Riak has two configuration files located in etc/ if you are using a source install and in /etc/riak if you used a binary install. The files are app.config and vm.args.
The app.config file is used to set various attributes for the node such as the backend the node will use to store data. The vm.args file is used to pass parameters to the Erlang node such as the name or cookie of the Erlang node.
Riak and the Erlang applications it depends on are configured by settings in the app.config file in the etc directory of the Riak node. The format of the file is similar to Erlang’s “.app” files:
```bash
[
{riak_core, [
{ring_state_dir, “data/ring”}
%% More riak_core settings…
]},
{riak_kv, [
{storage_backend, riak_dets_backend},
{riak_kv_dets_backend_root, “data/dets”}
```
Many configuration settings changed names and sections in the 0.10 release. Please backup your app.config file when upgrading and then copy your previous customizations to the proper places in the new file. See [[the transition notes|http://hg.basho.com/riak/raw/efc290fd9c23/TRANSITION]] for more information.
The settings related to handoff moved from riak_kv to riak_core in the 0.12 release. These are:
handoff_iphandoff_porthandoff_concurrency
The settings for web_ip and web_port are deprecated. The new configuration mechanism is to use a list of IPs and ports in the http{} section of riak_core of app.config.
The configuration for parameters for the Javascript VMs in the riak_kv section of app.config have changed and should be edited if your previous configuration didn’t use the default parameters. You can see the new default configuration parameters for the 0.14 app.config [[here|0-14-app-config]].
The name of the cluster. This currently has no visible effect, but could be useful for identifying multiple clusters within your larger infrastructure.
These are properties used for buckets that have not been explicitly defined (as outlined in the [[REST API]]).They are useful for setting default bucket behavior such as:
- the number of replicas stored (*"n_val")
- whether or not siblings are allowed (*allow_mult")
- the quorum values for get, put and delete requests (*r, w, dw, rw)
- global pre- and post-commit hooks (precommit, postcommit)
```erlang
{default_bucket_props, [{n_val,3},
{allow_mult,false},
{last_write_wins,false},
{precommit, []},
{postcommit, []},
{chash_keyfun, {riak_core_util, chash_std_keyfun}},
{linkfun, {modfun, riak_kv_wm_link_walker, mapreduce_linkfun}}
]}
```
How often nodes in the cluster will share information about their ring state, in milliseconds. (default: “60000”)
Number of vnodes, per physical node, allowed to perform handoff at once (default: “4”).
TCP port number for the handoff listener (default: “8099”)
The IP address the handoff listener will bind to. (default: “0.0.0.0”)
The directory on-disk in which to store the ring state (default: “data/ring”)
Riak’s ring state is stored on-disk by each node, such that each node may be restarted at any time (purposely, or via automatic failover) and know what its place in the cluster was before it terminated, without needing immediate access to the rest of the cluster.
The number of partitions to divide the hash space into (default: “64”)
By default, each Riak node will own ring_creation_size/(number of nodes in the cluster) partitions. It is generally a good idea to specify a “ring_creation_size” a few times the number of nodes in your cluster (e.g. specify 64-256 partitions for a 4-node cluster). This gives you room to expand the number of nodes in the cluster, without worrying about under-use due to owning too few partitions. This number should be a power of 2 (64, 128, 256, etc.).
The highest n_val that you generally intend to use. This affects how partitions are distributed amongst the cluster and how preflists are calculated, helping ensure that data is never stored to the same physical node more than once. You will only need to change this setting in rare circumstances.
Assuming ring_creation_size is a power of 2, the ideal value for this setting is both
- greater than or equal to the largest n_val of any bucket, and
- an even divisor of the number of partitions in your ring (ring_creation_size).
The default value is 4. For this to be effective at preventing hotspots, your cluster size (number of physical nodes) must be equal to or larger than target_n_val.
A list of ip addresses and ports on which Riak’s HTTP interface should listen (default: {"127.0.0.1", 8091 })
Riak’s HTTP interface will not be started if this setting is not defined.
A list of ip addresses and ports on which Riak’s HTTP interface should listen (default: not enabled)
Riak’s HTTPS interface will not be started if this setting is not defined.
You can override the default SSL key and certificate settings (default: etc/cert.pem, etc/key.pem)
A list of paths to add to the Erlang code path.
This setting is especially useful for allowing Riak to use external modules during map/reduce queries.
The base of the path in the URL exposing [[MapReduce]] via HTTP. (default: “mapred”)
The directory used to store a transient queue for pending map tasts (default: “data/mrqueue”)
The number of Javascript VMs started to handle map phases. (default: “8”)
The number of Javascript VMs started to handle reduce phases. (default: “6”)
The number of Javascript VMs started to handle pre-commit hooks.(default: “2”)
Number of items the mapper will fetch in one request. Larger values can impact read/write performance for non-MapReduce requests. (default: “5”)
The maximum amount of memory allocated to each Javascript virtual machine, in megabytes. (default: “8”)
The maximum amount of thread stack space to allocate to Javascript virtual machines, in megabytes. (default: “16”)
Number of obect held in the MapReduce cache. These will be ejected when the cache runs out of room or the bucket/key pair for that entry changes. (default: “10000”)
Where to load user-defined built in Javascript functions (default: unset)
The IP address that the [[Protocol Buffers interface|PBC API]] will bind to. (default: “127.0.0.1”) If not set, the PBC interface will not be started.
The port that the [[Protocol Buffers interface|PBC API]] will bind to. (default: 8087)
The base of the path in the URL exposing Riak’s HTTP interface (default: “riak”)
The default value will expose data at /riak/Bucket/Key. For example, changing this
setting to “bar” would expose the interface at /bar/Bucket/Key.
Enables the statistics-aggregator (/stats URL and riak-admin status command) if set to true. (default is true)
The base of the path in the URL exposing the statistics-aggregator. (default: “stats”)
The module name of the storage backend that Riak should use (default: “riak_kv_bitcask_backend”)
The storage format Riak uses is configurable. Riak will refuse to start if no storage backend is specified.
Available backends, and their additional configuration options are:
- riak_kv_bitcask_backend: data is stored in [[Bitcask|http://bitbucket.org/basho/bitcask]] append-only storage
- riak_kv_dets_backend: data is stored in DETS files
- riak_kv_dets_backend_root: root directory where the DETS files are stored (defualt: “data/dets”
- riak_kv_ets_backend: data is stored in ETS tables (in-memory)
- riak_kv_gb_trees_backend: data is stored in general balanced trees (in-memory)
- riak_kv_fs_backend: data is stored in binary files on the filesystem
riak_kv_fs_backendroot: root directory where the files are stored (ex:/var/lib/riak/data) - riak_kv_multi_backend: enables storing data for different buckets in different backends
Specify the backend to use for a bucket with riak_client:set_bucket(BucketName,[{backend, BackendName}] in Erlang or {"props":{"backend":"BackendName"}} in the [[REST API]].- multi_backend_default: default backend to use if none is specified for a bucket (one of the BackendName atoms specified in the multi_backend setting)
- multi_backend: list of backends to provide
Format of each backend specification is{BackendName, BackendModule, BackendConfig}, where BackendName is any atom, BackendModule is the name of the Erlang module implementing the backend (the same values you would provide as “storage_backend” settings), and BackendConfig is a parameter that will be passed to the “start/2” function of the backend module.
- riak_kv_cache_backend: a backend that behaves as an LRU-with-timed-expiry cache
- riak_kv_cache_backend_memory: maximum amount of memory to allocate, in megabytes (default: “100”)
- riak_kv_cache_backend_ttl: amount by which to extend an object’s expiry lease on each access, in seconds (default: “600”)
- riak_kv_cache_backend_max_ttl: maximum allowed lease time (default: “3600”)
There is currently no way to dynamically change the ttl per bucket. The current work around would be to define multiple “riak_cache_backends” under “riak_multi_backend” with different ttl values.
How long a map function is permitted to execute on a vnode before it times out and is retried on another vnode, in milliseconds. (default: “1000”)
Parameters for the Erlang node on which Riak runs are set in the vm.args file in the etc directory of the embedded Erlang node. Most of these settings can be left at their defaults until you are ready to tune performance.
Two settings you may be interested in right away, though, are “-name” and “-setcookie”. These control the Erlang node names (possibly host-specific), and Erlang inter-node communication access (cluster-specific), respectively.
The format of the file is fairly loose: all lines that do not begin with the “#” character are concatenated, and passed to the “erl” on the command line, as is.
More details about each of these settings can be found in the [[Erlang|http://www.erlang.org/doc/man/erl.html]] documentation for the “erl” Erlang virtual machine.
the name of the Erlang node (default: “riak@127.0.0.1”)
The default value, @riak@127.0.0.1@ will work for running Riak locally, but for distributed (multi-node) use, the value after the “@” should be changed to the IP address of the machine on which the node is running.
If you have properly-configured DNS, the short-form of this name can be used (for example: “riak”). The name of the node will then be “riak@Host.Domain”.
the cookie of the Erlang node (default: “riak”)
Erlang nodes grant or deny access based on the sharing of a previously-shared cookie. You should use the same cookie for every node in your Riak cluster, but it should be a not-easily-guessed string unique to your deployment, to prevent non-authorized access.
enable “heart” node monitoring (default: “/disabled/”)
Heart will restart nodes automatically, should they crash. However, heart is so good at restarting nodes that it can be difficult to prevent it from doing so. Enable heart once you are sure that you wish to have the node restarted automatically on failure.
enable kernel polling (default: “true”)
number of threads in the async thread pool (default: 5)
set host environment variables for Erlang
Enables Erlang’s SMP support. This is necessary for the innostore backend to work, even on single-processor systems. (default: “enable”)
If you are going to be rebuilding Riak often, you will want to edit the vm.args and app.config files in the rel/files directory. These files are used whenever a new release is generated using “make rel” or “rebar generate”. Each time a release is generated any existing release must first be destroyed. Changes made to release files (rel/riak/etc/vm.args, rel/riak/etc/app.config, etc.) would be lost when the release is destroyed.
rel/overlay directory instead of rel/files.