druid-docs-cn/configuration/human-readable-byte.md

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---
id: human-readable-byte
title: "Human-readable Byte Configuration Reference"
---
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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=<a path>` 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