Principle:OpenHands OpenHands Conversation Initiation
| Knowledge Sources | |
|---|---|
| Domains | Distributed_Systems, Conversation_Management |
| Last Updated | 2026-02-11 21:00 GMT |
Overview
Conversation initiation is the process of safely starting an agent conversation loop under concurrency control, using distributed locking to guarantee that exactly one server instance owns a given conversation at any point in time.
Description
In a multi-node deployment, multiple server instances may simultaneously attempt to start an agent loop for the same conversation identifier. Without coordination, this leads to duplicate processing, conflicting state mutations, and wasted compute resources. Conversation initiation solves this problem by employing a distributed lock (typically backed by an atomic compare-and-set store such as Redis) before spawning the agent loop. The initiating node acquires the lock, provisions resources, and begins the loop; any concurrent attempt on another node will observe the lock and defer.
The pattern encompasses three phases:
- Lock acquisition -- An atomic SET-if-not-exists (SET NX) operation claims ownership of the conversation.
- Resource provisioning -- The owning node allocates a runtime, configures credentials, and prepares the event stream.
- Loop start -- The agent loop begins processing events, and the lock is maintained for the lifetime of the conversation.
Usage
Use conversation initiation whenever:
- A user sends the first message in a new conversation.
- A conversation needs to be resumed on a potentially different cluster node after a failover.
- A replayed event stream must be rehydrated into a running agent loop.
This pattern is essential in any horizontally-scaled deployment where conversation ownership must be deterministic.
Theoretical Basis
The core mechanism relies on the leader election via atomic compare-and-set pattern from distributed systems theory.
Pseudocode:
function maybe_start_agent_loop(conversation_id, settings, user_id):
# Phase 1: Distributed lock acquisition
lock_key = "conversation_lock:" + conversation_id
acquired = atomic_set_if_not_exists(lock_key, self_node_id, ttl=LOCK_TTL)
if not acquired:
existing_owner = get(lock_key)
if existing_owner == self_node_id:
# We already own this conversation; return existing loop info
return get_existing_loop_info(conversation_id)
else:
# Another node owns this conversation; do not start
raise ConversationOwnedElsewhereError(existing_owner)
# Phase 2: Resource provisioning
try:
runtime = provision_runtime(conversation_id, settings)
configure_runtime(runtime, settings)
except ProvisioningError:
release_lock(lock_key)
raise
# Phase 3: Agent loop start
loop_info = start_agent_loop(runtime, user_id, settings)
return loop_info
Key invariants:
- At-most-one guarantee -- The atomic SET NX operation ensures that at most one node can successfully acquire the lock for a given conversation ID.
- Idempotency -- If the same node calls the function twice, it detects its own ownership and returns the existing loop rather than spawning a duplicate.
- Fail-safe release -- If provisioning fails after the lock is acquired, the lock must be explicitly released so another node can retry.
The TTL on the lock provides a safety net: if the owning node crashes without releasing the lock, the key expires and allows recovery by another node.