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PgHero Rails

Installation

Add this line to your application’s Gemfile:

gem "pghero"

And mount the dashboard in your config/routes.rb:

mount PgHero::Engine, at: "pghero"

Be sure to secure the dashboard in production.

Suggested Indexes

PgHero can suggest indexes to add. To enable, add to your Gemfile:

gem "pg_query", ">= 2"

and make sure query stats are enabled. Read about how it works here.

Authentication

For basic authentication, set the following variables in your environment or an initializer.

ENV["PGHERO_USERNAME"] = "link"
ENV["PGHERO_PASSWORD"] = "hyrule"

For Devise, use:

authenticate :user, -> (user) { user.admin? } do
  mount PgHero::Engine, at: "pghero"
end

Query Stats

Query stats can be enabled from the dashboard. If you run into issues, view the guide.

Historical Query Stats

To track query stats over time, run:

rails generate pghero:query_stats
rails db:migrate

And schedule the task below to run every 5 minutes.

rake pghero:capture_query_stats

Or with a scheduler like Clockwork, use:

PgHero.capture_query_stats

After this, a time range slider will appear on the Queries tab.

The query stats table can grow large over time. Remove old stats with:

rake pghero:clean_query_stats

or:

PgHero.clean_query_stats

By default, query stats are stored in your app’s database. Change this with:

ENV["PGHERO_STATS_DATABASE_URL"]

Historical Space Stats

To track space stats over time, run:

rails generate pghero:space_stats
rails db:migrate

And schedule the task below to run once a day.

rake pghero:capture_space_stats

Or with a scheduler like Clockwork, use:

PgHero.capture_space_stats

System Stats

CPU usage, IOPS, and other stats are available for:

Heroku and Digital Ocean do not currently have an API for database metrics.

Amazon RDS

Add this line to your application’s Gemfile:

gem "aws-sdk-cloudwatch"

By default, your application’s AWS credentials are used. To use separate credentials, add these variables to your environment:

PGHERO_ACCESS_KEY_ID=my-access-key
PGHERO_SECRET_ACCESS_KEY=my-secret
PGHERO_REGION=us-east-1

Finally, specify your DB instance identifier.

PGHERO_DB_INSTANCE_IDENTIFIER=my-instance

This requires the following IAM policy:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": "cloudwatch:GetMetricStatistics",
            "Resource": "*"
        }
    ]
}

Google Cloud SQL

Add this line to your application’s Gemfile:

gem "google-cloud-monitoring-v3"

Enable the Monitoring API and set up your credentials:

GOOGLE_APPLICATION_CREDENTIALS=path/to/credentials.json

Finally, specify your database id:

PGHERO_GCP_DATABASE_ID=my-project:my-instance

This requires the Monitoring Viewer role.

Azure Database

Add this line to your application’s Gemfile:

gem "azure_mgmt_monitor"

Get your credentials and add these variables to your environment:

AZURE_TENANT_ID=...
AZURE_CLIENT_ID=...
AZURE_CLIENT_SECRET=...
AZURE_SUBSCRIPTION_ID=...

Finally, set your database resource URI:

PGHERO_AZURE_RESOURCE_ID=/subscriptions/<subscription-id>/resourceGroups/<resource-group>/providers/Microsoft.DBforPostgreSQL/servers/<database-id>

This requires the Monitoring Reader role.

Customization & Multiple Databases

To customize PgHero, create config/pghero.yml with:

rails generate pghero:config

This allows you to specify multiple databases and change thresholds. Thresholds can be set globally or per-database.

With Postgres < 12, if multiple databases are in the same instance and use historical query stats, PgHero should be configured to capture them together.

databases:
  primary:
    url: ...
  other:
    url: ...
    capture_query_stats: primary

Permissions

We recommend setting up a dedicated user for PgHero.

Methods

Insights

PgHero.running_queries
PgHero.long_running_queries
PgHero.index_usage
PgHero.invalid_indexes
PgHero.missing_indexes
PgHero.unused_indexes
PgHero.unused_tables
PgHero.database_size
PgHero.relation_sizes
PgHero.index_hit_rate
PgHero.table_hit_rate
PgHero.total_connections

Kill queries

PgHero.kill(pid)
PgHero.kill_long_running_queries
PgHero.kill_all

Query stats

PgHero.query_stats_enabled?
PgHero.enable_query_stats
PgHero.disable_query_stats
PgHero.reset_query_stats
PgHero.query_stats
PgHero.slow_queries

Suggested indexes

PgHero.suggested_indexes
PgHero.best_index(query)

Security

PgHero.ssl_used?

Replication

PgHero.replica?
PgHero.replication_lag

If you have multiple databases, specify a database with:

PgHero.databases["db2"].running_queries

Users

Note: It’s unsafe to pass user input to these commands.

Create a user

PgHero.create_user("link")
# {password: "zbTrNHk2tvMgNabFgCo0ws7T"}

This generates and returns a secure password. The user has full access to the public schema.

Read-only access

PgHero.create_user("epona", readonly: true)

Set the password

PgHero.create_user("zelda", password: "hyrule")

Grant access to only certain tables

PgHero.create_user("navi", tables: ["triforce"])

Drop a user

PgHero.drop_user("ganondorf")

Upgrading

3.0.0

Breaking changes

  • Changed capture_query_stats to only reset stats for current database in Postgres 12+
  • Changed reset_query_stats to only reset stats for current database (use reset_instance_query_stats to reset stats for entire instance)
  • Removed access_key_id, secret_access_key, region, and db_instance_identifier methods (use aws_ prefixed methods instead)

Bonus

  • See where queries come from with Marginalia - comments appear on the Live Queries tab.
  • Get weekly news and articles with Postgres Weekly
  • Optimize your configuration with PgTune and pgBench