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Overview
Comment:Take care that a bug in the email alert sender results in missed alerts rather than an endless cascade of duplicate alerts.
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Timelines: family | ancestors | descendants | both | trunk
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SHA3-256:164c3d1a6a16ff2f6fc490cb139a110a424f0461344850ef7726017f080e67f4
User & Date: drh 2018-08-09 14:15:59
Context
2018-08-09
15:39
Improvements to formatting in generated emails to make them appear less like spam. Suggestions from "gahr" on the forum. check-in: 27404ad0 user: drh tags: trunk
14:15
Take care that a bug in the email alert sender results in missed alerts rather than an endless cascade of duplicate alerts. check-in: 164c3d1a user: drh tags: trunk
06:59
Minor improvements to forum.wiki check-in: 635d2f63 user: wyoung tags: trunk
Changes
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Changes to src/email.c.

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**   (3) Loop over all subscribers.  Compose and send one or more email
**       messages to each subscriber that describe the events for
**       which the subscriber has expressed interest and has
**       appropriate privileges.
**
**   (4) Update the pending_alerts table to indicate that alerts have been
**       sent.







*/
void email_send_alerts(u32 flags){
  EmailEvent *pEvents, *p;
  int nEvent = 0;
  Stmt q;
  const char *zDigest = "false";
  Blob hdr, body;
................................................................................
  const char *zRepoName;
  const char *zFrom;
  const char *zDest = (flags & SENDALERT_STDOUT) ? "stdout" : 0;
  EmailSender *pSender = 0;
  u32 senderFlags = 0;

  if( g.fSqlTrace ) fossil_trace("-- BEGIN email_send_alerts(%u)\n", flags);
  db_begin_transaction();
  email_schema(0);
  if( !email_enabled() ) goto send_alerts_done;
  zUrl = db_get("email-url",0);
  if( zUrl==0 ) goto send_alerts_done;
  zRepoName = db_get("email-subname",0);
  if( zRepoName==0 ) goto send_alerts_done;
  zFrom = db_get("email-self",0);
  if( zFrom==0 ) goto send_alerts_done;
  if( flags & SENDALERT_TRACE ){
    senderFlags |= EMAIL_TRACE;
  }
  pSender = email_sender_new(zDest, senderFlags);



  db_multi_exec(
    "DROP TABLE IF EXISTS temp.wantalert;"
    "CREATE TEMP TABLE wantalert(eventId TEXT, needMod BOOLEAN, sentMod);"
  );
  if( flags & SENDALERT_DIGEST ){
    /* Unmoderated changes are never sent as part of a digest */
    db_multi_exec(
................................................................................
      "        EXISTS(SELECT 1 FROM private WHERE rid=substr(eventid,2)),"
      "        sentMod"
      "   FROM pending_alert"
      "  WHERE sentSep IS FALSE;"
      "DELETE FROM wantalert WHERE needMod AND sentMod;"
    );
  }




  pEvents = email_compute_event_text(&nEvent, (flags & SENDALERT_DIGEST)!=0);
  if( nEvent==0 ) goto send_alerts_done;

























  blob_init(&hdr, 0, 0);
  blob_init(&body, 0, 0);
  db_prepare(&q,
     "SELECT"
     " hex(subscriberCode),"  /* 0 */
     " semail,"               /* 1 */
     " ssub,"                 /* 2 */
................................................................................
    blob_truncate(&hdr, 0);
    blob_truncate(&body, 0);
  }
  blob_reset(&hdr);
  blob_reset(&body);
  db_finalize(&q);
  email_free_eventlist(pEvents);
  if( (flags & SENDALERT_PRESERVE)==0 ){
    if( flags & SENDALERT_DIGEST ){
      db_multi_exec(
        "UPDATE pending_alert SET sentDigest=true"
        " WHERE eventid IN (SELECT eventid FROM wantalert);"
        "DELETE FROM pending_alert WHERE sentDigest AND sentSep;"
      );
    }else{
      db_multi_exec(
        "UPDATE pending_alert SET sentSep=true"
        " WHERE eventid IN (SELECT eventid FROM wantalert WHERE NOT needMod);"
        "UPDATE pending_alert SET sentMod=true"
        " WHERE eventid IN (SELECT eventid FROM wantalert WHERE needMod);"
        "DELETE FROM pending_alert WHERE sentDigest AND sentSep;"
      );
    }




  }
send_alerts_done:
  email_sender_free(pSender);
  if( g.fSqlTrace ) fossil_trace("-- END email_send_alerts(%u)\n", flags);
  db_end_transaction(0);
}

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**   (3) Loop over all subscribers.  Compose and send one or more email
**       messages to each subscriber that describe the events for
**       which the subscriber has expressed interest and has
**       appropriate privileges.
**
**   (4) Update the pending_alerts table to indicate that alerts have been
**       sent.
**
** Update 2018-08-09:  Do step (3) before step (4).  Update the
** pending_alerts table *before* the emails are sent.  That way, if
** the process malfunctions or crashes, some notifications may never
** be sent.  But that is better than some recurring bug causing
** subscribers to be flooded with repeated notifications every 60
** seconds!
*/
void email_send_alerts(u32 flags){
  EmailEvent *pEvents, *p;
  int nEvent = 0;
  Stmt q;
  const char *zDigest = "false";
  Blob hdr, body;
................................................................................
  const char *zRepoName;
  const char *zFrom;
  const char *zDest = (flags & SENDALERT_STDOUT) ? "stdout" : 0;
  EmailSender *pSender = 0;
  u32 senderFlags = 0;

  if( g.fSqlTrace ) fossil_trace("-- BEGIN email_send_alerts(%u)\n", flags);

  email_schema(0);
  if( !email_enabled() ) goto send_alerts_done;
  zUrl = db_get("email-url",0);
  if( zUrl==0 ) goto send_alerts_done;
  zRepoName = db_get("email-subname",0);
  if( zRepoName==0 ) goto send_alerts_done;
  zFrom = db_get("email-self",0);
  if( zFrom==0 ) goto send_alerts_done;
  if( flags & SENDALERT_TRACE ){
    senderFlags |= EMAIL_TRACE;
  }
  pSender = email_sender_new(zDest, senderFlags);

  /* Step (1):  Compute the alerts that need sending
  */
  db_multi_exec(
    "DROP TABLE IF EXISTS temp.wantalert;"
    "CREATE TEMP TABLE wantalert(eventId TEXT, needMod BOOLEAN, sentMod);"
  );
  if( flags & SENDALERT_DIGEST ){
    /* Unmoderated changes are never sent as part of a digest */
    db_multi_exec(
................................................................................
      "        EXISTS(SELECT 1 FROM private WHERE rid=substr(eventid,2)),"
      "        sentMod"
      "   FROM pending_alert"
      "  WHERE sentSep IS FALSE;"
      "DELETE FROM wantalert WHERE needMod AND sentMod;"
    );
  }

  /* Step 2: compute EmailEvent objects for every notification that
  ** needs sending.
  */
  pEvents = email_compute_event_text(&nEvent, (flags & SENDALERT_DIGEST)!=0);
  if( nEvent==0 ) goto send_alerts_done;

  /* Step 4a: Update the pending_alerts table to designate the
  ** alerts as having all been sent.  This is done *before* step (3)
  ** so that a crash will not cause alerts to be sent multiple times.
  ** Better a missed alert than being spammed with hundreds of alerts
  ** due to a bug.
  */
  if( (flags & SENDALERT_PRESERVE)==0 ){
    if( flags & SENDALERT_DIGEST ){
      db_multi_exec(
        "UPDATE pending_alert SET sentDigest=true"
        " WHERE eventid IN (SELECT eventid FROM wantalert);"
      );
    }else{
      db_multi_exec(
        "UPDATE pending_alert SET sentSep=true"
        " WHERE eventid IN (SELECT eventid FROM wantalert WHERE NOT needMod);"
        "UPDATE pending_alert SET sentMod=true"
        " WHERE eventid IN (SELECT eventid FROM wantalert WHERE needMod);"
      );
    }
  }

  /* Step 3: Loop over subscribers.  Send alerts
  */
  blob_init(&hdr, 0, 0);
  blob_init(&body, 0, 0);
  db_prepare(&q,
     "SELECT"
     " hex(subscriberCode),"  /* 0 */
     " semail,"               /* 1 */
     " ssub,"                 /* 2 */
................................................................................
    blob_truncate(&hdr, 0);
    blob_truncate(&body, 0);
  }
  blob_reset(&hdr);
  blob_reset(&body);
  db_finalize(&q);
  email_free_eventlist(pEvents);
















  /* Step 4b: Update the pending_alerts table to remove all of the
  ** alerts that have been completely sent.
  */
  db_multi_exec("DELETE FROM pending_alert WHERE sentDigest AND sentSep;");

send_alerts_done:
  email_sender_free(pSender);
  if( g.fSqlTrace ) fossil_trace("-- END email_send_alerts(%u)\n", flags);
  db_end_transaction(0);
}

/*