---
title: "Raft inside Queen: elections, timings, snapshots"
description: "Openraft decides who leads and when an entry is committed. The queue log files are the Raft log, heartbeats run every 100 ms, and a node that was away catches up or loads a snapshot."
---

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# Raft inside Queen: elections, timings, snapshots

The nodes agree on the log with Raft, through the openraft library. Raft decides who leads and when an entry is committed. An entry is committed when a majority of the nodes has written it and synced it to disk (fsync).

Queen has no separate Raft log: the queue log files are the log (see [Storage](/architecture/storage/)). The nodes talk on port 7400, over plain HTTP, with a shared token. The leader sends a heartbeat every 100 ms. If the followers hear nothing for one to two seconds, they elect a new leader.

A leader that hears from no majority for 1.5 seconds stops logging new writes and keeps them waiting, in order. After 3 seconds it hands leadership to another node.

**Figure.** Raft's timings in a cluster. The leader sends a heartbeat every 100 milliseconds. Followers that hear nothing for 1 to 2 seconds elect a new leader. A leader that hears from no majority for 1.5 seconds stops logging new writes and keeps them waiting in order; after 3 seconds it hands leadership to another node. A node that was away gets the entries it missed for up to 6 hours, while the leader's disk has room; after that it gets a snapshot, only the part it lacks, exits with code 75 and loads it at start.

The timings Raft runs on.

A node that was away gets the entries it missed from the leader, who keeps them for 6 hours while its disk has room. After that, the leader sends a snapshot instead: since 2.6, only the part the node is missing. The node exits with code 75 and loads the snapshot when it starts again.

Source: https://queenmq.com/architecture/raft/index.mdx