public async Task Invoke(HttpContext context, IBeatPulseService pulseService)
{
var request = context.Request;
if (!IsBeatPulseRequest(request, out string beatPulsePath))
{
await _next.Invoke(context);
return;
}
if (!await IsAuthenticatedRequest(context))
{
context.Response.StatusCode = StatusCodes.Status401Unauthorized;
return;
}
if (TryFromCache(beatPulsePath, out OutputLivenessMessage output))
{
await request.HttpContext
.Response
.WriteLivenessMessage(_options, output);
return;
}
output = new OutputLivenessMessage();
var responses = await pulseService.IsHealthy(beatPulsePath, _options, context);
if (!responses.Any())
{
// beat pulse path is not valid across any liveness
// return unavailable with not found reason.
output.SetNotFound();
}
else
{
// beat pulse is executed, set response
// messages and add to cache if is configured.
output.AddHealthCheckMessages(responses);
output.SetExecuted();
if (_options.CacheMode.UseServerMemory() && _options.CacheOutput)
{
_cache.TryAdd(beatPulsePath, output);
}
}
await request.HttpContext
.Response
.WriteLivenessMessage(_options, output);
}
bool TryFromCache(string path, out OutputLivenessMessage message)
{
message = null;
if (_options.CacheOutput &&
_options.CacheMode.UseServerMemory() &&
_cache.TryGetValue(path, out message))
{
var seconds = (DateTime.UtcNow - message.EndAtUtc).TotalSeconds;
if (_options.CacheDuration > seconds)
{
return(true);
}
else
{
_cache.TryRemove(path, out OutputLivenessMessage removed);
return(false);
}
}
return(false);
}
public static Task WriteLivenessMessage(this HttpResponse response, BeatPulseOptions options, OutputLivenessMessage message)
{
var defaultContentType = options.DetailedOutput ? "application/json" : "text/plain";
const string noCacheOptions = "no-cache, no-store, must-revalidate";
const string noCachePragma = "no-cache";
const string defaultExpires = "0";
response.Headers["Content-Type"] = new[] { defaultContentType };
if (options.CacheOutput)
{
if (options.CacheMode == CacheMode.Header || options.CacheMode == CacheMode.HeaderAndServerMemory)
{
response.Headers["Cache-Control"] = new[] { $"public, max-age={options.CacheDuration}" };
}
}
else
{
response.Headers["Cache-Control"] = new[] { noCacheOptions };
response.Headers["Pragma"] = new[] { noCachePragma };
response.Headers["Expires"] = new[] { defaultExpires };
}
response.StatusCode = message.Code;
var content = options.DetailedOutput ? JsonConvert.SerializeObject(message)
: Enum.GetName(typeof(HttpStatusCode), message.Code);
return(response.WriteAsync(content));
}
