Heroku buildpack: pgbouncer
This is a Heroku buildpack that allows one to run pgbouncer and stunnel in a dyno alongside application code. It is meant to be used in conjunction with other buildpacks.
The primary use of this buildpack is to allow for transaction pooling of PostgreSQL database connections among multiple workers in a dyno. For example, 10 unicorn workers would be able to share a single database connection, avoiding connection limits and Out Of Memory errors on the Postgres server.
It uses stunnel and pgbouncer.
FAQ
-
Q: Why should I use transaction pooling?
-
A: You have many workers per dyno that hold open idle Postgres connections and and you want to reduce the number of unused connections. This is a slightly more complete answer from stackoverflow
-
Q: Why shouldn't I use transaction pooling?
-
A: If you need to use named prepared statements, advisory locks, listen/notify, or other features that operate on a session level. Please refer to PGBouncer's feature matrix for all transaction pooling caveats.
Disable Prepared Statements
With Rails 4.1, you can disable prepared statements by appending
?prepared_statements=false
to the database's URI. Set the
PGBOUNCER_PREPARED_STATEMENTS
config var to false
for the buildpack to do
that for you.
Rails versions 4.0.0 - 4.0.3, reportedly can't disable prepared statements at all. Make sure your framework is up to date before troubleshooting prepared statements failures.
Rails 3.2 - 4.0 also requires an initializer to properly cast the prepared_statements configuration string as a boolean. This initializer is adapted from this commit. In file config/initializers/database_connection.rb insert the following:
require "active_record/connection_adapters/postgresql_adapter"
class ActiveRecord::ConnectionAdapters::PostgreSQLAdapter
alias initialize_without_config_boolean_coercion initialize
def initialize(connection, logger, connection_parameters, config)
if config[:prepared_statements] == 'false'
config = config.merge(prepared_statements: false)
end
initialize_without_config_boolean_coercion(connection, logger, connection_parameters, config)
end
end
Usage
Example usage:
$ ls -a
Gemfile Gemfile.lock Procfile config/ config.ru
$ heroku buildpacks:add https://github.com/heroku/heroku-buildpack-pgbouncer
Buildpack added. Next release on pgbouncer-test-app will use https://github.com/heroku/heroku-buildpack-pgbouncer.
Run `git push heroku master` to create a new release using this buildpack.
$ heroku buildpacks:add heroku/ruby
Buildpack added. Next release on pgbouncer-test-app will use:
1. https://github.com/heroku/heroku-buildpack-pgbouncer
2. https://github.com/heroku/heroku-buildpack-ruby
Run `git push heroku master` to create a new release using these buildpacks.
$ cat Procfile
web: bin/start-pgbouncer-stunnel bundle exec unicorn -p $PORT -c ./config/unicorn.rb -E $RACK_ENV
worker: bundle exec rake worker
$ git push heroku master
...
-----> Multipack app detected
-----> Fetching custom git buildpack... done
-----> pgbouncer-stunnel app detected
Using pgbouncer version: 1.5.4-heroku
Using stunnel version: 5.08
Using stack version: cedar-14
-----> Fetching and vendoring pgbouncer into slug
-----> Fetching and vendoring stunnel into slug
-----> Moving the configuration generation script into app/bin
-----> Moving the start-pgbouncer-stunnel script into app/bin
-----> pgbouncer/stunnel done
-----> Fetching custom git buildpack... done
...
The buildpack will install and configure pgbouncer and stunnel to connect to
DATABASE_URL
over a SSL connection. Prepend bin/start-pgbouncer-stunnel
to any process in the Procfile to run pgbouncer and stunnel alongside that process.
Multiple Databases
It is possible to connect to multiple databases through pgbouncer by setting
PGBOUNCER_URLS
to a list of config vars. Example:
$ heroku config:add PGBOUNCER_URLS="DATABASE_URL HEROKU_POSTGRESQL_ROSE_URL"
$ heroku run bash
~ $ env | grep 'HEROKU_POSTGRESQL_ROSE_URL\|DATABASE_URL'
HEROKU_POSTGRESQL_ROSE_URL=postgres://u9dih9htu2t3ll:password@ec2-107-20-228-134.compute-1.amazonaws.com:5482/db6h3bkfuk5430
DATABASE_URL=postgres://uf2782hv7b3uqe:password@ec2-50-19-210-113.compute-1.amazonaws.com:5622/deamhhcj6q0d31
~ $ bin/start-pgbouncer-stunnel env # filtered for brevity
HEROKU_POSTGRESQL_ROSE_URL=postgres://u9dih9htu2t3ll:password@127.0.0.1:6000/db2
DATABASE_URL=postgres://uf2782hv7b3uqe:password@127.0.0.1:6000/db1
Follower Replica Databases
As of v0.3.2 of this buildpack, it is possible to use pgbouncer to connect to
multiple databases that share a database name, such as a leader and follower.
To use, add the follower's config var to PGBOUNCER_URLS
as detailed in the
Multiple Databases section.
If you are using Octopus
Replication to send reads to
a replica, make sure to include the color url of your leader in the
SLAVE_DISABLED_FOLLOWERS
blacklist. Otherwise, Octopus will attempt to use
your leader as a read-only replica, potentially doubling your connection count.
Tweak settings
Some settings are configurable through app config vars at runtime. Refer to the appropriate documentation for pgbouncer and stunnel configurations to see what settings are right for you.
PGBOUNCER_POOL_MODE
Default is transactionPGBOUNCER_MAX_CLIENT_CONN
Default is 100PGBOUNCER_DEFAULT_POOL_SIZE
Default is 1PGBOUNCER_MIN_POOL_SIZE
Default is 0PGBOUNCER_RESERVE_POOL_SIZE
Default is 1PGBOUNCER_RESERVE_POOL_TIMEOUT
Default is 5.0 secondsPGBOUNCER_SERVER_LIFETIME
Default is 3600.0 secondsPGBOUNCER_SERVER_IDLE_TIMEOUT
Default is 600.0 secondsPGBOUNCER_URLS
should contain all config variables that will be overridden to connect to pgbouncer. For example, set this toAMAZON_RDS_URL
to send RDS connections through pgbouncer. The default isDATABASE_URL
.PGBOUNCER_CONNECTION_RETRY
Default is noPGBOUNCER_LOG_CONNECTIONS
Default is 1. If your app does not use persistent database connections, this may be noisy and should be set to 0.PGBOUNCER_LOG_DISCONNECTIONS
Default is 1. If your app does not use persistent database connections, this may be noisy and should be set to 0.PGBOUNCER_LOG_POOLER_ERRORS
Default is 1PGBOUNCER_STATS_PERIOD
Default is 60PGBOUNCER_SERVER_RESET_QUERY
Default is empty when pool mode is transaction, and "DISCARD ALL;" when session.PGBOUNCER_STUNNEL_LOGLEVEL
Default is notice (5). Set this var to pass a syslog level name or number value to stunnel. This corresponds to the stunnel global configuration option called "debug".ENABLE_STUNNEL_AMAZON_RDS_FIX
Default is unset. Set this var if you are connecting to an Amazon RDS instance of postgres. Addsoptions = NO_TICKET
which is documented to make stunnel work correctly after a dyno resumes from sleep. Otherwise, the dyno will lose connectivity to RDS.PGBOUNCER_IGNORE_STARTUP_PARAMETERS
Adds parameters to ignore when pgbouncer is starting. Some postgres libraries, like Go's pq, append this parameter, making it impossible to use this buildpack. Default is empty and the most common ignored parameter isextra_float_digits
. Multiple parameters can be seperated via commas. Example:PGBOUNCER_IGNORE_STARTUP_PARAMETERS="extra_float_digits, some_other_param"
For more info, see CONTRIBUTING.md