--- id: human-readable-byte title: "Human-readable Byte Configuration Reference" --- This page documents configuration properties related to bytes. These properties can be configured through 2 ways: 1. a simple number in bytes 2. a number with a unit suffix ## A number in bytes Given that cache size is 3G, there's a configuration as below ```properties # 3G bytes = 3_000_000_000 bytes druid.cache.sizeInBytes=3000000000 ``` ## A number with a unit suffix When you have to put a large number for some configuration as above, it is easy to make a mistake such as extra or missing 0s. Druid supports a better way, a number with a unit suffix. Given a disk of 1T, the configuration can be ```properties druid.segmentCache.locations=[{"path":"/segment-cache-00","maxSize":"1t"},{"path":"/segment-cache-01","maxSize":"1200g"}] ``` Note: in above example, both `1t` and `1T` are acceptable since it's case-insensitive. Also, only integers are valid as the number part. For example, you can't replace `1200g` with `1.2t`. ### Supported Units In the world of computer, a unit like `K` is ambiguous. It means 1000 or 1024 in different contexts, for more information please see [Here](https://en.wikipedia.org/wiki/Binary_prefix). To make it clear, the base of units are defined in Druid as below | Unit | Description | Base | |---|---|---| | K | Kilo Decimal Byte | 1_000 | | M | Mega Decimal Byte | 1_000_000 | | G | Giga Decimal Byte | 1_000_000_000 | | T | Tera Decimal Byte | 1_000_000_000_000 | | P | Peta Decimal Byte | 1_000_000_000_000_000 | | KiB | Kilo Binary Byte | 1024 | | MiB | Mega Binary Byte | 1024 * 1024 | | GiB | Giga Binary Byte | 1024 * 1024 * 1024 | | TiB | Tera Binary Byte | 1024 * 1024 * 1024 * 1024 | | PiB | Peta Binary Byte | 1024 * 1024 * 1024 * 1024 * 1024 | Unit is case-insensitive. `k`, `kib`, `KiB`, `kiB` are all acceptable. Here are two examples ```properties # 1G bytes = 1_000_000_000 bytes druid.cache.sizeInBytes=1g ``` ```properties # 256MiB bytes = 256 * 1024 * 1024 bytes druid.cache.sizeInBytes=256MiB ``` ## 配置文档 本部分内容列出来了每一种Druid服务的所有配置项 ### 推荐的配置文件组织方式 对于Druid的配置文件，一种推荐的结构组织方式为将配置文件放置在Druid根目录的`conf`目录下，如以下所示： ```json $ ls -R conf druid conf/druid: _common broker coordinator historical middleManager overlord conf/druid/_common: common.runtime.properties log4j2.xml conf/druid/broker: jvm.config runtime.properties conf/druid/coordinator: jvm.config runtime.properties conf/druid/historical: jvm.config runtime.properties conf/druid/middleManager: jvm.config runtime.properties conf/druid/overlord: jvm.config runtime.properties ``` 每一个目录下都有一个 `runtime.properties` 文件，该文件中包含了特定的Druid进程相关的配置项，例如 `historical` `jvm.config` 文件包含了每一个服务的JVM参数，例如堆内存属性等 所有进程共享的通用属性位于 `_common/common.runtime.properties` 中。 ### 通用配置 本节下的属性是应该在集群中的所有Druid服务之间共享的公共配置。 #### JVM配置最佳实践 在我们的所有进程中有四个需要配置的JVM参数 1. `-Duser.timezone=UTC` 该参数将JVM的默认时区设置为UTC。我们总是这样设置，不使用其他默认时区进行测试，因此本地时区可能会工作，但它们也可能会发现奇怪和有趣的错误。要在非UTC时区中发出查询，请参阅 [查询粒度](../querying/granularity.md) 2. `-Dfile.encoding=UTF-8` 这类似于时区，我们假设UTF-8进行测试。本地编码可能有效，但也可能导致奇怪和有趣的错误。 3. `-Djava.io.tmpdir=` 系统中与文件系统交互的各个部分都是通过临时文件完成的，这些文件可能会变得有些大。许多生产系统都被设置为具有小的（但是很快的）`/tmp`目录，这对于Druid来说可能是个问题，因此我们建议将JVM的tmp目录指向一些有更多内容的目录。此目录不应为volatile tmpfs。这个目录还应该具有良好的读写速度，因此应该强烈避免NFS挂载。 4. `-Djava.util.logging.manager=org.apache.logging.log4j.jul.LogManager` 这允许log4j2处理使用标准java日志的非log4j2组件（如jetty）的日志。 #### 扩展 #### 请求日志 #### SQL兼容的空值处理 ### Master #### Coordinator #### Overlord ### Data #### MiddleManager and Peons ##### SegmentWriteOutMediumFactory #### Indexer #### Historical ### Query #### Broker #### Router