ACS Error System - 6th ACS Workshop at UTFSM 2009

ACSError SystemBogdan Jeram(bjeram@eso.org)European Southern ObservatoryJuly 2005ESO

SummaryALMA Project• Features• Completions/Errors• Architecture• Error representation/structures/propagation• Error Trace• Code generation• Defining new errors• Programming language support• Remote error handlingJuly 2005 ACS Error System 2

FeaturesALMA Project• support for distributed and heterogeneoussystem• support synchronous and asynchronous calls• Errors traceability• support different programming language (eg.C++, Java, Python)• easy to use within all programming languagessupported by ACSJuly 2005 ACS Error System 3

Completions and ErrorsALMA Project• reporting how an action has completed• an action can complete:– erroneous (different ways)– successful (different ways)• completion for reporting:– errors– different success completion– intermediate status of an action• completions are superset of errorsJuly 2005 ACS Error System 4

ArchitectureALMA ProjectGUICompletion & Errordefinition(XML)Codegenerators(XSLT)CDB(Archive)Error LogBrowser(GUI)errorlibraryIDLJavaPythonApplicationC++Loggingsystemnot part oferror systemnot yet availableJuly 2005 ACS Error System 5

Error representationALMA Project• each completion/error is defined with twonumbers:– type (group)– code• OO mapping:– type -> namespace / IDL module– code -> completion class/ exception classJuly 2005 ACS Error System 6

Error structuresALMA Project• error trace (can not exist standalone)– type+code– severity: Error, Critical, Alert, Emergency– timestamp– source code info: line, file, routine– run-time info: process name, thread ID, host name– arbitrary data in name-value format (generic) or members• exception classes (contain error trace)• completion classes:– non-error– error (contain error trace)July 2005 ACS Error System 7

Arbitrary dataALMA Project• generic way: name-value pairs• members:– defined together with error: name, type and description(documentation)– generated getter/setter methods– stored in name-value pairs (accessed in a generic way)– new with ACS 4.1– just in C++, but can be accessed in Java and PythonJuly 2005 ACS Error System 8

Error TraceALMA Project• linked list of objects/structures/exceptions• chain of calls create an error trace: at eachlevel error information can be added• It is contained inside:– an exception– a completionJuly 2005 ACS Error System 9

Error TraceALMA Projectlength of error traceerror(n-1)error(n-2)depth of callserror1error0July 2005 ACS Error System 10

Example of error traceALMA ProjectACSErr::Completion* Ex::op(){er2 = newRecordNotFoundCompletion(“getRecord”);}er1 = newPositionNotObtainedCompletion(er2,“getPosition”)er1->returnCompletion();ACSErr::Completion *c = …->op();er = new PointingFailureCompletion(c,“routine”);er->log();er2er1 er2er1 er2er er1 er2July 2005 ACS Error System 11

Example of Error TraceALMA Projectf1(…)f2(…)er2 er1 er0er2 er1 er0f3(…)f4(…)er1er0er0July 2005 ACS Error System 12

Error propagationALMA Project• throwing exception:– just for reporting errors• returning/sending completion structure:– asynchronous actions/communications(callback mechanism)– reporting different success statuses of theoperation– where exceptions are not supported e.g. oldC++ compilersJuly 2005 ACS Error System 13

Error Definition (XML)ALMA Project...July 2005 ACS Error System 14

Code generationALMA ProjectCompletion&errordefinitionXML fileXSLT forIDLXSLT forC++XSLT forJavaXSLT forPythonIDL C++ Java PythonJuly 2005 ACS Error System 15

Programming language supportALMA Project• Supported languages:– IDL (remote)– C++– Java– Python• Generated code + libraryJuly 2005 ACS Error System 17

CORBA (remote) error handlingALMA Project• Common IDL structures:– error trace– completion+• Generated IDL code:– exceptionJuly 2005 ACS Error System 18

Class diagram of IDLALMA Project+previousError0..nErrorCodeACSErrTypeSeverityErrorCriticalAlertEmergency+errorCode+errorType+severityErrorTracefile : stringlineNum : longroutine : stringhost : stringprocess : stringthread : stringtimeStamp : unsigned long longshortDescription : string0..1+errorTraceCompletiontimeStamptypecode+dataNameValueSeq0..nNameValuename : stringvalue : stringJuly 2005 ACS Error System 19

IDL: Error Trace (1/2)ALMA Project• IDL structure to hold error trace information:ACSErr::ErrorTrace– error: type & code , severity (Error, Critical, Alert, Emergency)– timestamp– runtime information: process, thread, host– source information: file name, line number, routine name– additional info: pairs of name-value– “pointer” to the previous error• Error trace is not used standalone, but as a part of:– completion structure– exceptionsJuly 2005 ACS Error System 20

IDL: Error Trace (2/2)ALMA Projectstruct ErrorTrace {string file;long lineNum;string routine;string host;string process;string thread;TimeStamp timeStamp;string shortDescription;ACSErr::ACSErrType errorType;ACSErr::ErrorCode errorCode;ACSErr::Severity severity;NameValueSeq data;sequence previousError;};July 2005 ACS Error System 21

IDL: CompletionALMA Project• can contain ACSErr::ErrorTracestruct Completion {TimeStamp timeStamp;ACSErr::ACSErrType type;ACSErr::ErrorCode code;sequencepreviousError;};July 2005 ACS Error System 22

Example (remote) IDLALMA Project• error is sent around as return value or (in)outparameter of IDL structure(ACSErr::Completion):#include interface Ex {ACSErr::Completion op(…);}July 2005 ACS Error System 23

IDL: ExceptionsALMA Project• there is no exception hierarchy in IDL!• generated from XML error definition file• containers for ACSErr::ErrorTracemodule {};exception Ex {ErrorTrace error;};July 2005 ACS Error System 24

Example exception (remote) IDLALMA Project• error is send around as IDL exception(ACSErrTypeACSCourse::TargetNotFoundEx):#include interface Ex {void readFile(…) raises(ACSErrTypeACSCourse::TargetNotFoundEx);}July 2005 ACS Error System 25

ReferencesALMA Project• Doxygen documentation:$ACSROOT/man/api/html/acserr_8h.html• OCI, TAO Developers Guide version 1.1aChapter x: Error HandlingJuly 2005 ACS Error System 26

Exercise(s)ALMA Project• implement error handling in your“component”:– component operation(s) should returnCompletion or throw an exception (change IDLand implementation)July 2005 ACS Error System 27