/// <summary>
/// Implements the service as a <see cref="Task"/>.
/// </summary>
/// <returns>The <see cref="Task"/>.</returns>
private static async Task RunAsync()
{
var periodicTask =
new AsyncPeriodicTask(
pollInterval,
onTaskAsync:
async() =>
{
log.LogDebug(() => "Starting poll");
// We're going to collect the [hostname --> address] mappings into
// a specialized (semi-threadsafe) dictionary.
var hostAddresses = new HostAddresses();
// Retrieve the current hive definition from Consul if we don't already
// have it or it's different from what we've cached.
hiveDefinition = await HiveHelper.GetDefinitionAsync(hiveDefinition, terminator.CancellationToken);
log.LogDebug(() => $"Hive has [{hiveDefinition.NodeDefinitions.Count}] nodes.");
// Add the [NAME.HIVENAME.nhive.io] definitions for each cluster node.
foreach (var node in hiveDefinition.Nodes)
{
hostAddresses.Add($"{node.Name}.{hiveDefinition.Name}.nhive.io", IPAddress.Parse(node.PrivateAddress));
}
// Read the DNS entry definitions from Consul and add the appropriate
// host/addresses based on health checks, etc.
var targetsResult = (await consul.KV.ListOrDefault <DnsEntry>(HiveConst.ConsulDnsEntriesKey + "/", terminator.CancellationToken));
List <DnsEntry> targets;
if (targetsResult == null)
{
// The targets key wasn't found in Consul, so we're
// going to assume that there are no targets.
targets = new List <DnsEntry>();
}
else
{
targets = targetsResult.ToList();
}
log.LogDebug(() => $"Consul has [{targets.Count()}] DNS targets.");
await ResolveTargetsAsync(hostAddresses, targets);
// Generate a canonical [hosts.txt] file by sorting host entries by
// hostname and then by IP address.
//
// Unhealthy hosts will be assigned the unrouteable [0.0.0.0] address.
// The reason for this is subtle but super important.
//
// If we didn't do this, the DNS host would likely be resolved by a
// public DNS service, perhaps returning the IP address of a production
// endpoint.
//
// This could cause a disaster if the whole purpose of having a local
// DNS host defined to redirect test traffic to a test service. If
// the test service endpoints didn't report as healthy and [0.0.0.0]
// wasn't set, then test traffic could potentially hit the production
// endpoint and do serious damage.
var sbHosts = new StringBuilder();
var mappingCount = 0;
foreach (var host in hostAddresses.OrderBy(h => h.Key))
{
foreach (var address in host.Value.OrderBy(a => a.ToString()))
{
sbHosts.AppendLineLinux($"{address,-15} {host.Key}");
mappingCount++;
}
}
var unhealthyTargets = targets.Where(t => !hostAddresses.ContainsKey(t.Hostname) || hostAddresses[t.Hostname].Count == 0).ToList();
if (unhealthyTargets.Count > 0)
{
sbHosts.AppendLine();
sbHosts.AppendLine($"# [{unhealthyTargets.Count}] unhealthy DNS hosts:");
sbHosts.AppendLine();
var unhealthyAddress = "0.0.0.0";
foreach (var target in unhealthyTargets.OrderBy(h => h))
{
sbHosts.AppendLineLinux($"{unhealthyAddress,-15} {target.Hostname}");
}
}
// Compute the MD5 hash and compare it to the hash persisted to
// Consul (if any) to determine whether we need to update the
// answers in Consul.
var hostsTxt = sbHosts.ToString();
var hostsMD5 = NeonHelper.ComputeMD5(hostsTxt);
var currentMD5 = await consul.KV.GetStringOrDefault(HiveConst.ConsulDnsHostsMd5Key, terminator.CancellationToken);
if (currentMD5 == null)
{
currentMD5 = string.Empty;
}
if (hostsMD5 != currentMD5)
{
log.LogDebug(() => $"DNS answers have changed.");
log.LogDebug(() => $"Writing [{mappingCount}] DNS answers to Consul.");
// Update the Consul keys using a transaction.
var operations = new List <KVTxnOp>()
{
new KVTxnOp(HiveConst.ConsulDnsHostsMd5Key, KVTxnVerb.Set)
{
Value = Encoding.UTF8.GetBytes(hostsMD5)
},
new KVTxnOp(HiveConst.ConsulDnsHostsKey, KVTxnVerb.Set)
{
Value = Encoding.UTF8.GetBytes(hostsTxt)
}
};
await consul.KV.Txn(operations, terminator.CancellationToken);
}
log.LogDebug(() => "Finished poll");
return(await Task.FromResult(false));
},
onExceptionAsync:
async e =>
{
log.LogError(e);
return(await Task.FromResult(false));
},
onTerminateAsync:
async() =>
{
log.LogInfo(() => "Terminating");
await Task.CompletedTask;
});
terminator.AddDisposable(periodicTask);
await periodicTask.Run();
}
/// <summary>
/// Handles polling of Docker swarm about the hive nodes and updating the hive
/// definition and hash when changes are detected.
/// </summary>
/// <returns>The tracking <see cref="Task"/>.</returns>
private static async Task SwarmPollerAsync()
{
var periodicTask =
new AsyncPeriodicTask(
swarmPollInterval,
onTaskAsync:
async() =>
{
try
{
log.LogDebug(() => "SWARM-POLLER: Polling");
// Retrieve the current hive definition from Consul if we don't already
// have it or if it's different from what we've cached.
cachedHiveDefinition = await HiveHelper.GetDefinitionAsync(cachedHiveDefinition, terminator.CancellationToken);
// Retrieve the swarm nodes from Docker.
log.LogDebug(() => $"SWARM-POLLER: Querying [{docker.Settings.Uri}]");
var swarmNodes = await docker.NodeListAsync();
// Parse the node definitions from the swarm nodes and build a new definition with
// using the new nodes. Then compare the hashes of the cached and new hive definitions
// and then update Consul if they're different.
var currentHiveDefinition = NeonHelper.JsonClone <HiveDefinition>(cachedHiveDefinition);
currentHiveDefinition.NodeDefinitions.Clear();
foreach (var swarmNode in swarmNodes)
{
var nodeDefinition = NodeDefinition.ParseFromLabels(swarmNode.Labels);
nodeDefinition.Name = swarmNode.Hostname;
currentHiveDefinition.NodeDefinitions.Add(nodeDefinition.Name, nodeDefinition);
}
log.LogDebug(() => $"SWARM-POLLER: [{currentHiveDefinition.Managers.Count()}] managers and [{currentHiveDefinition.Workers.Count()}] workers in current hive definition.");
// Hive pets are not part of the Swarm, so Docker won't return any information
// about them. We'll read the pet definitions from [neon/global/pets-definition] in
// Consul. We'll assume that there are no pets if this key doesn't exist for
// backwards compatibility and robustness.
var petsJson = await HiveHelper.Consul.KV.GetStringOrDefault($"{HiveConst.GlobalKey}/{HiveGlobals.PetsDefinition}", terminator.CancellationToken);
if (petsJson == null)
{
log.LogDebug(() => $"SWARM-POLLER: [{HiveConst.GlobalKey}/{HiveGlobals.PetsDefinition}] Consul key not found. Assuming no pets.");
}
else
{
if (!string.IsNullOrWhiteSpace(petsJson))
{
// Parse the pet node definitions and add them to the hive definition.
var petDefinitions = NeonHelper.JsonDeserialize <Dictionary <string, NodeDefinition> >(petsJson);
foreach (var item in petDefinitions)
{
currentHiveDefinition.NodeDefinitions.Add(item.Key, item.Value);
}
log.LogDebug(() => $"SWARM-POLLER: [{HiveConst.GlobalKey}/{HiveGlobals.PetsDefinition}] defines [{petDefinitions.Count}] pets.");
}
else
{
log.LogDebug(() => $"SWARM-POLLER: [{HiveConst.GlobalKey}/{HiveGlobals.PetsDefinition}] is empty.");
}
}
// Fetch the hive summary and add it to the hive definition.
currentHiveDefinition.Summary = HiveSummary.FromHive(hive, currentHiveDefinition);
// Determine if the definition has changed.
currentHiveDefinition.ComputeHash();
if (currentHiveDefinition.Hash != cachedHiveDefinition.Hash)
{
log.LogInfo(() => "SWARM-POLLER: Hive definition has CHANGED. Updating Consul.");
await HiveHelper.PutDefinitionAsync(currentHiveDefinition, cancellationToken: terminator.CancellationToken);
cachedHiveDefinition = currentHiveDefinition;
}
else
{
log.LogDebug(() => "SWARM-POLLER: Hive definition is UNCHANGED.");
}
}
catch (KeyNotFoundException)
{
// We'll see this when no hive definition has been persisted to the
// hive. This is a serious problem. This is configured during setup
// and there should always be a definition in Consul.
log.LogError(() => $"SWARM-POLLER: No hive definition has been found at [{hiveDefinitionKey}] in Consul. This is a serious error that will have to be corrected manually.");
}
log.LogDebug(() => "SWARM-POLLER: Finished Poll");
return(await Task.FromResult(false));
},
onExceptionAsync:
async e =>
{
log.LogError("SWARM-POLLER", e);
return(await Task.FromResult(false));
},
onTerminateAsync:
async() =>
{
log.LogInfo(() => "SWARM-POLLER: Terminating");
await Task.CompletedTask;
});
terminator.AddDisposable(periodicTask);
await periodicTask.Run();
}
