PuppetDB: Configuring PuppetDB

PuppetDB has three main groups of settings:

• The init script’s configuration file, which sets the JVM heap size and the location of PuppetDB’s main config file.
• Logging settings, which go in the logback.xml file and can be changed without restarting PuppetDB.
• All other settings, which go in PuppetDB’s configuration file(s) and take effect after the service is restarted.

Init Script Config File

If you installed PuppetDB from packages or used the rake install installation method, an init script was created for PuppetDB. This script has its own configuration file, the location of which varies by platform and by package:

OS and Package	File
Red Hat-like (open source)	/etc/sysconfig/puppetdb
Red Hat-like (PE)	/etc/sysconfig/pe-puppetdb
Debian/Ubuntu (open source)	/etc/default/puppetdb
Debian/Ubuntu (PE)	/etc/default/pe-puppetdb

In this file, you can change the following settings:

• JAVA_BIN: the location of the Java binary.
• JAVA_ARGS: command line options for the Java binary, most notably the -Xmx (max heap size) flag.
• USER: the user PuppetDB should be running as.
• INSTALL_DIR: the directory into which PuppetDB is installed.
• CONFIG: the location of the PuppetDB config file, which may be a single file or a directory of .ini files.

Configuring the Java heap size

To change the JVM heap size for PuppetDB, edit the init script config file by setting a new value for the -Xmx flag in the JAVA_ARGS variable.

For example, to cap PuppetDB at 192MB of memory:

JAVA_ARGS="-Xmx192m"

To use 1GB of memory:

JAVA_ARGS="-Xmx1g"

Configuring JMX access

While all JMX metrics are exposed using the /metrics namespace, you can also expose direct JMX access using standard JVM means as documented here. This can be done using the JAVA_ARGS init script setting, similar to configuring the heap size.

For example, adding the following JVM options will open up a JMX socket on port 1099:

JAVA_ARGS="-Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.port=1099"

The Logback logging-config file

Logging is configured with a logback.xml file, whose location is defined with the logging-config setting. If you change the log settings while PuppetDB is running, it will apply the new settings without requiring a restart.

See the Logback documentation for more information about logging options.

The PuppetDB configuration file(s)

PuppetDB is configured using an INI-style config format with several [sections]. This is very similar to the format used by Puppet. All of the sections and settings described below belong in the PuppetDB config file(s).

Note: Whenever you change PuppetDB’s configuration settings, you must restart the service for the changes to take effect.

You can change the location of the main config file in the init script config file. This location can point to a single configuration file or a directory of .ini files. If you specify a directory (in conf.d style), PuppetDB will merge the .ini files in alphabetical order.

If you’ve installed PuppetDB from a package, by default it will use the conf.d config style. The default config directory is /etc/puppetlabs/puppetdb/conf.d. If you’re running from source, you may use the -c command-line argument to specify your config file or directory.

An example configuration file:

[global]
vardir = /var/lib/puppetdb
logging-config = /var/lib/puppetdb/logback.xml

[database]
subname = //localhost:5432/puppetdb

[puppetdb]
certificate-whitelist = /path/to/file/containing/certnames
disable-update-checking = false

[jetty]
port = 8080

Playing nice with the PuppetDB module

If you installed PuppetDB with the puppetlabs-puppetdb module, PuppetDB’s settings will be managed by Puppet. Most of the settings you care about can be configured with the module’s class parameters; see the module’s documentation for details.

If you do need to change those rare settings that the module doesn’t manage, you can do the following:

Create a new class in a new module (something like site::puppetdb::server::extra), declare any number of ini_setting resources as shown below, set the class to refresh the puppetdb::server class, and assign it to your PuppetDB server.

    # Site-specific PuppetDB settings. Declare this class on any node that gets the puppetdb::server class.
    class site::puppetdb::server::extra {

      # Restart the PuppetDB service if settings change
      Class[site::puppetdb::server::extra] ~> Class[puppetdb::server]

      # Get PuppetDB confdir
      include puppetdb::params
      $confdir = $puppetdb::params::confdir

      # Set resource defaults
      Ini_setting {
        ensure  => present,
        require => Class['puppetdb::server::validate_db'],
      }

      ini_setting {'puppetdb-extra-setting':
        path    => "${confdir}/global.ini",
        section => 'global',
        setting => <some-extra-setting>,
        value   => 'true',
      }
    }

[global] settings

The [global] section is used to configure application-wide behavior.

vardir

This defines the parent directory for the MQ’s data directory. The directory must exist and be writable by the PuppetDB user in order for the application to run.

logging-config

This describes the full path to a logback.xml file. Covering all the options available for configuring Logback is outside the scope of this guide: see the Logback documentation for exhaustive information.

If this setting isn’t provided, PuppetDB defaults to logging at INFO level to standard out.

If you installed from packages, PuppetDB will use the logback.xml file in the /etc/puppetdb/ or /etc/puppetlabs/puppetdb directory. Otherwise, you can find an example file in the ext directory of the source.

You can edit the logging configuration file while PuppetDB is running, and it will automatically react to changes after a few seconds.

update-server

The URL to query when checking for newer versions; defaults to https://updates.puppetlabs.com/check-for-updates. Overriding this setting may be useful if your PuppetDB server is firewalled and can’t make external HTTP requests. In this case you can configure a proxy server to send requests to the updates.puppetlabs.com URL and override this setting to point to your proxy server.

[puppetdb] settings

The [puppetdb] section is used to configure PuppetDB application-specific behavior.

certificate-whitelist

Optional. This describes the path to a file that contains a list of certificate names, one per line. Incoming HTTPS requests will have their certificates validated against this list of names and only those with an exact matching entry will be allowed through. (For a Puppet master, this compares against the value of the certname setting, rather than the dns_alt_names setting.)

If not supplied, PuppetDB uses standard HTTPS without any additional authorization. All HTTPS clients must still supply valid, verifiable SSL client certificates.

historical-catalogs-limit (PE only)

Note: This setting has no effect and will be retired in a future release.

disable-update-checking

Optional. Setting this to true disables checking for updated versions of PuppetDB and sending basic analytics data to Puppet. Defaults to false.

If disable-update-checking is set to false, PuppetDB checks for updates upon start or restart, and every 24 hours thereafter, and sends the following data to Puppet:

• Product name
• Database name
• Database version
• PuppetDB version
• IP address
• Data collection timestamp

The data Puppet collects provides just one of many methods we use for learning about our community of users. The more we know about how you use Puppet, the better we can address your needs. No personally identifiable information is collected, and the data we collect is never used or shared outside Puppet.

[database] settings

The [database] section configures PuppetDB’s database settings. PuppetDB stores its data in PostgreSQL.

FAQ: Why no MySQL or Oracle support?

MySQL lacks several features that PuppetDB relies on, most notably including recursive queries. We have no plans to ever support MySQL.

Depending on demand, Oracle support may be forthcoming in a future version of PuppetDB. This hasn’t been decided yet.

Using PostgreSQL

Before using the PostgreSQL backend, you must set up a PostgreSQL server. Note that users installing PuppetDB via the module will already have PostgreSQL configured properly and these steps should not be necessary.

Ensure that you have configured a PostgreSQL 9.6 server to include a user and empty database for PuppetDB, and to accept connections to that database as that user. Information on connection/authentication configuration in PostgreSQL can be found here. Docs on setting up users and databases can be found in the Getting Started section of the PostgreSQL manual.

Completely configuring PostgreSQL is beyond the scope of this guide, but a example setup is described below. First, you can create a user and database as follows:

$ sudo -u postgres sh
$ createuser -DRSP puppetdb
$ createdb -E UTF8 -O puppetdb puppetdb
$ exit

You should install the RegExp-optimized index extension pg_trgm. This may require installing the postgresql-contrib (or equivalent) package, depending on your distribution:

$ sudo -u postgres sh
$ psql puppetdb -c 'create extension pg_trgm'
$ exit

Next, you will most likely need to modify the pg_hba.conf file to allow for MD5 authentication from at least localhost. To locate the file you can either issue a locate pg_hba.conf command (if your distribution supports it) or consult your distribution’s documentation for the PostgreSQL confdir.

The following example pg_hba.conf file allows MD5 authentication from localhost for both IPv4 and IPv6 connections:

# TYPE  DATABASE   USER   CIDR-ADDRESS  METHOD
local   all        all                  md5
host    all        all    127.0.0.1/32  md5
host    all        all    ::1/128       md5

Restart PostgreSQL and ensure you can log in by running:

$ sudo service postgresql restart
$ psql -h localhost puppetdb puppetdb

To configure PuppetDB to use this database, put the following in the [database] section:

subname = //<HOST>:<PORT>/<DATABASE>
username = <USERNAME>
password = <PASSWORD>

Replace <HOST> with the DB server’s hostname. Replace <PORT> with the port on which PostgreSQL is listening. Replace <DATABASE> with the name of the database you’ve created for use with PuppetDB.

Using SSL With PostgreSQL

It’s possible to use SSL to protect connections to the database. There are several extra steps and considerations when doing so. See the PostgreSQL SSL setup page for complete details.

The main difference in the config file is that you must be sure to add ?ssl=true to the subname setting:

subname = //<HOST>:<PORT>/<DATABASE>?ssl=true

gc-interval

This controls how often, in minutes, to compact the database. The compaction process reclaims space and deletes unnecessary rows. If not supplied, the default is every 60 minutes. If set to zero, all database GC processes will be disabled.

node-ttl

Mark as ‘expired’ nodes that haven’t seen any activity (no new catalogs, facts, or reports) in the specified amount of time. Expired nodes behave the same as manually-deactivated nodes.

You may specify the time as a string using any of the following suffixes:

`d`  - days
`h`  - hours
`m`  - minutes
`s`  - seconds
`ms` - milliseconds

For example, a value of 30d would set the time-to-live to 30 days, and a value of 48h would set the time-to-live to 48 hours.

Nodes will be checked for staleness every gc-interval minutes. Manual deactivation will continue to work as always.

If unset, nodes are auto-expired after 7 days of inactivity. If set to 0s, auto-expiration of nodes is disabled.

node-purge-ttl

Automatically delete nodes that have been deactivated or expired for the specified amount of time. This will also delete all facts, catalogs, and reports for the relevant nodes. This TTL may be specified the same way as node-ttl above.

If unset, nodes are purged after 14 days. If set to 0s, auto-deletion of nodes is disabled.

node-purge-gc-batch-limit

Nodes will be purged in batches of this size, one batch per gc-interval. If unset, the batch limit will be 25, and if you expect to generate eligible nodes faster than that (on average), you should either increase this limit so that PuppetDB will be able to keep up, or complement the automatic GC process with manual purge_node requests to the cmd endpoint to cover the excess.

report-ttl

Automatically delete reports that are older than the specified amount of time. You may specify the time as a string using any of the suffixes described in the node-ttl section above.

Outdated reports will be deleted during the database garbage collection, which runs every gc-interval minutes.

If unset, the default value is 14 days.

subname

This describes where to find the database. It should be something like //<HOST>:<PORT>/<DATABASE>, replacing <HOST> with the DB server’s hostname, <PORT> with the port on which PostgreSQL is listening, and <DATABASE> with the name of the database. Append ?ssl=true to this if your PostgreSQL server is using SSL.

username

This is the username to use when connecting. Only used with PostgreSQL.

password

This is the password to use when connecting. Only used with PostgreSQL.

maximum-pool-size

From the HikariCP documentation:

“This property controls the maximum size that the pool is allowed to reach, including both idle and in-use connections. Basically this value will determine the maximum number of actual connections to the database backend. A reasonable value for this is best determined by your execution environment.”

When the pool reaches this size, and no idle connections are available, attempts to get a connection will wait for connection-timeout milliseconds before timing out.

The default value is 25. Note that PuppetDB will use one pool for writes and another for reads, so the total number of connections used will be twice this setting.

conn-max-age

The maximum time (in minutes), for a pooled connection to remain unused before it is closed off.

If not supplied, the default value is 60 minutes.

conn-lifetime

The maximum time (in minutes) a pooled connection should remain open. Any connections older than this setting will be closed off. Connections currently in use will not be affected until they are returned to the pool.

If not supplied, we won’t terminate connections based on their age alone.

connection-timeout

The maximum time to wait (in milliseconds) to acquire a connection from the pool of database connections. If not supplied, defaults to 1000.

facts-blacklist

Optional. A list of fact names to be ignored whenever submitted. The facts-blacklist-type determines whether the names are matched literally or as Java regular expresions.

The names must be comma-separated in an INI configuration file, or a list in a HOCON file:

• INI: facts-blacklist = fact1, fact2, fact3
• HOCON: facts-blacklist = ["fact1", "fact2", "fact3"]

When matching lterally, the entire fact name (not including the path) must completely match one of the facts-blacklist entries in order to be blacklisted. When matching regular expressions, the name must match the entire pattern. For example the pattern “xyz” will not match the fact “123xyzabc”, but “.xyz.” will.

facts-blacklist-type

Optional. When set to literal (or not set) the facts-blacklist names will be matched literally. When set to regex (the only other legal value), the names will be matched as Java regular expresions. See the facts-blacklist description above for additional information.

[read-database] settings

The [read-database] section configures PuppetDB’s read-database settings, useful when running a PostgreSQL Hot Standby cluster. Currently, only configuring a PostgreSQL read-database is supported. See the PostgreSQL documentation here for details on configuring the cluster. The [read-database] portion of the configuration is in addition to the [database] settings. If [read-database] is specified, [database] must also be specified.

To configure PuppetDB to use a read-only database from the cluster, add the following to the [read-database] section:

subname = //<HOST>:<PORT>/<DATABASE>
username = <USERNAME>
password = <PASSWORD>

Replace <HOST> with the DB server’s hostname. Replace <PORT> with the port on which PostgreSQL is listening. Replace <DATABASE> with the name of the database you’ve created for use with PuppetDB.

Using SSL With PostgreSQL

It’s possible to use SSL to protect connections to the database. There are several extra steps and considerations when doing so; see the PostgreSQL SSL setup page for complete details.

The main difference in the config file is that you must be sure to add ?ssl=true to the subname setting:

subname = //<HOST>:<PORT>/<DATABASE>?ssl=true

subname

This describes where to find the database. Set this to //<HOST>:<PORT>/<DATABASE> when using PostgreSQL, replacing <HOST> with the DB server’s hostname, <PORT> with the port on which PostgreSQL is listening, and <DATABASE> with the name of the database.

Append ?ssl=true to this if your PostgreSQL server is using SSL.

username

This is the username to use when connecting.

password

This is the password to use when connecting.

maximum-pool-size

From the HikariCP documentation:

“This property controls the maximum size that the pool is allowed to reach, including both idle and in-use connections. Basically this value will determine the maximum number of actual connections to the database backend. A reasonable value for this is best determined by your execution environment.”

When the pool reaches this size, and no idle connections are available, attempts to get a connection will wait for connection-timeout milliseconds before timing out.

The default value is 10.

conn-max-age

The maximum time (in minutes) for a pooled connection to remain unused before it is closed off.

If not supplied, the default value is 60 minutes.

conn-lifetime

The maximum time (in minutes) a pooled connection should remain open. Any connections older than this setting will be closed off. Connections currently in use will not be affected until they are returned to the pool.

If not supplied, we won’t terminate connections based on their age alone.

connection-timeout

The maximum time to wait (in milliseconds) to acquire a connection from the pool of database connections. If not supplied, defaults to 500.

[command-processing] Settings

The [command-processing] section configures the command-processing subsystem.

Every change to PuppetDB’s data stores arrives via commands that are inserted into a message queue (MQ). Command processor threads pull items off of that queue, persisting those changes.

threads

This defines how many command processing threads to use. Each thread can process a single command at a time. The number of threads can be tuned based on what you see in the performance dashboard.

This setting defaults to half the number of cores in your system.

concurrent-writes

This sets a limit on the number of threads that can write to the disk at any one time. The default value is the smaller number of half the number of CPU cores and 4.

If your load is low, your disk is fast (i.e. an SSD), and commands aren’t being processed quickly enough, then you could increasing this value in order to alleviate that, but this is unlikely to be the bottleneck for command processing.

reject-large-commands

This is a Boolean that enables rejecting (returning an HTTP 413 error) commands that are too large to process, such as a catalog that is too large, causing PuppetDB to run out of memory. This setting can be used along with max-command-size.

This setting is false by default.

max-command-size

This is an integer that specifies (in bytes) which commands are “too large” to process with PuppetDB. By default this setting is a fraction of the total heap space. It is strongly recommended that users set this manually as the default is probably too conservative. To help determine the current size of commands being processed, enable debug logging for the puppetlabs.puppetdb.middleware appender in the logback.xml. This setting has no effect when reject-large-commands is set to false.

[jetty] (HTTP) settings

The [jetty] section configures HTTP for PuppetDB.

Note: If you are using Puppet Enterprise and want to enable the PuppetDB dashboard from the PE console, refer to our guide to changing PuppetDB’s parameters for more information. PE users should not edit jetty.ini.

host

Sets the IP interface to listen on for unencrypted HTTP traffic. If not supplied, we bind to localhost, which will reject connections from anywhere but the PuppetDB server itself. To listen on all available interfaces, use 0.0.0.0.

To avoid DNS resolution confusion, if you wish to set this to something other than localhost, we reccomend using an IP address instead of a hostname.

Note: Unencrypted HTTP is the only way to view the performance dashboard, since PuppetDB uses host verification for SSL. However, it can also be used to make any call to PuppetDB’s API, including inserting exported resources and retrieving arbitrary data about your Puppet-managed nodes. If you enable cleartext HTTP, you MUST configure your firewall to protect unverified access to PuppetDB.

port

Establishes which port to use for unencrypted HTTP traffic. If not supplied, we won’t listen for unencrypted traffic at all.

max-threads

Sets the maximum number of threads assigned to responding to HTTP and HTTPS requests, effectively changing how many concurrent requests can be made at one time. Defaults to 50.

Note: Due to the behaviour of our web server (Jetty 9), this setting must be higher then the number of CPUs on your system or it will stop processing any HTTP requests.

ssl-host

Sets which IP interface to listen on for encrypted HTTPS traffic. If not supplied, we bind to localhost. To listen on all available interfaces, use 0.0.0.0.

To avoid DNS resolution confusion, if you wish to set this to something other than localhost, we reccomend using an IP address instead of a hostname

ssl-port

Establishes which port to use for encrypted HTTPS traffic. If not supplied, we won’t listen for encrypted traffic at all.

ssl-cert

Sets the path to the server certificate PEM file used by the PuppetDB web service for HTTPS. During the SSL handshake for a connection, certificates extracted from this file are presented to the client for the client’s use in validating the server. This file may contain a single certificate or a chain of certificates ordered from the end certificate first to the most-root certificate last. For example, a certificate chain could contain:

• An end certificate.
• An intermediate CA certificate with which the end certificate was issued.
• A root CA certificate with which the intermediate CA certificate was issued.

In the PEM file, the end certificate should appear first, the intermediate CA certificate should appear second, and the root CA certificate should appear last.

If a chain is present, it is not required to be complete. If a path has been specified for the ssl-cert-chain setting, the server will construct the cert chain starting with the first certificate found in the ssl-cert PEM and followed by any certificates in the ssl-cert-chain PEM. In the latter case, any certificates in the ssl-cert PEM beyond the first one are ignored.

ssl-key

This sets the path to the private key PEM file that corresponds with the ssl-cert, if used by the PuppetDB web service for HTTPS.

ssl-ca-cert

This sets the path to the CA certificate PEM file used for client authentication. Authorized clients must be signed by the CA that corresponds to this certificate.

cipher-suites

Optional. A comma-separated list of cryptographic ciphers to allow for incoming SSL connections. Valid names are listed in the official JVM cryptographic providers documentation. Note that you must use the all-caps cipher suite name.

If not supplied, PuppetDB will use only non-DHE cipher suites.

ssl-protocols

Optional. A comma-separated list of protocols to allow for incoming SSL connections. Valid names are listed in the official JVM cryptographic protocol documentation. Note that you must use the names with verbatim capitalization. For example: TLSv1, TLSv1.1, TLSv1.2.

If not supplied, PuppetDB uses a default of TLSv1, TLSv1.1, TLSv1.2. By default, SSLv3 is not included in that list due to known vulnerabilities. Users wanting to use SSLv3 need to explicitly specify it in their list.

ssl-crl-path

Optional. This describes a path to a Certificate Revocation List file. Incoming SSL connections will be rejected if the client certificate matches a revocation entry in the file.

ssl-cert-chain

This sets the path to a PEM with CA certificates for use in presenting a client with the server’s chain of trust. Certs found in this PEM file are appended after the first certificate from the ssl-cert PEM in the construction of the certificate chain. This is an optional setting. The certificates in the ssl-cert-chain PEM file should be ordered from the least-root CA certificate first to the most-root CA certificate last. For example, a certificate chain could contain:

• An end certificate.
• An intermediate CA certificate with which the end certificate was issued.
• A root CA certificate with which the intermediate CA certificate was issued.

The end certificate should appear in the ssl-cert PEM file. In the ssl-cert-chain PEM file, the intermediate CA certificate should appear first and the root CA certificate should appear last.

The chain is not required to be complete.

Note: This setting overrides the alternate configuration settings keystore and key-password.

access-log-config

Optional. This is a path to an XML file containing configuration information for the logback-access module. If present, a logger will be set up to log information about any HTTP requests Jetty receives according to the logging configuration, as long as the XML file pointed to exists and is valid. Information on configuring the logback-access module is available here.

A configuration file may resemble the following:

<configuration debug="false">
  <appender name="FILE" class="ch.qos.logback.core.FileAppender">
    <file>./dev-resources/access.log</file>
      <encoder>
        <pattern>%h %l %u %user %date "%r" %s %b</pattern>
      </encoder>
    </appender>
    <appender-ref ref="FILE" />
</configuration>

This example configures a FileAppender that outputs to a file, access.log, in the dev-resources directory. It will log the remote host making the request, the log name, the remote user making the request, the date/time of the request, the URL and method of the request, the status of the response, and the size in bytes of the response.

graceful-shutdown-timeout

After receiving a shutdown, this is the number of milliseconds the server will wait for in-flight requests to complete before actually shutting down. New requests will be blocked during this time. Defaults to 30000.

request-header-max-size

This sets the maximum size of an HTTP request header. If a header is sent that exceeds this value, Jetty will return an HTTP 413 error response. This defaults to 8192 bytes, and only needs to be configured if an exceedingly large header is being sent in an HTTP request.

[nrepl] settings

The [nrepl] section configures remote runtime modification. For more detailed info, see our guide to debugging with the remote REPL.

Enabling a remote REPL allows you to manipulate the behavior of PuppetDB at runtime. This should only be done for debugging purposes, and is thus disabled by default. An example configuration stanza:

[nrepl]
type = nrepl
port = 8082
host = 127.0.0.1

enabled

To enable the REPL, set to true. Defaults to false.

port

The port to use for the REPL.

host

Specifies the host or IP address for the REPL service to listen on. By default this is 127.0.0.1 only. As this is an insecure channel this is the only recommended setting for production environments.

If you wish to listen on all interfaces, you can specify 0.0.0.0, for example, although this is generally not recommended for production.

[developer] settings

The [developer] section contains configuration items that may be useful to users developing against the PuppetDB API. These settings may impede performance, and are not recommended for production use.

pretty-print

Enables/disables default pretty-printing of API responses. Defaults to false. Enabling default pretty-printing is not recommended in production because it incurs a penalty in data transfer speed and size. Users may override this setting on a per-query basis by supplying a ?pretty= parameter in the URL, valued true or false.

[sync] settings (Puppet Enterprise only)

The [sync] section of the PuppetDB configuration file is used to configure synchronization for a high-availability system. See the HA configuration guide for complete system configuration instructions.

remotes

The remotes configuration key indicates that PuppetDB should poll a remote PuppetDB server for changes. When it finds changed or updated records on that server, it will download the records and submit them to the local command queue.

In the configuration file, you specify a remote for each server you want to pull data from. It is perfectly reasonable, and expected, for two servers to pull data from each other. For each remote, you must provide:

• The remote server url. This is a root url which should include the protocol and port to use (eg. “https://puppetdb.myco.net:8081”). The protocol is mandatory and must be either “http” or “https”. If the port is not provided, it will default to 8080 for http and 8081 for https.

• The interval at which to poll the remote server for new data. This is formatted as a timespan with units (e.g. ‘2m’). See the node-ttl documentation for further reference.

You should not configure PuppetDB to sync with itself.

HOCON

If you are using HOCON to configure PuppetDB, use the following structure in your .conf file:

sync: {
  remotes: [{server_url: "https://remote-puppetdb.myco.net:8081",
             interval: 2m}]
}

ini

If you are using a .ini file to configure PuppetDB, use the following structure:

[sync]
server_urls = https://remote-puppetdb.myco.net:8081
intervals = 2m

Multiple values may be provided by comma-separating them, with no whitespace. You must have exactly the same number of entries in the server_urls and intervals values.