catalog connection error handling: avoid a copy

also avoid allocating string for port when constructing pg connection string

nexus/postgres-connection/src/lib.rs

@@ -1,3 +1,4 @@
+use std::fmt::Write;
 use openssl::ssl::{SslConnector, SslMethod, SslVerifyMode};
 use postgres_openssl::MakeTlsConnector;
 use pt::peerdb_peers::PostgresConfig;
@@ -10,15 +11,9 @@ pub fn get_pg_connection_string(config: &PostgresConfig) -> String {
         connection_string.push(':');
         connection_string.push_str(&urlencoding::encode(&config.password));
     }
-    connection_string.push('@');
-    connection_string.push_str(&config.host);
-    connection_string.push(':');
-    connection_string.push_str(&config.port.to_string());
-    connection_string.push('/');
-    connection_string.push_str(&config.database);
 
     // Add the timeout as a query parameter, sslmode changes here appear to be useless
-    connection_string.push_str("?connect_timeout=15");
+    write!(connection_string, "@{}:{}/{}?connect_timeout=15", config.host, config.port, config.database).ok();
 
     connection_string
 }

nexus/server/src/main.rs

@@ -1,5 +1,6 @@
 use std::{
     collections::{HashMap, HashSet},
+    fmt::Write,
     sync::Arc,
     time::Duration,
 };
@@ -1376,8 +1377,7 @@ pub async fn main() -> anyhow::Result<()> {
                         buf.put_i32(0);
                         buf.put(&b"FATAL"[..]);
                         buf.put_u8(0);
-                        let error_message = format!("Failed to connect to catalog: {}", e);
-                        buf.put(error_message.as_bytes());
+                        write!(buf, "Failed to connect to catalog: {e}").ok();
                         buf.put_u8(0);
                         buf.put_u8(b'\0');