Is it possible to get the log point on GAE? - google-app-engine

I'm wondering if it's possible to log the line/column number when i log an error. The GAE logging lib seems to store only the error message but I think it would be quite valuable to get the exact location of the error/log point like most logging libraries do.

What you request is definitely possible, you just need to be very explicit about it! I recommend Andrew Gerrand's excellent article at http://blog.golang.org/error-handling-and-go for general information on the issue, including notes specific to App Engine.
That article does not specifically address stack traces, but of course you could do those yourself, via http://golang.org/pkg/runtime/#Stack .
Let's be honest and admit that Go -- being by design more of a system-programming language than of an application-focused one -- doesn't do quite as much implicit, automatic hand-holding for you, as more app-oriented languages such as the other App Engine ones -- Java, Python, PHP... [*] but, Go does give you all the tools you need to do just as little, or as much, "supporting infrastructure", as you desire to have in support of your own apps!-)
[*] hey, you don't even get automatically by-default propagating exceptions, as you do for other languages -- nay, you're responsible for catching and dealing with errors yourself, oh the horror...!-)

You can use the runtime package to trace the caller(I assume that's basically what you want). There is no GAE specific issue and it has nothing to do with the error handling.
// The depth specifies how many stack frames above
// lives the source line to be identified in the log message.
func traceCaller(depth int)(string, int){
_, file, line, ok := runtime.Caller(2 + depth)
if !ok {
file = "???"
line = 1
} else {
slash := strings.LastIndex(file, "/")
if slash >= 0 {
file = file[slash+1:]
}
}
return file, line
}

Related

Decoding and decompressing AI9_DataStream within .eps files

Context: I am attempting to automate the inspection of eps files to detect a list of attributes, such as whether the file contains locked layers, embedded bitmap images etc.
So far we have found some of these things can be detected via inspection of the raw eps file data and its accompanying metadata (similar to the information returned by imagemagick.) However it seems that in files created by illustrator 9 and above the vast majority of this information is encoded within the "AI9_DataStream" portion of the file. This data is encoded via ascii85 and compressed. We have found some success in getting at this data by using: https://github.com/huandu/node-ascii85 to decode and nodes zlib library to decompress / unzip. (Our project is written in node / javascript). However it seems that in roughly half of our test cases / files the unzipping portion fails, throwing Z_DATA_ERROR / "incorrect data check".
Our method responsible for trying to decode:
export const decode = eps =>
new Promise((resolve, reject) => {
const lineDelimiters = /\r\n%|\r%|\n%/g;
const internal = eps.match(
/(%AI9_DataStream)([\s\S]*?)(AI9_PrivateDataEnd)/
);
const hasDataStream = internal && internal.length >= 2;
if (!hasDataStream) resolve('');
const encoded = internal[2].replace(lineDelimiters, '');
const decoded = ascii85.decode(encoded);
try {
zlib.unzip(decoded, (err, buffer) => {
// files can crash this process, for now we need to allow it
if (err) resolve('');
else resolve(buffer.toString('utf8'));
});
} catch (err) {
reject(err);
}
});
I am wondering if anyone out there has had any experience with this issue and has some insight into what might be causing this and whether there is an alternative avenue to explore for reliably decoding this data. Information on this topic seems a bit sparse so really anything that could get us going in the right direction would be very much appreciated.
Note: The buffers produced by the ascii85 decoding all have the same 78 9c header which should indicate standard zlib compression (and it does in fact decompress into parsable data about half the time without error)
Apparently we were misreading something about the ascii85 encoding. There is a ~> delimiter at the end of the encoded block that needs to be omitted from the string before decoding and subsequent unzipping.
So instead of:
/(%AI9_DataStream)([\s\S]*?)(AI9_PrivateDataEnd)/
Use:
/(%AI9_DataStream)([\s\S]*?)(~>)/
And you can get to the correct encoded / compressed data. So far this has produced human readable / regexable data in all of our current test cases so unless we are thrown another curve that seems to be the answer.
The only reliable method for getting content from PostScript is to run it through a PostScript interpreter, because PostScript is a programming language.
If you stick to a specific workflow with well understood input, then you may have some success in simple parsing, but that's about the only likely scenario which will work.
Note that EPS files don't have 'layers' and certainly don't have 'locked' layers.
You haven't actually pointed to a working example, but I suspect the content of the AI9_DataStream is not relevant to the EPS. Its probably a means for Illustrator to include its own native file format inside the EPS file, without it affecting a PostScript interpreter. This is how it works with AI-produced PDF files.
This means that when you reopen the EPS file with Adobe Illustrator, it ignores the EPS and uses the embedded native file, which magically grants you the ability to edit the file, including features like layers which cannot be represented in the EPS.

NancyFx will not display images

My last attempt: Don't even know what I'm doing anymore:
Get["/{any}/x.png"] = x => {
return Response.AsImage(Program.portal.ourRoot + "x.png");
};
Get["/{any}/{moreany}/x.png"] = x => {
return Response.AsImage(Program.portal.ourRoot + "x.png");
};
Get["/{any}/{moreany}/{extraany}/x.png"] = x => {
return Response.AsImage(Program.portal.ourRoot + "x.png");
};
What I currently have in my ConfigureConvetions (in the BootStrapper). I've tried a lot of permutations so far.
protected override void ConfigureConventions(NancyConventions conventions) {
//conventions.StaticContentsConventions.AddFile("x.png", ourRoot + "x.png");
conventions.StaticContentsConventions.Add(StaticContentConventionBuilder.AddFile("/portal/images/x.png", ourRoot + "x.png"));
conventions.StaticContentsConventions.Add(StaticContentConventionBuilder.AddDirectory("images", ourRoot, new string[] { "png" }));
conventions.StaticContentsConventions.Add(StaticContentConventionBuilder.AddDirectory("/portal/", ourRoot, new string[] { "png" }));
conventions.StaticContentsConventions.Add(StaticContentConventionBuilder.AddDirectory("/", ourRoot, new string[] { "png" }));
base.ConfigureConventions(conventions);
}
I have a CustomRootPathProvider that points to ourRoot (string, currently holds a direct C:\somepathstuffhere\ to a content directory).
I only need to serve a single image for my needs (at least, for now, things always tend to grow). I'm using the directory structure as variables, so I need to be able to serve this image from a very large amount of locations.
I have a copy of the image in my root folder, and in a directory called images (the "images" has had '/''s all over it, occasionally even through the middle). I am currently referencing the image with "/images/x.png", but I've tried from the root, just the name, and "images/x.png".
Thanks!
I will post back in the mean time if I figure it out (I'm assuming its something very simple.)
Solved: Worked Around? \ Non-Optimal
I changed my /images/x.png references to 'x.png', and then I dropped the extension reference to the following line.
conventions.StaticContentsConventions.Add(StaticContentConventionBuilder.AddDirectory("/", ourRoot));
Nancy started catching the 'x.png' image for the Root Page and the \Portal\ page. And then the 2nd Get /{any}/{moreany}/x.png started catching the rest of the 'x.png' requests (\Portal\Project).
I'm really not sure, why it started working all of a sudden. I've just been playing the permutation game.
The big non-optimal part, is every single directory's version of the image is treated as brand new. If anyone can solve this one for me, that'd be nice. If I figure out what to do to fix it myself, I will post back with my solution.
SOLVED
This solution won't interest anyone familiar with web programming. Its more of a new user pitfall situation. When I started setting up NancyFX I read the documentation fairly thoroughly (even if I didn't get it all on the first read). When I got to the web.config part, I first checked the Solution Explorer in VS and I didn't see one. So I just went into my project directory and created one (And there-in lies the problem). The one I made never applied settings to the project.
I figured it was a concept error, I just didn't know enough, to know where to look.\
Thx for the community's help! Hopefully my experience helps some other 1st time user out.

App Engine Instance ID

Is it possible to get info on what instance you're running on? I want to output just a simple identifier for which instance the code is currently running on for logging purposes.
Since there is no language tag, and seeing your profile history, I assume you are using GAE/J?
In that case, the instance ID information is embedded in one of the environment attributes that you could get via ApiProxy.getCurrentEnvironment() method. You could then extract the instance id from the resulting map using key BackendService.INSTANCE_ID_ENV_ATTRIBUTE.
Even though the key is stored in BackendService, this approach will also work for frontend instances. So in summary, the following code would fetch the instance ID for you:
String tInstanceId = ApiProxy.getCurrentEnvironment()
.getAttributes()
.get( BackendService.INSTANCE_ID_ENV_ATTRIBUTE )
.toString();
Please keep in mind that this approach is quite undocumented by Google, and might subject to change without warning in the future. But since your use case is only for logging, I think it would be sufficient for now.
With the advent of Modules, you can get the current instance id in a more elegant way:
ModulesServiceFactory.getModulesService().getCurrentInstanceId()
Even better, you should wrap the call in a try catch so that it will work correctly locally too.
Import this
import com.google.appengine.api.modules.ModulesException;
import com.google.appengine.api.modules.ModulesServiceFactory;
Then your method can run this
String instanceId = "unknown";
try{
instanceId = ModulesServiceFactory.getModulesService().getCurrentInstanceId();
} catch (ModulesException e){
instanceId = e.getMessage();
}
Without the try catch, you will get some nasty errors when running locally.
I have found this super useful for debugging when using endpoints mixed with pub-sub and other bits to try to determine why some things work differently and to determine if it is related to new instances.
Not sure about before, but today in 2021 the system environment variable GAE_INSTANCE appears to contain the instance id:
instanceId = System.getenv("GAE_INSTANCE")

chan->cdr no data after upgrade from Asterisk 1.4.21

I have a legacy Asterisk application in C which does authentication of users, routing and billing using MySQL. I have kept it with Asterisk 1.4.21 because none of the CDR data is returned in newer versions of Asterisk.
Apparently there have been some changes in 1.4.22 https://issues.asterisk.org/jira/browse/ASTERISK-13064 that have completely changed the way CDR-s are handled. Unfortunately no helpful information was given on how to properly migrate existing code.
They have changed the order of execution, the 'h' extension is called and the CDR data is reset.
My code:
ast_log(LOG_NOTICE,"Dialing string: '%s'\n", dialstr);
app = pbx_findapp("Dial");
if (app)
res = pbx_exec(chan, app, dialstr);
ast_log(LOG_NOTICE,"Return from pbx_exec '%i', Disposition: '%s'\n", res, ast_cdr_disp2str(chan->cdr->disposition));
Other parts of the code handle chan->cdr->billsec etc, but it always gives 0 values.
After a successful call I always get this log from CLI:
Return from pbx_exec '-1', Disposition: 'NO ANSWER' while the same code works fine on 1.4.21
One solution I heard is to use ast_reset() before Dial but I am not sure how to implement it.
Any help on how to adapt this application?
You can just get DIALSTATUS variable,that is enought for you application and will be supported in future releases.
pbx_builtin_getvar_helper(chan, "DIALSTATUS");

"ExistenceError" in simple AppEngine + Google Cloud Storage application

I have a simple AppEngine handler as follows:
class TestGS(webapp2.RequestHandler):
def get(self):
file_name = '/gs/ds_stats/testfile'
files.gs.create(file_name, mime_type='text/html')
with files.open(file_name, 'a') as file_handle:
file_handle.write("foo")
files.finalize(file_name)
However, when I call this handler, I get ExistenceError: ApplicationError: 105 at the line with files.open(....
This seems like a super simple scenario, and there's no indication at all as to why this is failing (especially since the files.gs.create right above it seems to have succeeded, though, is there any way to verify this?).
Looking through the source code, I see the following problems can cause this error:
if (e.application_error in
[file_service_pb.FileServiceErrors.EXISTENCE_ERROR,
file_service_pb.FileServiceErrors.EXISTENCE_ERROR_METADATA_NOT_FOUND,
file_service_pb.FileServiceErrors.EXISTENCE_ERROR_METADATA_FOUND,
file_service_pb.FileServiceErrors.EXISTENCE_ERROR_SHARDING_MISMATCH,
file_service_pb.FileServiceErrors.EXISTENCE_ERROR_OBJECT_NOT_FOUND,
file_service_pb.FileServiceErrors.EXISTENCE_ERROR_BUCKET_NOT_FOUND,
]):
raise ExistenceError()
That's a pretty large range of issues... Of course it doesn't tell me which one! And again, strange that the 'create' seems to work.
The problem turned out to be a lack of clarity in the documentation. files.gs.create returns a special 'writeable file path' which you need to feed in to open and finalize. A correct example looks like this:
class TestGS(webapp2.RequestHandler):
def get(self):
file_name = '/gs/ds_stats/testfile'
writable_file_name = files.gs.create(file_name, mime_type='text/html')
with files.open(writable_file_name, 'a') as file_handle:
file_handle.write("foo")
files.finalize(writable_file_name)

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