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Sniffing on connection failure

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Sniffing on connection failure

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Sniffing on connection is enabled by default when using a connection pool that allows reseeding. The only connection pool we ship with that allows this is the Sniffing connection pool.

This can be very handy to force a refresh of the connection pool’s known healthy nodes by asking the Elasticsearch cluster itself, and a sniff tries to get the nodes by asking each node it currently knows about, until one responds.

Here we seed our connection with 5 known nodes on ports 9200-9204, of which we think 9202, 9203, 9204 are master eligible nodes. Our virtualized cluster will throw once when doing a search on 9201. This should cause a sniff to be kicked off.

var audit = new Auditor(() => Framework.Cluster
    .Nodes(5)
    .MasterEligible(9202, 9203, 9204)
    .ClientCalls(r => r.SucceedAlways())
    .ClientCalls(r => r.OnPort(9201).Fails(Once)) 
    .Sniff(p => p.SucceedAlways(Framework.Cluster
        .Nodes(3)
        .MasterEligible(9200, 9202)
        .ClientCalls(r => r.OnPort(9201).Fails(Once))
        .Sniff(s => s.SucceedAlways(Framework.Cluster 
            .Nodes(3, 9210)
            .MasterEligible(9210, 9212)
            .ClientCalls(r => r.SucceedAlways())
            .Sniff(r => r.SucceedAlways())
        ))
    ))
    .SniffingConnectionPool()
    .Settings(s => s.DisablePing().SniffOnStartup(false))
);

audit = await audit.TraceCalls(
/** */
    new ClientCall {
        { HealthyResponse, 9200 },
        { pool =>  pool.Nodes.Count.Should().Be(5) }
    },
    new ClientCall {
        { BadResponse, 9201},
        { SniffOnFail },
        { SniffSuccess, 9202}, 
        { HealthyResponse, 9200},
        { pool =>  pool.Nodes.Count.Should().Be(3) } 
    },
    new ClientCall {
        { BadResponse, 9201},
        { SniffOnFail }, 
        { SniffSuccess, 9200},
        { HealthyResponse, 9210},
        { pool =>  pool.Nodes.Count.Should().Be(3) }
    },
    new ClientCall { { HealthyResponse, 9211 } },
    new ClientCall { { HealthyResponse, 9212 } },
    new ClientCall { { HealthyResponse, 9210 } },
    new ClientCall { { HealthyResponse, 9211 } },
    new ClientCall { { HealthyResponse, 9212 } },
    new ClientCall { { HealthyResponse, 9210 } },
    new ClientCall { { HealthyResponse, 9211 } },
    new ClientCall { { HealthyResponse, 9212 } },
    new ClientCall { { HealthyResponse, 9210 } }
);

	When the call fails on 9201, the following sniff succeeds and returns a new cluster state of healthy nodes. This cluster only has 3 nodes and the known masters are 9200 and 9202. A search on 9201 is setup to still fail once
	After this second failure on 9201, another sniff will happen which returns a cluster state that no longer fails but looks completely different; It’s now three nodes on ports 9210 - 9212, with 9210 and 9212 being master eligible.
	We assert we do a sniff on our first known master node 9202 after the failed call on 9201
	Our pool should now have three nodes
	We assert we do a sniff on the first master node in our updated cluster

Sniffing after ping failure

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Here we set up our cluster exactly the same as the previous setup Only we enable pinging (default is true) and make the ping fail

var audit = new Auditor(() => Framework.Cluster
    .Nodes(5)
    .MasterEligible(9202, 9203, 9204)
    .Ping(r => r.OnPort(9201).Fails(Once))
    .Sniff(p => p.SucceedAlways(Framework.Cluster
        .Nodes(3)
        .MasterEligible(9200, 9202)
        .Ping(r => r.OnPort(9201).Fails(Once))
        .Sniff(s => s.SucceedAlways(Framework.Cluster
            .Nodes(3, 9210)
            .MasterEligible(9210, 9211)
            .Ping(r => r.SucceedAlways())
            .Sniff(r => r.SucceedAlways())
        ))
    ))
    .SniffingConnectionPool()
    .Settings(s => s.SniffOnStartup(false))
);

audit = await audit.TraceCalls(
    new ClientCall {
        { PingSuccess, 9200 },
        { HealthyResponse, 9200 },
        { pool =>  pool.Nodes.Count.Should().Be(5) }
    },
    new ClientCall {
        { PingFailure, 9201},
        { SniffOnFail }, 
        { SniffSuccess, 9202},
        { PingSuccess, 9200},
        { HealthyResponse, 9200},
        { pool =>  pool.Nodes.Count.Should().Be(3) } 
    },
    new ClientCall {
        { PingFailure, 9201},
        { SniffOnFail }, 
        { SniffSuccess, 9200},
        { PingSuccess, 9210},
        { HealthyResponse, 9210},
        { pool =>  pool.Nodes.Count.Should().Be(3) }
    },
    new ClientCall {
        { PingSuccess, 9211 },
        { HealthyResponse, 9211 }
    },
    new ClientCall {
        { PingSuccess, 9212 },
        { HealthyResponse, 9212 }
    },
    new ClientCall { { HealthyResponse, 9210 } }, 
    new ClientCall { { HealthyResponse, 9211 } },
    new ClientCall { { HealthyResponse, 9212 } },
    new ClientCall { { HealthyResponse, 9210 } }
);

	We assert we do a sniff on our first known master node 9202
	Our pool should now have three nodes
	We assert we do a sniff on the first master node in our updated cluster
	9210 was already pinged after the sniff returned the new nodes

Client uses publish address

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var audit = new Auditor(() => Framework.Cluster
        .Nodes(2)
        .MasterEligible(9200)
        .Ping(r => r.OnPort(9200).Fails(Once))
        .Sniff(p => p.SucceedAlways(Framework.Cluster
                .Nodes(10)
                .MasterEligible(9200, 9202, 9201)
                .PublishAddress("10.0.12.1")
        ))
        .SniffingConnectionPool()
        .Settings(s => s.SniffOnStartup(false))
);

Action<Audit, string, int> hostAssert = (a, host, expectedPort) =>
{
    a.Node.Uri.Host.Should().Be(host);
    a.Node.Uri.Port.Should().Be(expectedPort);
};

audit = await audit.TraceCalls(
    new ClientCall {
        { PingFailure, a => hostAssert(a, "localhost", 9200)},
        { SniffOnFail },
        { SniffSuccess, a => hostAssert(a, "localhost", 9200)},
        { PingSuccess, a => hostAssert(a, "10.0.12.1", 9200)},
        { HealthyResponse,  a => hostAssert(a, "10.0.12.1", 9200)},
        { pool =>  pool.Nodes.Count.Should().Be(10) } 
    }
);

Our pool should now have 10 nodes

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