I'm a newbie to Crystal-lang.
I'm trying the Http Server example given in the crystal-lang docs.
require "http/server"
server = HTTP::Server.new(8080) do |context|
context.response.content_type = "text/plain"
context.response.print "Hello world! The time is #{Time.now}"
end
puts "Listening on http://127.0.0.1:8080"
server.listen
When I run this code I'm getting the following error.
Error in httpserv.cr:3: no overload matches 'HTTP::Server.new' with type Int32
Overloads are:
- HTTP::Server.new(handlers : Array(HTTP::Handler), &handler)
- HTTP::Server.new(&handler)
- HTTP::Server.new(handlers : Array(HTTP::Handler))
- HTTP::Server.new(handler : HTTP::Handler | HTTP::Handler::Proc)
server = HTTP::Server.new(8080) do |context|
What I can gather from this is I need to specify some methods/functions for handling the HTTP requests, but I'm not getting how to do that.
What is the correct way to do that is my question?
Thanks in advance.
The HTTP::Server API has changed in the latest release Crystal 0.25.0. It's use is documented in the recent API docs (the 0.25.0 release docs have a slight error, but it's fixed on master).
As you can see from the error message, the signature of Server.new has changed. It now only accepts some form of handler. You already have that defined in your example in the do block. The constructor no longer accepts a port number, but you need to call #bind_tcp seperately.
Your example should now look like this:
require "http/server"
server = HTTP::Server.new do |context|
context.response.content_type = "text/plain"
context.response.print "Hello world! The time is #{Time.now}"
end
address = server.bind_tcp 8080
puts "Listening on http://#{address}"
server.listen
Related
I am using WsReceive() function of the ATEasy framework and wanted to ask what is the meaning of the values "aioDefault
and aioDisableWsReceiveEarlyReturn" of "enMode" parameter?
I found this in the ATEASY documentation:
If enMode, input receive mode includes aioDisableWsReceiveEarlyReturn,
it prevents WsReceive from an "early return" when there is a momentary
interruption in the data being received.
And this from the online help of ateasy (By a tip of an expert from the ateasy forum) :
If sEos parameter is an empty string and aioDisableWsReceiveEarlyReturn mode flag is not used (default case), the function will return immediately if characters are found in the input buffer, and the timeout will be ignored. Using the aioDisableWsReceiveEarlyReturn flag will ensure that the function will return only if the timeout is reached or all lBytes characters were received.
I am defining a pipeline in data factory, I had some errors that I correct.
The first activity is calling an usql script to do some aggregation, I changed the script plenty of time but the error is still:
[{"errorId":"E_CSC_USER_SYNTAXERROR","severity":"Error","component":"CSC","source":"USER","message":"syntax
error. Final statement did not end with a semicolon","details":"at
token 'usql', line 4\r\nnear the ###:\r\n**************\r\nCLARE
#lineitemsfile string =
\"/datalakerepo/input/2016/01/01lineitems.txt\";\nDECLARE #ordersfile
string = \"/datalakerepo/input/2016/01/01orders.txt\";\nsales.usql ###
\n","description":"Invalid syntax found in the
script.","resolution":"Correct the script syntax, using expected
token(s) as a
guide.","helpLink":"","filePath":"","lineNumber":4,"startOffset":228,"endOffset":232}].
seem like not all usql script is read from the data factory, so I though that may be the "rerun in upstream in pipeline" have something to do with this, like clear cache from previous script.
Anyone knows what "rerun in upstream in pipeline" does?
Many thanks!
"Rerun with upstream in pipeline" basically means "recalculate with all dependencies". For example, if one has pipeline1 -> dataset1 -> pipeline2 and tries to rerun pipeline2 with dependecies, then pipeline1 and pipeline2 will be both executed. I believe it works same with several chained activities within single pipeline.
I have a Dynamodb table with a few fields - my_id is the PrimaryKey. In the API gateway I set up a response with a method that takes in a parameter {my_id}.
Then I have an Integration Request mapping template that takes the passed in parameter and queries the table to return all the fields that match.
Then I have an Integration response mapping template that cleans up the returned items the way I want.
This all works perfect.
The thing I can't figure out how to do is if the parameter that is passed in doesn't match anything in the table, how do I get it to change from a 200 status into a 404?
From what I can tell when the passed in parameter doesn't match anything it doesn't cause an error, it just doesn't return anything.
It seems like I need to change the mapping template on the Integration response to first check if the params are empty and then somehow tell it to change the response status.
I can find info about this type of thing with people using Lambda, but I am not using Lambda - just the Dynamodb table and the API Gateway.
You can use Mapping Template to convert the response that you get from DDB and overrride the response code. You can get more details in the link https://docs.aws.amazon.com/apigateway/latest/developerguide/apigateway-override-request-response-parameters.html
If you are using cloud formation, you can do this by using below snippet
IntegrationResponses:
- StatusCode: "200"
ResponseTemplates:
application/json: |
{
"payload" : {
}
},
}
IntegrationResponses:
- StatusCode: "200"
ResponseTemplates:
application/json: |
#set($inputRoot = $input.path('$'))
#if($inputRoot.toString().contains("Item"))
$input.json("$")
#set($context.responseOverride.status = 200)
#else
#set($context.responseOverride.status = 404)
#end
Api gateway currently supports mapping the status code using the status code of the integration response (Here dynamodb response code). The only workaround is to use a lambda function which outputs different error messages that can be mapped using a error regex http://docs.aws.amazon.com/apigateway/latest/developerguide/how-to-method-settings-execution-console.html.
I am attempting to return an object from a AWS Lambda function instead of a simple string.
// ...
context.fail({
"email": "Email address is too short",
"firstname": "First name is too short"
});
// ...
I have already used the errorMessage for mapping error responses to status codes and that has been great:
// ...
context.fail('That "username" has already been taken.');
// ...
Am I simply trying to do something that the AWS API Gateway does not afford?
I have also already found this article which helped: Is there a way to change the http status codes returned by Amazon API Gateway?.
Update
Since time of writing, lambda has updated the invocation signature and now passes event, context, callback.
Instead of calling context.done(err, res) you should use callback(err, res). Note that what was true for context.done still applies to the callback pattern.
Should also add that with API Gateways proxy and integration implementation this entire thread is pretty much obsolete.
I recommend reading this article if you are integrating API Gateway with Lambda: http://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-create-api-as-simple-proxy-for-lambda.html
Original response below
First things first, let's clear a few things up.
context.done() vs. context.fail()/context.success
context.done(error, result); is nothing but a wrapper around context.fail(error); and context.success(response);
The Lambda documentation clearly states that result is ignored if error is non null:
If the Lambda function was invoked using the RequestResponse (synchronous) invocation type, the method returns response body as follows:
If the error is null, set the response body to the string representation of result. This is similar to the context.succeed().
If the error is not null, set the response body to error.
If the function is called with a single argument of type error, the error value will be populated in the response body.
http://docs.aws.amazon.com/lambda/latest/dg/nodejs-prog-model-context.html
What this means is that it won't matter whether you use a combination of fail/success or done, the behaviour is exactly the same.
API Gateway and Response Code Mapping
I have tested every thinkable combination of response handling from Lambda in combination with Response code mapping in API Gateway.
The conclusion of these tests are that the "Lambda Error RegExp" is only executed against a Lambda error, i.e: you have to call context.done(error);or context.fail(error); for the RegExp to actually trigger.
Now, this presents a problem as, has already been noted, Lambda takes your error and sticks it in an object and calls toString() on whatever you supplied:
{ errorMessage: yourError.toString() }
If you supplied an error object you'll get this:
{ errorMessage: "[object Object]" }
Not very helpful at all.
The only workaround I have found thus far is to call
context.fail(JSON.stringify(error));
and then in my client do:
var errorObject = JSON.parse(error.errorMessage);
It's not very elegant but it works.
As part of my error I have a property called "code". It could look something like this:
{
code: "BadRequest",
message: "Invalid argument: parameter name"
}
When I stringify this object I get:
"{\"code\":\"BadRequest\",\"message\":\"Invalid argument: parameter name\"}"
Lambda will stick this string in the errorMessage property of the response and I can now safely grep for .*"BadRequest".* in the API Gateway response mapping.
It's very much a hack that works around two somewhat strange quirks of Lambda and API Gateway:
Why does Lambda insist on wrapping the error instead of just giving
it back as is?
Why doesn't API Gateway allow us to grep in the
Lambda result, only the error?
I am on my way to open a support case with Amazon regarding these two rather odd behaviours.
You don't have to use context.fail, use success but send different statusCode and an errorMessage, here is an example of how i format my output:
try {
// Call the callable function with the defined array parameters
// All the function called here will be catched if they throw exceptions
result.data = callable_function.apply(this, params);
result.statusCode = 200;
result.operation = operation;
result.errorMessage = ""
} catch (e) {
result.data = [];
result.statusCode = 500;
result.errorMessage = e.toString();
result.method = method;
result.resource = resource;
}
// If everything went smooth, send back the result
// If context succeed is not called AWS Lambda will fire the function
// again because it is not successfully exited
context.succeed(result);
Use the consumer logic to handle different errors case logic, don't forget that you pay for the time your function is running...
You should replace the use of your context.fail with context.done and use context.fail only for very serious Lambda function failures since it doesn't allow more than one output parameter. Integration Response is able to match mapping template by performing regex on the first parameter passed to context.done this also maps HTTP status code to the response. You can't pass this response status code directly from Lambda since it's the role of API Gateway Integration Response to abstract the HTTP protocol.
See the following:
context.done('Not Found:', <some object you can use in the model>);
and the Integration Response panel this setting:
You can replicate similar approach for any kind of error. You should also create and map the error model to your response.
For those who tried everything put on this question and couldn't make this work (like me), check the thedevkit comment on this post (saved my day):
https://forums.aws.amazon.com/thread.jspa?threadID=192918
Reproducing it entirely below:
I've had issues with this myself, and I believe that the newline
characters are the culprit.
foo.* will match occurrences of "foo" followed by any characters
EXCEPT newline. Typically this is solved by adding the '/s' flag, i.e.
"foo.*/s", but the Lambda error regex doesn't seem to respect this.
As an alternative you can use something like: foo(.|\n)*
I have a lighttpd server running locally. If I load a static file on the server (through an html5 audio tag), it plays and seeks fine.
However, seeking doesn't work when running a dev server (web.py/CherryPy) or if I return the bytes via a defined action url instead of as a static file. It won't load the duration either.
According to the "HTTP byte range requests" section in this Opera Page it's something to do with support for byte range requests/partial content responses. The content is treated as streaming instead.
What I don't understand is:
If the browser has the whole file downloaded surely it can display the duration, and surely it can seek.
What I need to do on the web server to enable byte range requests (for non-static urls).
Any advice would be most gratefully received.
Here's some web.py code to get you started (just happened to need this as well and ran into your question):
## experimental partial content support
## perhaps this shouldn't be enabled by default
range = web.ctx.env.get('HTTP_RANGE')
if range is None:
return result
total = len(result)
_, r = range.split("=")
partial_start, partial_end = r.split("-")
start = int(partial_start)
if not partial_end:
end = total-1
else:
end = int(partial_end)
chunksize = (end-start)+1
web.ctx.status = "206 Partial Content"
web.header("Content-Range", "bytes %d-%d/%d" % (start, end, total))
web.header("Accept-Ranges", "bytes")
web.header("Content-Length", chunksize)
return result[start:end+1]
Google tells me you have to use the staticFilter for byte ranges to work in CherryPy - but that is for static files only. Luckily this posting also includes pointers on how to do it for non-static data :-)