[Nexthop][fboss2-dev] Replace file-based config versioning with Git by benoit-nexthop · Pull Request #825 · facebook/fboss

benoit-nexthop · 2026-01-20T17:06:10Z

Pre-submission checklist

I've ran the linters locally and fixed lint errors related to the files I modified in this PR. You can install the linters by running pip install -r requirements-dev.txt && pre-commit install
pre-commit run

Summary

Replace the basic file-based configuration versioning mechanism with Git-based versioning for the CLI config session.

Key changes:

Add new Git class providing a simple interface for Git operations: init, commit, log, show, etc
Use folly::Subprocess with full path /usr/bin/git for all Git commands
Replace revision files (agent-rN.conf + symlink) with atomic writes to agent.conf tracked in a local Git repository
Use Git commit SHAs as revision identifiers instead of rN format
Update RevisionList validation to accept Git SHAs (7+ hex chars)

Repository initialization:

Automatically initialize Git repo if it doesn't exist
Automatically create initial commit if repo has no commits but config file exists
Use --shared=group flag and umask 0002 to ensure .git directory is group-writable when /etc/coop is group-writable

Commands updated:

config history: Shows Git commit log with SHA, author, timestamp, message
config session diff: Uses git show to compare commits
config session commit: Creates Git commits with username as author
config rollback: Reads config from Git history and creates new commit

Note: this change is part of a series, the previous one is #809, the next one is #832.

Test Plan

Test updates:

Update all CLI config tests to use Git-based setup
Initialize Git repo and create initial commit in test fixtures
Added new unit tests for the Git layer

Sample usage

Simple change and session commit:

[admin@fboss101 benoit]$ ./fboss2-dev show interface eth1/1/1
+-----------+--------+-------+------+------+------------------------------+-------------+
| Interface | Status | Speed | VLAN | MTU  | Addresses                    | Description |
-----------------------------------------------------------------------------------------
| eth1/1/1  | down   | 800G  | 2001 | 9000 | 10.0.0.0/24                  | demo        |
|           |        |       |      |      | 2400::/64                    |             |
|           |        |       |      |      | fe80::b4db:91ff:fe95:ff07/64 |             |
-----------------------------------------------------------------------------------------
[admin@fboss101 benoit]$ ./fboss2-dev config interface eth1/1/1 description hello
Successfully set description for interface(s) eth1/1/1
[admin@fboss101 benoit]$ ./fboss2-dev config session diff
--- current live config
+++ session config
@@ -2200,7 +2200,7 @@
     "ports": [
       {
         "conditionalEntropyRehash": false,
-        "description": "demo",
+        "description": "hello",
         "drainState": 0,
         "expectedLLDPValues": {
           "2": "eth1/5/1"
[admin@fboss101 benoit]$ ./fboss2-dev config session commit
Config session committed successfully as b8245b4 and config reloaded.
[admin@fboss101 benoit]$ ./fboss2-dev config history | head
 Commit    Author  Commit Time              Message                
------------------------------------------------------------------------
 b8245b40  admin   2026-01-21 11:13:57  Config commit by admin        
 7241abad  admin   2026-01-21 11:12:51  Config commit by admin        
 02fe511c  admin   2026-01-21 10:51:36  Config commit by admin        
 e5650a98  admin   2026-01-21 10:51:35  Config commit by admin        
 ad07138f  admin   2026-01-21 10:51:35  Config commit by admin        
 1845e710  admin   2026-01-21 10:51:35  Config commit by admin        
 ede5a527  admin   2026-01-20 14:28:10  Config commit by admin        
 e900ef88  admin   2026-01-20 14:23:25  Config commit by admin   
[admin@fboss101 benoit]$ cd /etc/coop
[admin@fboss101 coop]$ git -c safe.directory=/etc/coop show
commit b8245b40b2b3c8797cbeed2fb91161e5440b7fd9 (HEAD -> main)
Author: admin <fboss-cli@localhost>
Date:   Wed Jan 21 11:13:57 2026 -0800

    Config commit by admin

diff --git a/cli/agent.conf b/cli/agent.conf
index 406b341..f61516f 100644
--- a/cli/agent.conf
+++ b/cli/agent.conf
@@ -2200,7 +2200,7 @@
     "ports": [
       {
         "conditionalEntropyRehash": false,
-        "description": "demo",
+        "description": "hello",
         "drainState": 0,
         "expectedLLDPValues": {
           "2": "eth1/5/1"
diff --git a/cli/cli_metadata.json b/cli/cli_metadata.json
index 68f340a..6c6a925 100644
--- a/cli/cli_metadata.json
+++ b/cli/cli_metadata.json
@@ -1,6 +1,6 @@
 {
   "action": {},
   "commands": [
-    "config interface eth1/1/1 description demo"
+    "config interface eth1/1/1 description hello"
   ]
 }
\ No newline at end of file

Rollback flow:

[admin@fboss101 benoit]$ ./fboss2-dev config interface eth1/1/1 description hello2
Successfully set description for interface(s) eth1/1/1
[admin@fboss101 benoit]$ ./fboss2-dev config session commit
Config session committed successfully as 476f9ee and config reloaded.
[admin@fboss101 benoit]$ ./fboss2-dev config history | head
 Commit    Author  Commit Time              Message                
------------------------------------------------------------------------
 476f9ee4  admin   2026-01-21 11:15:23  Config commit by admin        
 b8245b40  admin   2026-01-21 11:13:57  Config commit by admin        
 7241abad  admin   2026-01-21 11:12:51  Config commit by admin      <-- we're going to rollback to here
 02fe511c  admin   2026-01-21 10:51:36  Config commit by admin        
 e5650a98  admin   2026-01-21 10:51:35  Config commit by admin        
 ad07138f  admin   2026-01-21 10:51:35  Config commit by admin        
 1845e710  admin   2026-01-21 10:51:35  Config commit by admin        
 ede5a527  admin   2026-01-20 14:28:10  Config commit by admin        
[admin@fboss101 benoit]$ ./fboss2-dev config rollback 7241abad
Successfully rolled back. New commit: 8be163e7. Config reloaded.
[admin@fboss101 benoit]$ ./fboss2-dev show interface eth1/1/1
+-----------+--------+-------+------+------+------------------------------+-------------+
| Interface | Status | Speed | VLAN | MTU  | Addresses                    | Description |
-----------------------------------------------------------------------------------------
| eth1/1/1  | down   | 800G  | 2001 | 9000 | 10.0.0.0/24                  | demo        |
|           |        |       |      |      | 2400::/64                    |             |
|           |        |       |      |      | fe80::b4db:91ff:fe95:ff07/64 |             |
-----------------------------------------------------------------------------------------
[admin@fboss101 benoit]$ ./fboss2-dev config history | head
 Commit    Author  Commit Time          Message                       
---------------------------------------------------------------------------
 8be163e7  admin   2026-01-21 11:17:26  Rollback to 7241abad by admin 
 476f9ee4  admin   2026-01-21 11:15:23  Config commit by admin        
 b8245b40  admin   2026-01-21 11:13:57  Config commit by admin        
 7241abad  admin   2026-01-21 11:12:51  Config commit by admin        
 02fe511c  admin   2026-01-21 10:51:36  Config commit by admin        
 e5650a98  admin   2026-01-21 10:51:35  Config commit by admin        
 ad07138f  admin   2026-01-21 10:51:35  Config commit by admin        
 1845e710  admin   2026-01-21 10:51:35  Config commit by admin    
[admin@fboss101 benoit]$ cd /etc/coop
[admin@fboss101 coop]$ git -c safe.directory=/etc/coop show
commit 8be163e7cd60574278dc7201b157e4238fa55380 (HEAD -> main)
Author: admin <fboss-cli@localhost>
Date:   Wed Jan 21 11:17:26 2026 -0800

    Rollback to 7241abad by admin

diff --git a/cli/agent.conf b/cli/agent.conf
index d918bae..406b341 100644
--- a/cli/agent.conf
+++ b/cli/agent.conf
@@ -2200,7 +2200,7 @@
     "ports": [
       {
         "conditionalEntropyRehash": false,
-        "description": "hello2",
+        "description": "demo",
         "drainState": 0,
         "expectedLLDPValues": {
           "2": "eth1/5/1"
diff --git a/cli/cli_metadata.json b/cli/cli_metadata.json
index 5435c54..68f340a 100644
--- a/cli/cli_metadata.json
+++ b/cli/cli_metadata.json
@@ -1,6 +1,6 @@
 {
   "action": {},
   "commands": [
-    "config interface eth1/1/1 description hello2"
+    "config interface eth1/1/1 description demo"
   ]
 }
\ No newline at end of file

Summary: **Pre-submission checklist** - [x] I've ran the linters locally and fixed lint errors related to the files I modified in this PR. You can install the linters by running `pip install -r requirements-dev.txt && pre-commit install` - [x] `pre-commit run` Now every config command is saved in the CLI session metadata so we can easily tell what commands were used in a given session. The metadata is now also saved along the config when we commit the session. A future commit will make rollback also rely on this metadata to decide whether or not to restart the agent. Note: this change is part of a series, the previous one is #805, the next one is #825. Pull Request resolved: #809 Test Plan: New unit tests added. ## Sample usage ``` [admin@fboss101 ~]$ ~/benoit/fboss2-dev config interface eth1/1/1 description this is a test. Successfully set description for interface(s) eth1/1/1 [admin@fboss101 ~]$ ~/benoit/fboss2-dev config interface eth1/1/1 mtu 1500 Successfully set MTU for interface(s) eth1/1/1 to 1500 [admin@fboss101 ~]$ ls -l ~/.fboss2/ total 216 -rw-r--r-- 1 admin admin 213174 Jan 13 13:00 agent.conf -rw-r--r-- 1 admin admin 141 Jan 13 13:00 conf_metadata.json [admin@fboss101 ~]$ cat ~/.fboss2/conf_metadata.json { "action": {}, "commands": [ "config interface eth1/1/1 description this is a test.", "config interface eth1/1/1 mtu 1500" ] } [admin@fboss101 ~]$ ~/benoit/fboss2-dev config session commit Config session committed successfully as r6 and config reloaded. [admin@fboss101 ~]$ ls -l /etc/coop/cli/ total 1292 -rw-r--r-- 1 root root 213185 Jan 13 12:52 agent-r1.conf -rw-r--r-- 1 admin admin 213194 Jan 13 12:56 agent-r2.conf -rw-r--r-- 1 admin admin 108 Jan 13 12:56 agent-r2.metadata.json -rw-r--r-- 1 admin admin 213185 Jan 13 12:56 agent-r3.conf -rw-r--r-- 1 admin admin 99 Jan 13 12:56 agent-r3.metadata.json -rw-r--r-- 1 admin admin 213185 Jan 13 12:58 agent-r4.conf -rw-r--r-- 1 admin admin 80 Jan 13 12:58 agent-r4.metadata.json -rw-r--r-- 1 admin admin 213185 Jan 13 12:58 agent-r5.conf -rw-r--r-- 1 admin admin 80 Jan 13 12:58 agent-r5.metadata.json -rw-r--r-- 1 admin admin 213174 Jan 13 13:00 agent-r6.conf -rw-r--r-- 1 admin admin 141 Jan 13 13:00 agent-r6.metadata.json [admin@fboss101 ~]$ cat /etc/coop/cli/agent-r6.metadata.json { "action": {}, "commands": [ "config interface eth1/1/1 description this is a test.", "config interface eth1/1/1 mtu 1500" ] } ``` Reviewed By: KevinYakar Differential Revision: D93669865 Pulled By: joseph5wu fbshipit-source-id: 9c37dfd88a59d8e76bdb09f30d0c55897c4e889f

Replace the basic file-based configuration versioning mechanism with Git-based versioning for the CLI config session. Key changes: - Add new Git class (Git.h/cpp) providing a simple interface for Git operations: init, commit, log, show, resolveRef, getHead, hasCommits - Use folly::Subprocess with full path /usr/bin/git for all Git commands - Replace revision files (agent-rN.conf + symlink) with atomic writes to agent.conf tracked in a local Git repository - Use Git commit SHAs as revision identifiers instead of rN format - Update RevisionList validation to accept Git SHAs (7+ hex chars) Repository initialization: - Automatically initialize Git repo if it doesn't exist - Automatically create initial commit if repo has no commits but config file exists - Use --shared=group flag and umask 0002 to ensure .git directory is group-writable when /etc/coop is group-writable Commands updated: - config history: Shows Git commit log with SHA, author, timestamp, message - config session diff: Uses git show to compare commits - config session commit: Creates Git commits with username as author - config rollback: Reads config from Git history and creates new commit Test updates: - Update all CLI config tests to use Git-based setup - Initialize Git repo and create initial commit in test fixtures

meta-codesync · 2026-03-02T23:59:44Z

@joseph5wu has imported this pull request. If you are a Meta employee, you can view this in D94975358.

joseph5wu

There're some improvement comments about how to properly manage the full sha vs short sha, to avoid mis-using them in your code. Please consider to improve the logic in the future PRs.
I'll land this PR for now to unblock your rebase effort

joseph5wu · 2026-03-03T00:26:03Z

fboss/cli/fboss2/commands/config/session/CmdConfigSessionCommit.cpp


  // Build message based on what actions were taken
  std::string message;
+  std::string shortSha = result.commitSha.substr(0, 7);


Would like to see a common utility function for getShortSha(const std::string& commitSha).
Or a more organized way to getFullSha() or getShortSha() from the result.
This will avoid mis-using the wrong sha string.
Could be addressed in future diff

Just to be clear, you can always use the long or the short sha1, as long as it's a unique prefix (just like when using git directly). But other than that, yes, we can add a little helper function to clip the string.

joseph5wu · 2026-03-03T00:29:35Z

fboss/cli/fboss2/commands/config/session/CmdConfigSessionDiff.cpp

+      throw std::runtime_error(
+          "Failed to read current config from " + cliConfigPath);
+    }
+    return {content, "current live config"};


Will it be a problem that you don't give a shortSha of the current revision here?
In line 42, you always return shortSha revision for non-current case.

You can pass anything that git will accept: short sha1, full sha1, branch or tag name, any other ref...

joseph5wu · 2026-03-03T00:40:24Z

fboss/cli/fboss2/commands/config/session/CmdConfigSessionDiff.cpp

+  std::string content = git.fileAtRevision(resolvedSha, "cli/agent.conf");
+  return {content, revision.substr(0, 8)};


Now I think your Git can have to provide a getShortSha()

Yes it's inconsistent with the other file, good catch. It doesn't matter in practice but I agree it would be better to be consistent. We can fix this in this PR if you want, it's such a small change it wouldn't hurt anything.

meta-codesync · 2026-03-03T17:00:08Z

@joseph5wu merged this pull request in 307355c.

…esolution (#832) Summary: **Pre-submission checklist** - [x] I've ran the linters locally and fixed lint errors related to the files I modified in this PR. You can install the linters by running `pip install -r requirements-dev.txt && pre-commit install` - [x] `pre-commit run` When multiple users have concurrent config sessions, the first user to commit succeeds, but subsequent users get an error because their session is based on a stale commit. Previously, whoever committed last would overwrite changes of other users that committed before them. This commit adds a `config session rebase` command that: 1. Takes the diff between the config as of the base commit and the session 2. Re-applies this diff on top of the current HEAD (similar to git rebase) 3. Uses a recursive 3-way merge algorithm for JSON objects 4. Detects and reports conflicts at specific JSON paths 5. Updates the session's base to the current HEAD on success The 3-way merge algorithm handles: - Objects: recursively merges each key - Arrays: element-by-element merge if sizes match - Scalars: conflict if both head and session changed differently from base Note: this change is part of a series, the previous one is #825, the next one is #837. Pull Request resolved: #832 Test Plan: Add unit tests covering: - Successful rebase with non-conflicting changes - Rebase failure when changes conflict - Rebase not needed when session is already up-to-date ## Sample usage TBD Reviewed By: srikrishnagopu Differential Revision: D95099578 Pulled By: joseph5wu fbshipit-source-id: b665afa35a43829981ce9dd8434abf5b3942882a

meta-cla bot added the CLA Signed label Jan 20, 2026

benoit-nexthop mentioned this pull request Jan 20, 2026

[Nexthop][fboss2-dev] Save the config commands to CLI metadata and in session commit. #809

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[Nexthop][fboss2-dev] Add config session rebase command for concurrent session conflict resolution #832

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[Nexthop][fboss2-dev] Replace file-based config versioning with Git#825

[Nexthop][fboss2-dev] Replace file-based config versioning with Git#825
benoit-nexthop wants to merge 1 commit intofacebook:mainfrom
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		std::string content = git.fileAtRevision(resolvedSha, "cli/agent.conf");
		return {content, revision.substr(0, 8)};

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