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//! Background poller that bridges DynamoDB Streams -> Lambda event source mappings.
//!
//! Periodically checks Lambda state for enabled event source mappings
//! pointing to DynamoDB streams, reads stream records, and invokes Lambda
//! functions with batches of records.
use std::collections::HashMap;
use std::sync::Arc;
use std::time::Duration;
use chrono::Utc;
use serde_json::json;
use fakecloud_core::delivery::LambdaDelivery;
use fakecloud_dynamodb::state::SharedDynamoDbState;
use fakecloud_lambda::state::{LambdaInvocation, SharedLambdaState};
/// DynamoDB Streams -> Lambda event source mapping poller.
pub struct DynamoDbStreamsLambdaPoller {
dynamodb_state: SharedDynamoDbState,
lambda_state: SharedLambdaState,
lambda_delivery: Option<Arc<dyn LambdaDelivery>>,
/// Track the last processed sequence number per mapping
checkpoints: parking_lot::RwLock<HashMap<String, String>>,
}
impl DynamoDbStreamsLambdaPoller {
pub fn new(dynamodb_state: SharedDynamoDbState, lambda_state: SharedLambdaState) -> Self {
Self {
dynamodb_state,
lambda_state,
lambda_delivery: None,
checkpoints: parking_lot::RwLock::new(HashMap::new()),
}
}
pub fn with_lambda_delivery(mut self, delivery: Arc<dyn LambdaDelivery>) -> Self {
self.lambda_delivery = Some(delivery);
self
}
pub async fn run(self: Arc<Self>) {
let mut interval = tokio::time::interval(Duration::from_millis(500));
loop {
interval.tick().await;
self.poll().await;
}
}
async fn poll(&self) {
// Collect enabled mappings that point to DynamoDB streams
let mappings: Vec<(String, String, String, i64)> = {
let lambda = self.lambda_state.read();
lambda
.event_source_mappings
.values()
.filter(|m| {
m.enabled
&& m.event_source_arn.contains(":dynamodb:")
&& m.event_source_arn.contains("/stream/")
})
.map(|m| {
(
m.uuid.clone(),
m.event_source_arn.clone(),
m.function_arn.clone(),
m.batch_size,
)
})
.collect()
};
if mappings.is_empty() {
return;
}
for (mapping_id, stream_arn, function_arn, batch_size) in mappings {
// Extract table name from stream ARN
// Format: arn:aws:dynamodb:region:account:table/TableName/stream/timestamp
let table_name = if let Some(table_part) = stream_arn.split(":table/").nth(1) {
table_part.split('/').next().unwrap_or("")
} else {
continue;
};
// Get checkpoint for this mapping
let checkpoint = self.checkpoints.read().get(&mapping_id).cloned();
// Read stream records from DynamoDB
let records = {
let dynamodb = self.dynamodb_state.read();
let table = match dynamodb.tables.get(table_name) {
Some(t) => t,
None => continue,
};
if !table.stream_enabled {
continue;
}
let stream_records = table.stream_records.read();
// Filter records after checkpoint
let mut filtered: Vec<_> = stream_records
.iter()
.filter(|r| {
if let Some(ref cp) = checkpoint {
&r.dynamodb.sequence_number > cp
} else {
true
}
})
.take(batch_size.max(0) as usize)
.cloned()
.collect();
// Sort by sequence number to ensure order
filtered
.sort_by(|a, b| a.dynamodb.sequence_number.cmp(&b.dynamodb.sequence_number));
filtered
};
if records.is_empty() {
continue;
}
// Build Lambda event payload
let event = json!({
"Records": records.iter().map(|record| {
let mut event_record = json!({
"eventID": record.event_id,
"eventName": record.event_name,
"eventVersion": record.event_version,
"eventSource": record.event_source,
"awsRegion": record.aws_region,
"dynamodb": {
"Keys": record.dynamodb.keys,
"SequenceNumber": record.dynamodb.sequence_number,
"SizeBytes": record.dynamodb.size_bytes,
"StreamViewType": record.dynamodb.stream_view_type,
},
"eventSourceARN": record.event_source_arn,
});
if let Some(ref new_img) = record.dynamodb.new_image {
event_record["dynamodb"]["NewImage"] = json!(new_img);
}
if let Some(ref old_img) = record.dynamodb.old_image {
event_record["dynamodb"]["OldImage"] = json!(old_img);
}
event_record
}).collect::<Vec<_>>()
});
let payload = serde_json::to_string(&event).unwrap_or_default();
// Invoke Lambda
if let Some(ref delivery) = self.lambda_delivery {
match delivery.invoke_lambda(&function_arn, &payload).await {
Ok(_) => {
tracing::info!(
function_arn = %function_arn,
record_count = records.len(),
"DynamoDB Streams->Lambda invocation succeeded"
);
// Update checkpoint to last processed sequence number
if let Some(last_record) = records.last() {
self.checkpoints.write().insert(
mapping_id.clone(),
last_record.dynamodb.sequence_number.clone(),
);
}
}
Err(e) => {
tracing::error!(
function_arn = %function_arn,
error = %e,
"DynamoDB Streams->Lambda invocation failed"
);
}
}
} else {
// No delivery mechanism, just record
let mut lambda = self.lambda_state.write();
lambda.invocations.push(LambdaInvocation {
function_arn: function_arn.clone(),
payload: payload.clone(),
timestamp: Utc::now(),
source: "dynamodb:streams".to_string(),
});
// Update checkpoint
if let Some(last_record) = records.last() {
self.checkpoints
.write()
.insert(mapping_id, last_record.dynamodb.sequence_number.clone());
}
}
}
}
}