cli: debug zip returns incomplete data

[tbg]

This code here queries various table against a single node, but it should query them on all nodes.

For the gossip-based tables this is less of a problem than for the metrics, which are strictly per node. I'm looking at an issue right now where the debug zip metrics of all nodes would've been really helpful, but I only have the metrics of one node.

cockroach/pkg/cli/zip.go

Lines 210 to 222 in 9f44f85

	for _, item := range []struct {
	query, name string
	}{
	{"SELECT * FROM crdb_internal.gossip_liveness;", gossipLivenessName},
	{"SELECT * FROM crdb_internal.gossip_network;", gossipNetworkName},
	{"SELECT * FROM crdb_internal.gossip_nodes;", gossipNodesName},
	{"SELECT * FROM crdb_internal.node_metrics;", metricsName},
	{"SELECT * FROM crdb_internal.gossip_alerts;", alertsName},
	} {
	if err := dumpTableDataForZip(z, sqlConn, item.query, item.name); err != nil {
	return errors.Wrap(err, item.name)
	}
	}

[tbg]

cc @dsaveliev who's taking a look at this.

I just realized this is a bit more complex than it seems. For example, to query node_metrics for another node, you'd naively need to open SQL connections to other nodes, which is not generally possible.

Instead, we should grab /_status/vars which contains pretty much the same information. In the long run, if we use SQL for more of this information, we need facilities inside of SQL that allows proxying data from other nodes, but this is less urgent.

[tbg]

#36167