1.`-Duser.timezone=UTC` This sets the default timezone of the JVM to UTC. We always set this and do not test with other default timezones, so local timezones might work, but they also might uncover weird and interesting bugs.
2.`-Dfile.encoding=UTF-8` This is similar to timezone, we test assuming UTF-8. Local encodings might work, but they also might result in weird and interesting bugs.
3.`-Djava.io.tmpdir=<a path>` Various parts of the system that interact with the file system do it via temporary files, and these files can get somewhat large. Many production systems are set up to have small (but fast) `/tmp` directories, which can be problematic with Druid so we recommend pointing the JVM’s tmp directory to something with a little more meat.
|`druid.extensions.remoteRepositories`|If this is not set to '[]', Druid will try to download extensions at the specified remote repository.|["http://repo1.maven.org/maven2/", "https://metamx.artifactoryonline.com/metamx/pub-libs-releases-local"]|
|`druid.request.logging.type`|Choices: noop, file, emitter. How to log every request.|noop|
#### File Request Logging
Daily request logs are stored on disk.
|Property|Description|Default|
|--------|-----------|-------|
|`druid.request.logging.dir`|Historical, Realtime and Broker nodes maintain request logs of all of the requests they get (interacton is via POST, so normal request logs don’t generally capture information about the actual query), this specifies the directory to store the request logs in|none|
#### Emitter Request Logging
Every request is emitted to some external location.
|Property|Description|Default|
|--------|-----------|-------|
|`druid.request.logging.feed`|Feed name for requests.|none|
|`druid.monitoring.monitors`|Sets list of Druid monitors used by a node. See below for names and more information. For example, you can specify monitors for a Broker with `druid.monitoring.monitors=["com.metamx.metrics.SysMonitor","com.metamx.metrics.JvmMonitor"]`.|none (no monitors)|
|`io.druid.client.cache.CacheMonitor`|Emits metrics (to logs) about the segment results cache for Historical and Broker nodes. Reports typical cache statistics include hits, misses, rates, and size (bytes and number of entries), as well as timeouts and and errors.|
|`com.metamx.metrics.SysMonitor`|This uses the [SIGAR library](http://www.hyperic.com/products/sigar) to report on various system activities and statuses. Make sure to add the [sigar library jar](https://repository.jboss.org/nexus/content/repositories/thirdparty-uploads/org/hyperic/sigar/1.6.5.132/sigar-1.6.5.132.jar) to your classpath if using this monitor.|
|`io.druid.server.metrics.ServerMonitor`|Reports statistics on Historical nodes.|
The Druid servers emit various metrics and alerts via something we call an Emitter. There are three emitter implementations included with the code, a "noop" emitter, one that just logs to log4j ("logging", which is used by default if no emitter is specified) and one that does POSTs of JSON events to a server ("http"). The properties for using the logging emitter are described below.
|`druid.emitter.logging.loggerClass`|Choices: HttpPostEmitter, LoggingEmitter, NoopServiceEmitter, ServiceEmitter. The class used for logging.|LoggingEmitter|
|`druid.emitter.logging.logLevel`|Choices: debug, info, warn, error. The log level at which message are logged.|info|
|`druid.emitter.http.timeOut`|The timeout for data reads.|PT5M|
|`druid.emitter.http.flushMillis`|How often to internal message buffer is flushed (data is sent).|60000|
|`druid.emitter.http.flushCount`|How many messages can the internal message buffer hold before flushing (sending).|500|
|`druid.emitter.http.recipientBaseUrl`|The base URL to emit messages to. Druid will POST JSON to be consumed at the HTTP endpoint specified by this property.|none|
These properties specify the jdbc connection and other configuration around the metadata storage. The only processes that connect to the metadata storage with these properties are the [Coordinator](Coordinator.html) and [Indexing service](Indexing-service.html).
This config is used to find the [Indexing Service](Indexing-Service.html) using Curator service discovery. Only required if you are actually running an indexing service.
|`druid.selectors.indexing.serviceName`|The druid.service name of the indexing service Overlord node. To start the Overlord with a different name, set it with this property. |overlord|
You can optionally configure how to announce and unannounce Znodes in ZooKeeper (using Curator). For normal operations you do not need to override any of these configs.
