[GraphQL] Set Connection Timeout (MystenLabs#16199)

## Description

Use the request timeout configuration to also bound the time a
connection to the DB is held open for, to prevent long-lived connections
from lingering while the underlying request has been cleaned up.

## Test Plan

```
sui-graphql-rpc$ cargo nextest run
sui-graphql-e2e-tests$ cargo nextest run --features pg_integration
```

crates/sui-graphql-rpc/src/config.rs

@@ -22,7 +22,7 @@ const MAX_TYPE_ARGUMENT_WIDTH: u32 = 32;
 const MAX_TYPE_NODES: u32 = 256;
 const MAX_MOVE_VALUE_DEPTH: u32 = 128;
 
-const DEFAULT_REQUEST_TIMEOUT_MS: u64 = 40_000;
+pub(crate) const DEFAULT_REQUEST_TIMEOUT_MS: u64 = 40_000;
 
 const DEFAULT_IDE_TITLE: &str = "Sui GraphQL IDE";
 

crates/sui-graphql-rpc/src/context_data/db_data_provider.rs

@@ -2,11 +2,11 @@
 // SPDX-License-Identifier: Apache-2.0
 
 use crate::{
-    config::DEFAULT_SERVER_DB_POOL_SIZE,
+    config::{DEFAULT_REQUEST_TIMEOUT_MS, DEFAULT_SERVER_DB_POOL_SIZE},
     error::Error,
     types::{address::Address, sui_address::SuiAddress, validator::Validator},
 };
-use std::collections::BTreeMap;
+use std::{collections::BTreeMap, time::Duration};
 use sui_indexer::{
     apis::GovernanceReadApiV2, indexer_reader::IndexerReader, PgConnectionPoolConfig,
 };
@@ -30,15 +30,21 @@ impl PgManager {
 
     /// Create a new underlying reader, which is used by this type as well as other data providers.
     pub(crate) fn reader(db_url: impl Into<String>) -> Result<IndexerReader, Error> {
-        Self::reader_with_config(db_url, DEFAULT_SERVER_DB_POOL_SIZE)
+        Self::reader_with_config(
+            db_url,
+            DEFAULT_SERVER_DB_POOL_SIZE,
+            DEFAULT_REQUEST_TIMEOUT_MS,
+        )
     }
 
     pub(crate) fn reader_with_config(
         db_url: impl Into<String>,
         pool_size: u32,
+        timeout_ms: u64,
     ) -> Result<IndexerReader, Error> {
         let mut config = PgConnectionPoolConfig::default();
         config.set_pool_size(pool_size);
+        config.set_connection_timeout(Duration::from_millis(timeout_ms));
         IndexerReader::new_with_config(db_url, config)
             .map_err(|e| Error::Internal(format!("Failed to create reader: {e}")))
     }

crates/sui-graphql-rpc/src/server/builder.rs

@@ -258,6 +258,10 @@ impl ServerBuilder {
         let reader = PgManager::reader_with_config(
             config.connection.db_url.clone(),
             config.connection.db_pool_size,
+            // Bound each connection in a request with the overall request timeout, to bound DB
+            // utilisation (in the worst case we will use 2x the request timeout time in DB wall
+            // time).
+            config.service.limits.request_timeout_ms,
         )
         .map_err(|e| Error::Internal(format!("Failed to create pg connection pool: {}", e)))?;