refactor: update email result handling to accommodate null values in reminders

backend/src/entities/cron-jobs/cron-jobs.service.ts

@@ -127,15 +127,21 @@ export class CronJobsService {
     }
   }
 
-  private async sendEmailResultsToSlack(results: Array<ICronMessagingResults>): Promise<void> {
+  private async sendEmailResultsToSlack(results: Array<ICronMessagingResults | null>): Promise<void> {
+    const filteredResults = results.filter((result) => !!result);
+    const nullResultsCount = results.length - filteredResults.length;
     const chunkSize = 20;
-    for (let i = 0; i < results.length; i += chunkSize) {
-      const chunk = results.slice(i, i + chunkSize);
+    for (let i = 0; i < filteredResults.length; i += chunkSize) {
+      const chunk = filteredResults.slice(i, i + chunkSize);
       const message = this.emailCronResultToSlackString(chunk);
       if (!message) {
         continue;
       }
       await slackPostMessage(message, Constants.EXCEPTIONS_CHANNELS);
     }
+    if (nullResultsCount > 0) {
+      const timedOutMessage = `The system timed out while sending results to ${nullResultsCount} email addresses.`;
+      await slackPostMessage(timedOutMessage, Constants.EXCEPTIONS_CHANNELS);
+    }
   }
 }

backend/src/entities/email/email/email.service.ts

@@ -78,7 +78,7 @@ export class EmailService {
     return await this.sendEmailToUser(letterContent);
   }
 
-  public async sendRemindersToUsers(userEmails: Array<string>): Promise<Array<ICronMessagingResults>> {
+  public async sendRemindersToUsers(userEmails: Array<string>): Promise<Array<ICronMessagingResults | null>> {
     const queue = new PQueue({ concurrency: 8 });
     const mailingResults: Array<SMTPTransport.SentMessageInfo | void> = await Promise.all(
       userEmails.map(async (email: string) => {
@@ -229,7 +229,7 @@ export class EmailService {
     return await this.emailTransporterService.transportEmail(emailMessage);
   }
 
-  private async sendReminderToUser(email: string): Promise<SMTPTransport.SentMessageInfo> {
+  private async sendReminderToUser(email: string): Promise<SMTPTransport.SentMessageInfo | null> {
     const letterContent: IMessage = {
       from: this.emailFrom,
       to: email,
@@ -272,19 +272,19 @@ export class EmailService {
     });
   }
 
-  private buildMailingResults(results: Array<SMTPTransport.SentMessageInfo | void>): Array<ICronMessagingResults> {
-    return results
-      .map((result) => {
-        if (!result) {
-          return;
-        }
-        const { messageId, accepted, rejected } = result;
-        return {
-          messageId: messageId ? messageId : undefined,
-          accepted: accepted ? accepted : undefined,
-          rejected: rejected ? rejected : undefined,
-        };
-      })
-      .filter((result) => !!result);
+  private buildMailingResults(
+    results: Array<SMTPTransport.SentMessageInfo | void>,
+  ): Array<ICronMessagingResults | null> {
+    return results.map((result) => {
+      if (!result) {
+        return null;
+      }
+      const { messageId, accepted, rejected } = result;
+      return {
+        messageId: messageId ? messageId : undefined,
+        accepted: accepted ? accepted : undefined,
+        rejected: rejected ? rejected : undefined,
+      };
+    });
   }
 }