feat(flow-control): support source max inflight count in global setting

docs/docs/core/flow_def.mdx

@@ -151,6 +151,13 @@ If nothing changed during the last refresh cycle, only list operations will be p
 
 :::
 
+#### Concurrency control
+
+You can pass the following arguments to `add_source()` to control the concurrency of the source operation:
+
+*   `max_inflight_count`: the maximum number of concurrent inflight requests for the source operation.
+
+The default value can be specified by [`DefaultExecutionOptions`](/docs/core/settings#defaultexecutionoptions) or corresponding [environment variable](/docs/core/settings#list-of-environment-variables).
 
 ### Transform
 

docs/docs/core/settings.mdx

@@ -60,6 +60,7 @@ You have two ways to launch CocoIndex:
 
 *   `app_namespace` (type: `str`, required): The namespace of the application.
 *   `database` (type: `DatabaseConnectionSpec`, required): The connection to the Postgres database.
+*   `default_execution_options` (type: `DefaultExecutionOptions`, optional): The default execution options for the flow.
 
 ### App Namespace
 
@@ -104,13 +105,20 @@ If you use the Postgres database hosted by [Supabase](https://supabase.com/), pl
 
 :::
 
+### DefaultExecutionOptions
+
+`DefaultExecutionOptions` is used to configure the default execution options for the flow. It has the following fields:
+
+*   `source_max_inflight_count` (type: `int`, optional): The maximum number of concurrent inflight requests for source operations.  This only provides an default value, and can be overridden by the `max_inflight_count` argument passed to `FlowBuilder.add_source()` on per-source basis.
+
 ## List of Environment Variables
 
 This is the list of environment variables, each of which has a corresponding field in `Settings`:
 
 | environment variable | corresponding field in `Settings` | required? |
 |---------------------|-------------------|----------|
+| `COCOINDEX_APP_NAMESPACE` | `app_namespace` | No |
 | `COCOINDEX_DATABASE_URL` | `database.url` | Yes |
 | `COCOINDEX_DATABASE_USER` | `database.user` | No |
 | `COCOINDEX_DATABASE_PASSWORD` | `database.password` | No |
-| `COCOINDEX_APP_NAMESPACE` | `app_namespace` | No |
+| `COCOINDEX_SOURCE_MAX_INFLIGHT_COUNT` | `default_execution_options.source_max_inflight_count` | No |

python/cocoindex/setting.py

@@ -43,6 +43,14 @@ class DatabaseConnectionSpec:
     password: str | None = None
 
 
+@dataclass
+class DefaultExecutionOptions:
+    """Default execution options."""
+
+    # The maximum number of concurrent inflight requests.
+    source_max_inflight_count: int | None = 256
+
+
 def _load_field(
     target: dict[str, Any],
     name: str,
@@ -55,7 +63,15 @@ def _load_field(
         if required:
             raise ValueError(f"{env_name} is not set")
     else:
-        target[name] = value if parse is None else parse(value)
+        if parse is None:
+            target[name] = value
+        else:
+            try:
+                target[name] = parse(value)
+            except Exception as e:
+                raise ValueError(
+                    f"failed to parse environment variable {env_name}: {value}"
+                ) from e
 
 
 @dataclass
@@ -64,6 +80,7 @@ class Settings:
 
     database: DatabaseConnectionSpec | None = None
     app_namespace: str = ""
+    default_execution_options: DefaultExecutionOptions | None = None
 
     @classmethod
     def from_env(cls) -> Self:
@@ -79,9 +96,22 @@ def from_env(cls) -> Self:
         else:
             database = None
 
+        exec_kwargs: dict[str, Any] = dict()
+        _load_field(
+            exec_kwargs,
+            "source_max_inflight_count",
+            "COCOINDEX_SOURCE_MAX_INFLIGHT_COUNT",
+            parse=int,
+        )
+        default_execution_options = DefaultExecutionOptions(**exec_kwargs)
+
         app_namespace = os.getenv("COCOINDEX_APP_NAMESPACE", "")
 
-        return cls(database=database, app_namespace=app_namespace)
+        return cls(
+            database=database,
+            app_namespace=app_namespace,
+            default_execution_options=default_execution_options,
+        )
 
 
 @dataclass

src/builder/analyzer.rs

@@ -361,6 +361,7 @@ impl DataScopeBuilder {
 }
 
 pub(super) struct AnalyzerContext {
+    pub lib_ctx: Arc<LibContext>,
     pub flow_ctx: Arc<FlowInstanceContext>,
 }
 
@@ -687,6 +688,13 @@ impl AnalyzerContext {
             .typ
             .clone();
         let output = op_scope.add_op_output(import_op.name, output_type)?;
+
+        let max_inflight_count =
+            (import_op.spec.execution_options.max_inflight_count).or_else(|| {
+                self.lib_ctx
+                    .default_execution_options
+                    .source_max_inflight_count
+            });
         let result_fut = async move {
             trace!("Start building executor for source op `{}`", op_name);
             let executor = executor.await?;
@@ -697,9 +705,7 @@ impl AnalyzerContext {
                 primary_key_type,
                 name: op_name,
                 refresh_options: import_op.spec.refresh_options,
-                concurrency_controller: utils::ConcurrencyController::new(
-                    import_op.spec.execution_options.max_inflight_count,
-                ),
+                concurrency_controller: utils::ConcurrencyController::new(max_inflight_count),
             })
         };
         Ok(result_fut)
@@ -1013,7 +1019,10 @@ pub async fn analyze_flow(
     AnalyzedSetupState,
     impl Future<Output = Result<ExecutionPlan>> + Send + use<>,
 )> {
-    let analyzer_ctx = AnalyzerContext { flow_ctx };
+    let analyzer_ctx = AnalyzerContext {
+        lib_ctx: get_lib_context()?,
+        flow_ctx,
+    };
     let root_data_scope = Arc::new(Mutex::new(DataScopeBuilder::new()));
     let root_op_scope = OpScope::new(ROOT_SCOPE_NAME.to_string(), None, root_data_scope);
     let mut import_ops_futs = Vec::with_capacity(flow_inst.import_ops.len());
@@ -1125,7 +1134,10 @@ pub async fn analyze_transient_flow<'a>(
     impl Future<Output = Result<TransientExecutionPlan>> + Send + 'a,
 )> {
     let mut root_data_scope = DataScopeBuilder::new();
-    let analyzer_ctx = AnalyzerContext { flow_ctx };
+    let analyzer_ctx = AnalyzerContext {
+        lib_ctx: get_lib_context()?,
+        flow_ctx,
+    };
     let mut input_fields = vec![];
     for field in flow_inst.input_fields.iter() {
         let analyzed_field = root_data_scope.add_field(field.name.clone(), &field.value_type)?;

src/builder/flow_builder.rs

@@ -320,6 +320,7 @@ impl FlowBuilder {
             },
         };
         let analyzer_ctx = AnalyzerContext {
+            lib_ctx: self.lib_context.clone(),
             flow_ctx: self.flow_inst_context.clone(),
         };
         let analyzed = py
@@ -417,6 +418,7 @@ impl FlowBuilder {
         };
 
         let analyzer_ctx = AnalyzerContext {
+            lib_ctx: self.lib_context.clone(),
             flow_ctx: self.flow_inst_context.clone(),
         };
         let analyzed = py
@@ -464,6 +466,7 @@ impl FlowBuilder {
         };
 
         let analyzer_ctx = AnalyzerContext {
+            lib_ctx: self.lib_context.clone(),
             flow_ctx: self.flow_inst_context.clone(),
         };
         let analyzed = py

src/lib_context.rs

@@ -195,6 +195,8 @@ pub struct LibContext {
     pub db_pools: DbPools,
     pub persistence_ctx: Option<PersistenceContext>,
     pub flows: Mutex<BTreeMap<String, Arc<FlowContext>>>,
+
+    pub default_execution_options: settings::DefaultExecutionOptions,
 }
 
 impl LibContext {
@@ -262,6 +264,7 @@ pub fn create_lib_context(settings: settings::Settings) -> Result<LibContext> {
         db_pools,
         persistence_ctx,
         flows: Mutex::new(BTreeMap::new()),
+        default_execution_options: settings.default_execution_options,
     })
 }
 
@@ -296,26 +299,9 @@ mod tests {
         assert!(db_pools.pools.lock().unwrap().is_empty());
     }
 
-    #[test]
-    fn test_settings_structure_without_database() {
-        let settings = settings::Settings {
-            database: None,
-            app_namespace: "test".to_string(),
-        };
-
-        // Test that we can create the basic structure
-        assert!(settings.database.is_none());
-        assert_eq!(settings.app_namespace, "test");
-    }
-
     #[test]
     fn test_lib_context_without_database() {
-        let settings = settings::Settings {
-            database: None,
-            app_namespace: "test".to_string(),
-        };
-
-        let lib_context = create_lib_context(settings).unwrap();
+        let lib_context = create_lib_context(settings::Settings::default()).unwrap();
         assert!(lib_context.persistence_ctx.is_none());
         assert!(lib_context.require_builtin_db_pool().is_err());
     }
@@ -329,7 +315,7 @@ mod tests {
                 user: None,
                 password: None,
             }),
-            app_namespace: "test".to_string(),
+            ..Default::default()
         };
 
         // This would fail at runtime due to invalid connection, but we're testing the structure

src/settings.rs

@@ -7,13 +7,20 @@ pub struct DatabaseConnectionSpec {
     pub password: Option<String>,
 }
 
-#[derive(Deserialize, Debug)]
+#[derive(Deserialize, Debug, Default)]
+pub struct DefaultExecutionOptions {
+    pub source_max_inflight_count: Option<u32>,
+}
+
+#[derive(Deserialize, Debug, Default)]
 pub struct Settings {
     #[serde(default)]
     pub database: Option<DatabaseConnectionSpec>,
     #[serde(default)]
     #[allow(dead_code)] // Used via serialization/deserialization to Python
     pub app_namespace: String,
+    #[serde(default)]
+    pub default_execution_options: DefaultExecutionOptions,
 }
 
 #[cfg(test)]