RUST-803 Conditionally use hello for monitoring (#600)

Author: patrickfreed

benchmarks/src/bench/mod.rs

@@ -138,7 +138,7 @@ pub async fn drop_database(uri: &str, database: &str) -> Result<()> {
 
     let hello = client
         .database("admin")
-        .run_command(doc! { "ismaster": true }, None)
+        .run_command(doc! { "hello": true }, None)
         .await?;
 
     client.database(&database).drop(None).await?;

benchmarks/src/bench/run_command.rs

@@ -31,7 +31,7 @@ impl Benchmark for RunCommandBenchmark {
         Ok(RunCommandBenchmark {
             db,
             num_iter: options.num_iter,
-            cmd: doc! { "ismaster": true },
+            cmd: doc! { "hello": true },
             uri: options.uri,
         })
     }

benchmarks/src/main.rs

@@ -219,7 +219,7 @@ async fn run_benchmarks(
                 let run_command =
                     bench::run_benchmark::<RunCommandBenchmark>(run_command_options).await?;
 
-                comp_score += score_test(run_command, RUN_COMMAND_BENCH, 0.16, more_info);
+                comp_score += score_test(run_command, RUN_COMMAND_BENCH, 0.13, more_info);
             }
 
             // Small doc insertOne

src/client/auth/mod.rs

@@ -383,7 +383,7 @@ impl Credential {
     }
 
     /// If the mechanism is missing, append the appropriate mechanism negotiation key-value-pair to
-    /// the provided isMaster command document.
+    /// the provided hello or legacy hello command document.
     pub(crate) fn append_needed_mechanism_negotiation(&self, command: &mut Document) {
         if let (Some(username), None) = (self.username.as_ref(), self.mechanism.as_ref()) {
             command.insert(

src/client/executor.rs

@@ -31,6 +31,7 @@ use crate::{
         UNKNOWN_TRANSACTION_COMMIT_RESULT,
     },
     event::command::{CommandFailedEvent, CommandStartedEvent, CommandSucceededEvent},
+    hello::LEGACY_HELLO_COMMAND_NAME_LOWERCASE,
     operation::{
         AbortTransaction,
         AggregateTarget,
@@ -70,7 +71,7 @@ lazy_static! {
     pub(crate) static ref HELLO_COMMAND_NAMES: HashSet<&'static str> = {
         let mut hash_set = HashSet::new();
         hash_set.insert("hello");
-        hash_set.insert("ismaster");
+        hash_set.insert(LEGACY_HELLO_COMMAND_NAME_LOWERCASE);
         hash_set
     };
 }

src/client/options/mod.rs

@@ -410,8 +410,7 @@ pub struct ClientOptions {
     #[builder(default)]
     pub driver_info: Option<DriverInfo>,
 
-    /// The amount of time each monitoring thread should wait between sending an isMaster command
-    /// to its respective server.
+    /// The amount of time each monitoring thread should wait between performing server checks.
     ///
     /// The default value is 10 seconds.
     #[builder(default)]

src/cmap/conn/command.rs

@@ -8,7 +8,7 @@ use crate::{
     bson::Document,
     client::{options::ServerApi, ClusterTime, HELLO_COMMAND_NAMES, REDACTED_COMMANDS},
     error::{Error, ErrorKind, Result},
-    is_master::{IsMasterCommandResponse, IsMasterReply},
+    hello::{HelloCommandResponse, HelloReply},
     operation::{CommandErrorBody, CommandResponse},
     options::{ReadConcern, ReadConcernInternal, ReadConcernLevel, ServerAddress},
     selection_criteria::ReadPreference,
@@ -244,12 +244,12 @@ impl RawCommandResponse {
             .map_err(|_| Error::invalid_authentication_response(mechanism_name))
     }
 
-    pub(crate) fn to_is_master_response(&self, round_trip_time: Duration) -> Result<IsMasterReply> {
-        match self.body::<CommandResponse<IsMasterCommandResponse>>() {
+    pub(crate) fn to_hello_reply(&self, round_trip_time: Duration) -> Result<HelloReply> {
+        match self.body::<CommandResponse<HelloCommandResponse>>() {
             Ok(response) if response.is_success() => {
                 let server_address = self.source_address().clone();
                 let cluster_time = response.cluster_time().cloned();
-                Ok(IsMasterReply {
+                Ok(HelloReply {
                     server_address,
                     command_response: response.body,
                     round_trip_time,

src/cmap/conn/stream_description.rs

@@ -1,6 +1,6 @@
 use std::time::Duration;
 
-use crate::{client::options::ServerAddress, is_master::IsMasterReply, sdam::ServerType};
+use crate::{client::options::ServerAddress, hello::HelloReply, sdam::ServerType};
 
 /// Contains information about a given server in a format digestible by a connection.
 #[derive(Debug, Default, Clone)]
@@ -32,24 +32,27 @@ pub(crate) struct StreamDescription {
     /// can be included in a write batch.  If more than this number of writes are included, the
     /// server cannot guarantee space in the response document to reply to the batch.
     pub(crate) max_write_batch_size: i64,
+
+    /// Whether the server associated with this connection supports the `hello` command.
+    pub(crate) hello_ok: bool,
 }
 
 impl StreamDescription {
-    /// Constructs a new StreamDescription from an IsMasterReply.
-    pub(crate) fn from_is_master(reply: IsMasterReply) -> Self {
+    /// Constructs a new StreamDescription from a `HelloReply`.
+    pub(crate) fn from_hello_reply(reply: &HelloReply) -> Self {
         Self {
-            server_address: reply.server_address,
+            server_address: reply.server_address.clone(),
             initial_server_type: reply.command_response.server_type(),
             max_wire_version: reply.command_response.max_wire_version,
             min_wire_version: reply.command_response.min_wire_version,
-            sasl_supported_mechs: reply.command_response.sasl_supported_mechs,
-            // TODO RUST-204: Add "saslSupportedMechs" if applicable.
+            sasl_supported_mechs: reply.command_response.sasl_supported_mechs.clone(),
             logical_session_timeout: reply
                 .command_response
                 .logical_session_timeout_minutes
                 .map(|mins| Duration::from_secs(mins as u64 * 60)),
             max_bson_object_size: reply.command_response.max_bson_object_size,
             max_write_batch_size: reply.command_response.max_write_batch_size,
+            hello_ok: reply.command_response.hello_ok.unwrap_or(false),
         }
     }
 
@@ -78,6 +81,7 @@ impl StreamDescription {
             logical_session_timeout: Some(Duration::from_secs(30 * 60)),
             max_bson_object_size: 16 * 1024 * 1024,
             max_write_batch_size: 100_000,
+            hello_ok: false,
         }
     }
 }

src/cmap/conn/wire/mod.rs

@@ -1,7 +1,5 @@
 mod header;
 mod message;
-#[cfg(test)]
-mod test;
 mod util;
 
 pub(crate) use self::{message::Message, util::next_request_id};