[#3127] Fix for Redis Sentinel client doesn't reconnect after connection failure

[mayankkapoor]

When a Redis Sentinel goes down and comes back up, the node-redis client fails to reconnect, throwing "None of the sentinels are available". This is likely a regression introduced in v5.9.0 (commit 73413e086c — "fix: resolve doubly linked list push issue (#3085)").

Root Cause: #handleSentinelFailure() (added in v5.9.0) permanently removes the sentinel node from #sentinelRootNodes via splice() when its connection drops. When #reset() then calls observe(), the sentinel list is empty (or missing that node), so reconnection is impossible.

Secondary issue: The sentinel list update in transform() (line 1350) compares only array lengths (analyzed.sentinelList.length != this.#sentinelRootNodes.length), so even if reconnection succeeds via another sentinel, a removed node may never be restored if the list sizes happen to match.

• Task 1: Fix #handleSentinelFailure — stop permanently removing sentinel nodes

  • File: packages/client/lib/sentinel/index.ts (lines 934–942)
  • Remove the splice() call. A transient TCP disconnect (which happens during sentinel restart) should not permanently delete the node from the root list. Just call #reset() to trigger reconnection, matching v5.8.3 behavior.
  • Before (broken): typescript #handleSentinelFailure(node: RedisNode) { const found = this.#sentinelRootNodes.findIndex( (rootNode) => rootNode.host === node.host && rootNode.port === node.port ); if (found !== -1) { this.#sentinelRootNodes.splice(found, 1); } this.#reset(); }
  • After (fixed): typescript #handleSentinelFailure(node: RedisNode) { this.#reset(); }

• Task 2: Fix sentinel list update condition in transform()

  • File: packages/client/lib/sentinel/index.ts (line 1350)
  • Replace the length-only comparison with a proper content comparison so that nodes removed or added are always detected.
  • Before: typescript if (analyzed.sentinelList.length != this.#sentinelRootNodes.length) {
  • After — compare actual content: typescript if (!areSentinelListsEqual(analyzed.sentinelList, this.#sentinelRootNodes)) {
  • Add a helper (either inline or as a small private method) that compares host+port of each node, not just array length.

• Task 3: Run existing tests to confirm no regressions

  • Run npm test in the packages/client directory
  • Look for and run any sentinel-specific test files

• Task 4: Verify the fix scenario

  • Confirm #sentinelRootNodes retains the original sentinel entry after disconnect
  • Confirm observe() retries that sentinel and succeeds once it's back online
  • Confirm no "None of the sentinels are available" error after sentinel restart

Description

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Checklist

• Does npm test pass with this change (including linting)?
• Is the new or changed code fully tested?
• Is a documentation update included (if this change modifies existing APIs, or introduces new ones)?

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