@langchain/langgraph
Version:
62 lines (61 loc) • 2.28 kB
JavaScript
require("../constants.cjs");
//#region src/pregel/replay.ts
/**
* Tracks subgraph checkpoint loading during parent-graph time travel.
*
* When a parent replays from a historical checkpoint, nested subgraphs must
* load the checkpoint that existed *before* the replay point on their first
* visit, then fall back to normal latest-checkpoint loading on later visits
* within the same run.
*/
var ReplayState = class {
/** Parent checkpoint ID used as the `before` cursor for subgraph lookups. */
checkpointId;
#visitedNs = /* @__PURE__ */ new Set();
/**
* @param checkpointId - Checkpoint ID from the parent graph at the replay point.
*/
constructor(checkpointId) {
this.checkpointId = checkpointId;
}
/**
* Whether this is the first visit to a logical subgraph namespace in the run.
*
* Task-id suffixes are stripped so the same subgraph invoked across loop
* iterations shares one visit record.
*
* @param checkpointNs - Subgraph checkpoint namespace.
*/
#isFirstVisit(checkpointNs) {
const stableNs = checkpointNs.includes(":") ? checkpointNs.slice(0, checkpointNs.lastIndexOf(":")) : checkpointNs;
if (this.#visitedNs.has(stableNs)) return false;
this.#visitedNs.add(stableNs);
return true;
}
/**
* Load the checkpoint tuple for a subgraph namespace during replay.
*
* On the first visit to `checkpointNs`, returns the latest checkpoint saved
* before {@link ReplayState.checkpointId}. On subsequent visits, delegates to
* `checkpointer.getTuple` for the current config.
*
* @param checkpointNs - Subgraph checkpoint namespace.
* @param checkpointer - Checkpointer shared with the parent graph.
* @param checkpointConfig - Runnable config for the subgraph lookup.
* @returns The resolved checkpoint tuple, if any.
*/
async getCheckpoint(checkpointNs, checkpointer, checkpointConfig) {
if (this.#isFirstVisit(checkpointNs)) {
const results = [];
for await (const saved of checkpointer.list(checkpointConfig, {
before: { configurable: { checkpoint_id: this.checkpointId } },
limit: 1
})) results.push(saved);
return results.length > 0 ? results[0] : void 0;
}
return await checkpointer.getTuple(checkpointConfig) ?? void 0;
}
};
//#endregion
exports.ReplayState = ReplayState;
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