refactor: add deltalake-gcp crate

crates/deltalake-core/Cargo.toml

@@ -135,7 +135,6 @@ datafusion = [
     "parquet",
 ]
 datafusion-ext = ["datafusion"]
-gcs = ["object_store/gcp"]
 json = ["parquet/json"]
 python = ["arrow/pyarrow"]
 unity-experimental = ["reqwest", "hyper"]

crates/deltalake-gcp/Cargo.toml

@@ -0,0 +1,31 @@
+[package]
+name = "deltalake-gcp"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+deltalake-core = { path = "../deltalake-core" }
+lazy_static = "1"
+
+# workspace depenndecies
+async-trait = { workspace = true }
+bytes = { workspace = true }
+futures = { workspace = true }
+tracing = { workspace = true }
+object_store = { workspace = true, features = ["gcp"]}
+thiserror = { workspace = true }
+tokio = { workspace = true }
+regex = { workspace = true }
+url = { workspace = true }
+
+[dev-dependencies]
+chrono = { workspace = true }
+serial_test = "3"
+deltalake-test = { path = "../deltalake-test" }
+pretty_env_logger = "*"
+rand = "0.8"
+serde_json = { workspace = true }
+tempfile = "3"
+
+[features]
+integration_test = []

crates/deltalake-gcp/src/config.rs

@@ -0,0 +1,163 @@
+//! Auxiliary module for generating a valig Google cloud configuration.
+//!
+//! Google offers few ways to authenticate against storage accounts and
+//! provide credentials for a service principal. Some of this configutaion may
+//! partially be specified in the environment. This module establishes a structured
+//! way how we discover valid credentials and some heuristics on how they are prioritized.
+use std::collections::{hash_map::Entry, HashMap};
+use std::str::FromStr;
+
+use object_store::gcp::GoogleConfigKey;
+use object_store::Error as ObjectStoreError;
+
+use crate::error::Result;
+
+lazy_static::lazy_static! {
+    static ref CREDENTIAL_KEYS: Vec<GoogleConfigKey> =
+    Vec::from_iter([
+        GoogleConfigKey::ServiceAccountKey,
+        GoogleConfigKey::ApplicationCredentials,
+    ]);
+}
+
+/// Credential
+enum GcpCredential {
+    /// Using the service account key
+    ServiceAccountKey,
+    /// Using application credentials
+    ApplicationCredentials,
+}
+
+impl GcpCredential {
+    /// required configuration keys for variant
+    fn keys(&self) -> Vec<GoogleConfigKey> {
+        match self {
+            Self::ServiceAccountKey => Vec::from_iter([GoogleConfigKey::ServiceAccountKey]),
+            Self::ApplicationCredentials => {
+                Vec::from_iter([GoogleConfigKey::ApplicationCredentials])
+            }
+        }
+    }
+}
+
+/// Helper struct to create full configuration from passed options and environment
+///
+/// Main concern is to pick the desired credential for connecting to starage backend
+/// based on a provided configuration and configuration set in the environment.
+pub(crate) struct GcpConfigHelper {
+    config: HashMap<GoogleConfigKey, String>,
+    env_config: HashMap<GoogleConfigKey, String>,
+    priority: Vec<GcpCredential>,
+}
+
+impl GcpConfigHelper {
+    /// Create a new [`ConfigHelper`]
+    pub fn try_new(
+        config: impl IntoIterator<Item = (impl AsRef<str>, impl Into<String>)>,
+    ) -> Result<Self> {
+        let mut env_config = HashMap::new();
+        for (os_key, os_value) in std::env::vars_os() {
+            if let (Some(key), Some(value)) = (os_key.to_str(), os_value.to_str()) {
+                if key.starts_with("GOOGLE_") {
+                    if let Ok(config_key) = GoogleConfigKey::from_str(&key.to_ascii_lowercase()) {
+                        env_config.insert(config_key, value.to_string());
+                    }
+                }
+            }
+        }
+
+        Ok(Self {
+            config: config
+                .into_iter()
+                .map(|(key, value)| Ok((GoogleConfigKey::from_str(key.as_ref())?, value.into())))
+                .collect::<Result<_, ObjectStoreError>>()?,
+            env_config,
+            priority: Vec::from_iter([
+                GcpCredential::ServiceAccountKey,
+                GcpCredential::ApplicationCredentials,
+            ]),
+        })
+    }
+
+    /// Check if all credential keys are contained in passed config
+    fn has_full_config(&self, cred: &GcpCredential) -> bool {
+        cred.keys().iter().all(|key| self.config.contains_key(key))
+    }
+
+    /// Check if any credential keys are contained in passed config
+    fn has_any_config(&self, cred: &GcpCredential) -> bool {
+        cred.keys().iter().any(|key| self.config.contains_key(key))
+    }
+
+    /// Check if all credential keys can be provided using the env
+    fn has_full_config_with_env(&self, cred: &GcpCredential) -> bool {
+        cred.keys()
+            .iter()
+            .all(|key| self.config.contains_key(key) || self.env_config.contains_key(key))
+    }
+
+    /// Generate a cofiguration augmented with options from the environment
+    pub fn build(mut self) -> Result<HashMap<GoogleConfigKey, String>> {
+        let mut has_credential = false;
+
+        // try using only passed config options
+        if !has_credential {
+            for cred in &self.priority {
+                if self.has_full_config(cred) {
+                    has_credential = true;
+                    break;
+                }
+            }
+        }
+
+        // try partially avaialbe credentials augmented by environment
+        if !has_credential {
+            for cred in &self.priority {
+                if self.has_any_config(cred) && self.has_full_config_with_env(cred) {
+                    for key in cred.keys() {
+                        if let Entry::Vacant(e) = self.config.entry(key) {
+                            e.insert(self.env_config.get(&key).unwrap().to_owned());
+                        }
+                    }
+                    has_credential = true;
+                    break;
+                }
+            }
+        }
+
+        // try getting credentials only from the environment
+        if !has_credential {
+            for cred in &self.priority {
+                if self.has_full_config_with_env(cred) {
+                    for key in cred.keys() {
+                        if let Entry::Vacant(e) = self.config.entry(key) {
+                            e.insert(self.env_config.get(&key).unwrap().to_owned());
+                        }
+                    }
+                    has_credential = true;
+                    break;
+                }
+            }
+        }
+
+        let omit_keys = if has_credential {
+            CREDENTIAL_KEYS.clone()
+        } else {
+            Vec::new()
+        };
+
+        // Add keys from the environment to the configuration, as e.g. client configuration options.
+        // NOTE We have to specifically configure omitting keys, since workload identity can
+        // work purely using defaults, but partial config may be present in the environment.
+        // Preference of conflicting configs (e.g. msi resource id vs. client id is handled in object store)
+        for key in self.env_config.keys() {
+            if !omit_keys.contains(key) {
+                if let Entry::Vacant(e) = self.config.entry(*key) {
+                    e.insert(self.env_config.get(key).unwrap().to_owned());
+                }
+            }
+        }
+
+        Ok(self.config)
+    }
+}

crates/deltalake-gcp/src/error.rs

@@ -0,0 +1,21 @@
+use deltalake_core::errors::DeltaTableError;
+
+pub(crate) type Result<T, E = Error> = std::result::Result<T, E>;
+
+#[derive(thiserror::Error, Debug)]
+pub(crate) enum Error {
+    #[error("failed to parse config: {0}")]
+    Parse(String),
+
+    #[error(transparent)]
+    ObjectStore(#[from] object_store::Error),
+}
+
+impl From<Error> for DeltaTableError {
+    fn from(e: Error) -> Self {
+        match e {
+            Error::Parse(msg) => DeltaTableError::Generic(msg),
+            Error::ObjectStore(e) => DeltaTableError::ObjectStore { source: e },
+        }
+    }
+}

crates/deltalake-gcp/src/lib.rs

@@ -0,0 +1,68 @@
+use std::collections::HashMap;
+use std::str::FromStr;
+use std::sync::Arc;
+
+use deltalake_core::logstore::{default_logstore, logstores, LogStore, LogStoreFactory};
+use deltalake_core::storage::{
+    factories, url_prefix_handler, ObjectStoreFactory, ObjectStoreRef, StorageOptions,
+};
+use deltalake_core::{DeltaResult, Path};
+use object_store::gcp::GoogleConfigKey;
+use object_store::parse_url_opts;
+use url::Url;
+
+mod config;
+pub mod error;
+
+trait GcpOptions {
+    fn as_gcp_options(&self) -> HashMap<GoogleConfigKey, String>;
+}
+
+impl GcpOptions for StorageOptions {
+    fn as_gcp_options(&self) -> HashMap<GoogleConfigKey, String> {
+        self.0
+            .iter()
+            .filter_map(|(key, value)| {
+                Some((
+                    GoogleConfigKey::from_str(&key.to_ascii_lowercase()).ok()?,
+                    value.clone(),
+                ))
+            })
+            .collect()
+    }
+}
+
+#[derive(Clone, Default, Debug)]
+pub struct GcpFactory {}
+
+impl ObjectStoreFactory for GcpFactory {
+    fn parse_url_opts(
+        &self,
+        url: &Url,
+        options: &StorageOptions,
+    ) -> DeltaResult<(ObjectStoreRef, Path)> {
+        let config = config::GcpConfigHelper::try_new(options.as_gcp_options())?.build()?;
+        let (store, prefix) = parse_url_opts(url, config)?;
+        Ok((url_prefix_handler(store, prefix.clone())?, prefix))
+    }
+}
+
+impl LogStoreFactory for GcpFactory {
+    fn with_options(
+        &self,
+        store: ObjectStoreRef,
+        location: &Url,
+        options: &StorageOptions,
+    ) -> DeltaResult<Arc<dyn LogStore>> {
+        Ok(default_logstore(store, location, options))
+    }
+}
+
+/// Register an [ObjectStoreFactory] for common Google Cloud [Url] schemes
+pub fn register_handlers(_additional_prefixes: Option<Url>) {
+    let factory = Arc::new(GcpFactory {});
+    let scheme = &"gs";
+    let url = Url::parse(&format!("{}://", scheme)).unwrap();
+    factories().insert(url.clone(), factory.clone());
+    logstores().insert(url.clone(), factory.clone());
+}