NPE in EmailGenerator.generateFeedbackSessionReminderEmails

[damithc]

v7.10.x, production

This error happened about 25 times in the last 4 days. It hasn't happened earlier. So, either a change on GAE/Sendgrid side or a change in our latest version could be causing it.

Error Message: teammates.common.util.Logger severe: Unexpected error while sending emails:
java.lang.NullPointerException
at teammates.logic.api.EmailGenerator.generateFeedbackSessionReminderEmails(EmailGenerator.java:95)
at teammates.ui.webapi.FeedbackSessionRemindParticularUsersEmailWorkerAction.execute(FeedbackSessionRemindParticularUsersEmailWorkerAction.java:50)
at teammates.ui.webapi.FeedbackSessionRemindParticularUsersEmailWorkerAction.execute(FeedbackSessionRemindParticularUsersEmailWorkerAction.java:18)
at teammates.ui.webapi.WebApiServlet.invokeServlet(WebApiServlet.java:93)
at teammates.ui.webapi.WebApiServlet.doPost(WebApiServlet.java:47)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:848)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1780)
at com.googlecode.objectify.ObjectifyFilter.doFilter(ObjectifyFilter.java:48)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1767)
at com.google.apphosting.utils.servlet.JdbcMySqlConnectionCleanupFilter.doFilter(JdbcMySqlConnectionCleanupFilter.java:60)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1767)
at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:583)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143)
at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:524)
at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:226)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:134)
at com.google.apphosting.runtime.jetty9.ParseBlobUploadHandler.handle(ParseBlobUploadHandler.java:111)
at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1182)
at com.google.apphosting.runtime.jetty9.AppEngineWebAppContext.doHandle(AppEngineWebAppContext.java:187)
at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:513)
at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:185)
at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1112)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
at com.google.apphosting.runtime.jetty9.AppVersionHandlerMap.handle(AppVersionHandlerMap.java:293)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:134)
at org.eclipse.jetty.server.Server.handle(Server.java:539)
at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:333)
at com.google.apphosting.runtime.jetty9.RpcConnection.handle(RpcConnection.java:216)
at com.google.apphosting.runtime.jetty9.RpcConnector.serviceRequest(RpcConnector.java:81)
at com.google.apphosting.runtime.jetty9.JettyServletEngineAdapter.serviceRequest(JettyServletEngineAdapter.java:134)
at com.google.apphosting.runtime.JavaRuntime$RequestRunnable.dispatchServletRequest(JavaRuntime.java:772)
at com.google.apphosting.runtime.JavaRuntime$RequestRunnable.dispatchRequest(JavaRuntime.java:735)
at com.google.apphosting.runtime.JavaRuntime$RequestRunnable.run(JavaRuntime.java:705)
at com.google.apphosting.runtime.ThreadGroupPool$PoolEntry.run(ThreadGroupPool.java:261)
at java.lang.Thread.run(Thread.java:748)

[madanalogy]

Strange, the only changes to EmailGenerator was in #10914 though it doesn't seem anything there will cause an NPE. I'll take a closer look sometime next week when I have more time if no one has yet by then