Configuring Riak CS

For Riak CS to operate properly it must know how to connect to Riak. A Riak CS node typically runs on the same server as its corresponding Riak node, which means that changes will only be necessary if Riak is configured using non-default settings.

Riak CS’s settings typically reside in a CS node’s riak-cs.conf and advanced.config files, both of which are typically located in the /etc/riak-cs directory. The newer riak-cs.conf file is a simple list of configuration = option pairs, but there are some configuration options that can only be changed through the advanced.config file. That file looks something like:

{riak_cs, [
    {parameter1, value},
    {parameter2, value},
    %% and so on...

If you’re updating from a version of Riak CS prior to 2.0.0 – when the riak-cs.conf file was introduced – you can still use the old-style app.config configuration file in place of the riak-cs.conf/advanced.config pair. The app.config file has identical syntax to the advanced.config file, so any examples that use the advanced.config syntax can be directly translated to the app.config file.

Please note that the older app.config file supersedes the newer configuration files. If an app.config file is present, neither the riak-cs.config nor the advanced.config will be used.

Note on Legacy app.config

If you are upgrading to Riak CS 2.0 from a previous version of Riak and plan to continue usage of the legacy app.config file, please note that some configuration options have changed names. Most notably, the IP/Port format has changed in 2.0 for Stanchion, Riak, and Riak CS. To view these changes, please review the Rolling Upgrades Document.

For a comprehensive listing of available parameters and a full list of app.config parameters, see the Full Configuration Reference.

The sections below walk you through some of the main configuration categories that you will likely encounter while operating Riak CS.

Host and Port

To connect Riak CS to Riak, make sure that the following parameter is set to the host and port used by Riak:

  • riak_host — Replace with the IP address and port number of the Riak node you want Riak CS to connect to.

You will also need to set the host listener for Riak CS:

  • listener — Replace with the IP address and port number of the Riak CS node if you are running CS non-locally. Make sure that the port number does not conflict with the riak_host port number of the Riak node and the Riak CS node that are running on the same machine.
Note on IP addresses

The IP address you enter here must match the IP address specified for the Protocol Buffers interface in the Riak riak.conf file unless Riak CS is running on a completely different network, in which case address translation is required.

After making any changes to the riak-cs.conf file in Riak CS, restart the node if it is already running.

Specifying the Stanchion Node

If you’re running a single Riak CS node, you don’t have to change the Stanchion settings because Stanchion runs on the local host. If your Riak CS system has multiple nodes, however, you must specify the IP address and port for the Stanchion node and whether or not SSL is enabled.

The Stanchion settings reside in the Riak CS riak-cs.conf file, which is located in the /etc/riak-cs directory of each Riak CS node.

To set the host and port for Stanchion, make sure the following parameter is set to the host and port used by Stanchion:

  • stanchion_host — replace with the IP address and port number of the Stanchion node

Enabling SSL

SSL is disabled by default in Stanchion, i.e. the stanchion_ssl variable is set to off. If Stanchion is configured to use SSL, change this variable to on. The following example configuration would set the Stanchion host to localhost, the port to 8085 (the default), and set up Stanchion to use SSL:

stanchion_host =
stanchion_ssl = on
{riak_cs, [
    %% Other configs
    {stanchion_host, {"", 8085}},
    {stanchion_ssl, true},
    %% Other configs

Specifying the Node Name

You can also set a more useful name for the Riak CS node, which is helpful to identify the node from which requests originate during troubleshooting. This setting resides in the Riak CS riak-cs.conf configuration file, or the old- style vm.args file which is also located in the /etc/riak-cs directory. This would set the name of the Riak CS node to riak_cs@

nodename = riak_cs@
-name riak_cs@

Change to the IP address or hostname for the server on which Riak CS is running.

Specifying the Admin User

The admin user is authorized to perform actions such as creating users or obtaining billing statistics. An admin user account is no different from any other user account. You must create an admin user to use Riak CS.

Note on anonymous user creation

Before creating an admin user, you must first set anonymous_user_creation = on in the Riak CS riak-cs.conf (or set {anonymous_user_creation, true} in the old-style advanced.config/app.config). You may disable this again once the admin user has been created.

To create an account for the admin user, use an HTTP POST request with the username you want to use for the admin account. The following is an

curl -H 'Content-Type: application/json' \
  -XPOST http://<host>:<port>/riak-cs/user \
  --data '{"email":"", "name":"admin"}'

The JSON response will look something like this:

  "display_name" : "admin",
  "email" : "",
  "id" : "8d6f05190095117120d4449484f5d87691aa03801cc4914411ab432e6ee0fd6b",
  "key_id" : "OUCXMB6I3HOZ6D0GWO2D",
  "key_secret" : "a58Mqd3qN-SqCoFIta58Mqd3qN7umE2hnunGag==",
  "name" : "admin_example",
  "status" : "enabled"

You can optionally send and receive XML if you set the Content-Type to application/xml, as in this example:

Once the admin user exists, you must specify the credentials of the admin user on each node in the Riak CS system. The admin user credential settings reside in the Riak CS riak-cs.conf file, which is located in the /etc/riak-cs directory. Paste the key_id string between the quotes for the admin.key. Paste the key_secret string into the admin.secret variable, as shown here:

admin.key = OUCXMB6I3HOZ6D0GWO2D
admin.secret = a58Mqd3qN-SqCoFIta58Mqd3qN7umE2hnunGag==
{riak_cs, [
           %% Admin user credentials
           {admin_key, "OUCXMB6I3HOZ6D0GWO2D"},
           {admin_secret, "a58Mqd3qN-SqCoFIta58Mqd3qN7umE2hnunGag=="},
           %% Other configs

Bucket Restrictions

If you wish, you can limit the number of buckets created per user. The default maximum is 100. Please note that if a user exceeds the bucket creation limit, they are still able to perform other actions, including bucket deletion. You can change the default limit using the max_buckets_per_user parameter in each node’s advanced.config file—there is no equivalent configuration for the riak-cs.conf file. The example configuration below would set the maximum to 1000:

{riak_cs, [
           %% Other configs
           {max_buckets_per_user, 1000},
           %% Other configs

If you want to avoid setting a limit on per-user bucket creation, you can set max_buckets_per_user to unlimited.

Connection Pools

Riak CS uses two distinct connection pools for communication with Riak: a primary and a secondary pool.

The primary connection pool is used to service the majority of API requests related to the upload or retrieval of objects. It is identified in the configuration file as pool.request.size. The default size of this pool is 128.

The secondary connection pool is used strictly for requests to list the contents of buckets. The separate connection pool is maintained in order to improve performance. This secondary connection pool is identified in the configuration file as pool.list.size. The default size of this pool is 5.

The following shows the connection_pools default configuration entry that can be found in the app.config file:

pool.request.size = 128
pool.request.overflow = 0
pool.list.size = 5
pool.list.overflow = 0
{riak_cs, [
           %% Other configs
            {request_pool, {128, 0} },
            {bucket_list_pool, {5, 0} }
           %% Other configs

The value for each pool split into pairs, with the first number representing the normal size of the pool. This is representative of the number of concurrent requests of a particular type that a Riak CS node may service. The second number represents the number of allowed overflow pool requests that are allowed. It is not recommended that you use any value other than 0 for the overflow amount unless careful analysis and testing has shown it to be beneficial for a particular use case.


We strongly recommend that you take care when setting the value of the pb_backlog setting in Riak. When a Riak CS node is started, each connection pool begins to establish connections to Riak. This can result in a thundering herd problem in which connections in the pool believe they are connected to Riak, but in reality some of the connections have been reset. Due to TCP RST packet rate limiting (controlled by net.inet.icmp.icmplim) some of the connections may not receive notification until they are used to service a user’s request. This manifests itself as an {error, disconnected} message in the Riak CS logs and an error returned to the user.

Enabling SSL in Riak CS

ssl.certfile = "./etc/cert.pem"
ssl.keyfile = "./etc/key.pem"
{ssl, [
    {certfile, "./etc/cert.pem"},
    {keyfile, "./etc/key.pem"}

Replace the text in quotes with the path and filename for your SSL encryption files. By default, there’s a cert.pem and a key.pem in each node’s /etc directory. You’re free to use those or to supply your own.

Please note that you may also need to provide a certificate authority, aka a CA cert. If you do, you must use the advanced.config file, and specify its location using the cacertfile parameter. Unlike certfile and keyfile, the cacertfile parameter is not commented out. You will need to add it yourself. Here’s an example configuration with this parameter included:

{ssl, [
       {certfile, "./etc/cert.pem"},
       {keyfile, "./etc/key.pem"},
       {cacertfile, "./etc/cacert.pem"}
      %% Other configs

Instructions on creating your own CA cert can be found here.

Proxy vs. Direct Configuration

Riak CS can interact with S3 clients in one of two ways:

  • A proxy configuration enables an S3 client to communicate with Riak CS as if it were Amazon S3 itself, i.e. using typical Amazon URLs.
  • A direct configuration requires that an S3 client connecting to Riak CS be configured for an “S3-compatible service,” i.e. with a Riak CS endpoint that is not masquerading as Amazon S3. Examples of such services include Transmit, s3cmd, and DragonDisk.


To establish a proxy configuration, configure your client’s proxy settings to point to Riak CS cluster’s address. Then configure your client with Riak CS credentials.

When Riak CS receives the request to be proxied, it services the request itself and responds back to the client as if the request went to S3.

On the server side, the root_host configuration in the riak-cs.conf file must be set to because all of the bucket URLs request by the client will be destined for This is the default.

Note: One issue with proxy configurations is that many GUI clients only allow for one proxy to be configured for all connections. For customers trying to connect to both S3 and Riak CS, this can prove problematic.


The establish a direct configuration, the cs_root_host in the riak_cs section of app.config must be set to the FQDN of your Riak CS endpoint, as all of the bucket URLs will be destined for the FQDN endpoint.

You will also need wildcard DNS entries for any child of the endpoint to resolve to the endpoint itself. Here’s an example:

Garbage Collection Settings

The following options are available to make adjustments to the Riak CS garbage collection system. More details about garbage collection in Riak CS are available in Garbage Collection.

  • gc.leeway_period (leeway_seconds in advanced.config or app.config) — The amount of time that must elapse before an object version that has been explicitly deleted or overwritten is eligible for garbage collection. The default value is 24h (24 hours).
  • gc.interval (gc_interval in advanced.config or app.config) — The interval at which the garbage collection daemon runs to search for and reap eligible object versions. The default value is 15m (15 minutes). It is important that you have only one garbage collection daemon running in a cluster at any point in time. To disable the daemon on a node, set the gc.interval parameter to infinity.
  • gc.retry_interval (gc_retry_interval in advanced.config or app.config) — The amount of time that must elapse before another attempt is made to write a record for an object manifest in the pending_delete state to the garbage collection eligibility bucket. In general, this timeout should never expire, but may if an error condition caused the original record in the garbage collection eligibility bucket to be removed prior to the reaping process completing. The default value is 6h (6 hours).
  • gc.max_workers (gc.max_workers in advanced.config or app.config) — The maximum number of worker processes that may be started by the garbage collection daemon to use for concurrent reaping of garbage-collection-eligible objects. The default value is 2.
  • active_delete_threshold (active_delete_threshold in advanced.config or app.config) — Blocks of objects smaller than the threshold are synchronously deleted while their manifests are marked as scheduled_delete. The default value is 0.

There are some additional settings that may only be configured in the advanced.config or app.config configuration files. None of the below settings are available through the riak-cs.conf configuration file.

  • epoch_start — The time that the garbage collection daemon uses to begin collecting keys from the garbage collection eligibility bucket. Records in this bucket use keys based on the epoch time the record is created + leeway_seconds. The default is 0 and should be sufficient for general use. A case for adjusting this value is if the secondary index query run by the garbage collection daemon continually times out. Raising the starting value can decrease the range of the query and make it more likely the query will succeed. The value must be specified in Erlang binary format. e.g. to set it to 10, specify <<"10">>.
  • initial_gc_delay — The number of seconds to wait in addition to the gc_interval value before the first execution of the garbage collection daemon when the Riak CS node is started. Note: Originally, this setting was used to stagger the execution of GC on multiple nodes; we no longer recommend running multiple GC daemons. Correspondingly, we do not recommend setting initial_gc_delay.
  • max_scheduled_delete_manifests — The maximum number of manifests (representative of object versions) that can be in the scheduled_delete state for a given key. A value of unlimited means there is no maximum, and pruning will not happen based on count. An example of where this option is useful is a use case involving a lot of churn on a fixed set of keys in a time frame that is relatively short compared to the leeway_seconds value. This can result in the manifest objects reaching a size that can negatively impact system performance. The default value is unlimited.
  • gc_batch_size — This option represents the size used for paginating the results of the secondary index query. The default value is 1000.
Deprecated Configurations

While Riak CS 2.0.0 still allows the configuration of gc_paginated_indexes, it is strongly recommended that these settings not be used. This setting has been deprecated, and will be removed in the next major release.

Other Riak CS Settings

For a complete listing of configurable parameters for Riak CS, see the configuration reference document.