Enable DNS Resolving via TCP in case of Timeout

[cgm-aw]

Hi everyone,

I noticed that Vertx enables Netty DNS Resolving via TCP (see https://github.com/eclipse-vertx/vert.x/blob/4.5.17/src/main/java/io/vertx/core/impl/resolver/DnsResolverProvider.java#L108):
builder.socketChannelFactory(() -> (SocketChannel) vertx.transport().channelFactory(false).newChannel());

However, this sets "retryOnTimeout" to "false". It would be nice if Vertx would enable TCP resolving on timeouts - maybe just with some kind of environment variable for toggling, like this:

builder.socketChannelFactory(() -> (SocketChannel) vertx.transport().channelFactory(false).newChannel(), Boolean.getBoolean("vertx.dns.retryOnTimeout"));

I'm happy to provide a PR if you approve of this.

Best regards

Contribution

Me

[cgm-aw]

By the way, I think #5114 requests the same thing.

[vietj]

@cgm-aw this should be configured using vertx options or address resolver options, contribution is welcome

[cgm-aw]

Done: #5692
I just noticed this is flagged for 5.x, I based the fix on 4.x. Not sure what your policy on backports is - should I base the fix on 5.x?

[vietj]

we can backport very small features