Galactic Database

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# Galactic Database

<div class="contributors-line">
		<a href="/training-material/hall-of-fame/martenson/" class="contributor-badge contributor-martenson"><img src="/training-material/assets/images/orcid.png" alt="orcid logo" width="36" height="36"/><img src="https://avatars.githubusercontent.com/martenson?s=36" alt="Martin Čech avatar" width="36" class="avatar" />
    Martin Čech</a><a href="/training-material/hall-of-fame/nsoranzo/" class="contributor-badge contributor-nsoranzo"><img src="/training-material/assets/images/orcid.png" alt="orcid logo" width="36" height="36"/><img src="https://avatars.githubusercontent.com/nsoranzo?s=36" alt="Nicola Soranzo avatar" width="36" class="avatar" />
    Nicola Soranzo</a><a href="/training-material/hall-of-fame/natefoo/" class="contributor-badge contributor-natefoo"><img src="/training-material/assets/images/orcid.png" alt="orcid logo" width="36" height="36"/><img src="https://avatars.githubusercontent.com/natefoo?s=36" alt="Nate Coraor avatar" width="36" class="avatar" />
    Nate Coraor</a><a href="/training-material/hall-of-fame/hexylena/" class="contributor-badge contributor-hexylena"><img src="/training-material/assets/images/orcid.png" alt="orcid logo" width="36" height="36"/><img src="https://avatars.githubusercontent.com/hexylena?s=36" alt="Helena Rasche avatar" width="36" class="avatar" />
    Helena Rasche</a>
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# Galactic Database

.left[Galaxy uses a database for:]
* Galaxy objects and all their relations (users, histories, datasets, workflows)
* Job state persistence, job dispatching

.left[Galaxy does not use a database for:]
* Dataset **contents**: files on disk

???

- Galaxy objects like users, histories, datasets, and workflows are stored in the database.
- All job information is likewise stored there.
- User and reference data, however, are stored outside of the database.
- You will want to backup both user data and your database.

---

# Defaults

* Galaxy uses the [SQLAlchemy](http://www.sqlalchemy.org/) database abstraction layer. This allows for different database servers to be plugged in.
* By default Galaxy automatically creates and uses an [SQLite](https://sqlite.org/) database during the first startup.
  * The database is in the file `database/universe.sqlite`

???

- Galaxy uses SQLAlchemy for interacting with databases.
- This allows Galaxy to transparently use sqlite or postgres.

---
# Choices

* SQLite
  * Useful for single-user Galaxy or development.
* **PostgreSQL**
  * The recommended standard for anything serious.
* ~~MySQL~~
  * Supported by SQLAlchemy but Galaxy is not tested against it.

???

- sqlite is fine in development, but should not be used for production.
- postgres is the best for any production server.
- Do not use mysql if possible.

---
# Sizing

Galaxy rarely deletes from the database, most objects are *marked* deleted.

Allocate at least 20 GB of disk to start, 50+ GB if expanding would be difficult.

8-16 GB memory should be sufficient.

Recommended: Run PostgreSQL on a different server for resource isolation.

???

- Data is not removed from the database, so plan accordingly.
- Allocated at least 20 GB of disk to start, and 50 if expanding later is difficult.
- The RAM usage is usually not significant.
- We recommend running the database on a separate server from Galaxy for better isolation.

---
# Configuration

`database_connection` is specified as a [database URL](http://docs.sqlalchemy.org/en/latest/core/engines.html#database-urls) in `galaxy.yml`
  * Default SQLite:
      `sqlite:///./database/universe.sqlite?isolation_level=IMMEDIATE`

* Local PostgreSQL (socket):
       `postgresql:///<db_name>[?host=/var/run/postgresql]`

* Network PostgreSQL:
      `postgresql://[user][:password]@<host>[:5432]/<db_name>`

???

- The parameter database_connection tells galaxy where the database is.
- There are several styles, depending on how you connect to your database.

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# New Database

On first startup with an empty database, Galaxy creates its schema

???

- On first startup with an empty database, Galaxy creates its schema.

---
# Migrations

Changes in the Galaxy DB model (when upgrading Galaxy) are captured incrementally in the form of [atomic scripts](https://github.com/galaxyproject/galaxy/tree/dev/lib/galaxy/model/migrate/versions).

Each script can both upgrade and downgrade a DB.

```console
$ ./manage_db.sh upgrade
$ ./manage_db.sh downgrade --version=132
```

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- Whenever Galaxy is upgraded, there may be changes to the database schema.
- These are stored in migration scripts, and you can use the manage db script to up or downgrade.

---
# Tuning - Pool

If the server logs errors about not having enough database pool connections.

| Galaxy config option                  | default value | usegalaxy.org value |
| ------                                | ------------- | ------------------- |
| `database_engine_option_pool_size`    | `5`           | `10`                |
| `database_engine_option_max_overflow` | `10`          | `20`                |

[Values for usegalaxy.org](https://github.com/galaxyproject/usegalaxy-playbook/blob/master/env/main/group_vars/all/galaxy_config_vars.yml)

???

- Databases have a limited number of connection slots.
- Galaxy can pool connections, and re-use existing connections from a pool when it needs to query the DB.
- There are a couple of options for controlling pooling.
- The defaults are generally fine until you see errors.

---
# Tuning - Server-side cursors

If large database query results are causing memory or response time issues in the Galaxy process, leave it on server
(PostgreSQL only, recommended).

| Galaxy config option                         | default value | usegalaxy.org value |
| ------                                       | ------------- | ------------------- |
| `database_engine_option_server_side_cursors` | `false`       | `true`              |

???

- Large queries may slow down Galaxy or the DB.
- You can enable server side cursors to help with this.

---
# Tuning - Slow query logging

Queries slower than this threshold (in s) will be logged at debug level.

| Galaxy config option       | default value | usegalaxy.org value |
| ------                     | ------------- | ------------------- |
| `slow_query_log_threshold` | `0`           | `2`                 |

???

- If you notice slow responses, you can enable slow query logging.
- This will print a message in your Galaxy log if a query takes more than a specified time period.
- This can be useful to help you debug issues.

---
# Tuning - TS install database

Galaxy can track Tool Shed data in a separate DB.

| Galaxy config option          | default value                  | usegalaxy.org value |
| ------                        | -------------                  | ------------------- |
| `install_database_connection` | value of `database_connection` | SQLite DB in CVMFS  |

All other database config options but prefixed with `install_` are also available.

.left[This allows:]
* Bootstrapping fresh Galaxy instances with prebuilt/tested tool sets
* Atomic installation/rollback (esp. with SQLite: backup and restore DB file)

???

- Galaxy can track tool shed data in a separate database
- This can enable deploying Galaxies with prebuilt tool sets

---
# Access through model

Python script to access Galaxy's database layer **via the Galaxy model**.

```console
(venv)$ python -i scripts/db_shell.py --config config/galaxy.yml
>>> new_user = User('foo@example.org', 'secret')
>>> new_user.username = 'foo'
>>> sa_session.add(new_user)
>>> sa_session.flush()
>>> sa_session.query(User).all()
```

???

- You can use the Galaxy python models to interact with the database.
- After activating the galaxy virtual environment, you can use the DB shell script to interface.
- This can allow scripting tasks like resetting passwords.

---
# Useful queries

Captured in [gxadmin](/training-material/topics/admin/tutorials/gxadmin/slides.html) ([tutorial](/training-material/topics/admin/tutorials/gxadmin/tutorial.html))

???

- Many useful DB queries are captured in gxadmin
- Look into this if you need to query the database for information like running jobs or recent users.

---

## Thank You!

This material is the result of a collaborative work. Thanks to the [Galaxy Training Network](https://training.galaxyproject.org) and all the contributors!

<div class="contributors-line">
		Authors: <a href="/training-material/hall-of-fame/martenson/" class="contributor-badge contributor-martenson"><img src="/training-material/assets/images/orcid.png" alt="orcid logo" width="36" height="36"/><img src="https://avatars.githubusercontent.com/martenson?s=36" alt="Martin Čech avatar" width="36" class="avatar" />
    Martin Čech</a><a href="/training-material/hall-of-fame/nsoranzo/" class="contributor-badge contributor-nsoranzo"><img src="/training-material/assets/images/orcid.png" alt="orcid logo" width="36" height="36"/><img src="https://avatars.githubusercontent.com/nsoranzo?s=36" alt="Nicola Soranzo avatar" width="36" class="avatar" />
    Nicola Soranzo</a><a href="/training-material/hall-of-fame/natefoo/" class="contributor-badge contributor-natefoo"><img src="/training-material/assets/images/orcid.png" alt="orcid logo" width="36" height="36"/><img src="https://avatars.githubusercontent.com/natefoo?s=36" alt="Nate Coraor avatar" width="36" class="avatar" />
    Nate Coraor</a><a href="/training-material/hall-of-fame/hexylena/" class="contributor-badge contributor-hexylena"><img src="/training-material/assets/images/orcid.png" alt="orcid logo" width="36" height="36"/><img src="https://avatars.githubusercontent.com/hexylena?s=36" alt="Helena Rasche avatar" width="36" class="avatar" />
    Helena Rasche</a>
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