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Elasticsearch.Net and NEST: the .NET clients [5.x] » Client Concepts - Elasticsearch.Net » Sniffing periodically
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Sniffing periodicallyedit

Connection pools that return true for SupportsReseeding can be configured to sniff periodically. In addition to sniffing on startup and sniffing on failures, sniffing periodically can benefit scenarios where clusters are often scaled horizontally during peak hours. An application might have a healthy view of a subset of the nodes but without sniffing periodically it will never find the nodes that have been added to help out with load

var audit = new Auditor(() => Framework.Cluster
    .Nodes(10)
    .MasterEligible(9202, 9203, 9204)
    .ClientCalls(r => r.SucceedAlways())
    .Sniff(s => s.SucceedAlways(Framework.Cluster
        .Nodes(100)
        .MasterEligible(9202, 9203, 9204)
        .ClientCalls(r => r.SucceedAlways())
        .Sniff(ss => ss.SucceedAlways(Framework.Cluster
            .Nodes(10)
            .MasterEligible(9202, 9203, 9204)
            .ClientCalls(r => r.SucceedAlways())
        ))
    ))
    .SniffingConnectionPool()
    .Settings(s => s
        .DisablePing()
        .SniffOnConnectionFault(false)
        .SniffOnStartup(false)
        .SniffLifeSpan(TimeSpan.FromMinutes(30))
    )
);

healty cluster all nodes return healthy responses

audit = await audit.TraceCalls(
    new ClientCall { { HealthyResponse, 9200 } },
    new ClientCall { { HealthyResponse, 9201 } },
    new ClientCall { { HealthyResponse, 9202 } },
    new ClientCall { { HealthyResponse, 9203 } },
    new ClientCall { { HealthyResponse, 9204 } },
    new ClientCall { { HealthyResponse, 9205 } },
    new ClientCall { { HealthyResponse, 9206 } },
    new ClientCall { { HealthyResponse, 9207 } },
    new ClientCall { { HealthyResponse, 9208 } },
    new ClientCall { { HealthyResponse, 9209 } },
    new ClientCall {
        { HealthyResponse, 9200 },
        { pool => pool.Nodes.Count.Should().Be(10) }
    }
);

Now let’s forward the clock 31 minutes, our sniff lifespan should now go state and the first call should do a sniff which discovered we scaled up to a 100 nodes!

audit.ChangeTime(d => d.AddMinutes(31));

a sniff is done first and it prefers the first node master node

audit = await audit.TraceCalls(
    new ClientCall {
{ SniffOnStaleCluster },
        { SniffSuccess, 9202 },
        { HealthyResponse, 9201 },
        { pool => pool.Nodes.Count.Should().Be(100) }
    }
);

audit.ChangeTime(d => d.AddMinutes(31));

a sniff is done first and it prefers the first node master node

audit = await audit.TraceCalls(
    new ClientCall {
{ SniffOnStaleCluster },
        { SniffSuccess, 9202 },
        { HealthyResponse, 9200 },
        { pool => pool.Nodes.Count.Should().Be(10) }
    }
);
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