diff --git a/dap-lib/src/doh_client/dns_message.rs b/dap-lib/src/doh_client/dns_message.rs
index 211b616..30e6ed8 100644
--- a/dap-lib/src/doh_client/dns_message.rs
+++ b/dap-lib/src/doh_client/dns_message.rs
@@ -12,14 +12,16 @@ use hickory_proto::{
 };
 use std::{net::IpAddr, str::FromStr};
 
-// https://github.com/aaronriekenberg/rust-doh-proxy/blob/master/src/doh/request_key.rs
 #[derive(Debug, Clone, Hash, Eq, PartialEq, Ord, PartialOrd)]
+/// QueryKey is a tuple of query name, query type and query class
+/// https://github.com/aaronriekenberg/rust-doh-proxy/blob/master/src/doh/request_key.rs
 pub struct QueryKey {
   pub query_name: String,
   pub query_type: RecordType,
   pub query_class: DNSClass,
 }
 #[derive(Debug, Clone, Hash, Eq, PartialEq, Ord, PartialOrd)]
+/// Request is a sorted list of QueryKey
 pub struct Request(pub Vec<QueryKey>);
 impl TryFrom<&Message> for Request {
   type Error = anyhow::Error;
@@ -46,14 +48,17 @@ impl TryFrom<&Message> for Request {
   }
 }
 
+/// Check if the message is a DNS query
 pub fn is_query(packet_buf: &[u8]) -> anyhow::Result<Message> {
   is(packet_buf, MessageType::Query)
 }
 
+/// Check if the message is a DNS response
 pub fn is_response(packet_buf: &[u8]) -> anyhow::Result<Message> {
   is(packet_buf, MessageType::Response)
 }
 
+/// Check if the message is a DNS query or response
 fn is(packet_buf: &[u8], mtype: MessageType) -> anyhow::Result<Message> {
   let msg = decode(packet_buf)?;
   if msg.message_type() == mtype {
@@ -70,16 +75,19 @@ fn is(packet_buf: &[u8], mtype: MessageType) -> anyhow::Result<Message> {
   }
 }
 
+/// Decode a DNS message
 pub fn decode(packet_buf: &[u8]) -> anyhow::Result<Message> {
   Message::from_bytes(packet_buf).map_err(|e| anyhow!("Undecodable packet buffer as DNS message: {}", e))
 }
 
+/// Encode a DNS message
 pub fn encode(msg: &Message) -> anyhow::Result<Vec<u8>> {
   msg
     .to_bytes()
     .map_err(|e| anyhow!("Failed to encode DNS message: {}", e))
 }
 
+/// Build a DNS query message for A record
 pub fn build_query_a(fqdn: &str) -> anyhow::Result<Message> {
   let qname: Name = Name::from_ascii(fqdn).unwrap();
   let mut query = Query::query(qname, RecordType::A);
@@ -105,6 +113,7 @@ pub fn build_query_a(fqdn: &str) -> anyhow::Result<Message> {
   Ok(msg)
 }
 
+/// Build a DNS response message with NXDOMAIN
 pub fn build_response_nx(msg: &Message) -> Message {
   let mut res = msg.clone();
   res.set_message_type(hickory_proto::op::MessageType::Response);
@@ -113,6 +122,7 @@ pub fn build_response_nx(msg: &Message) -> Message {
   res
 }
 
+/// Build a DNS response message for given QueryKey and IP address
 pub fn build_response_given_ipaddr(
   msg: &Message,
   q_key: &QueryKey,
diff --git a/dap-lib/src/doh_client/doh_client_main.rs b/dap-lib/src/doh_client/doh_client_main.rs
index 633fb2d..6e933cd 100644
--- a/dap-lib/src/doh_client/doh_client_main.rs
+++ b/dap-lib/src/doh_client/doh_client_main.rs
@@ -301,7 +301,7 @@ impl DoHClient {
   }
 }
 
-// TODO: implement ResolveIps for DoHClient
+// ResolveIps for DoHClient
 #[async_trait]
 impl ResolveIps for Arc<DoHClient> {
   /// Resolve ip addresses of the given domain name
diff --git a/dap-lib/src/globals.rs b/dap-lib/src/globals.rs
index ad51b2a..ba5b103 100644
--- a/dap-lib/src/globals.rs
+++ b/dap-lib/src/globals.rs
@@ -1,4 +1,4 @@
-use crate::{constants::*, doh_client::DoHMethod, http_client::HttpClient};
+use crate::{constants::*, doh_client::DoHMethod};
 use auth_client::AuthenticationConfig;
 use std::{
   net::{IpAddr, SocketAddr},
@@ -10,8 +10,6 @@ use url::Url;
 #[derive(Debug)]
 /// Global objects containing shared resources
 pub struct Globals {
-  // /// HTTP client shared by DoH client and authentication client, etc.
-  // pub http_client: Arc<HttpClient>,
   /// proxy configuration
   pub proxy_config: ProxyConfig,
 
@@ -42,20 +40,19 @@ pub struct ProxyConfig {
   /// timeout for HTTP requests (DoH, ODoH, and authentication requests)
   pub http_timeout_sec: Duration,
 
-  // doh, odoh, modoh target settings
+  /// doh, odoh, modoh target settings
   pub target_config: TargetConfig,
 
-  // odoh and modoh nexthop
+  /// odoh and modoh nexthop settings
   pub nexthop_relay_config: Option<NextHopRelayConfig>,
 
-  // modoh
+  /// modoh relay settings
   pub subseq_relay_config: Option<SubseqRelayConfig>,
 
-  // authentication
+  /// authentication settings
   pub authentication_config: Option<AuthenticationConfig>,
   // pub query_plugins: Option<QueryPluginsApplied>,
   // pub min_ttl: u32, // TTL of overridden response
-  // pub credential: Arc<RwLock<Option<Credential>>>,
 }
 
 #[derive(PartialEq, Eq, Debug, Clone)]