fix(replication): Mitigate connection hangs on serverless Postgres

- Adds a 500ms delay after preflight checks to allow the connection pool to release connections before pg_dump is executed.
- Sets a 30-second connection timeout (PGCONNECT_TIMEOUT) for all pg_dump and pg_dumpall commands to prevent indefinite hangs.

Author: taariq

CHANGELOG.md

@@ -2,6 +2,13 @@
 
 All notable changes to this project will be documented in this file.
 
+## [5.3.15] - 2025-12-03
+
+### Fixed
+
+- **Fix connection hang during preflight checks for SerenDB/Neon targets**: A 500ms delay was added after preflight checks and before any `pg_dump` operations. This allows the connection pool to clean up connections opened during preflight, preventing connection exhaustion that would cause `pg_dumpall` to hang indefinitely on serverless PostgreSQL providers with strict connection limits.
+- **Mitigate connection pool exhaustion hangs with timeout**: All `pg_dump` and `pg_dumpall` commands now execute with a 30-second connection timeout (`PGCONNECT_TIMEOUT=30`). This prevents indefinite hangs if the connection pool is exhausted and makes failures detectable instead of causing silent hangs.
+
 ## [5.3.14] - 2025-12-03
 
 ### Fixed

Cargo.lock

@@ -212,6 +212,11 @@ pub async fn init(
         .context("Source and target validation failed")?;
     tracing::info!("✓ Verified source and target are different databases");
 
+    // Force connection cleanup before subprocess operations
+    // Preflight connections should be out of scope, but ensure pool is released
+    tracing::debug!("Waiting for connection pool cleanup...");
+    tokio::time::sleep(std::time::Duration::from_millis(500)).await;
+
     // Create managed temporary directory for dump files
     // Unlike TempDir, this survives SIGKILL and is cleaned up on next startup
     let temp_path =

src/commands/init.rs

@@ -54,6 +54,9 @@ pub async fn dump_globals(source_url: &str, output_path: &str) -> Result<()> {
                 cmd.env(env_var, value);
             }
 
+            // Set connection timeout to prevent hangs on pool exhaustion
+            cmd.env("PGCONNECT_TIMEOUT", "30"); // Fail after 30 seconds
+
             cmd.status().context(
                 "Failed to execute pg_dumpall. Is PostgreSQL client installed?\n\
                  Install with:\n\
@@ -516,6 +519,9 @@ pub async fn dump_schema(
                 cmd.env(env_var, value);
             }
 
+            // Set connection timeout to prevent hangs on pool exhaustion
+            cmd.env("PGCONNECT_TIMEOUT", "30"); // Fail after 30 seconds
+
             cmd.status().context(
                 "Failed to execute pg_dump. Is PostgreSQL client installed?\n\
                  Install with:\n\
@@ -644,6 +650,9 @@ pub async fn dump_data(
                 cmd.env(env_var, value);
             }
 
+            // Set connection timeout to prevent hangs on pool exhaustion
+            cmd.env("PGCONNECT_TIMEOUT", "30"); // Fail after 30 seconds
+
             cmd.status().context(
                 "Failed to execute pg_dump. Is PostgreSQL client installed?\n\
                  Install with:\n\