Conflict Resolution

TODO: This section is under development. Basic conflict resolution patterns are outlined below.

Overview

When multiple clients attempt to modify the same SCIM resource simultaneously, conflicts can occur. This guide covers strategies for detecting and resolving these conflicts using ETags and version control.

Conflict Detection

ETag-Based Detection

#![allow(unused)]
fn main() {
use scim_server::{ConditionalResult, ETag};

async fn update_user_with_conflict_detection(
    provider: &impl ResourceProvider,
    user_id: &str,
    data: serde_json::Value,
    expected_etag: &ETag,
) -> Result<ScimUser, ConflictError> {
    let context = RequestContext::new("update", None);
    
    match provider.conditional_update("User", user_id, data, expected_etag, &context).await? {
        ConditionalResult::Success(user) => Ok(user),
        ConditionalResult::VersionMismatch(conflict) => {
            Err(ConflictError::VersionMismatch {
                expected: expected_etag.clone(),
                current: conflict.current_version,
                resource_id: user_id.to_string(),
            })
        },
        ConditionalResult::NotFound => Err(ConflictError::ResourceNotFound),
    }
}
}

Resolution Strategies

1. Last-Writer-Wins

#![allow(unused)]
fn main() {
// Simple approach: retry with latest version
async fn retry_with_latest(
    provider: &impl ResourceProvider,
    user_id: &str,
    data: serde_json::Value,
) -> Result<ScimUser, Box<dyn std::error::Error>> {
    let context = RequestContext::new("retry", None);
    
    // Get current version
    let current = provider.get_resource("User", user_id, &context).await?
        .ok_or("User not found")?;
    
    // Apply update with current version
    provider.update_resource("User", user_id, data, &context).await
}
}

2. Three-Way Merge

TODO: Implement sophisticated merge strategies for complex conflicts.

3. Client-Side Resolution

TODO: Add examples for client-side conflict resolution patterns.

Error Handling

#![allow(unused)]
fn main() {
#[derive(Debug)]
pub enum ConflictError {
    VersionMismatch {
        expected: ETag,
        current: ETag,
        resource_id: String,
    },
    ResourceNotFound,
    MergeConflict {
        field: String,
        local_value: serde_json::Value,
        remote_value: serde_json::Value,
    },
}

impl std::fmt::Display for ConflictError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            ConflictError::VersionMismatch { expected, current, resource_id } => {
                write!(f, "Version conflict on {}: expected {}, got {}", 
                       resource_id, expected, current)
            },
            ConflictError::ResourceNotFound => write!(f, "Resource not found"),
            ConflictError::MergeConflict { field, .. } => {
                write!(f, "Merge conflict in field: {}", field)
            },
        }
    }
}
}

Best Practices

1. Always use ETags for update operations
2. Implement retry logic with exponential backoff
3. Provide clear error messages to clients
4. Log conflicts for monitoring and debugging

TODO: Add more sophisticated conflict resolution algorithms and patterns.