Client not able to reconnect instantly when a node gets down then up again with multi-node configuration #1714

pgayvallet · 2022-06-15T06:48:45Z

🐛 Bug Report

When configured with multiple ES nodes, if all nodes get offline (then online again) at the same time, the client takes time before being able to successfully reconnect

To Reproduce

Using a local 2 node ES cluster (es version 8.2 not that is really matters):

es-node-1 config

cluster.name: test-cluster
node.name: node-1
xpack.security.enabled: false
http.port: 9201
cluster.initial_master_nodes: ["node-1", "node-2"]

es-node-2 config

cluster.name: test-cluster
node.name: node-2
xpack.security.enabled: false
http.port: 9202
cluster.initial_master_nodes: ["node-1", "node-2"]

test script

const elasticsearch = require('@elastic/elasticsearch');

const client = new elasticsearch.Client({
  sniffOnStart: false,
  sniffOnConnectionFault: false,
  sniffInterval: false,
  nodes: ['http://localhost:9201', 'http://localhost:9202'],
});

const delay = (ms) => new Promise((resolve) => setTimeout(resolve, ms));

const ping = async () => {
  try {
    await client.ping();
    console.log('ping successful');
  } catch (e) {
    console.log('error during ping: ', e.message);
  }
};

const chainPing = async () => {
  await ping();
  await delay(1000);
  chainPing();
}

chainPing();

Scenarios

1. stop node 1, then restart node 1

All ok, all calls successful

2. stop node 2, then restart node 2

All ok, all calls successful

3. stop node 1, stop node 2, restart node 1, restart node 2

When both nodes are down, we see errors error during ping: There are no living connections (which is expected)
Once both nodes get up again, the errors remain for a given period of time for all calls (which should not occur)
From my tests, this period seems to be approximatively 6 minutes

4. stop node 1, restart node 1, stop node 2, restart node 2

stopping and restarting node 1 causes no problem, however as soon as the second node is stopped, we observe the same behavior as the previous scenario: the Client does not retry to connect to node1 instantly, and need approx 6minutes before doing so

Expected behavior

When node goes down and up again, the client should be able to reconnect to them as soon as they're up and running again, especially if all nodes are considered down

FWIW, this is working as expected for a single-node configuration. When the client is configured with a single node, when the node is down, we get a slightly different error (connect ECONNREFUSED 127.0.0.1:9201), and the client is able to communicate with ES again as soon as the node is back on.

I'm assuming this is because the Client is implementing an eviction strategy and an eviction period in case of down node when configured with multi-node. I also assume the strategy don't handle the case where all nodes are down at the same time, where it should more actively try to reconnect to at least one node.

Your Environment

node version: 16.14.2
@elastic/elasticsearch version: reproduced on 8.0.0 and elasticsearch-canary@8.2.0-canary.2
os: Mac

The text was updated successfully, but these errors were encountered:

pgayvallet · 2022-06-16T12:18:57Z

Issue reproduced on v8.2.0 and v8.0.0, and not reproduced on 7.17.0. This was likely introduced by the internal changes to the transport layer during 8.0.0

pgayvallet · 2022-06-16T12:53:55Z

WeightedConnectionPool seems to be the culprit here.

Looking at the code, ClusterConnectionPool, which is the old (7.x) implementation, has an internal mechanism to try to resurrect down nodes when calling getConnection.

WeightedConnectionPool on the other hand, does not have such mechanism.

I unfortunately don't have enough understanding of the code to understand how the nodes are put back alive when using WeightedConnectionPool, or where this approximative 6mins duration is coming from

EDIT: I also see that the tests for the weighted pool with dead nodes are commented:

https://github.com/elastic/elastic-transport-js/blob/a95f72658be4a77f4c023c5484b64e7bb8ea4421/test/unit/weighted-connection-pool.test.ts#L99-L107

Which may indicate that's there is indeed a problem here. Also worth noting that there's no test asserting the behavior when all nodes are dead.

pgayvallet · 2022-06-16T15:07:20Z

Sample test reproducing the issue

  t.test('3 Connections, same weight', t => {
    const pool = new WeightedConnectionPool({ Connection: HttpConnection })
    pool.addConnection([
      'http://localhost:9200/',
      'http://localhost:9201/',
      'http://localhost:9202/'
    ]);

    for (let i = 0; i < 30; i++) {
      const con = pool.getConnection(opts);
      if(con) {
        pool.markDead(con)
      }
    }

    const order: string[] = [];

    try {
      for (let i = 0; i < 100; i++) {
        const connection = pool.getConnection(opts);
        order.push(connection ? connection.id : 'none');
      }
      console.log(order)
      t.pass('Distribution is ok')
    } catch (err: any) {
      t.error(err)
    }

    t.end()
  })

output:

test/unit/weighted-connection-pool.test.ts 1> [
test/unit/weighted-connection-pool.test.ts 1>   'none', 'none', 'none', 'none', 'none', 'none', 'none',
test/unit/weighted-connection-pool.test.ts 1>   'none', 'none', 'none', 'none', 'none', 'none', 'none',
test/unit/weighted-connection-pool.test.ts 1>   'none', 'none', 'none', 'none', 'none', 'none', 'none',
test/unit/weighted-connection-pool.test.ts 1>   'none', 'none', 'none', 'none', 'none', 'none', 'none',
test/unit/weighted-connection-pool.test.ts 1>   'none', 'none', 'none', 'none', 'none', 'none', 'none',
test/unit/weighted-connection-pool.test.ts 1>   'none', 'none', 'none', 'none', 'none', 'none', 'none',
test/unit/weighted-connection-pool.test.ts 1>   'none', 'none', 'none', 'none', 'none', 'none', 'none',
test/unit/weighted-connection-pool.test.ts 1>   'none', 'none', 'none', 'none', 'none', 'none', 'none',
test/unit/weighted-connection-pool.test.ts 1>   'none', 'none', 'none', 'none', 'none', 'none', 'none',
test/unit/weighted-connection-pool.test.ts 1>   'none', 'none', 'none', 'none', 'none', 'none', 'none',
test/unit/weighted-connection-pool.test.ts 1>   'none', 'none', 'none', 'none', 'none', 'none', 'none',
test/unit/weighted-connection-pool.test.ts 1>   'none', 'none', 'none', 'none', 'none', 'none', 'none',
test/unit/weighted-connection-pool.test.ts 1>   'none', 'none', 'none', 'none', 'none', 'none', 'none',
test/unit/weighted-connection-pool.test.ts 1>   'none', 'none', 'none', 'none', 'none', 'none', 'none',
test/unit/weighted-connection-pool.test.ts 1>   'none', 'none'
test/unit/weighted-connection-pool.test.ts 1> ]

This test passes though:

  t.test('3 Connections, same weight', t => {
    const pool = new WeightedConnectionPool({ Connection: HttpConnection })
    pool.addConnection([
      'http://localhost:9200/',
      'http://localhost:9201/',
      'http://localhost:9202/'
    ]);

    for (let i = 0; i < 30; i++) {
      pool.markDead(pool.connections[0]);
      pool.markDead(pool.connections[1]);
      pool.markDead(pool.connections[2]);
    }

    const order: string[] = [];

    try {
      for (let i = 0; i < 100; i++) {
        const connection = pool.getConnection(opts);
        order.push(connection ? connection.id : 'none');
      }
      console.log(order)
      t.pass('Distribution is ok')
    } catch (err: any) {
      t.error(err)
    }

    t.end()
  })

as it outputs

test/unit/weighted-connection-pool.test.ts 1> [
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/', 'http://localhost:9201/', 'http://localhost:9202/',
test/unit/weighted-connection-pool.test.ts 1>   'http://localhost:9200/'
test/unit/weighted-connection-pool.test.ts 1> ]

So there's an interaction by alternating the getConnection and markDead calls. Note that this is what happen in an actual production scenario, as the transport requests a connection, fails the call with it because the node is down, and then flag the connection as dead

pgayvallet · 2022-06-16T15:18:29Z

I then ran

  t.test('3 Connections, same weight', t => {
    const pool = new WeightedConnectionPool({ Connection: HttpConnection })
    pool.addConnection([
      'http://localhost:9200/',
      'http://localhost:9201/',
      'http://localhost:9202/',
      'http://localhost:9203/'
    ]);

    for (let i = 0; i < 10; i++) {
      const con = pool.getConnection(opts);
      if(con) {
        pool.markDead(con)
      }
    }

    let count = 0;

    try {
      for (let i = 0; i < 10000; i++) {
        const connection = pool.getConnection(opts);
        if(connection) {
          break
        }
        count++;
      }
      console.log(`count: ${count}`);
      t.pass('Distribution is ok')
    } catch (err: any) {
      t.error(err)
    }

    t.end()
  })

Making the number of initial failing calls, and the number of nodes, vary to see the amount of getConnection calls required before the pool actually returns a connection to a node.

The results:

2 nodes - 20 failing calls - count: 395
2 nodes - 30 failing calls - count: 385
2 nodes - 40 failing calls - count: 375

3 nodes - 10 failing calls - count: 252
3 nodes - 20 failing calls - count: 242
3 nodes - 30 failing calls - count: 232
3 nodes - 40 failing calls - count: 222

4 nodes - 10 failing calls - count: 0 (!)
4 nodes - 20 failing calls - count: 169
4 nodes - 30 failing calls - count: 159
4 nodes - 40 failing calls - count: 149

TinaHeiligers · 2022-06-16T16:05:45Z

4 nodes - 10 failing calls - count: 0 (!)

seems strange, considering at first glance the fewer the number of failing calls, the higher the count for 2 and 3 nodes.

pgayvallet · 2022-06-16T16:20:30Z

Yea, I have no idea why exactly, maybe there's a minimum amount of calls to have depending on number of nodes, or something. We could try with more nodes to see, but at this point, I think we collected enough element for a maintainer to pick that issue up eventually.

TinaHeiligers · 2022-06-16T17:31:31Z

I think we collected enough element for a maintainer to pick that issue up eventually.

Agreed.

jodevsa · 2022-07-29T13:41:38Z

I've opened an issue describing the main problem and the root cause here: elastic/elastic-transport-js#53

github-actions · 2023-11-14T01:48:37Z

This issue is stale because it has been open 90 days with no activity. Remove the stale label, or leave a comment, or this will be closed in 14 days.

github-actions · 2024-02-13T01:47:24Z

This issue is stale because it has been open 90 days with no activity. Remove the stale label, or leave a comment, or this will be closed in 14 days.

github-actions · 2024-10-29T02:02:57Z

This issue is stale because it has been open 90 days with no activity. Remove the stale label, or leave a comment, or this will be closed in 14 days.

pgayvallet added the bug label Jun 15, 2022

azasypkin mentioned this issue Jun 16, 2022

8.2.2: Kibana with multiple ES hosts won't connect to remaining ES hosts after failure of active host elastic/kibana#134301

Closed

pgayvallet changed the title ~~Client not able to reconnect instantly if all nodes get down then up at the same time.~~ Client not able to reconnect instantly when a node gets down then up again with multi-node configuration Jun 16, 2022

pgayvallet added the v8.x label Jun 16, 2022

pgayvallet mentioned this issue Jun 17, 2022

ES Client: use ClusterConnectionPool instead of WeightedConnectionPool elastic/kibana#134628

Merged

1 task

rudolf mentioned this issue Jul 29, 2022

WeightedConnectionPool.getConnection returns null that leads to NoLivingConnectionsError error elastic/elastic-transport-js#53

Open

JoshMock added the transport label Aug 14, 2023

github-actions bot added the stale label Nov 14, 2023

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sheldhur mentioned this issue Nov 21, 2023

Reconnection is not supported pinojs/pino-elasticsearch#72

Open

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Client not able to reconnect instantly when a node gets down then up again with multi-node configuration #1714

Client not able to reconnect instantly when a node gets down then up again with multi-node configuration #1714

pgayvallet commented Jun 15, 2022 •

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pgayvallet commented Jun 16, 2022

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pgayvallet commented Jun 16, 2022

pgayvallet commented Jun 16, 2022

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TinaHeiligers commented Jun 16, 2022

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github-actions bot commented Oct 29, 2024

Client not able to reconnect instantly when a node gets down then up again with multi-node configuration #1714

Client not able to reconnect instantly when a node gets down then up again with multi-node configuration #1714

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pgayvallet commented Jun 15, 2022 • edited Loading

🐛 Bug Report

To Reproduce

Scenarios

1. stop node 1, then restart node 1

2. stop node 2, then restart node 2

3. stop node 1, stop node 2, restart node 1, restart node 2

4. stop node 1, restart node 1, stop node 2, restart node 2

Expected behavior

Your Environment

pgayvallet commented Jun 16, 2022

pgayvallet commented Jun 16, 2022 • edited Loading

pgayvallet commented Jun 16, 2022

pgayvallet commented Jun 16, 2022

TinaHeiligers commented Jun 16, 2022

pgayvallet commented Jun 16, 2022

TinaHeiligers commented Jun 16, 2022

jodevsa commented Jul 29, 2022 • edited Loading

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github-actions bot commented Oct 29, 2024

pgayvallet commented Jun 15, 2022 •

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jodevsa commented Jul 29, 2022 •

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