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https://github.com/scaleoutsean/longhorny
Longhorny is a Python script for configuration and storage replication management of SolidFire cluster and volume pairs
https://github.com/scaleoutsean/longhorny
async hyper-v kubernetes netapp proxmox replication solidfire storage sync trident vmware
Last synced: 20 days ago
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Longhorny is a Python script for configuration and storage replication management of SolidFire cluster and volume pairs
- Host: GitHub
- URL: https://github.com/scaleoutsean/longhorny
- Owner: scaleoutsean
- License: apache-2.0
- Created: 2024-06-09T17:59:34.000Z (27 days ago)
- Default Branch: master
- Last Pushed: 2024-06-15T18:04:30.000Z (21 days ago)
- Last Synced: 2024-06-15T19:23:31.362Z (21 days ago)
- Topics: async, hyper-v, kubernetes, netapp, proxmox, replication, solidfire, storage, sync, trident, vmware
- Language: Python
- Homepage:
- Size: 70.3 KB
- Stars: 1
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Lists
- awesome-solidfire - Longhorny - based replication management. It supports only 1-to-1 cluster and volume relationships. It may be used to pair/unpair clusters, pair/unpair volumes, change direction of replication, and more. Language: Python 3. There's a short [demo](https://rumble.com/v513r8w-project-longhorny.html) (5m11s) if you want to see the main features (Resources and Solutions / Backup, Restore, DR and BC (Site Failover))
README
- [Longhorny](#longhorny)
- [What can it do?](#what-can-it-do)
- [What you **need to know**](#what-you-need-to-know)
- [Production use](#production-use)
- [Objectives](#objectives)
- [Requirements](#requirements)
- [How to run](#how-to-run)
- [Optional data](#optional-data)
- [Cluster-scope actions](#cluster-scope-actions)
- [Volume-scope actions](#volume-scope-actions)
- [Site-scope actions](#site-scope-actions)
- [Command examples](#command-examples)
- [Some --data examples](#some---data-examples)
- [Cluster](#cluster)
- [Volume](#volume)
- [Miscellaneous stuff](#miscellaneous-stuff)
- [PowerShell to help](#powershell-to-help)
- [Site object (SRC, DST) and Longhorny CLI arguments](#site-object-src-dst-and-longhorny-cli-arguments)
- [Volume objects on SolidFire](#volume-objects-on-solidfire)
- [Testing and development environment](#testing-and-development-environment)
- [Note on SolidFire SDK for Python](#note-on-solidfire-sdk-for-python)
- [Random development notes](#random-development-notes)
# Longhorny
Longhorny is a CLI tool for SolidFire storage replication-related management.
It grew out of my need to list cluster and volume pairs - which is something I've desired to add to [SFC v2](https://github.com/solidfire/sfc) - and other necessary and unnecessary stuff that was added as I got carried away.
The code in this repository is permissively licensed, so feel free to use and modify within the terms of the permissive Apache License 2.0. With a bit of extra work you could use the elements of this script to modify it for multi-relationship clusters or other purposes (e.g. send these to Splunk, etc.).
## What can it do?
Quite a few things and most of them sort of work. Examples:
- Pair two clusters for replication. Also list and unpair (if they have no paired volumes between them).
- Pair one or more volume pairs for replication. Also list and unpair (one pair at a time).
- Find mismatched volume pairs.
- Take a snapshot of all volumes at the source.
- Reverse replication direction for all paired volumes.
- Change replication mode for all or selected volumes (at the source).
- Prime the remote site using a list of volumes from the source site.
Each of these actions takes 1-2 seconds, so if you have a tidy and organized environment that isn't yet automated, Longhorny can hopefully save you some time.
With Longhorny you can create 100 volumes at the remote site and set up volume pairing relationships in 10 seconds, for example. If you have 2 SolidFire clusters you may have done that, but if you stand-up new Kubernetes or Hyper-V clusters often, maybe you'd like to use some help.
The same goes for site failover and failback. 10 seconds to failover, 10 seconds to failback (sync-back time is change- and network-dependent, but if not much has changed at the remote site, you may be able to sync back in 5 minutes).
If you don't want to read the whole page:
- There's a minimalistic tutorial in [tutorial.md](./tutorial.md)
- If you prefer videos, there's a [5m11s video](https://rumble.com/v513r8w-project-longhorny.html) with main features
## What you **need to know**
**The recommended action is `--list`**, while the rest may or may not work for you. While basic care has been taken to avoid creating problems, I am the only person who wrote and tested this script so far, so I wouldn't run configuration-modifying actions against production clusters without prior testing. I myself only need the `list` action - okay, I need `mismatched` and `report` actions as well - while the others were added as convenience but may not be rock-solid.
Longhorny is is **limited to supporting a simple 1-to-1, exclusively paired clusters**. One SRC cluster, one DST cluster, one pairing. It is expected to reject actions when it spots either the source or the destination has another cluster relationship, so in order to work with multiple clusters you'd have to modify the code.
Longhorny presently **requires that API access to both sites be available**. If one site is down or unreachable, you may use [PowerShell commands](#powershell-to-help) to quickly force changes of the surviving site. Of course, you may also modify the source code to not attempt connecting to the remote SolidFire cluster and use Python functions in the code on only one side.
Currently Longhorny is not opinionated on **volume ownership**, to make experimentation easy and possible out-of-box. Since the administrator can't control account IDs, it's expected that each site will have a different account ID. But, what happens if we have multiple application clusters and need to use replicate volumes that belong to multiple accounts? That's common and Longhorny doesn't prevent you from doing that: if you tell it to pair volumes SRC/10 and DST/20, it'll do it. Or if you tell it to prime SRC Vol ID 100 that belongs to account SRC/1 for a destination account ID 7 and another from SRC/2 for DST/8, it will do that too. Then you'll have paired volumes owned by multiple tenants. So far, so good. But when you reverse replication or take a "site" snapshot, all paired volumes will be impacted as Longhorny doesn't distinguish between accounts, volume naming patterns. It could, but it's a slippery slope for a script of this scope, considering the risk of having some workloads on site A, others on site B, and failover done based on several criteria (if account ID = 7 and volume name like "pvc-"). It can be done, of course, but I'd like to see at least 1-2 other contributors so that I'm not the only person who writes and tests such workflows. So at that point Longhorny can't help you perform account scoped actions: you'd have to improve it to be able to do that, or perform such actions outside of Longhorny.
## Production use
Apart from `--list` and other "no modifications" actions, I wouldn't just download Longhorny and use it in a production environment. But that doesn't mean it couldn't be used without issues. I'd recommend the following as a path to production use:
- DIY users:
- download SolidFire Demo VM (see [testing and development](#testing-and-development-environment))
- [RTFM](https://docs.netapp.com/us-en/element-software/)
- read [NetApp Element Software Remote Replication - Feature Description and Deployment Guide (TR-4741)](https://www.netapp.com/media/10607-tr4741.pdf)
- find a small and necessary scope, test, and see if it works for you. Modify or outsource if you can't do it on your own
- Enterprise: same as DIY, plus you can pay your systems integrator or NetApp to do that work for you
## Objectives
Longhorny's objective is to provide visibility into replicated SolidFire cluster and volume pairs - really just `list`-like actions, so that I can gather and send stuff to [SolidFire Collector](https://github.com/scaleoutsean/sfc) for SolidFire admins' viewing pleasure.
Everything beyond that is extra (and maybe nice to have, assuming it works), but that's also what makes it deserve a repository of its own as it has other uses. So far I've already done more than I expected and I decided to publish the script to see if anyone has uses for other actions and/or wants to contribute.
I am not committed to expanding or improving Longhorny but I may do it if I come up with new ideas for it. For example, recently I wrote a script for mapping Kubernetes/Trident volumes to SolidFire volume IDs (available in [Awesome SolidFire](https://github.com/scaleoutsean/awesome-solidfire)), so the output of that script (i.e. a list of a Kubernetes cluster's volume IDs) could be used as the input to Longhorny. Are you thinking what I'm thinking?
That, by the way, is the main reason why Longhorny doesn't output pretty tables. It's not an end in itself. Even now, most of Longhorny's output is Python lists or dictionaries that can be assigned to variables in Python shell for additional follow-up processing, but its code can be easily reused and incorporated in other scripts.
## Requirements
- SolidFire >=12.3 (also Element SDS, NetApp HCI storage)
- Python 3.10 (higher may 3.1x versions may be fine)
- SolidFire SDK Python >12.3 (see [notes on that](#note-on-solidfire-sdk-for-python))
## How to run
First we need to select one of the scopes (cluster, volume, site) and then one of the actions available in the scope (further below). Among the positional arguments below, `src` and `dst` are usually required for most actions.
```sh
~$ longhorny -h
usage: longhorny.py [-h] [--dry DRY] [--tlsv TLSV] [--src SRC] [--dst DST] {cluster,volume,site} ...
positional arguments:
{cluster,volume,site}
options:
-h, --help show this help message and exit
--dry DRY Dry run mode. It is NOT available for all actions, so don not make the assumption that with --dry any action will be zero impact.
Enable with --dry on. Default: off.
--tlsv TLSV Accept only verifiable TLS certificate when working with SolidFire cluster(s) with --tlsv 1. Default: 0.
--src SRC Source cluster: MVIP, username, password as a dictionary in Bash string representation: --src "{ 'mvip': '10.1.1.1',
'username':'admin', 'password':'*'}".
--dst DST Destination cluster: MVIP, username, password as a dictionary in Bash string representation: --src "{ 'mvip': '10.2.2.2',
'username':'admin', 'password':'*'}".
```
Note that `--dry` **is ignored** by many operations/actions. For example, every `--list` action ignores it. For more on `--dry` see the examples in which you're interested. If I remember correctly initially there are three of the more dangerous actions that consider `--dry on`, but additional actions may be made aware of it. Don't assume it's been implemented for everything that may be dangerous is all I'm saying. You may check the code and add it by yourself.
There are `cluster`-, `volume`-, and `site`-level actions. For most of them you **must** provide a source (`--src`) and a destination (`--dst`). In some cases it is important that `--src` is really the source (i.e. the cluster where replication "originates" and where the volumes are read-write), so I encourage you to always verify that assignment.
If your "SolidFires" have snake-oil TLS certificates, just omit `tlsv` (TLS verification) to leave it as-is (to accept snake-oil TLS certificates). Obviously, that's not what you should do, but I know most will. If you want to upload a valid TLS certificate to SolidFire clusters, see [this](https://scaleoutsean.github.io/2020/11/24/scary-bs-postman-ssl-certs.html) or RTFM. It takes 5 minutes to do it and then you can use `--tlsv 1` and avoid MITM attacks.
### Optional data
Some volume and site actions require or may accept `--data DATA`. Example:
```sh
longhorny --src SRC --dst volume --list --data "135,230"
```
Without `--data`, all paired volumes get listed. If you have dozens and want to check just one pair, then that's the way
Data format for `DATA` varies depending on action, but scope help (`volume -h`, `site -h`) has examples whenever `--data` argument is available or required. See more in [Command examples](#command-examples).
### Cluster-scope actions
```sh
~$ longhorny cluster -h
usage: longhorny.py cluster [-h] [--data DATA] (--list | --pair | --unpair)
options:
-h, --help show this help message and exit
--data DATA Optional data input for selected cluster actions (where indicated in site action help). Not all cluster actions require or accept it.
--list List cluster pairing between SRC and DST clusters. Requires paired SRC and DST clusters. Ignores --data because each cluster params are
always available from --src, --dst.
--pair Pair SRC and DST for replication. Requires SRC and DST without existing pairing relationships. Multi-relationships are not supported.
Ignores --data.
--unpair Unpair SRC and DST clusters. Requires SRC and DST in exclusive, mutual pairing relationship and no volume pairings. Ignores --data.
```
`list` lists paired clusters. Harmless.
`pair` changes cluster configuration on both sides: SRC gets paired with DST. No data is destroyed, but if this action succeeds SRC and DST (clusters) will be in a paired relationship.
`unpair` does the opposite from `pair`. It also changes cluster configuration on both sides (by removing the sole cluster pairing relationship), so be very careful if you have replication relationships set up - you shouldn't be able to `unpair` if there is at least one valid volumes replication pair, but be careful nevertheless.
### Volume-scope actions
```sh
~$ longhorny volume -h
usage: longhorny.py volume [-h] [--data DATA]
(--list | --pair | --unpair | --prime-dst | --mismatched | --reverse | --snapshot | --set-mode | --set-status | --report)
options:
-h, --help show this help message and exit
--data DATA Optional data input for selected volume actions (where indicated in volume action help). Not all volume actions require or accept it.
--list List volumes correctly paired for replication between SRC and DST cluster. Requires paired SRC and DST clusters. Optional --data argument
lists specific volume pair(s).
--pair Pair volumes for Async replication between SRC and DST clusters. Takes a semicolon-delimited list of volume IDs from SRC and DST in --data
(e.g. --data "111,555;112,600"). Requires paired SRC and DST clusters.
--unpair Unpair volumes paired for replication between SRC and DST clusters. Requires paired SRC and DST clusters and at least one volume pairing
relationship. Takes --data argument with only one pair at a time. Ex: --data "111,555".
--prime-dst Prepare DST cluster for replication by creating volumes from SRC. Creates volumes with identical properties (name, size, etc.) on DST. .
Takes one 2-element list of account IDs (SRC account ID,DST account ID) and another of volume IDs on SRC. Ex: --data "1,22;444,555".
--mismatched Check for and report any volumes in asymmetric pair relationships (one-sided and volume size mismatch). Requires paired SRC and DST
clusters. Ignores --data.
--reverse Reverse direction of volume replication. You should stop workloads using current SRC (readWrite) volumes before using this action as SRC
side will be flipped to replicationTarget and SRC iSCSI clients disconnected. Ignores --data.
--snapshot Take crash-consistent snapshot of all volumes paired for replication at SRC. Use --data to specify non-default retention (1-720) in hours
and snapshot name (<16b string). Ex: --data "24;apple". Default: "168;long168h-snap".
--set-mode Change replication mode on specific SRC volumes ID(s) in active replication relationship to DST. Mode: Sync, Async, SnapshotsOnly. Example:
--data "SnapshotsOnly;101,102,103"). Requires existing cluster and volume pairing relationships between SRC and DST. WARNING: SnapshotsOnly
replicates nothing if no snapshots are enabled for remote replication (create_snapshot(enable_remote_replication=True)).
--set-status Set all SRC relationships to resume or pause state in --data. Ex: --data "pause" sets all SRC volume relationships to manual pause. --data
"resume" resumes paused replication at SRC. (WARNING: applies to SRC, not DST).
--report TODO: Report volume pairing relationships between SRC and DST, including mismatched and bidirectional. Requires paired SRC and DST
clusters. Optional --data arguments: all, SRC, DST (default: all).
```
Yeah, I know, I got carried away.
Ok, so `list` does the same thing as it for clusters - it also lists, only volumes. Harmless. `report`, below, is equally harmless.
`pair` pairs volumes. This may be disruptive! Say you have a workload on DST using Volume ID 52. Now you pair Volume ID 3 from SRC with Volume ID 52 from DST with `--pair "3,52"` and Longhorny yanks the volume from your workload at the destination site making it read-only (i.e. replicationTarget, which means read-only)! Yikes! Except Longhorny doesn't do that - it will reject to pair two volumes with the identical access property (readWrite, in this case). You'd have to set Volume ID 52 at the destination to replicationTarget before `pair` with DST/52 could do anything for you.
`unpair` does the opposite from `pair`. Longhorny **cannot know if the volumes you aim to unpair are in use**. To minimize the idiotic moves (present parties excluded), Longhorny does not accept more than one unpair pair (?) at a time. `--data "1,51;2,52 volume --pair` will work, but `--data "1,51;2,52 volume --unpair` shouldn't. But you can create a Bash loop and run Longhorny if you want to unpair many pairs at once. Unpaired volumes aren't "deleted" or anything like that, they're just unpaired.
`prime-dst` creates *new* volumes, but is a low action. As the help string says, its `DATA` format is different from regular `volume`-scope actions:
- The first element is a pair of integers: Account ID at SRC and Account ID at DST, e.g. `10,20;`
- The second is a list of integers, e.g. `101,102,103,104`: volume IDs owned by the first Account ID 10 from `--src` site
Therefore, `--src SRC --dst DST --data "10,20;101,102,103,104" volume --prime-dst` would take volumes 101-104 belonging to the account ID 10 at the SRC site and create very similar (apart from volume IDs, for example) volumes for the account ID 20 at the DST site. Then we could prepare those new volumes for pairing so that the source site's volume IDs 101-104 can be paired with (say) the destination site's volume IDs 40-43 using `--data "101,40;102,41;103,42;104,43 volume --pair`. Diff-priming the destination would be useful when a bunch of volumes are added to the source side, but I don't know if anyone has that problem so I haven't attempted to solve it.
Note that `prime-dst` changes the new volumes at the destination to `replicationTarget`, based on the logic that most users would want to immediately pair them. If you need to flip them to readWrite mode (and later back, for pairing), see the PowerShell commands below.
`mismatched` aims to find mismatched volumes on both the source and destination cluster. Maybe one site's volume is bigger, SRC/101 is paired to DST/40, but DST/40 isn't paired to SRC/101, etc. The idea is if you have a bunch of volumes and things seem out of control, maybe `mismatched` can save you troubleshooting time.
Can Longhorny help you recover from a mismatch? It could, but I don't like the idea of "helping" you change the state of a bunch of mismatched volumes at once. See the example of a two-side mismatch further below, and imagine you have dozens. Before fixing that, one should ask how did they even get in that situation and what else might be wrong. To recover from a mismatch, the remaining one-sided relationship must be deleted, and only then a new one created, so as you can imagine it's a sensitive operation when guessing is involved.
A simple way to recover is delete the one-sided relationships reported by `--mismatched` (they can't be "restored" anyway) and use the volume IDs to create new ones from the side specified in `--src`. (See the example in examples section.)
`reverse` changes the direction of replication, so obviously this one is **dangerous**. If SRC is replicationTarget and DST is readWrite (that is, replication flows DST=>SRC), `reverse` flips that so that replication starts flowing SRC=>DST. This **may cause** unplanned downtime if you're not careful because flipping a volume from readWrite to replicationTarget disconnects all iSCSI clients, so if you issue this against the wrong `--src` and `--dst`, you may start getting calls, alerts and emails soon after that.
I think `volume --reverse`, as currently implemented, will really work only for DR/BC rehearsals when you have to run it once to try DST cluster and then reverse again to return to SRC as "production". Why is there no ability to failover selected volumes?
- If you need to failover a handful of volumes no matter where the rest of them run, that's just 5 lines of PowerShell
- It's easy to take a list of IDs and failover just those volumes, but the next problem becomes when you want to flip the rest of them (or flip those back)? Who's going to figure out what should be replicated where? I think this can get messy quickly and at least with my level of skills (i.e. not high) I don't think I'd want to take on that task
- A simpler, safer and less ambitious idea is to use a smaller, dedicated script for dealing with groups of volumes. If you have 12 Kubernetes clusters and each Kubernetes admin runs their own script with their SolidFire storage account ID in `--data "${ACCOUNT_ID}"`, it's fine to offload all pairing and flipping to them. But if you do that then the SolidFire storage admin should in my opinion go into "100% read-only" mode and just use `list` and `report` send output to something like SolidFire Collector and observe in Grafana what the Kubernetes guys are up to
`snapshot` does what you think it does - it takes a snapshot to minimize potential damage before one makes a stupid or desperate move. Note that Longhorny never deletes volumes, so snapshots are safe from whatever you do in Longhorny. But if you mix in other code that deletes volumes or worse, snapshots may still be destroyed together with volumes by that other code, in which case we could take a site-replicating snapshot (Longhorny doesn't do that, as it could cause a surge of data replication activity, then we may need to wait until that's done (assuming DST is available at all), etc. so ... no).
Anyway, `DATA` setting is optional for `snapshot` action and by default snapshot of all local volumes is taken so that it expires in 168h (1 week). You may override that with something like `--data "72;mysnap"` (expiration: `72` hours; snapshot name `mysnap`). And they're taken individually, so if you need to take some snapshots of Consistency Groups, do it separately if you can't stop those applications prior to running Longhorny's `snapshot` action. I've been thinking about adding additional options but --data "..." isn't very good and would need a rewrite to make those options action-specific which would take more work, so not for time being.
`set-mode` helps you change the default (Async) to other (Sync, or SnapshotOnly) mode. SolidFire's volume-pairing API method has Async hard-coded in it, so once remote pairing has been done you may use `set-mode` to change to another and back. RTFM and the TR linked at the top for additional details.
`set-status` pauses or resumes replication. If replication is going from DST=>SRC (i.e. DST side is read-write) and you need to pause replication at source if replication you would run `--src DST --dst SRC --data "pause" volume --set-status` (because DST is the source). That would put all volumes in manually paused state. Similarly, `--data "resume"` would resume. If you wanted to pause the destination (in this case, SRC) you'd try `--src SRC --data "pause" volume --set-status`.
TODO: `report` is like `list`, a completely read-only action, except that it its result is slightly different. "Slightly???" Why do we need yet another action for that? List *actually* lists volume pairing relationships, whereas `report` reports on volume pairings, and if I wanted to see what's misconfigured or broken, `report` may give me that whereas `list` may not. Given that both INs and OUTs are very different, I don't want to bloat `list` to 500 lines of code. I'm still thinking what I'd like to see and how it should be shown.
### Site-scope actions
**CAUTION:** these may be **dangerous**. I'm not sure there's a strong case for them, so they are work-in-progress and may not care about `--dry on`. I would advise against using them without prior testing of the exact scenarios you aim to deal with or visual code inspection.
```sh
~$ longhorny site -h
usage: longhorny.py site [-h] [--data DATA] (--detach-site | --set-access)
options:
-h, --help show this help message and exit
--data DATA Optional data input for selected site actions (where indicated in site action help). Not all site actions require or accept it.
--detach-site Remove replication relationships on SRC cluster for the purpose of taking over when DST is unreachable. Requires paired SRC and DST
clusters. WARNING: there is no way to re-attach. Disconnected cluster- and volume-relationships need to be removed and re-created.
--set-access Change access property on all SRC volumes with replication relationship to DST. Options: readWrite, replicationTarget (ex: --data
"readWrite"). Requires existing cluster and volume pairing relationships between SRC and DST. WARNING: may stop/interrupt DST->SRC or
SRC->DST replication.
```
TODO: `detach-site` attempts to remove all replication configuration from --src (`--src SRC`).
`set-access` changes access mode on volumes paired for replication **at the source**. To change access mode for the other site, use `--src OTHER`.
When I started working on site actions I thought they may be useful, but later I realized it can be a slippery slope. For example, the remote site DST may or may not be offline. If it's offline (or for whatever reason unreachable), site actions will not be able to work as they attempt to connect to `--dst` as well which means actions may not be useful for their main use case.
So, as-is, they can't work without Longhorny connecting to DST although `site` actions don't *do* anything to `--dst` site. But `site` actions *may* need to get some information from DST, so the next question is do we want to change the requirement for `--src --dst` when an action is a site-level action and maybe work without some information we need or limit ourselves to the situation where both sites are reachable. For time being I chose to leave the `--dst` requirement in place. Remember that even if you don't supply `--dst DST`, Longhorny may configure `--dst` with `DST` from your OS environment if you've set it.
## Command examples
If you're not sure how something works, I may post all examples and details in a demo video which I'll link from here as well.
But more importantly, I wouldn't suggest to anyone to use Longhorny on real clusters without having own VM-based sandbox where experimentation may be done freely.
### Some --data examples
```sh
~$ volume --src SRC --dst DST --list --data "111,222" # list only SRC/DST pair 111,222
~$ volume --src SRC --dst DST --prime-dst --data "1,10;333,444" # use SRC-side Account ID 1's volumes 333 and 444 as templates for priming Account 10 on DST site
~$ volume --src SRC --dst DST --snapshot --data "1;test" # take a snapshot of all paired SRC volumes, retain for 1 hour, and name each "test"
```
### Cluster
Checks if SRC and DST are paired and if so, outputs their pairing configuration.
**Pair clusters** without offering the passwords, so that you get prompted to enter them:
```sh
~$ ./longhorny.py --src "{ 'mvip': '192.168.1.30', 'username':'admin', 'password':''}" --dst "{ 'mvip': '192.168.105.32', 'username':'admin', 'password':''}" cluster --pair
Enter password for SRC cluster:
Enter password for DST cluster:
```
See [towards the bottom](#site-object-src-dst-and-longhorny-cli-arguments) for other ways to provide `--src` and `--dst` values to Longhorny.
**List** cluster pairing, if any:
```sh
longhorny cluster --list
```
Output:
```raw
{'PROD': [{'clusterName': 'DR',
'clusterPairID': 55,
'clusterPairUUID': 'b9322478-3779-4cd3-908f-2a48f22202fe',
'clusterUUID': 'bgn0',
'latency': 1,
'mvip': '192.168.105.32',
'status': 'Connected',
'version': '12.5.0.897'}],
'DR': [{'clusterName': 'PROD',
'clusterPairID': 61,
'clusterPairUUID': 'b9322478-3779-4cd3-908f-2a48f22202fe',
'clusterUUID': 'wcwb',
'latency': 1,
'mvip': '192.168.1.30',
'status': 'Connected',
'version': '12.5.0.897'}]}
```
What's what? Apart from the very obvious:
- `clusterPairUUID` is the unique ID of the pairing relationship, specific to this and only this pairing relationship. It's expected to be the same for each cluster
- `latency` (ms) - this guides us in determining appropriate replication mode (e.g. 1ms is good for Sync, 10ms is not)
- `status` - `connected` is good, `connecting` is good for the first 5 seconds and after that may indicate firewall or other network problems (see the NetApp TR at the top, RTFM, etc.)
Longhorny lists cluster pairing only for SRC and DST and only if SRC and DST both have one and only one relationship that is mutual and completely configured (as in, not "pending", etc.).
If nothing is returned, then they're not properly paired. If you try and set it up with `cluster --pair` or from the Web UI both of those can work but only if neither SRC and DST have any other relationships.
Longhorny can't get into a situation where SRC or DST get paired when either side has existing relationship(s). You *can* set those up later on your own, but then `cluster --list` and other commands may stop working because it tries to detect, and reject to do anything, in such situations.
Longhorny won't pair SRC and DST if either SRC or DST has anything but 0 existing cluster relationships, or if SolidFire rejects it (due to network problems, different major version of Element OS, etc.). Review the error, SolidFire KBs, docs, etc. and try to fix it.
**Unpair clusters** works regardless which site is provided as the source and which as the destination, as it checks both sides to make sure there's one and only one relationship on each.
```sh
longhorny --src SRC --dst DST cluster --unpair
```
Longhorny's `cluster --unpair` won't unpair SRC and/or DST cluster if:
- either SRC or DST has anything but one and only one cluster pairing and the paired party is the other cluster
- Example 1: cluster DST is paired with cluster SOME - fail (no can do)
- Example 2: clusters SRC and DST have a pending peering relationship: fail. Delete that pending relationship and re-try
- there are existing volume replication pairs
- Longhorny fails for any as we want to avoid accidental unpairing of relationships with some other cluster involved
## Volume
`volume --list` does what you think it does: given a SRC and a DST cluster, it checks if cluster pairing is in place and spits out a list of properly paired volumes between them. Remember, there's no "direction" in this configuration: SolidFire replication is readWrite to replicationTarget, so to know what's replicated to what, you won't find that in this output here. This lists volume pairing relationships (and that's why I'm thinking to add `volume report` action).
```raw
[{'clusterPairID': 55,
'localVolumeID': 158,
'localVolumeName': 'test',
'remoteVolumeName': 'testr',
'remoteReplicationMode': 'Async',
'remoteReplicationPauseLimit': 3145728000,
'remoteReplicationStateSnapshots': 'PausedDisconnected',
'remoteReplicationState': 'PausedDisconnected',
'remoteVolumeID': 260,
'volumePairUUID': '44df1d5e-8694-4ed1-bdaf-fa773fb9b165'},
{'clusterPairID': 55,
'localVolumeID': 164,
'localVolumeName': 'srcorig',
'remoteVolumeName': 'dstorig',
'remoteReplicationMode': 'Async',
'remoteReplicationPauseLimit': 3145728000,
'remoteReplicationStateSnapshots': 'PausedDisconnected',
'remoteReplicationState': 'PausedDisconnected',
'remoteVolumeID': 391,
'volumePairUUID': '3406d44a-081c-4841-8838-46f14feaac5e'}]
```
Both volume relationships are Async, the pairs are `[(158,260),(164,391)]`. If we wanted to `pair` these we'd do `--data "158,260;164,391"`.
**Pair volumes** for replication. To replicate volume IDs 1 and 2 from site SRC to site DST, you need DST volumes to exist prior to running this action and they must have some identical properties and one different property:
- Same volume size in bytes (`volume['totalSize']`)
- Same volume block size (4096 or 512e) (`volume['blockSize']`)
- *Opposite* access mode (that is, while the source side must be `readWrite`, the destination must be `replicationTarget`)
You may also want the same QoS settings or QoS Policy contents, but that's optional.
```sh
longhorny --src SRC --dst DST volume --pair --data "1,44;2,45"
```
Output of `volume --pair` is the same as `volume --list` - it returns all paired volumes if it succeeds. If it fails, it tells you what went wrong.
Another reminder about the direction of replication: volume IDs 1 and 2 exist at SRC so assumed that `--src` is readWrite. The direction is decided by access mode (goes from readWrite to replicationTarget volume), but Longhorny considers IDs in the order of SRC, DST. That is, if both sites have volumes 1, 2, 44, and 45, then the direction would flow from the site specified with `--src`.
No account ID, QoS settings or other non-essential details are asked for because in this action the destination volumes must already exist and this Longhorny `volume` level operation does not touch storage account assignment or modify any volume settings except the replication-related settings (pair, unpair, reverse, etc.). Only `--prime-dst` can create new volumes, but even that action does not delete volumes.
If there's no cluster peering between SRC and DST cluster, volume pairing operation will fail immediately. SolidFire requires cluster peering to be in place before volume pairs can be configured.
**Unpair** with dry run ON:
```sh
~$ longhorny.py --dry on volume --unpair --data "163,390"
VOLUMES REPORT FOR SPECIFIED VOLUME PAIR(S): [(163, 390)]
[{'clusterPairID': 55,
'localVolumeID': 163,
'localVolumeName': 'srcvol',
'remoteVolumeName': 'dstvol',
'remoteReplicationMode': 'SnapshotsOnly',
'remoteReplicationPauseLimit': 3145728000,
'remoteReplicationStateSnapshots': 'PausedDisconnected',
'remoteReplicationState': 'PausedDisconnected',
'remoteVolumeID': 390,
'volumePairUUID': '9e626d68-1037-459c-b097-360433f6e65b'}]
===> Dry run: replication relationship for volume IDs that would be removed (SRC, DST): [(163, 390)]
```
**Unpair without dry run** (default) is almost identical. One volume pair *at most* can be unpaired at a time, in order to prevent disasters due to typos.
```raw
VOLUMES REPORT FOR SPECIFIED VOLUME PAIR(S): [(163, 390)]
[{'clusterPairID': 55,
'localVolumeID': 163,
'localVolumeName': 'srcvol',
'remoteVolumeName': 'dstvol',
'remoteReplicationMode': 'SnapshotsOnly',
'remoteReplicationPauseLimit': 3145728000,
'remoteReplicationStateSnapshots': 'PausedDisconnected',
'remoteReplicationState': 'PausedDisconnected',
'remoteVolumeID': 390,
'volumePairUUID': '9e626d68-1037-459c-b097-360433f6e65b'}]
WARNING:root:Dry run in unpair action is OFF. Value: off
WARNING:root:Volume IDs unpaired at SRC/DST: {'local': 163, 'remote': 390}
```
**Reverse replication direction** with `--reverse` action. There's a 15 second count-down before direction change.
**Important assumption**: in this scenario I assume the entire cluster of something (Hyper-V, etc) needs to be made active at the destination and **all paired volumes need to be reversed in terms of replication direction** to be made available for read-write access. There's no attempt to take a list of volume IDs, some account ID or whatever and failover just two volumes for one database or an individual account's volumes (see [PowerShell](#powershell-to-help) examples for these "small scope" actions). Don't use this action if you want to failover just some of the paired volumes.
If you change access status to replicationTarget all existing iSCSI connections to the volume are instantly terminated. You should stop workloads on the site that needs to change to replicationTarget mode or they'll be disconnected anyway (which is disruptive to clients using the volume(s) and may lead to unplanned downtime or even data loss). Also expect some routine OS-level errors on the host side if they remain logged into targets switching to replicationTarget access mode, but those can likely be ignored as long as volumes going to replicationTarget mode have been dismounted (although they may still be logged on by the host).
I assume that in normal life if replication is flowing from `--src SRC` to `--dst DST`, no one will try reverse the direction *unless* they can't access the source site. So as far as the risk of reversing in the wrong direction is concerned, it's rather small: if the source site goes down, you won't be able to "reverse" anyway because Longhorny won't be able to connect to that site to coordinate. You'll have to do this manually, by selecting all volumes set to replicate from SRC to DST on the destination cluster, pause that replication, and switch the DST side to readWrite. In other words, unilaterally change the surviving site to read-write mode.
**Prime destination volumes** when you're setting up a DR site and have many volumes to create at the destination at once.
- Pair clusters if they aren't paired
- Prime the DST cluster
- Pair a bunch of volumes
Priming does the following:
- List all SRC volumes which we intend to replicate
- Get the volumes' properties and recreate the same on the DST cluster for provided Account ID (that exists at the destination)
Priming requires two mandatory and one optional input:
- (required) pair of accounts IDs; one from the source (to whom the volumes belong) and one from the destination, to whom the new volumes should be assigned
- (required) list of volume IDs from the source - their properties will be used to create volumes at the remote site
```sh
~$ longhorny --src SRC --dst DST volume --prime-dst --data "1,5;640,641,642"
```
The above uses volumes 640-642 from the source site's Account ID 1 as templates for three new volumes at the remote site. The destination account ID is 5.
Find **mismatched** volumes with `volume --mismatched`. It gives a view from the source vs. a view from the destination and - if the views aren't symmetric - a warning that makes it easier to figure it out may be logged at the end.
```raw
WARNING:root:Volume ID 169 is paired on SRC but not on DST cluster.
WARNING:root:Volume ID 391 is paired on DST but not on SRC cluster.
WARNING:root:Mismatch found at SRC: vol ID 169 in relationship 6164784e-3b80-41b2-9673-5d9f006cc49a found at SRC, but relationship from paired SRC volume ID is missing: 407.
WARNING:root:Mismatch found at DST: vol ID 391 in relationship f4b57253-d8b6-4c89-b4c2-f73f65784b69 found at SRC, but relationship from paired SRC volume ID is missing: 164.
MISMATCHED PAIRED VOLUMES ONLY:
[{'PROD': {'volumeID': 169,
'volumePairUUID': '6164784e-3b80-41b2-9673-5d9f006cc49a',
'mismatchSite': 'DR',
'remoteVolumeID': 407}},
{'DR': {'volumeID': 391,
'volumePairUUID': 'f4b57253-d8b6-4c89-b4c2-f73f65784b69',
'remoteSite': 'PROD',
'remoteVolumeID': 164}}]
```
`mismatched` output also contains a list of all paired volumes with volume-level (not volume pairing-level) details, which makes it convenient for copy-paste into other commands (or sending to an infrastructure monitoring system, which was the original idea - to use this in SFC). In the case above, as volume-pair relationships can't be "restored", a way to recover is:
- Manually remove 407,169 at DR and 164,391 at PROD site
- Run `--src PROD --dst DR --data "169,407;164,391 volume --pair` to rebuild the relationships
- Potentially `--set-mode` to `SnapshotsOnly` or `Sync` if those weren't `Async` before getting damaged
**Unpair volumes** is a sensitive operation. Although it "only" unpairs and doesn't delete volumes, it's suggested to use it with `--dry on` (default is `off`!) before actually letting it remove a pairing.
```sh
longhorny -dry on --data "167,393" volume --unpair
```
With `--dry on`, we only get a "preview" similar to this:
```raw
Remove data tuple: [(167, 393)]
===> Dry run: replication relationship for volume IDs that would be removed (SRC, DST): [(167, 393)]
```
**Snapshot** currently takes a snapshot of *all* volumes at the source. In DATA, the first digit is "retention in hours" (1-720) and the second part is snapshot name.
```sh
longhorny --src SRC --dst DST volume --snapshot --data "1;long1h"
```
The main idea is to be able to roll-back locally (these snapshots are not replicated) to something before making desperate moves. Since snapshots are taken individually, if you have applications that use multiple volumes, you should stop them before running this command.
## Miscellaneous stuff
### PowerShell to help
I mentioned several times how `site`-level commands (currently) may not be able to do anything meaningful without the ability to connect to the destination API, and that I'm still thinking what to do about that.
The problem is the logic of such workflows can become very complicate, but if you know what the situation is and what you want to do, it's to suspend replication on all volumes at one site from Python or PowerShell. Since SolidFire CLI (in Python) is no longer maintained and PowerShell is superior, I'll use this section to give simple PowerShell examples for folks who need to perform quick actions.
**CAUTION:** this pauses replication on *all* paired volumes on the cluster you're connected to and goes **without confirmation**.
```powershell
Get-SFVolumePair | Set-SFVolumePair -PausedManual $True
```
Fun fact I just discovered: `Get-SFVolumePair` output doesn't even show any difference "before vs. after" as far as replication state is concerned. We have to use `Get-SFVolumePair | ConvertTo-Json` to see it, which helps the cause for `--data 'pause' volume --set-status` (if its output can be made easier to view and use).
To go back, simply reverse.
```powershell
Get-SFVolumePair | Set-SFVolumePair -PausedManual $False
```
The reason this is simple is we know exactly what we want to do, we don't care about the other site, and there are no if/else scenarios. Just flip 'em here and now.
Flipping the surviving site's access mode from replicationTarget to readWrite is also very easy when that's the only thing that has to be done.
```powershell
Get-SFVolumePair | Set-SFVolume -Access readWrite
```
If you do `-Confirm:$False` then it just goes on and flips the entire site to readWrite, which is fine if the other site is dead and you can't properly reverse with `volume --reverse`, for example.
To filter out (or in) just selected volumes:
```powershell
PS > Get-SFVolume | Select-Object -Property VolumeID,Name | Where-Object -Property Name -Match "pvc-*"
VolumeID Name
-------- ----
59 pvc-ba3213cd-01bc-4920-b1c7-708ed89e5730
111 pvc-8d31e43b-f942-4cf8-94db-a08762c745ee
112 pvc-14a51322-16c8-4b95-a7e4-28d9963450b3
113 pvc-4fb5d7f5-4d98-429e-ab36-1b2118b7e55c
115 pvc-fc799089-9559-4d97-84c8-d98e9dfbf884
116 pvc-a7b61fe0-7e9d-40f4-bc06-9c1623adade4
117 pvc-9812208f-72f5-41d8-9348-4fb42db8e6af
120 pvc-bd1254e7-4102-4b58-960c-70be158c75fc
121 pvc-58d35404-479b-4c5d-a67b-d96521f63ce2
122 pvc-afc3936c-9cd4-47bb-bdf1-b1c46fd910ad
123 pvc-c47a3f9f-4628-4e3b-8a86-313ec02f49b4
124 pvc-515bccf3-577b-4149-9633-9da86913c933
125 pvc-910cc289-64b8-4cc9-a411-524fd713d950
127 pvc-a9531e89-7900-4265-9910-030142b4646a
133 pvc-4bf6f5e2-bd1c-4908-88d0-62ecd66f6d33
139 pvc-d793176f-2484-48ea-9255-f70215a7c5f7
157 pvc-a5f21571-e002-493f-b2dc-df01f40c1fa1
```
We can pipe that to `Set-SFVolume` or store result in a variable, e.g. `$kvols`, and then pipe that to some other command:
```powershell
$kvols.VolumeID | Set-SFVolume -Access readWrite
```
Again, 2 lines vs. 100, when you don't have to consider a variety of other possibilities.
That's why there's no urgency to further develop `site`-level commands, although it'd be nice to have them if I had some ideas about specific use cases to address with Longhorny.
### Site object (SRC, DST) and Longhorny CLI arguments
SRC and DST are KV pairs of SolidFire mvip and two credential-related fields, i.e. `mvip`, `username`, and `password`.
There are several more or less frustrating ways to provide these to Longhorny.
I like this one, because to swap SRC and DST I just change the three letters in each of `--src` and `--dst`, but if you run several commands this way, sooner or later you'll forget to change back and execute a command against the wrong site.
```sh
longhorny --src "{ 'mvip': '192.168.1.30', 'username':'admin', 'password':'*******'}" --dst "{ 'mvip': '192.168.105.32', 'username':'admin', 'password':'*******'}" cluster --list
```
Alternatively, paste your config to shell variables SRC and DST before running.
```sh
SRC="{ 'mvip': '192.168.1.30', 'username':'admin', 'password':''}"
DST="{ 'mvip': '192.168.105.32', 'username':'admin', 'password':''}"
longhorny cluster --list
Enter password for SRC cluster:
Enter password for DST cluster:
```
Longhorny loads `--src` from the OS environmental variable SRC and `--dst` from DST. This is probably the worst way because you don't even see 'em. You can verify what you are about to run 10 times and still run it against the wrong site.
For me the best way to run Longhorny is:
- Two shell terminals (one dragged to left (or to the top) and the other to the right (or to the bottom))
- The left has `--src SRC --dst DST`, the right has `--src DST --dst SRC` (with or without password value provided in the site object string)
Then you just go to the correct "site terminal" and as long as you don't copy over *entire* lines (with the wrong --src and --dst in them), you can be fine.
Then Longhorny uses SolidFire Python SDK to establish a connection to each site.
### Volume objects on SolidFire
A SolidFire volume may be identified by volume ID (integer) or name (integer or string). The former is guaranteed to be unique, while the latter is not.
Many sites do not have duplicate volume names (within the site), but they *may* have them - e.g. in different KVM clusters - and it shouldn't be happening. Instead, some naming conventions should be used (e.g `clusterName-teamName-volumeName`).
Volume ID is guaranteed to be unique per cluster. That's why Longhorny only uses volume IDs while names *may* be provided in logs or output, but are never used in anything that changes SolidFire configuration.
## Testing and development environment
For production use, I strongly recommend having two single-node test clusters.
- The SolidFire API is unlikely to change at this point, but iSCSI client behavior or Python or other bits and pieces
- If you use Kubernetes, that is a fast-moving target, and then there's also NetApp Trident. Sometimes major changes happen in months, so having a testbed where you can compare results of before, after various upgrades is mandatory
Here's what you need for testing and development:
- Two mid-sized VMs for SolidFire "sites" - 2 x 16 GB RAM (NOTE: SolidFire Demo VM is an OVA file, and if you don't have VMware you can use the free ESXi 7, deploy it to KVM or Hyper-V, and deploy OVA to ESXi VM - which requires 16 GB per VM plus say 4 GB for ESXi)
- Two mid-sized VMs for compute "site" resource, e.g. Hyper-V, KVM, Kubernetes, etc. - 2 x 16 GB RAM
You can get the free SolidFire Demo VM from NetApp Support (login required). It's limited to 100 volumes - more than enough for testing. SolidFire Demo VM allows multiple storage accounts (each being a different iSCSI client), so just two SolidFire VMs can accommodate testing with several VMs simulating different Kubernetes or other clusters at each "site" (VM group). SolidFire Demo VM is well-behaved and an excellent tool for test/development as long as you don't need high performance (it's limited to 3000 IOPS).
### Note on SolidFire SDK for Python
As of now it's a mess because SolidFire SDK 12.3.1 was released, but there are several bugs that impact methods used by Longhorny, and you must install it with `python3 setup.py` (and even then it will still claim it's 12.3.0.0).
- [Update version-related info and publish on PyPi](https://github.com/solidfire/solidfire-sdk-python/issues/60)
- [Usage of dash-separated 'description-file' will not be supported starting Sep 26, 2024](https://github.com/solidfire/solidfire-sdk-python/issues/65)
Older versions are available with `pip`, but may have bugs that have been solved since.
See the Github [issues](https://github.com/solidfire/solidfire-sdk-python/issues) for more.
## Random development notes
If you spot some "inconvenient" behavior or logic, it exists because I couldn't make it more "convenient" while being careful. If something "looks wrong", Longhorny doesn't try to be smart and "handle it for you". Instead, it prefers to exit and let you figure it out yourself.
It's easier to fix or review what Longhorny complained about than figure out what the heck just happened to 245 of your production volumes. Longhorny attempts to never do what you didn't unambiguously tell it to do.
But, pull requests that improve the code and eliminate bugs are welcome.
Some notes on the script itself: it's not DRY - because I didn't set out to write all those similar actions at first and was lazy to DRY the code after that - and tests are missing - because there are currently just 0 users and I am busy and don't have time to learn how to write parametrized tests.
Unlike in SFC v2 (where I've removed SolidFire Python SDK), here I used SolidFire Python SDK as the "default" and standard tool widely used by those who have more than one cluster.