Loud and Quiet¶

Every change to an Alert Group is either Loud or Quiet. A Loud change should make people's devices ring. A Quiet change should only update what they see when they look. Muster fixes the loudness of every change; you decide only whom a Loud change Mentions.

The rule behind it is simple, and it is the same in Mattermost and Telegram: an edit never notifies anybody. Editing a message, even to add a Mention, does not ring a phone. So a Loud change is always a new message, a new Root message or a reply in the Thread, and a Quiet change is an edit of the Root message or a new message without a Mention.

Which changes are Loud¶

A new Alert Group starts

Loud, as a new Root message · mentions: the Destination's new_alert_group setting

New Alerts join a firing Alert Group

Loud, as a Thread reply; batched · mentions: new_alerts

New Alerts join an acknowledged or snoozed Alert Group

Quiet · mentions: nobody

A Reopen into firing

Loud · mentions: reopen

A Reopen into acknowledged

Loud · mentions: the Owner only

A Reopen into snoozed

Quiet · mentions: nobody

A Snooze ends while Alerts still fire

Loud, listing what accumulated · mentions: snooze_ended

A rise to Urgent that ends a Snooze or removes an acknowledgement

Loud, with the reason · mentions: the Owner it removed, and rise_to_urgent

A rise in Severity level that changes nothing else

Quiet · mentions: nobody

A Takeover

Loud · mentions: the previous Owner

An ack timeout notice

Loud · mentions: ack_timeout

A Reminder

Loud · mentions: the Owner

Auto-unacknowledge

Loud, with the reason · mentions: the Owner it removed

The Owner is disabled or deleted

Loud · mentions: nobody

Several notices missed during downtime

Loud, as one reply · mentions: as the notices it stands for

Acknowledge, Unacknowledge, Snooze, Unsnooze, Resolve, Unresolve

Quiet · mentions: nobody

An Alert resolves, is replaced or continues, or its annotations change

Quiet · mentions: nobody

The system resolves the Alert Group

Quiet, with a Thread reply that gives the reason · mentions: nobody

A Note

Quiet, and not sent to messengers · mentions: nobody

The pattern: Muster rings when something needs a human who may not be looking, such as a new problem, one that returned, one that nobody took, or one that someone took and went quiet. It does not ring for what a person just did, because that person is looking. The Takeover is the only result of a person's command that is Loud, because the previous Owner has just lost the Alert Group.

Delivery adds a few cases of its own:

You cannot change the loudness of an event. You can change whom it Mentions.

What Loud means in each Destination¶

Mattermost

A Loud change is a new post, with its Mentions in the text of the post.

A Quiet change is an edit, or a new post without a Mention.

Telegram

A Loud change is a new message, in the channel for a Root message and in the discussion group for a Thread reply.

A Quiet change is an edit, or a new message sent with disable_notification.

Bridge

A Loud change is a new message that the bridge posts with notify on, with its Mentions.

A Quiet change is an edit, or a new message that the bridge posts without a notification where it declares quiet_messages.

Outgoing webhook

A Loud change is an event with notify true (events mode), or .Notify true in a template (template mode).

A Quiet change is notify false.

A few details:

• Mattermost. A reply in a Thread notifies the Thread's followers by their own settings, and a Mention makes the person a follower. So Quiet means "without a Mention", not "nobody is notified". Mentions are in the text of the post and never in the attachment, because a Mention in an attachment notifies with an empty notification. See Who gets notified.
• Telegram. disable_notification silences the sound but does not remove the push. Only members of the channel's discussion group get Thread replies, and the automatic copy of every Root message rings them, even for a Quiet one. Tell the people on call to join the group and mute the channel itself. See Known limitation: Quiet Root messages ring the group.
• Bridge. Whether the bridge can post without a notification depends on the bridge. A bridge that does not declare quiet_messages posts a Quiet message as an ordinary one, without Mentions.
• Outgoing webhook. Muster rings nothing itself. In events mode every event is sent, Quiet ones too, with notify telling what a person-facing system should do with it. Your receiver decides, for example, to call a phone only when notify is true. See events mode and Recipes.

Mentions¶

A Mention is a deliberate @-reference that Muster adds to a message so that a person is notified. Muster adds a Mention only where this page says it does. Alert data never mention anyone: an @ in a label or an annotation is neutralized with a zero-width space, so @channel in a label notifies nobody.

Whom a Loud change Mentions¶

Each Destination has a Mention setting for each of six kinds of Loud change:

• new_alert_group, new_alerts, reopen, ack_timeout, snooze_ended and rise_to_urgent.

For each, the Destination chooses nobody (the default for all six), everyone in the chat, chosen Muster users, or messenger groups. What a Destination type offers:

Some Mentions are not a setting. A Reminder and an auto-unacknowledge always Mention the Owner, a Takeover Mentions the previous Owner, and a Reopen into acknowledged Mentions only the Owner.

Account links¶

A Mention of a user needs an Account link: the tie between a Muster user and their account in the messenger. The people who are Mentioned, and the Owner above all, link their accounts from their profile; see Link your messenger accounts. Muster renders a Mention in the messenger's own form:

• Mattermost: @username;
• Telegram: a link to the person, whose text is the display name;
• Bridge: a marker that a bridge with native_mentions renders as the messenger's mention and any other bridge as the person's name.

A user without an Account link is named by their display name as plain text, which notifies nobody. So choosing a user for a Mention setting, or being an Owner, rings a phone only once that person has linked their account. The footer of a Root message names a person by their messenger username without @, which does not notify them either.

For an outgoing webhook, Muster does not know the receiver's markup, so the Mention is data: the event's mentions list, and .Mentions in a template, with the target's type, id, name and login. Your receiver or your template turns it into whatever the receiving system understands.

Storm summaries¶

When many Alert Groups start at once, one Route can flood a Destination. A Storm is a Route creating more new Alert Groups in one minute than its Storm threshold (route.storm_threshold, 20 by default). Then each of the Route's Destinations gets one Storm summary instead of a message per Alert Group:

• The summary is Loud only when it first appears, and Mentions as a new Alert Group does (new_alert_group).
• Urgent Alert Groups are still posted on their own, first.
• Its updates and its final state are Quiet. When the rate has stayed below the threshold for 5 minutes (delivery.storm_calm_period), the summary shows its final state, and the Alert Groups that are still open are posted gradually and Quietly. Those that already resolved are not posted.
• Messengers and the template mode of outgoing webhooks follow Storms. The events mode does not: it receives every event.

Why the rule is fixed¶

A rule of thumb for on-call: the phones should ring for problems that need a human, and nothing else. Because an edit is always silent, a person can acknowledge, snooze and resolve all day, and the message changes under their eyes without a sound; and because the loudness of every change is fixed, a team never has to wonder whether a change will ring. The Mention settings are the one place to tune who rings.