Easysearch、Elasticsearch、Amazon OpenSearch 快照兼容对比

在当今的数据驱动时代，搜索引擎的快照功能在数据保护和灾难恢复中至关重要。本文将对 EasySearch、Elasticsearch 和 Amazon OpenSearch 的快照兼容性进行比较，分析它们在快照创建、恢复、存储格式和跨平台兼容性等方面的特点，帮助大家更好地理解这些搜索引擎的差异，从而选择最适合自己需求的解决方案。

启动集群

Easysearch

sysctl -w vm.max_map_count=262144

Amazon OpenSearch

Elasticsearch

由于这个docker compose没有关于kibana的配置，所以我们还是用Console添加原生的Elasticsearch集群

集群信息

快照还原的步骤

快照前的准备

插件安装

本次测试选择把索引快照备份到Amazon S3，所以需要使用S3 repository plugin，这个插件添加了对使用 Amazon S3 作为快照/恢复存储库的支持。

Easysearch和OpenSearch集群自带了这个插件，所以无需额外安装。

对于自己部署的三节点Elasticsearch则需要进入每一个节点运行安装命令然后再重启集群，建议使用自动化运维工具来做这步，安装命令如下:

sudo bin/elasticsearch-plugin install repository-s3

如果不再需要这个插件，可以这样删除。

sudo bin/elasticsearch-plugin remove repository-s3

由于需要和Amazon Web Services打交道，所以我们需要设置IAM凭证，这个插件可以从EC2 IAM instance profile，ECS task role 以及EKS的Service account读取相应的凭证。

对于托管的Amazon OpenSearch来说，我们无法在托管的EC2上绑定我们的凭证，所以需要新建一个OpenSearchSnapshotRole，然后通过当前的用户把这个角色传递给服务，也就是我们说的IAM:PassRole。

创建OpenSearchSnapshotRole，策略如下：

{"Version": "2012-10-17","Statement": [{"Action": ["s3:ListBucket"],"Effect": "Allow","Resource": ["arn:aws:s3:::bucket-name"]},{"Action": ["s3:GetObject","s3:PutObject","s3:DeleteObject"],"Effect": "Allow","Resource": ["arn:aws:s3:::bucket-name/*"]}]
}

信任关系如下：

{"Version": "2012-10-17","Statement": [{"Effect": "Allow","Principal": {"Service": "es.amazonaws.com"},"Action": "sts:AssumeRole"}]
}

然后在我们的IAM user上加上PassRole的权限，这样我们就可以把OpenSearchSnapshotRole传递给OpenSearch集群。

{"Version": "2012-10-17","Statement": [{"Effect": "Allow","Action": "iam:PassRole","Resource": "arn:aws:iam::123456789012:role/OpenSearchSnapshotRole"}]
}

注册存储库

在源集群执行注册

PUT /_snapshot/snapshot-repo-name
{"type": "s3","settings": {"bucket": "<bucket-name>","base_path": "<bucket-prefix>",

在目标集群同样执行这个语句，为了防止覆盖源集群存储库的数据，将 “readonly”: true 添加到"settings" PUT 请求中，这样就只有一个集群具有对存储库的写入权限。

PUT /_snapshot/snapshot-repo-name
{"type": "s3","settings": {"bucket": "<bucket-name>","base_path": "<bucket-prefix>","readonly": true,

对于OpenSearch来说，还需要执行passrole，所以还需要添加role_arn这个字段，由于IAM:PassRole需要对HTTP 请求做signV4日签名，所以这部常常使用Postman来完成。把角色传递过去之后，接下来的快照还原操作就可以在OpenSearch Dashboard中进行操作了。

需要注意的是，需要在auth这里输入AccessKey，SecretKey，AWS Region，Service Name（es）来做SignV4的签名。

请求体如下：

{"type": "s3","settings": {"bucket": "<bucket-name>","base_path": "<bucket-prefix>","readonly": true,"role_arn": "arn:aws:iam::123456789012:role/OpenSearchSnapshotRole"}
}

• 查看所有注册的存储库：
  • GET _snapshot：这个命令返回所有已注册的快照存储库列表及其基本信息。

GET _snapshot

{"es_repository": {"type": "s3","settings": {"bucket": "your-s3-bucket-name","region": "your-s3-bucket-region"}}
}

• 查看特定存储库的详细信息：
  GET _snapshot/es_repository：这个命令返回名为es_repository的存储库的详细配置信息，包括存储桶名称、区域和其他设置。

GET _snapshot/es_repository

{"es_repository": {"type": "s3","settings": {"bucket": "your-s3-bucket-name","region": "your-s3-bucket-region","access_key": "your-access-key","secret_key": "your-secret-key"}}
}

• 查看特定存储库中的快照：
  GET _cat/snapshots/es_repository?v：这个命令返回es_repository存储库中的所有快照及其详细信息，包括快照ID、状态、开始时间、结束时间、持续时间、包含的索引数量、成功和失败的分片数量等。

GET _cat/snapshots/es_repository?v

id                     status start_epoch start_time end_epoch end_time duration indices successful_shards failed_shards total_shards
snapshot_1             SUCCESS 1628884800 08:00:00   1628888400 09:00:00 1h       3       10                0             10
snapshot_2             SUCCESS 1628971200 08:00:00   1628974800 09:00:00 1h       3       10                0             10

创建索引快照

# PUT _snapshot/my_repository/<my_snapshot_{now/d}>
PUT _snapshot/my_repository/my_snapshot
{"indices": "my-index,logs-my_app-default",
}

根据快照的大小不同，完成快照可能需要一些时间。默认情况下，create snapshot API 只会异步启动快照过程，该过程在后台运行。要更改为同步调用，可以将 wait_for_completion 查询参数设置为 true。

PUT _snapshot/my_repository/my_snapshot?wait_for_completion=true

另外还可以使用 clone snapshot API 克隆现有的快照。要监控当前正在运行的快照，可以使用带有 _current 请求路径参数的 get snapshot API。

GET _snapshot/my_repository/_current

如果要获取参与当前运行快照的每个分片的完整详细信息，可以使用 get snapshot status API。

GET _snapshot/_status

成功创建快照之后，就可以在S3上看到备份的数据块文件，这个是正确的快照层级结构：

需要注意的是， “base_path”: ""这里最好不要加/，虽然不影响同集群迁移，这个会为我们在不同厂商的搜索引擎中迁移遇到问题，可能是这样的，所以需要注意。所以在Open Search中还原Elasticsearch就遇到了这个问题：

{"error": {"root_cause": [{"type": "snapshot_missing_exception","reason": "[easy_repository:2/-jOQ0oucQDGF3hJMNz-vKQ] is missing"}],"type": "snapshot_missing_exception","reason": "[easy_repository:2/-jOQ0oucQDGF3hJMNz-vKQ] is missing","caused_by": {"type": "no_such_file_exception","reason": "Blob object [11111/indices/7fv2zAi4Rt203JfsczUrBg/meta-YGnzxZABRBxW-2vqcmci.dat] not found: The specified key does not exist. (Service: S3, Status Code: 404, Request ID: R71DDHX4XXM0434T, Extended Request ID: d9M/HWvPvMFdPhB6KX+wYCW3ZFqeFo9EoscWPkulOXWa+TnovAE5PlemtuVzKXjlC+rrgskXAus=)"}},"status": 404
}

恢复索引快照

POST _snapshot/my_repository/my_snapshot_2099.05.06/_restore
{"indices": "my-index,logs-my_app-default",
}

各个集群的还原

1. Elasticsearch 7.10.2 的快照可以还原到Easysearch和Amazon OpenSearch

2. 从Easysearch 1.8.2还原到Elasticsearch 7.10.2报错如下：

{"error": {"root_cause": [{"type": "snapshot_restore_exception","reason": "[s3_repository:1/a2qV4NYIReqvgW6BX_nxxw] cannot restore index [my_indexs] because it cannot be upgraded"}],"type": "snapshot_restore_exception","reason": "[s3_repository:1/a2qV4NYIReqvgW6BX_nxxw] cannot restore index [my_indexs] because it cannot be upgraded","caused_by": {"type": "illegal_state_exception","reason": "The index [[my_indexs/ALlTCIr0RJqtP06ouQmf0g]] was created with version [1.8.2] but the minimum compatible version is [6.0.0-beta1]. It should be re-indexed in Elasticsearch 6.x before upgrading to 7.10.2."}},"status": 500
}

3. 从Amazon OpenSearch 2.1.3还原到Elasticsearch 7.10.2报错如下（无论是否开启兼容模式）：

{"error": {"root_cause": [{"type": "snapshot_restore_exception","reason": "[aos:2/D-oyYSscSdCbZFcmPZa_yg] the snapshot was created with Elasticsearch version [36.34.78-beta2] which is higher than the version of this node [7.10.2]"}],"type": "snapshot_restore_exception","reason": "[aos:2/D-oyYSscSdCbZFcmPZa_yg] the snapshot was created with Elasticsearch version [36.34.78-beta2] which is higher than the version of this node [7.10.2]"},"status": 500
}

4. 从Easysearch 1.8.2还原到Amazon OpenSearch2.13报错如下（无论是否开启兼容模式）：

{"error": {"root_cause": [{"type": "snapshot_restore_exception","reason": "[easy_repository:2/LE18AWHlRJu9rpz9BJatUQ] cannot restore index [my_indexs] because it cannot be upgraded"}],"type": "snapshot_restore_exception","reason": "[easy_repository:2/LE18AWHlRJu9rpz9BJatUQ] cannot restore index [my_indexs] because it cannot be upgraded","caused_by": {"type": "illegal_state_exception","reason": "The index [[my_indexs/VHOo7yfDTRa48uhQvquFzQ]] was created with version [1.8.2] but the minimum compatible version is OpenSearch 1.0.0 (or Elasticsearch 7.0.0). It should be re-indexed in OpenSearch 1.x (or Elasticsearch 7.x) before upgrading to 2.13.0."}},"status": 500
}

以下是兼容性对比，每行第一列代表源集群，第一行代表目标集群：

快照兼容对比	Easysearch 1.8.2	Elasticsearch 7.10.2	OpenSearch 2.13
Easysearch 1.8.2	兼容	不兼容	不兼容
Elasticsearch 7.10.2	兼容	兼容	兼容
OpenSearch 2.13	不兼容	不兼容	兼容

Elasticsearch的兼容列表官方的列表如下：

参考文献

开始使用 Elastic Stack 和 Docker Compose：第 1 部分
https://www.elastic.co/cn/blog/getting-started-with-the-elastic-stack-and-docker-compose

Docker Compose 部署多节点Elasticsearch

https://www.elastic.co/guide/en/elasticsearch/reference/7.10/docker.html#docker-compose-file

repository-s3 教程

https://www.elastic.co/guide/en/elasticsearch/reference/8.14/repository-s3.html

https://www.elastic.co/guide/en/elasticsearch/plugins/7.10/repository-s3.html

snapshot-restore

https://www.elastic.co/guide/en/elasticsearch/reference/7.10/snapshot-restore.html

在亚马逊 OpenSearch 服务中创建索引快照

https://docs.amazonaws.cn/zh_cn/opensearch-service/latest/developerguide/managedomains-snapshots.html#managedomains-snapshot-restore

教程：迁移至 Amazon OpenSearch Service

https://docs.amazonaws.cn/zh_cn/opensearch-service/latest/developerguide/migration.html