[Nexthop][fboss2-dev] Add config session rebase command for concurrent session conflict resolution
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This was referenced Jan 26, 2026
1. Some of the configuration commands like QoS buffer pool modification
requires an agent restart and some are hitless. Inorder to take
appropriate action during the commit, track the highest impact action by
storing the same in `$HOME/.fboss2/action_level` at the end of each
configuration change. The proposed change only prints a warning if the
action needs to be taken. Later this can be modified to perform the
action automatically
2. Add QoS buffer pool configuration commands
```
- fboss2 config qos buffer-pool <name> shared-bytes <value>
- fboss2 config qos buffer-pool <name> headroom-bytes <value>
- fboss2 config qos buffer-pool <name> reserved-bytes <value>
```
1. Updated existing UT for action information
2. Added new tests for QoS buffer bool configurations.
```
[admin@fboss101 ~]$ ~/benoit/fboss2-dev config qos buffer-pool testpool headroom-bytes 1024
Successfully set headroom-bytes for buffer-pool 'testpool' to 1024
[admin@fboss101 ~]$ ~/benoit/fboss2-dev config session diff
--- current live config
+++ session config
@@ -121,6 +121,12 @@
"arpAgerInterval": 5,
"arpRefreshSeconds": 20,
"arpTimeoutSeconds": 60,
+ "bufferPoolConfigs": {
+ "testpool": {
+ "headroomBytes": 1024,
+ "sharedBytes": 0
+ }
+ },
"clientIdToAdminDistance": {
"0": 20,
"1": 1,
[admin@fboss101 ~]$ ll ~/.fboss2
total 216
-rw-r--r-- 1 admin admin 213283 Jan 13 05:15 agent.conf
-rw-r--r-- 1 admin admin 42 Jan 13 05:15 conf_metadata.json
[admin@fboss101 ~]$ cat ~/.fboss2/conf_metadata.json
{
"action": {
"WEDGE_AGENT": "AGENT_RESTART"
}
}
```
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…mand. This doesn't yet automatically create the VLAN if it doesn't exist.
A recent merge introduced a duplicate command by mistake (bad merge on my part) and this escaped because of lack of test coverage. Also make sure we keep `cmake/CliFboss2Test.cmake` sorted.
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.
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
…esolution 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 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 NOS-3962 #done
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Pre-submission checklist
pip install -r requirements-dev.txt && pre-commit installpre-commit runSummary
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 rebasecommand that:The 3-way merge algorithm handles:
Note: this change is part of a series, the previous one is #825, the next one is #837.
Test Plan
Add unit tests covering:
Sample usage
TBD