Ensure replset member on port 27017 is primary

Author: eramongodb

.mci.yml

@@ -191,6 +191,48 @@ functions:
                 echo "{ \"releases\": { \"default\": \"$MONGODB_BINARIES\" }}" > $MONGO_ORCHESTRATION_HOME/orchestration.config
                 ./.evergreen/run-orchestration.sh
 
+                # Ensure server on port 27017 is the primary server.
+                if [[ "$TOPOLOGY" == replica_set ]]; then
+                  # Replset members should be on the following ports.
+                  declare hosts="localhost:27017,localhost:27018,localhost:27019"
+
+                  # Authentication may be required.
+                  declare creds
+                  if [[ -n "$AUTH" ]]; then
+                    creds="bob:pwd123@"
+                  else
+                    creds=""
+                  fi
+
+                  declare uri
+                  printf -v uri "mongodb://%s%s" "$creds" "$hosts"
+
+                  # Raise the priority of the member on port 27017. Others should have priority 1.
+                  declare script
+                  printf -v script "%s\n%s\n%s\n" \
+                    "let c = rs.conf()" \
+                    "c.members.find((m) => m.host.includes('27017')).priority = 10" \
+                    "rs.reconfig(c)"
+
+                  mongosh --quiet "$uri" --eval "$script"
+
+                  # Wait up to a minute for member on port 27017 to become primary.
+                  wait_for_primary() {
+                    for _ in $(seq 60); do
+                      if mongosh --quiet "$uri" --eval "quit(rs.hello().primary.includes('27017') ? 0 : 1)"; then
+                        return 0
+                      else
+                        sleep 1
+                      fi
+                    done
+                    echo "Could not set replset member on port 27017 as primary"
+                    return 1
+                  }
+                  echo "Waiting for replset member 27017 to become primary..."
+                  wait_for_primary
+                  echo "Waiting for replset member 27017 to become primary... done."
+                fi
+
                 # Copy mongocryptd up so other functions can find it later, since we can't share PATHs
                 if [ -f $MONGODB_BINARIES/mongocryptd ]; then
                     cp $MONGODB_BINARIES/mongocryptd ../mongocryptd