Post mortem report for incident on Aug 26, 2024 #473
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rubhanazeem
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hennevogel
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Aug 28, 2024
| Describe what went well, what went wrong and where we go lucky during the resolution of this problem. | ||
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| - Ensure all connected tables have the same column sizes. |
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There is not only one way to do this. This requires knowledge of the system architecture.
One thing I can point out for this is a through review.
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Then this isn't something we learned. We know we should do code-review :)
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Maybe it rather points to a bad architectural decision that we should revise?
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I've improved this reasoning 🙂
hennevogel
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Aug 28, 2024
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@darix brought up some worthwhile thoughts in openSUSE/open-build-service#16751 |
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I've checked the conversation. Sounds like we are going with the migration to change column size |
For sure but what about the other things mentioned? Like more sophisticated exception handling... |
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Done. I've mentioned this in action items |
hennevogel
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Aug 29, 2024
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| Classify the severity of this problem. We usually say: | ||
| - service degradation: if only a few customers where impacted | ||
| - severe service degradation: if nearly every customer was impacted | ||
| - downtime: if every visit to the OBS ended up on some error page | ||
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| <!-- | |
| Classify the severity of this problem. We usually say: | |
| - service degradation: if only a few customers where impacted | |
| - severe service degradation: if nearly every customer was impacted | |
| - downtime: if every visit to the OBS ended up on some error page | |
| --> |
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Maybe this will revive the excerpt on the index page...
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| What happened, for how long and who was impacted by it? | ||
| For customers to be able to identify if their problem related to this post mortem or not. | ||
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| What happened, for how long and who was impacted by it? | |
| For customers to be able to identify if their problem related to this post mortem or not. | |
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| How did you resolve or work around this problem? | ||
| For customers and community to understand what happened technically. | ||
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| How did you resolve or work around this problem? | |
| For customers and community to understand what happened technically. | |
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| Are there any actions we are going to do that are not done yet? | ||
| For customers and community to be able to follow up on this. | ||
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| Are there any actions we are going to do that are not done yet? | |
| For customers and community to be able to follow up on this. | |
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| Describe what went well, what went wrong and where we go lucky during the resolution of this problem. | ||
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| Describe what went well, what went wrong and where we go lucky during the resolution of this problem. | |
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hennevogel
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Aug 29, 2024
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| On Friday, August 23rd at 11:59 UTC, Email and Web notifications stopped working until August 26th at 10:16 UTC. | ||
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| In the notification creation process, the `payload` field in the `events` table is copied to the `event_payload` field in the `notifications` table. These fields are required to have the same column size, but we discovered they don't have the same size. |
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| In the notification creation process, the `payload` field in the `events` table is copied to the `event_payload` field in the `notifications` table. These fields are required to have the same column size, but we discovered they don't have the same size. | |
| The cause of this was mis-matching database table column size restrictions we did not notice. |
| For customers to be able to identify if their problem related to this post mortem or not. | ||
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| On Friday, August 23rd at 11:59 UTC, Email and Web notifications stopped working until August 26th at 10:16 UTC. |
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| On Friday, August 23rd at 11:59 UTC, Email and Web notifications stopped working until August 26th at 10:16 UTC. | |
| No user of build.opensuse.org received notifications via the web interface / email from Friday, August 23rd at 11:59 UTC until Monday, August 26th at 10:16 UTC. No notification / email was lost, all of them got delivered with a delay. Some of them with a delay of several days. |
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| title: "Degraded performance of OBS Web and Email Notifications system" | |||
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| title: "Degraded performance of OBS Web and Email Notifications system" | |
| title: "Service degradation of OBS Web and Email Notifications system" |
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| In the notification creation process, the `payload` field in the `events` table is copied to the `event_payload` field in the `notifications` table. These fields are required to have the same column size, but we discovered they don't have the same size. | ||
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| As a result, when the system attempted to create a notification for an event with a long description in its payload, an exception was raised, causing the notification creation process to fail. |
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| As a result, when the system attempted to create a notification for an event with a long description in its payload, an exception was raised, causing the notification creation process to fail. | |
| As a result, when the system attempted to create a notification an exception was raised, causing the notification creation process to fail entirely. |
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| ## Detection | ||
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| We received the first Grafana alert on Friday, August 23rd at 15:00 UTC, indicating that no notifications had been sent in the last three hours. Upon checking Errbit, we found a single exception with over 100,000 occurrences |
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| We received the first Grafana alert on Friday, August 23rd at 15:00 UTC, indicating that no notifications had been sent in the last three hours. Upon checking Errbit, we found a single exception with over 100,000 occurrences | |
| We received the first alert on Friday, August 23rd at 15:00 UTC, indicating that no notifications had been sent in the last three hours. |
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| ## Root Cause | ||
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| The root cause of the problem was a mismatch in column sizes between the `payload` field in the `events` table and the `event_payload` field in the `notifications` table. Because of this mismatch, when the system attempted to create a notification from an event with a very long description in its payload, an exception was raised, that blocked the creation of further email and web notifications. |
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Suggested change
| The root cause of the problem was a mismatch in column sizes between the `payload` field in the `events` table and the `event_payload` field in the `notifications` table. Because of this mismatch, when the system attempted to create a notification from an event with a very long description in its payload, an exception was raised, that blocked the creation of further email and web notifications. | |
| In February we changed the size limitations of the `payload` field in the `events` table from TEXT to MEDIUMTEXT ([PR#15649](https://github.com/openSUSE/open-build-service/pull/15649)). During the notification process we copy the content of this column to another to the `event_payload` field in the `notifications` table with it TEXT. This mismatch caused an exception to be raised when the system attempted to create a notification from an event with a very long `payload` column. | |
| Additionally the queue the handles the notification creations work sequentially, with a very many retries and very long hold off time. That blocked the creation of *all* email and web notifications. |
| For customers and community to understand what happened technically. | ||
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| We were able to identify the problematic event, take a backup of that event, and then delete it. After this, the system began to recover gradually. |
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| We were able to identify the problematic event, take a backup of that event, and then delete it. After this, the system began to recover gradually. | |
| We identified the problematic event and took it out of the queue. After this, the system began to recover itself gradually. |
| | Action Item | Owner | | ||
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| | [Data migration to update column size](https://github.com/openSUSE/open-build-service/pull/16751) | Developer Team | | ||
| | [Improve exception handling](ihttps://github.com/openSUSE/open-build-service/pull/16751#issuecomment-2309776466) | Developer Team | |
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A comment in a PR is not a way for us to track work...
| Describe what went well, what went wrong and where we go lucky during the resolution of this problem. | ||
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| - Ensure that all connected tables have consistent column sizes by thoroughly reviewing the system architecture. We recognize that there is close coupling of components, and this design can be improved. |
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And where are we going to do that? And when?
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| - Ensure that all connected tables have consistent column sizes by thoroughly reviewing the system architecture. We recognize that there is close coupling of components, and this design can be improved. | ||
| - We had failed notifications in delayed jobs, and that saved us from data loss. |
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I'm not sure I understand what you want to say here...
danidoni
reviewed
Sep 10, 2024
| | Action Item | Owner | | ||
| |--- |--- | | ||
| | [Data migration to update column size](https://github.com/openSUSE/open-build-service/pull/16751) | Developer Team | | ||
| | [Improve exception handling](ihttps://github.com/openSUSE/open-build-service/pull/16751#issuecomment-2309776466) | Developer Team | |
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Suggested change
| | [Improve exception handling](ihttps://github.com/openSUSE/open-build-service/pull/16751#issuecomment-2309776466) | Developer Team | | |
| | [Improve exception handling](https://github.com/openSUSE/open-build-service/pull/16751#issuecomment-2309776466) | Developer Team | |
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