cache_enabled=False to bypass the caches without waiting for a release, and read gw.cache_enabled to confirm the effective value. Within a TTL, an object written by another client may not be visible yet.

The gateway performs no authentication by default — it must run behind network-level access control. See the top-level project README for the full security posture. You can optionally enable SigV4 auth by passing auth_secret="..." to Gateway(...) (or the --auth-secret CLI flag / auth_secret TOML key). When set, a valid signature is required (unsigned requests are rejected, wrong secret → 403 SignatureDoesNotMatch), so clients use normal signing (any access-key id + that secret) instead of anonymous / aws_skip_signature. When unset (the default), the gateway accepts both anonymous and signed requests.

Reading data through the gateway

Once the gateway is running, point any S3 client at its endpoint. The examples below assume the gateway was started with hdfs_root="/data" and bucket_name="hdfs", exposing a hive-partitioned table at s3://hdfs/seed_parquet/country=us/year=2021/data.parquet.

By default all clients use anonymous / unsigned access (the gateway has no auth). The endpoint is http://<gw.address> — e.g. http://127.0.0.1:39111. If you started the gateway with auth_secret, drop the anonymous / aws_skip_signature flags and pass any access-key id plus that secret instead.

polars

import polars as pl

ep = f"http://{gw.address}"
so = {
    "aws_skip_signature": "true",
    "aws_endpoint_url": ep,
    "aws_allow_http": "true",
}
# Whole directory tree (hive partition columns are recovered automatically):
df = pl.read_parquet(f"s3://hdfs/seed_parquet/", storage_options=so)
# Or a recursive glob (polars expands it client-side into S3 listings):
df = pl.read_parquet(f"s3://hdfs/seed_parquet/country=*/year=*/*.parquet", storage_options=so)

DuckDB

import duckdb

ep = f"http://{gw.address}"
host = ep.replace("http://", "")
duckdb.sql("INSTALL httpfs; LOAD httpfs;")
duckdb.sql(f"SET s3_endpoint='{host}';")
duckdb.sql("SET s3_use_ssl=false;")
duckdb.sql("SET s3_access_key_id='';")
duckdb.sql("SET s3_secret_access_key='';")
duckdb.sql("SET s3_session_token='';")
duckdb.sql("SET s3_url_style='path';")

# DuckDB's httpfs reads a directory tree via a recursive glob:
df = duckdb.sql("SELECT * FROM read_parquet('s3://hdfs/seed_parquet/**')").df()

pandas (pyarrow engine)

import pandas as pd

ep = f"http://{gw.address}"
so = {
    "anon": "true",
    "endpoint_url": ep,
    "client_kwargs": {"endpoint_url": ep},
}
# pandas delegates s3:// URIs to fsspec/s3fs, not pyarrow's native S3 filesystem.
df = pd.read_parquet("s3://hdfs/seed_parquet/", storage_options=so)

pandas (s3fs / fsspec engine)

import pandas as pd

ep = f"http://{gw.address}"
so = {
    "anon": "true",
    "endpoint_url": ep,
    "client_kwargs": {"endpoint_url": ep},
}
df = pd.read_parquet("s3://hdfs/seed_parquet/", storage_options=so)

pyarrow (native S3FileSystem)

import pyarrow.dataset as ds
import pyarrow.fs as pafs

ep = f"http://{gw.address}"
host = ep.replace("http://", "")
s3 = pafs.S3FileSystem(anonymous=True, endpoint_override=host, scheme="http")
# pyarrow wants a "bucket/key" path, not a full s3:// URI.
dataset = ds.dataset("hdfs/seed_parquet", format="parquet", filesystem=s3, partitioning="hive")
table = dataset.to_table()

Note on path forms. Only polars and DuckDB expand glob patterns (country=*/year=*) client-side into real S3 listings; the other engines pass the glob literally to the gateway, which cannot match it. For a whole partitioned table, use the directory form (s3://hdfs/seed_parquet/).