CDRIVER-3532 unify behavior around configuration for replica set discovery

Author: rcsanchez97

src/libmongoc/doc/mongoc_uri_has_option.rst

@@ -0,0 +1,24 @@
+:man_page: mongoc_uri_has_option
+
+mongoc_uri_has_option()
+=======================
+
+Synopsis
+--------
+
+.. code-block:: c
+
+  bool
+  mongoc_uri_has_option (const mongoc_uri_t *uri, const char *option);
+
+Parameters
+----------
+
+* ``uri``: A :symbol:`mongoc_uri_t`.
+* ``option``: The name of an option, case insensitive.
+
+Description
+-----------
+
+Returns true if the option was present in the initial MongoDB URI.
+

src/libmongoc/doc/mongoc_uri_t.rst

@@ -174,6 +174,7 @@ MONGOC_URI_HEARTBEATFREQUENCYMS            heartbeatfrequencyms              The
 MONGOC_URI_SERVERSELECTIONTIMEOUTMS        serverselectiontimeoutms          A timeout in milliseconds to block for server selection before throwing an exception. The default is 30,0000ms (30 seconds).
 MONGOC_URI_SERVERSELECTIONTRYONCE          serverselectiontryonce            If "true", the driver scans the topology exactly once after server selection fails, then either selects a server or returns an error. If it is false, then the driver repeatedly searches for a suitable server for up to ``serverSelectionTimeoutMS`` milliseconds (pausing a half second between attempts). The default for ``serverSelectionTryOnce`` is "false" for pooled clients, otherwise "true". Pooled clients ignore serverSelectionTryOnce; they signal the thread to rescan the topology every half-second until serverSelectionTimeoutMS expires.
 MONGOC_URI_SOCKETCHECKINTERVALMS           socketcheckintervalms             Only applies to single threaded clients. If a socket has not been used within this time, its connection is checked with a quick "isMaster" call before it is used again. Defaults to 5,000ms (5 seconds).
+MONGOC_URI_DIRECTCONNECTION                directconnection                  If "true", the driver connects to a single server directly and will not monitor additional servers.  If "false", the driver connects based on the presence and value of the ``replicaSet`` option.
 ========================================== ================================= =========================================================================================================================================================================================================================
 
 Setting any of the \*TimeoutMS options above to ``0`` will be interpreted as "use the default value".
@@ -303,6 +304,7 @@ MONGOC_URI_SLAVEOK                         slaveok                           Whe
     mongoc_uri_get_tls
     mongoc_uri_get_username
     mongoc_uri_get_write_concern
+    mongoc_uri_has_option
     mongoc_uri_new
     mongoc_uri_new_for_host_port
     mongoc_uri_new_with_error

src/libmongoc/src/mongoc/mongoc-topology.c

@@ -210,6 +210,8 @@ mongoc_topology_new (const mongoc_uri_t *uri, bool single_threaded)
    uint32_t id;
    const mongoc_host_list_t *hl;
    mongoc_rr_data_t rr_data;
+   bool has_directconnection;
+   bool directconnection;
 
    BSON_ASSERT (uri);
 
@@ -328,12 +330,35 @@ mongoc_topology_new (const mongoc_uri_t *uri, bool single_threaded)
 
    /*
     * Set topology type from URI:
-    *   - if we've got a replicaSet name, initialize to RS_NO_PRIMARY
-    *   - otherwise, if the seed list has a single host, initialize to SINGLE
+    *   + if directConnection=true
+    *     - whether or not we have a replicaSet name, initialize to SINGLE
+    *     (directConnect with SRV or multiple hosts triggers a URI parse error)
+    *   + if directConnection=false
+    *     - if we've got a replicaSet name, initialize to RS_NO_PRIMARY
+    *     - otherwise, initialize to UNKNOWN
+    *   + if directConnection was not specified in the URI (old behavior)
+    *     - if we've got a replicaSet name, initialize to RS_NO_PRIMARY
+    *     - otherwise, if the seed list has a single host, initialize to SINGLE
     *   - everything else gets initialized to UNKNOWN
     */
+   has_directconnection = mongoc_uri_has_option (
+      uri, MONGOC_URI_DIRECTCONNECTION);
+   directconnection = has_directconnection &&
+      mongoc_uri_get_option_as_bool (uri, MONGOC_URI_DIRECTCONNECTION, false);
    hl = mongoc_uri_get_hosts (topology->uri);
-   if (mongoc_uri_get_replica_set (topology->uri)) {
+   if (service && !has_directconnection) {
+      init_type = MONGOC_TOPOLOGY_UNKNOWN;
+   } else if (has_directconnection) {
+      if (directconnection) {
+         init_type = MONGOC_TOPOLOGY_SINGLE;
+      } else {
+         if (mongoc_uri_get_replica_set (topology->uri)) {
+            init_type = MONGOC_TOPOLOGY_RS_NO_PRIMARY;
+         } else {
+            init_type = MONGOC_TOPOLOGY_UNKNOWN;
+         }
+      }
+   } else if (mongoc_uri_get_replica_set (topology->uri)) {
       init_type = MONGOC_TOPOLOGY_RS_NO_PRIMARY;
    } else {
       if (hl && hl->next) {
@@ -1656,4 +1681,4 @@ _mongoc_topology_bypass_cooldown (mongoc_topology_t *topology)
 {
    BSON_ASSERT (topology->single_threaded);
    topology->scanner->bypass_cooldown = true;
-}
+}

src/libmongoc/src/mongoc/mongoc-uri.c

@@ -702,6 +702,14 @@ mongoc_uri_bson_append_or_replace_key (bson_t *options,
 }
 
 
+bool
+mongoc_uri_has_option (const mongoc_uri_t *uri, const char *key)
+{
+   bson_iter_t iter;
+
+   return bson_iter_init_find_case (&iter, &uri->options, key);
+}
+
 bool
 mongoc_uri_option_is_int32 (const char *key)
 {
@@ -731,6 +739,7 @@ bool
 mongoc_uri_option_is_bool (const char *key)
 {
    return !strcasecmp (key, MONGOC_URI_CANONICALIZEHOSTNAME) ||
+          !strcasecmp (key, MONGOC_URI_DIRECTCONNECTION) ||
           !strcasecmp (key, MONGOC_URI_JOURNAL) ||
           !strcasecmp (key, MONGOC_URI_RETRYREADS) ||
           !strcasecmp (key, MONGOC_URI_RETRYWRITES) ||
@@ -1390,6 +1399,41 @@ mongoc_uri_finalize_auth (mongoc_uri_t *uri,
    return true;
 }
 
+static bool
+mongoc_uri_finalize_directconnection (mongoc_uri_t *uri, bson_error_t *error)
+{
+   bool directconnection = false;
+
+   directconnection =
+      mongoc_uri_get_option_as_bool (uri, MONGOC_URI_DIRECTCONNECTION, false);
+   if (!directconnection) {
+      return true;
+   }
+
+   /* URI options spec: "The driver MUST report an error if the
+    * directConnection=true URI option is specified with an SRV URI, because
+    * the URI may resolve to multiple hosts. The driver MUST allow specifying
+    * directConnection=false URI option with an SRV URI." */
+   if (uri->is_srv) {
+      MONGOC_URI_ERROR (
+         error, "%s", "SRV URI not allowed with directConnection option");
+      return false;
+   }
+
+   /* URI options spec: "The driver MUST report an error if the
+    * directConnection=true URI option is specified with multiple seeds." */
+   if (uri->hosts && uri->hosts->next) {
+      MONGOC_URI_ERROR (
+         error,
+         "%s",
+         "Multiple seeds not allowed with directConnection option");
+      return false;
+   }
+
+   return true;
+
+}
+
 static bool
 mongoc_uri_parse_before_slash (mongoc_uri_t *uri,
                                const char *before_slash,
@@ -1502,6 +1546,10 @@ mongoc_uri_parse (mongoc_uri_t *uri, const char *str, bson_error_t *error)
       goto error;
    }
 
+   if (!mongoc_uri_finalize_directconnection (uri, error)) {
+      goto error;
+   }
+
    bson_free (before_slash);
    return true;
 

src/libmongoc/src/mongoc/mongoc-uri.h

@@ -40,6 +40,7 @@
 #define MONGOC_URI_CANONICALIZEHOSTNAME "canonicalizehostname"
 #define MONGOC_URI_CONNECTTIMEOUTMS "connecttimeoutms"
 #define MONGOC_URI_COMPRESSORS "compressors"
+#define MONGOC_URI_DIRECTCONNECTION "directconnection"
 #define MONGOC_URI_GSSAPISERVICENAME "gssapiservicename"
 #define MONGOC_URI_HEARTBEATFREQUENCYMS "heartbeatfrequencyms"
 #define MONGOC_URI_JOURNAL "journal"
@@ -120,6 +121,8 @@ mongoc_uri_get_password (const mongoc_uri_t *uri);
 MONGOC_EXPORT (bool)
 mongoc_uri_set_password (mongoc_uri_t *uri, const char *password);
 MONGOC_EXPORT (bool)
+mongoc_uri_has_option (const mongoc_uri_t *uri, const char *key);
+MONGOC_EXPORT (bool)
 mongoc_uri_option_is_int32 (const char *key);
 MONGOC_EXPORT (bool)
 mongoc_uri_option_is_int64 (const char *key);