Aerospike randomly returning nil errors when using Query() with Go client

I'm experiencing some strange behavior. I'm trying to set up a small webapp that fetches some data using Aerospike 3.5 Community running on an Ubuntu 12.04 server. I'm using the default aerospike.conf file (using the 'test' namespace) and am following the example of how to query here.

When I attempt to query some records with a filter, the Errors channel randomly is returning a nil error. (This example points to my dev database instance).

To replicate, compile and run the following multiple times, you'll see either data returned or a panic:

package main

import (
	"fmt"

	"github.com/aerospike/aerospike-client-go"
)

func main() {

	c, err := aerospike.NewClient("52.7.157.46", 3000)
	if err != nil {
		panic(err)
	}

	recs := liststuff(c)

	fmt.Printf("got results: %v", recs)
}

func liststuff(client *aerospike.Client) []*aerospike.Record {

	// fetch some records with a filter
	stm := aerospike.NewStatement("test", "products")
	stm.Addfilter(aerospike.NewEqualFilter("visible", 1))
	fmt.Println("querying...")
	recordset, err := client.Query(nil, stm)
	if err != nil {
		panic(err)
	}

	// collect results into a slice
	recs := []*aerospike.Record{}
L:
	for {
		select {
		case rec, chanOpen := <-recordset.Records:
			if !chanOpen {
				break L
			}
			fmt.Println("found record %v", rec)
			recs = append(recs, rec)
		case err := <-recordset.Errors:
			if err != nil {
				panic(err)
			} else {
				panic(fmt.Errorf("error nil when it should exist"))
			}
			return nil
		}
	}

	return recs
}

Just to post an update, both Errors and Records channels are closed automatically when the record stream is over from the server-side, hence the nil value from the Errors channel.

So this wasn't an error after all. We've updated the thread in our Aerospike user forum post accordingly.

I'm not familiar with the aerospike package but running your example code show that it always panics no matter if it returns data or not.

That means that the Errors channel always sends either an error or nil. If that's the expected behavior you'd have to handle it accordingly and only panic when the error is not nil.

Sending nil on the channel still means that a value is being sent on the channel and it will trigger the select statement. Thus the panic on a nil error.

The randomness you see, i.e. sometimes data is returned and sometimes it isn't is due to the nature of the select statement. If both data and a nil error are being sent at the same time both cases are true and select will pseudo randomly select one of the two.

> If one or more of the communications can proceed, a single one that
> can proceed is chosen via a uniform pseudo-random selection.
> Otherwise, if there is a default case, that case is chosen. If there
> is no default case, the "select" statement blocks until at least one
> of the communications can proceed.

If it selects the data channel first it will print the data and then on the next iteration select the error channel and panic. If it picks the error channel first it panics and the data never prints.

Turns out it's a legit bug and should be fixed soon: https://discuss.aerospike.com/t/aerospike-randomly-returning-nil-errors-when-using-query-with-go-client/1346