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feat(xapi/VM_{checkpoint,snapshot}): HTTP sync hook (#6423)
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| # VM Sync Hook | ||
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| > This feature is currently _unstable_ and might change or be removed in the future. | ||
| > | ||
| > Feedbacks are very welcome on the [project bugtracker](https://github.com/vatesfr/xen-orchestra/issues). | ||
| > This feature is not currently supported for backups done with XO Proxy. | ||
| Before snapshotting (with or without memory, ie checkpoint), XO can notify the VM via an HTTP request. | ||
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| A typical use case is to make sure the VM is in a consistent state during the snapshot process, for instance by making sure database writes are flushed to the disk. | ||
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| > This request will only be sent if the VM is in a running state. | ||
| ## Configuration | ||
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| The feature is opt-in via a tag on the VM: `xo:notify-on-snapshot`. | ||
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| By default, it will be an HTTPS request on the port `1727`, on the first IP address reported by the VM. | ||
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| If the _VM Tools_ (i.e. management agent) are not installed on the VM or if you which to use another URL, you can specify this in the tag: `xo:notify-on-snapshot=<URL>`. | ||
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| To guarantee the request comes from XO, a secret must be provided in the `xo-server`'s (and `xo-proxy` if relevant) configuration: | ||
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| ```toml | ||
| [xapiOptions] | ||
| syncHookSecret = 'unique long string to ensure the request comes from XO' | ||
| ``` | ||
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| ## Specification | ||
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| XO will waits for the request to be answered before starting the snapshot, but will not wait longer than _1 minute_. | ||
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| If the request fails for any reason, XO will go ahead with snapshot immediately. | ||
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| ```http | ||
| GET /sync HTTP/1.1 | ||
| Authorization: Bearer dW5pcXVlIGxvbmcgc3RyaW5nIHRvIGVuc3VyZSB0aGUgcmVxdWVzdCBjb21lcyBmcm9tIFhP | ||
| ``` | ||
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| When the snapshot is finished, another request will be sent: | ||
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| ```http | ||
| GET /post-sync HTTP/1.1 | ||
| Authorization: Bearer dW5pcXVlIGxvbmcgc3RyaW5nIHRvIGVuc3VyZSB0aGUgcmVxdWVzdCBjb21lcyBmcm9tIFhP | ||
| ``` | ||
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| The created snapshot will have the special `xo:synced` tag set to make it identifiable. | ||
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| ## Example server in Node | ||
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| `index.cjs`: | ||
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| ```js | ||
| const exec = require('node:util').promisify(require('node:child_process').execFile) | ||
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| const SECRET = 'unique long string to ensure the request comes from XO' | ||
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| const HANDLERS = { | ||
| __proto__: null, | ||
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| async '/sync'() { | ||
| // actions to do before the VM is snapshotted | ||
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| // in this example, the Linux command `sync` is called: | ||
| await exec('sync') | ||
| }, | ||
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| async '/post-sync'() { | ||
| // actions to do after the VM is snapshotted | ||
| }, | ||
| } | ||
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| function checkAuthorization(req) { | ||
| try { | ||
| const { authorization } = req.headers | ||
| if (authorization !== undefined) { | ||
| const parts = authorization.split(' ') | ||
| if (parts.length >= 1 && parts[0].toLowerCase() === 'bearer') { | ||
| return Buffer.from(parts[1], 'base64').toString() === SECRET | ||
| } | ||
| } | ||
| } catch (error) { | ||
| console.warn('checkAuthorization', error) | ||
| } | ||
| return false | ||
| } | ||
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| async function main() { | ||
| // generate a self-signed certificate | ||
| const [, key, cert] = | ||
| /^(-----BEGIN PRIVATE KEY-----.+-----END PRIVATE KEY-----\n)(-----BEGIN CERTIFICATE-----.+-----END CERTIFICATE-----\n)$/s.exec( | ||
| (await exec('openssl', ['req', '-batch', '-new', '-x509', '-nodes', '-newkey', 'rsa:2048', '-keyout', '-'])) | ||
| .stdout | ||
| ) | ||
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| const server = require('node:https').createServer({ cert, key }, async function onRequest(req, res) { | ||
| if (!checkAuthorization(req)) { | ||
| res.statusCode = 403 | ||
| return res.end('Forbidden') | ||
| } | ||
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| const handler = HANDLERS[req.url.split('?')[0]] | ||
| if (handler === undefined || req.method !== 'GET') { | ||
| res.statusCode = 404 | ||
| return res.end('Not Found') | ||
| } | ||
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| try { | ||
| await handler() | ||
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| res.statusCode = 200 | ||
| res.end('Ok') | ||
| } catch (error) { | ||
| console.warn(error) | ||
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| if (!res.headersSent) { | ||
| res.statusCode = 500 | ||
| res.write('Internal Error') | ||
| } | ||
| res.end() | ||
| } | ||
| }) | ||
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| await new Promise((resolve, reject) => { | ||
| server.on('close', resolve).on('error', reject).listen(1727) | ||
| }) | ||
| } | ||
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| main().catch(console.warn) | ||
| ``` |
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