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模块:FERRET

Pigsty 内置了对 “FerertDB” 的原生部署支持 —— 它为 PostgreSQL 添加了 MongoDB 线缆协议级别的 API 兼容支持!

使用 FerretDB 为 PostgreSQL 添加 MongoDB 兼容的协议支持! 配置 | 管理 | 剧本 | 监控 | 参数


概览

MongoDB 曾经是一项令人惊叹的技术,让开发者能够抛开关系型数据库的“模式束缚”,快速构建应用程序。然而随着时间推移,MongoDB 放弃了它的开源本质,将许可证更改为 SSPL,这使得许多开源项目和早期商业项目无法使用它。大多数 MongoDB 用户其实并不需要 MongoDB 提供的高级功能,但他们确实需要一个易于使用的开源文档数据库解决方案。为了填补这个空白,FerretDB 应运而生。

PostgreSQL 的 JSON 功能支持已经足够完善了:二进制存储 JSONB,GIN 任意字段索引 ,各种 JSON 处理函数,JSON PATH 和 JSON Schema,它早已是一个功能完备,性能强大的文档数据库了。但是提供替代的功能,和直接仿真还是不一样的。FerretDB 可以为使用 MongoDB 驱动的应用程序提供一个丝滑迁移到 PostgreSQL 的过渡方案。

Pigsty 在 1.x 中就提供了基于 Docker 的 FerretDB 模板,在 v2.3 中更是提供了原生部署支持。它作为一个选装项,对丰富 PostgreSQL 生态大有裨益。Pigsty 社区已经与 FerretDB 社区成为了合作伙伴,后续将进行深度的合作与适配支持。


配置

在部署 Mongo (FerretDB) 集群前,你需要先在配置清单中使用相关参数定义好它。

下面的例子将默认的单节点 pg-meta 集群的 meta 数据库作为 FerretDB 的底层存储:

ferret:
  hosts: { 10.10.10.10: { mongo_seq: 1 } }
  vars:
    mongo_cluster: ferret
    mongo_pgurl: 'postgres://dbuser_meta:[email protected]:5432/meta'

这里 mongo_clustermongo_seq 属于不可或缺的身份参数,对于 FerretDB 来说,还有一个必须提供的参数是 mongo_pgurl,指定了底层 PG 的位置。

您可以使用 服务 来接入高可用的 PostgreSQL 集群,并部署多个 FerretDB 实例副本并绑定 L2 VIP 以实现 FerretDB 层本身的高可用。

ferret:
  hosts:
    10.10.10.45: { mongo_seq: 1 }
    10.10.10.46: { mongo_seq: 2 }
    10.10.10.47: { mongo_seq: 3 }
  vars:
    mongo_cluster: ferret
    mongo_pgurl: 'postgres://test:[email protected]:5436/test'
    vip_enabled: true
    vip_vrid: 128
    vip_address: 10.10.10.99
    vip_interface: eth1

管理

创建Mongo集群

配置清单定义好MONGO集群后,您可以使用以下命令完成安装。

./mongo.yml -l ferret   # 在 ferret 分组上安装“MongoDB/FerretDB”

因为 FerretDB 使用了 PostgreSQL 作为底层存储,所以重复运行此剧本通常并无大碍。

移除Mongo集群

要移除 Mongo/FerretDB 集群,运行 mongo.yml 剧本的子任务:mongo_purge,并使用 mongo_purge 命令行参数即可:

./mongo.yml -e mongo_purge=true -t mongo_purge

连接到FerretDB

你可以使用 MongoDB 连接串,用任何语言的 MongoDB 驱动访问 FerretDB,这里以上面安装的 mongosh 命令行工具为例:

mongosh 'mongodb://dbuser_meta:[email protected]:27017?authMechanism=PLAIN'
mongosh 'mongodb://test:[email protected]:27017/test?authMechanism=PLAIN'

Pigsty 管理的 PostgreSQL 集群默认使用 scram-sha-256 作为默认的认证方式,因此,您必须使用 PLAIN 认证方式连接至 FerretDB。 参阅 FerretDB:认证 获取详细信息。

你也可以使用其他 PostgreSQL 用户来访问 FerretDB,只要在连接串中指定即可:

mongosh 'mongodb://dbuser_dba:[email protected]:27017?authMechanism=PLAIN'

快速上手

你可以连接到 FerretDB 并假装它是一个 MongoDB 集群。

$ mongosh 'mongodb://dbuser_meta:[email protected]:27017?authMechanism=PLAIN'

MongoDB 的命令会被翻译为SQL命令,在底下的 PostgreSQL 中执行:

use test                            # CREATE SCHEMA test;
db.dropDatabase()                   # DROP SCHEMA test;
db.createCollection('posts')        # CREATE TABLE posts(_data JSONB,...)
db.posts.insert({                   # INSERT INTO posts VALUES(...);
    title: 'Post One',body: 'Body of post one',category: 'News',tags: ['news', 'events'],
    user: {name: 'John Doe',status: 'author'},date: Date()}
)
db.posts.find().limit(2).pretty()   # SELECT * FROM posts LIMIT 2;
db.posts.createIndex({ title: 1 })  # CREATE INDEX ON posts(_data->>'title');

如果你不是很熟悉 MongoDB,这里有一个快速上手教程,同样适用于 FerretDB: Perform CRUD Operations with MongoDB Shell

如果你希望生成一些样例负载,可以使用 mongosh 执行以下的简易测试剧本:

cat > benchmark.js <<'EOF'
const coll = "testColl";
const numDocs = 10000;

for (let i = 0; i < numDocs; i++) {  // insert
  db.getCollection(coll).insert({ num: i, name: "MongoDB Benchmark Test" });
}

for (let i = 0; i < numDocs; i++) {  // select
  db.getCollection(coll).find({ num: i });
}

for (let i = 0; i < numDocs; i++) {  // update
  db.getCollection(coll).update({ num: i }, { $set: { name: "Updated" } });
}

for (let i = 0; i < numDocs; i++) {  // delete
  db.getCollection(coll).deleteOne({ num: i });
}
EOF

mongosh 'mongodb://dbuser_meta:[email protected]:27017?authMechanism=PLAIN' benchmark.js

你可以查阅 FerretDB 支持的 MongoDB命令,同时还有一些已知的区别,对于基本的使用来说,通常不是什么大问题。


剧本

Pigsty 提供了一个内置的剧本: mongo.yml,用于在节点上安装 FerretDB 集群。

mongo.yml

该剧本由以下子任务组成:

  • mongo_check :检查 mongo 身份参数
  • mongo_dbsu :创建操作系统用户 mongod
  • mongo_install :安装 mongo/ferretdb RPM包
  • mongo_purge :清理现有 mongo/ferretdb 集群(默认不执行)
  • mongo_config :配置 mongo/ferretdb
    • mongo_cert :签发 mongo/ferretdb SSL证书
  • mongo_launch :启动 mongo/ferretdb 服务
  • mongo_register:将 mongo/ferretdb 注册到 Prometheus 监控中

监控

MONGO 模块提供了一个简单的监控面板:Mongo Overview

Mongo Overview

Mongo Overview: Mongo/FerretDB 集群概览

这个监控面板提供了关于 FerretDB 的基本监控指标,因为 FerretDB 底层使用了 PostgreSQL,所以更多的监控指标,还请参考 PostgreSQL 监控。

mongo-overview.jpg


参数

MONGO 模块中提供了9个相关的配置参数,如下表所示:

参数 类型 级别 注释
mongo_seq int I mongo 实例号,必选身份参数
mongo_cluster string C mongo 集群名,必选身份参数
mongo_pgurl pgurl C/I mongo/ferretdb 底层使用的 PGURL 连接串,必选
mongo_ssl_enabled bool C mongo/ferretdb 是否启用SSL?默认为 false
mongo_listen ip C mongo 监听地址,默认留控则监听所有地址
mongo_port port C mongo 服务端口,默认使用 27017
mongo_ssl_port port C mongo TLS 监听端口,默认使用 27018
mongo_exporter_port port C mongo exporter 端口,默认使用 9216
mongo_extra_vars string C MONGO 服务器额外环境变量,默认为空白字符串
# mongo_cluster:        #CLUSTER  # mongo cluster name, required identity parameter
# mongo_seq: 0          #INSTANCE # mongo instance seq number, required identity parameter
# mongo_pgurl: 'postgres:///'     # mongo/ferretdb underlying postgresql url, required
mongo_ssl_enabled: false          # mongo/ferretdb ssl enabled, false by default
mongo_listen: ''                  # mongo/ferretdb listen address, '' for all addr
mongo_port: 27017                 # mongo/ferretdb listen port, 27017 by default
mongo_ssl_port: 27018             # mongo/ferretdb tls listen port, 27018 by default
mongo_exporter_port: 9216         # mongo/ferretdb exporter port, 9216 by default
mongo_extra_vars: ''              # extra environment variables for mongo/ferretdb

1 - 指标列表

Pigsty MONGO 模块提供的完整监控指标列表与释义

MONGO 模块包含有 54 类可用监控指标。

Metric Name Type Labels Description
ferretdb_client_accepts_total Unknown error, cls, ip, ins, instance, job N/A
ferretdb_client_duration_seconds_bucket Unknown error, le, cls, ip, ins, instance, job N/A
ferretdb_client_duration_seconds_count Unknown error, cls, ip, ins, instance, job N/A
ferretdb_client_duration_seconds_sum Unknown error, cls, ip, ins, instance, job N/A
ferretdb_client_requests_total Unknown cls, ip, ins, opcode, instance, command, job N/A
ferretdb_client_responses_total Unknown result, argument, cls, ip, ins, opcode, instance, command, job N/A
ferretdb_postgresql_metadata_databases gauge cls, ip, ins, instance, job The current number of database in the registry.
ferretdb_postgresql_pool_size gauge cls, ip, ins, instance, job The current number of pools.
ferretdb_up gauge cls, version, commit, ip, ins, dirty, telemetry, package, update_available, uuid, instance, job, branch, debug FerretDB instance state.
go_gc_duration_seconds summary cls, ip, ins, instance, quantile, job A summary of the pause duration of garbage collection cycles.
go_gc_duration_seconds_count Unknown cls, ip, ins, instance, job N/A
go_gc_duration_seconds_sum Unknown cls, ip, ins, instance, job N/A
go_goroutines gauge cls, ip, ins, instance, job Number of goroutines that currently exist.
go_info gauge cls, version, ip, ins, instance, job Information about the Go environment.
go_memstats_alloc_bytes gauge cls, ip, ins, instance, job Number of bytes allocated and still in use.
go_memstats_alloc_bytes_total counter cls, ip, ins, instance, job Total number of bytes allocated, even if freed.
go_memstats_buck_hash_sys_bytes gauge cls, ip, ins, instance, job Number of bytes used by the profiling bucket hash table.
go_memstats_frees_total counter cls, ip, ins, instance, job Total number of frees.
go_memstats_gc_sys_bytes gauge cls, ip, ins, instance, job Number of bytes used for garbage collection system metadata.
go_memstats_heap_alloc_bytes gauge cls, ip, ins, instance, job Number of heap bytes allocated and still in use.
go_memstats_heap_idle_bytes gauge cls, ip, ins, instance, job Number of heap bytes waiting to be used.
go_memstats_heap_inuse_bytes gauge cls, ip, ins, instance, job Number of heap bytes that are in use.
go_memstats_heap_objects gauge cls, ip, ins, instance, job Number of allocated objects.
go_memstats_heap_released_bytes gauge cls, ip, ins, instance, job Number of heap bytes released to OS.
go_memstats_heap_sys_bytes gauge cls, ip, ins, instance, job Number of heap bytes obtained from system.
go_memstats_last_gc_time_seconds gauge cls, ip, ins, instance, job Number of seconds since 1970 of last garbage collection.
go_memstats_lookups_total counter cls, ip, ins, instance, job Total number of pointer lookups.
go_memstats_mallocs_total counter cls, ip, ins, instance, job Total number of mallocs.
go_memstats_mcache_inuse_bytes gauge cls, ip, ins, instance, job Number of bytes in use by mcache structures.
go_memstats_mcache_sys_bytes gauge cls, ip, ins, instance, job Number of bytes used for mcache structures obtained from system.
go_memstats_mspan_inuse_bytes gauge cls, ip, ins, instance, job Number of bytes in use by mspan structures.
go_memstats_mspan_sys_bytes gauge cls, ip, ins, instance, job Number of bytes used for mspan structures obtained from system.
go_memstats_next_gc_bytes gauge cls, ip, ins, instance, job Number of heap bytes when next garbage collection will take place.
go_memstats_other_sys_bytes gauge cls, ip, ins, instance, job Number of bytes used for other system allocations.
go_memstats_stack_inuse_bytes gauge cls, ip, ins, instance, job Number of bytes in use by the stack allocator.
go_memstats_stack_sys_bytes gauge cls, ip, ins, instance, job Number of bytes obtained from system for stack allocator.
go_memstats_sys_bytes gauge cls, ip, ins, instance, job Number of bytes obtained from system.
go_threads gauge cls, ip, ins, instance, job Number of OS threads created.
mongo_up Unknown cls, ip, ins, instance, job N/A
process_cpu_seconds_total counter cls, ip, ins, instance, job Total user and system CPU time spent in seconds.
process_max_fds gauge cls, ip, ins, instance, job Maximum number of open file descriptors.
process_open_fds gauge cls, ip, ins, instance, job Number of open file descriptors.
process_resident_memory_bytes gauge cls, ip, ins, instance, job Resident memory size in bytes.
process_start_time_seconds gauge cls, ip, ins, instance, job Start time of the process since unix epoch in seconds.
process_virtual_memory_bytes gauge cls, ip, ins, instance, job Virtual memory size in bytes.
process_virtual_memory_max_bytes gauge cls, ip, ins, instance, job Maximum amount of virtual memory available in bytes.
promhttp_metric_handler_errors_total counter job, cls, ip, ins, instance, cause Total number of internal errors encountered by the promhttp metric handler.
promhttp_metric_handler_requests_in_flight gauge cls, ip, ins, instance, job Current number of scrapes being served.
promhttp_metric_handler_requests_total counter job, cls, ip, ins, instance, code Total number of scrapes by HTTP status code.
scrape_duration_seconds Unknown cls, ip, ins, instance, job N/A
scrape_samples_post_metric_relabeling Unknown cls, ip, ins, instance, job N/A
scrape_samples_scraped Unknown cls, ip, ins, instance, job N/A
scrape_series_added Unknown cls, ip, ins, instance, job N/A
up Unknown cls, ip, ins, instance, job N/A

2 - 常见问题

Pigsty FerretDB 模块常见问题答疑

安装MongoSH

您可以使用 MongoSH 作为客户端工具访问 FerretDB 集群

cat > /etc/yum.repos.d/mongo.repo <<EOF
[mongodb-org-6.0]
name=MongoDB Repository
baseurl=https://repo.mongodb.org/yum/redhat/$releasever/mongodb-org/6.0/$basearch/
gpgcheck=1
enabled=1
gpgkey=https://www.mongodb.org/static/pgp/server-6.0.asc
EOF
yum install -y mongodb-mongosh

当然,您也可以直接安装 mongosh 的 RPM 包:

rpm -ivh https://mirrors.tuna.tsinghua.edu.cn/mongodb/yum/el7/RPMS/mongodb-mongosh-1.9.1.x86_64.rpm