介绍

为了对 table 的一些行为进行控制，Pegasus 提供了 table 环境变量，又称之为 app envs。

Table 环境变量以 map 的形式存储在该表的元数据中（Thrift 结构 app_info 中），并持久化到 Apache Zookeeper 上。

通过 shell 工具的 ls 命令查看表信息，最后一列 envs_count 指明了该表的环境变量个数。例如：

>>> ls
[general_info]
app_id  status     app_name  app_type  partition_count  replica_count  is_stateful  create_time          drop_time  drop_expire  envs_count
2       AVAILABLE  temp      pegasus   8                3              true         2024-04-15_06:58:38  -          -            1

如果要查看具体的 table 环境变量，则需要使用 get_app_envs 命令。

Table 环境变量具有如下特性：

作为 table 的元数据持久化到 Apache Zookeeper 上。
可以通过命令行动态修改，修改成功后会立即更新到 Apache Zookeeper 上。
通过 Meta Server 和 Replica Server 的周期性同步消息 config_sync 同步给各个 Replica Server 生效。

由于是周期性同步，所以环境变量更新后可能不会在 Replica Server 上立即生效，而是有一个延迟。这个延迟时间依赖于配置 config_sync_interval_ms 的值，默认是 30 秒。
环境变量的 key 通常使用 . 分隔，方便分类。

目前通过 table 环境变量支持的功能如：

控制命令

Pegasus 的 Shell 工具中提供了操作 table 环境变量的命令。这些命令执行前都需要先执行 use <table_name> 选择需要操作的表。

get_app_envs

参考：get_app_envs 命令

set_app_envs

参考：set_app_envs 命令

del_app_envs

参考：del_app_envs 命令

clear_app_envs

参考：clear_app_envs 命令

支持的环境变量

从 Pegasus 2.6 开始，可通过 Meta Server 的 HTTP 接口 /envs/list 获取所有支持的 table 环境变量。例如：

$ curl 127.0.0.1:34601/envs/list
{
  "business.info": {
    "limitation": "",
    "sample": "",
    "type": "string"
  },
  "default_ttl": {
    "limitation": ">= 0",
    "sample": "86400",
    "type": "unsigned int32"
  },
  "manual_compact.disabled": {
    "limitation": "true | false",
    "sample": "true",
    "type": "bool"
  },
  "manual_compact.max_concurrent_running_count": {
    "limitation": ">= 0",
    "sample": "8",
    "type": "unsigned int32"
  },
  "manual_compact.once.bottommost_level_compaction": {
    "limitation": "force | skip",
    "sample": "skip",
    "type": "string"
  },
  "manual_compact.once.target_level": {
    "limitation": "-1 or >= 1",
    "sample": "6",
    "type": "unsigned int64"
  },
  "manual_compact.once.trigger_time": {
    "limitation": "> 0, timestamp (in seconds) to trigger the once manual compaction",
    "sample": "1700000000",
    "type": "unsigned int64"
  },
  "manual_compact.periodic.bottommost_level_compaction": {
    "limitation": "force | skip",
    "sample": "skip",
    "type": "string"
  },
  "manual_compact.periodic.target_level": {
    "limitation": "-1 or >= 1",
    "sample": "6",
    "type": "unsigned int64"
  },
  "manual_compact.periodic.trigger_time": {
    "limitation": "",
    "sample": "",
    "type": "string"
  },
  "replica.backup_request_throttling": {
    "limitation": "<size[K|M]>*<delay|reject>*<milliseconds>",
    "sample": "10000*delay*100,20000*reject*100",
    "type": "string"
  },
  "replica.deny_client_request": {
    "limitation": "timeout*all | timeout*write | timeout*read | reconfig*all | reconfig*write | reconfig*read",
    "sample": "timeout*all",
    "type": "string"
  },
  "replica.read_throttling": {
    "limitation": "<size[K|M]>*<delay|reject>*<milliseconds>",
    "sample": "10000*delay*100,20000*reject*100",
    "type": "string"
  },
  "replica.read_throttling_by_size": {
    "limitation": "",
    "sample": "20000*delay*100,20000*reject*100",
    "type": "string"
  },
  "replica.rocksdb_block_cache_enabled": {
    "limitation": "true | false",
    "sample": "true",
    "type": "bool"
  },
  "replica.rocksdb_iteration_threshold_time_ms": {
    "limitation": ">= 0",
    "sample": "1000",
    "type": "unsigned int64"
  },
  "replica.slow_query_threshold": {
    "limitation": ">= 20",
    "sample": "1000",
    "type": "unsigned int64"
  },
  "replica.split.validate_partition_hash": {
    "limitation": "true | false",
    "sample": "true",
    "type": "bool"
  },
  "replica.write_throttling": {
    "limitation": "<size[K|M]>*<delay|reject>*<milliseconds>",
    "sample": "10000*delay*100,20000*reject*100",
    "type": "string"
  },
  "replica.write_throttling_by_size": {
    "limitation": "<size[K|M]>*<delay|reject>*<milliseconds>",
    "sample": "10000*delay*100,20000*reject*100",
    "type": "string"
  },
  "replica_access_controller.allowed_users": {
    "limitation": "",
    "sample": "",
    "type": "string"
  },
  "replica_access_controller.ranger_policies": {
    "limitation": "",
    "sample": "",
    "type": "string"
  },
  "rocksdb.allow_ingest_behind": {
    "limitation": "true | false",
    "sample": "true",
    "type": "bool"
  },
  "rocksdb.checkpoint.reserve_min_count": {
    "limitation": "> 0",
    "sample": "2",
    "type": "unsigned int32"
  },
  "rocksdb.checkpoint.reserve_time_seconds": {
    "limitation": ">= 0",
    "sample": "3600",
    "type": "unsigned int32"
  },
  "rocksdb.num_levels": {
    "limitation": "In range [1, 10]",
    "sample": "6",
    "type": "unsigned int64"
  },
  "rocksdb.usage_scenario": {
    "limitation": "bulk_load | normal | prefer_write",
    "sample": "normal",
    "type": "string"
  },
  "rocksdb.write_buffer_size": {
    "limitation": "In range [16777216, 536870912]",
    "sample": "16777216",
    "type": "unsigned int64"
  },
  "user_specified_compaction": {
    "limitation": "",
    "sample": "",
    "type": "string"
  }
}