Add retry for email sending (#2963).2963-retry-email

7 files changed, 169 insertions, 1 deletions

diff --git a/src/lib/email.cc b/src/lib/email.cc
index 028624c69..f0ff9f910 100644
--- a/src/lib/email.cc
+++ b/src/lib/email.cc
@@ -21,6 +21,7 @@
 
 #include "compose.hpp"
 #include "config.h"
+#include "dcpomatic_log.h"
 #include "email.h"
 #include "exceptions.h"
 #include "util.h"
@@ -110,6 +111,25 @@ Email::get_data(void* ptr, size_t size, size_t nmemb)
 
 
 void
+Email::send_with_retry(string server, int port, EmailProtocol protocol, int retries, string user, string password)
+{
+	int this_try = 0;
+	while (true) {
+		try {
+			send(server, port, protocol, user, password);
+			return;
+		} catch (NetworkError& e) {
+			LOG_ERROR("Error %1 when trying to send email on attempt %2 of 3", e.what(), this_try + 1, retries);
+			if (this_try == (retries - 1)) {
+				throw;
+			}
+		}
+		++this_try;
+	}
+}
+
+
+void
 Email::send(string server, int port, EmailProtocol protocol, string user, string password)
 {
 	_email = "Date: " + rfc_2822_date(time(nullptr)) + "\r\n"
diff --git a/src/lib/email.h b/src/lib/email.h
index ac4703453..0ef68379b 100644
--- a/src/lib/email.h
+++ b/src/lib/email.h
@@ -35,6 +35,7 @@ public:
 	void add_attachment (boost::filesystem::path file, std::string name, std::string mime_type);
 
 	void send (std::string server, int port, EmailProtocol protocol, std::string user = "", std::string password = "");
+	void send_with_retry(std::string server, int port, EmailProtocol protocol, int retries, std::string user = "", std::string password = "");
 
 	std::string notes () const {
 		return _notes;
diff --git a/src/lib/kdm_with_metadata.cc b/src/lib/kdm_with_metadata.cc
index d09f6930b..b6e027ef3 100644
--- a/src/lib/kdm_with_metadata.cc
+++ b/src/lib/kdm_with_metadata.cc
@@ -277,7 +277,7 @@ send_emails(
 		};
 
 		try {
-			email.send(config->mail_server(), config->mail_port(), config->mail_protocol(), config->mail_user(), config->mail_password());
+			email.send_with_retry(config->mail_server(), config->mail_port(), config->mail_protocol(), 5, config->mail_user(), config->mail_password());
 		} catch (...) {
 			log_details(email);
 			throw;
diff --git a/test/email_test.cc b/test/email_test.cc
new file mode 100644
index 000000000..2402c1d07
--- /dev/null
+++ b/test/email_test.cc
@@ -0,0 +1,43 @@
+/*
+    Copyright (C) 2025 Carl Hetherington <cth@carlh.net>
+
+    This file is part of DCP-o-matic.
+
+    DCP-o-matic is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    DCP-o-matic is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with DCP-o-matic.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+
+
+#include "lib/email.h"
+#include "smtp_server.h"
+#include "test.h"
+#include <boost/test/unit_test.hpp>
+#include <boost/thread.hpp>
+
+
+auto constexpr port = 31925;
+
+
+BOOST_AUTO_TEST_CASE(email_retry_test)
+{
+	boost::thread thread([]() {
+		run_smtp_server(port, true);
+		run_smtp_server(port, true);
+		run_smtp_server(port, false);
+	});
+
+	Email email("carl@crunchcinema.com", { "bob@snacks.com" }, "Louder crisps - possible?", "These crisps just aren't loud enough.  People can still hear the film.");
+	email.send_with_retry("localhost", port, EmailProtocol::PLAIN, 3);
+}
+
diff --git a/test/smtp_server.cc b/test/smtp_server.cc
new file mode 100644
index 000000000..c6802bded
--- /dev/null
+++ b/test/smtp_server.cc
@@ -0,0 +1,79 @@
+/*
+    Copyright (C) 2025 Carl Hetherington <cth@carlh.net>
+
+    This file is part of DCP-o-matic.
+
+    DCP-o-matic is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    DCP-o-matic is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with DCP-o-matic.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+
+
+#include "smtp_server.h"
+#include <boost/asio.hpp>
+#include <iostream>
+#include <string>
+
+
+using std::string;
+using boost::asio::ip::tcp;
+
+
+void
+run_smtp_server(int port, bool fail)
+{
+	boost::asio::io_context context;
+	tcp::acceptor acceptor(context, tcp::endpoint(tcp::v4(), port));
+	tcp::socket socket(context);
+	acceptor.accept(socket);
+
+	auto send = [&socket](string message) {
+		boost::system::error_code error;
+		boost::asio::write(socket, boost::asio::buffer(message + "\r\n"), boost::asio::transfer_all(), error);
+	};
+
+	auto receive = [&socket]() {
+		boost::asio::streambuf buffer;
+		boost::asio::read_until(socket, buffer, "\n");
+		return string{
+			std::istreambuf_iterator<char>(&buffer),
+			std::istreambuf_iterator<char>()
+		};
+	};
+
+	send("220 smtp.example.com ESMTP Postfix");
+	/* EHLO */
+	receive();
+	send("250-smtp.example.com Hello mate [127.0.0.1]");
+	send("250-SIZE 14680064");
+	send("250-PIPELINING");
+	send("250 HELP");
+	/* MAIL FROM */
+	receive();
+	send("250 Ok");
+	/* RCPT TO */
+	if (fail) {
+		return;
+	}
+	receive();
+	send("250 Ok");
+	/* DATA */
+	receive();
+	send("354 End data with <CR><LF>.<CR><LF>");
+	/* Email body */
+	receive();
+	send("250 Ok");
+	/* QUIT */
+	receive();
+}
+
diff --git a/test/smtp_server.h b/test/smtp_server.h
new file mode 100644
index 000000000..f3cc1d0a9
--- /dev/null
+++ b/test/smtp_server.h
@@ -0,0 +1,23 @@
+/*
+    Copyright (C) 2025 Carl Hetherington <cth@carlh.net>
+
+    This file is part of DCP-o-matic.
+
+    DCP-o-matic is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    DCP-o-matic is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with DCP-o-matic.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+
+
+extern void run_smtp_server(int port, bool fail);
+
diff --git a/test/wscript b/test/wscript
index b04e244be..7b4e484d6 100644
--- a/test/wscript
+++ b/test/wscript
@@ -81,6 +81,7 @@ def build(bld):
                  dcp_subtitle_test.cc
                  digest_test.cc
                  dkdm_recipient_list_test.cc
+                 email_test.cc
                  empty_caption_test.cc
                  empty_test.cc
                  encryption_test.cc
@@ -154,6 +155,7 @@ def build(bld):
                  shuffler_test.cc
                  skip_frame_test.cc
                  socket_test.cc
+                 smtp_server.cc
                  srt_subtitle_test.cc
                  ssa_subtitle_test.cc
                  stream_test.cc