SERVER-7965 Make the timestamp format settable in servers.

From the command line or config file, --logTimestampFormat=(ctime|iso8601-utc|iso8601-local).

The beginning of the Unix Epoch is formatted as follows in the three formats,
assuming America/New_York for the time zone.

  ctime:         Wed Dec 31 19:00:00.000
  iso8601-utc:   1970-01-01T00:00:00.000Z
  iso8601-local: 1969-12-31T19:00:00.000+0500

The default remains the same as in prior versions, "ctime".

2 files changed, 31 insertions, 1 deletions

diff --git a/src/mongo/logger/message_event_utf8_encoder.cpp b/src/mongo/logger/message_event_utf8_encoder.cpp
index cf6225b3ffc..e8f30cef9c1 100644
--- a/src/mongo/logger/message_event_utf8_encoder.cpp
+++ b/src/mongo/logger/message_event_utf8_encoder.cpp
@@ -24,13 +24,23 @@
 namespace mongo {
 namespace logger {
 
+    static MessageEventDetailsEncoder::DateFormatter _dateFormatter = dateToCtimeString;
+
+    void MessageEventDetailsEncoder::setDateFormatter(DateFormatter dateFormatter) {
+        _dateFormatter = dateFormatter;
+    }
+
+    MessageEventDetailsEncoder::DateFormatter MessageEventDetailsEncoder::getDateFormatter() {
+        return _dateFormatter;
+    }
+
     MessageEventDetailsEncoder::~MessageEventDetailsEncoder() {}
     std::ostream& MessageEventDetailsEncoder::encode(const MessageEventEphemeral& event,
                                                      std::ostream &os) {
 
         static const size_t maxLogLine = 10 * 1024;
 
-        os << dateToCtimeString(event.getDate()) << ' ';
+        os << _dateFormatter(event.getDate()) << ' ';
         StringData contextName = event.getContextName();
         if (!contextName.empty()) {
             os << '[' << contextName << "] ";
diff --git a/src/mongo/logger/message_event_utf8_encoder.h b/src/mongo/logger/message_event_utf8_encoder.h
index 948f39508bd..e6baca7d6ee 100644
--- a/src/mongo/logger/message_event_utf8_encoder.h
+++ b/src/mongo/logger/message_event_utf8_encoder.h
@@ -15,8 +15,11 @@
 
 #pragma once
 
+#include <string>
+
 #include "mongo/logger/encoder.h"
 #include "mongo/logger/message_event.h"
+#include "mongo/util/time_support.h"
 
 namespace mongo {
 namespace logger {
@@ -26,6 +29,23 @@ namespace logger {
      */
     class MessageEventDetailsEncoder : public Encoder<MessageEventEphemeral> {
     public:
+        typedef std::string (*DateFormatter)(Date_t);
+
+        /**
+         * Sets the date formatter function for all instances of MessageEventDetailsEncoder.
+         *
+         * Only and always safe to call during single-threaded execution, as in during start-up
+         * intiailization.
+         */
+        static void setDateFormatter(DateFormatter dateFormatter);
+
+        /**
+         * Gets the date formatter function in use by instances of MessageEventDetailsEncoder.
+         *
+         * Always safe to call.
+         */
+        static DateFormatter getDateFormatter();
+
         virtual ~MessageEventDetailsEncoder();
         virtual std::ostream& encode(const MessageEventEphemeral& event, std::ostream& os);
     };