Alexei,
I think it's ok to do error conversion if it makes sense, but better to
preserve the root cause whenever possible.
Another way to solve the described scenario is to introduce something like
checked IgniteRetryAgainException, which forces the user to retry or ignore
it.
It's difficult to foresee exactly at this point what is the best solution
without knowing the exact scenario.
Andrey,
I've just realized your proposal to add IGN to each string code. This is ok
to me, for example IGN-TBL-0001
ср, 21 апр. 2021 г. в 17:49, Alexey Goncharuk <alexey.goncha...@gmail.com>:
> Aleksei,
>
> > The method should always report root cause, in your example it will be
> > B-xxxx, no matter which module API is called
>
> I may be wrong, but I doubt this will be usable for an end-user. Let's
> imagine that the same root exception was raised in different contexts
> resulting in two outcomes. The first one is safe to retry (say, the root
> cause led to a transaction prepare failure), but the second outcome may be
> a state in which no matter how many retries will be attempted, the
> operation will never succeed. Only the upper-level layer can tell the
> difference and return a proper message to the user, so I would say that
> some error conversion/wrapping will be required no matter what.
>
> --AG
>
> пт, 16 апр. 2021 г. в 16:31, Alexei Scherbakov <
> alexey.scherbak...@gmail.com
> >:
>
> > чт, 15 апр. 2021 г. в 18:21, Andrey Mashenkov <
> andrey.mashen...@gmail.com
> > >:
> >
> > > Hi Alexey,
> > > I like the idea.
> > >
> > > 1.
> > >
> > > > TBL-0001 is a *string representation* of the error. It is built
> from
> > 2
> > > > byte scope id (mapped to name TBL) and 2 byte number (0001). Both
> > > > internally packed in int. No any kind of parsing will be necessary to
> > > read
> > > > scope/category.
> > >
> > > I think Alexey mean if it will be possible to make smth like that
> > >
> > > catch (IgniteException e) {
> > > if (e.getScope() == "TBL" && e.getCode() == 1234)
> > > continue; // E.g. retry my TX
> > > }
> > >
> > > It looks useful to me.
> > >
> >
> > I have in mind something like this:
> >
> > public class IgniteException extends RuntimeException {
> > private int errorCode;
> >
> > public IgniteException(ErrorScope scope, int code, String message,
> > Throwable cause) {
> > super(message, cause);
> > this.errorCode = make(scope, code);
> > }
> >
> > public boolean matches(ErrorScope scope, int code) {
> > return errorCode == make(scope, code);
> > }
> >
> > private int make(ErrorScope scope, int code) {
> > return ((scope.ordinal() << 16) | code);
> > }
> >
> > public ErrorScope scope() {
> > return ErrorScope.values()[errorCode >> 16];
> > }
> >
> > public int code() {
> > return 0xFFFF & errorCode;
> > }
> >
> > public static void main(String[] args) {
> > IgniteException e = new IgniteException(ErrorScope.RAFT, 1,
> "test",
> > null);
> >
> > System.out.println(e.matches(ErrorScope.RAFT, 2));
> > System.out.println(e.scope());
> > System.out.println(e.code());
> >
> > try {
> > throw e;
> > }
> > catch (IgniteException ee) {
> > System.out.println(ee.matches(ErrorScope.RAFT, 1));
> > }
> > }
> > }
> >
> >
> > >
> > > 2. How you see a cross-module exception throwing?
> > > Assume, user call -> module A, which recursively call -> module B,
> which
> > > fails.
> > > So, module A component calls a module B component and got an Exception
> > with
> > > "B-1234" exception.
> > > Module A do not expect any exception here and doesn't take care of
> > "B-xxx"
> > > error codes, but only "A-yyyy.
> > > Should it rethrow exception with "A-unknown" (maybe "UNK-0001") code
> > > or reuse "B-xxxx" code with the own message, pointing original
> exception
> > as
> > > a cause for both cases?
> > >
> > > The first approach may looks confusing, while the second one produces
> too
> > > many "UNK-" codes.
> > > What code should get the user in that case?
> > >
> > >
> > >
> > The method should always report root cause, in your example it will be
> > B-xxxx, no matter which module API is called.
> >
> >
> > >
> > >
> > >
> > > On Thu, Apr 15, 2021 at 5:36 PM Alexei Scherbakov <
> > > alexey.scherbak...@gmail.com> wrote:
> > >
> > > > чт, 15 апр. 2021 г. в 14:26, Ilya Kasnacheev <
> > ilya.kasnach...@gmail.com
> > > >:
> > > >
> > > > > Hello!
> > > > >
> > > > > > All public methods throw only unchecked
> > > > > org.apache.ignite.lang.IgniteException containing aforementioned
> > > fields.
> > > > > > Each public method must have a section in the javadoc with a list
> > of
> > > > all
> > > > > possible error codes for this method.
> > > > >
> > > > > I don't think this is feasible at all.
> > > > > Imagine javadoc for cache.get() method featuring three pages of
> > > possible
> > > > > error codes thrown by this method.
> > > > >
> > > >
> > > > Of course there is no need to write 3 pages of error codes, this
> makes
> > no
> > > > sense.
> > > > I think we can use error ranges here, or, probably, document most
> > > important
> > > > error scenarios.
> > > > The point here is to try to document errors as much as possible.
> > > >
> > > >
> > > > > Also, updated every two weeks to account for changes in
> > > > > underlying mechanisms.
> > > > >
> > > > > There is still a confusion between "error code for any error in
> logs"
> > > and
> > > > > "error code for any pair of method & exception". Which one are we
> > > > > discussing really?
> > > > >
> > > > > This is impossible to track or test, but is susceptible for common
> > > > > error-hiding antipattern where all exceptions are caught in
> > cache.get()
> > > > and
> > > > > discarded, and instead a brand new CH-0001 "error in cache.get()"
> is
> > > > thrown
> > > > > to the user.
> > > > >
> > > > > Which is certainly not something that anybody wants.
> > > > >
> > > >
> > > > Certainly not. We are talking here about root cause - what is exactly
> > the
> > > > reason for method call failure.
> > > >
> > > >
> > > > >
> > > > > Regards,
> > > > > --
> > > > > Ilya Kasnacheev
> > > > >
> > > > >
> > > > > чт, 15 апр. 2021 г. в 13:03, Vladislav Pyatkov <
> vldpyat...@gmail.com
> > >:
> > > > >
> > > > > > Hi Alexei,
> > > > > >
> > > > > > > Each public method *must *have a section in the javadoc with a
> > list
> > > > of
> > > > > > all possible error codes for this method.
> > > > > >
> > > > > > I consider it is redundant, because any public exception can be
> > > thrown
> > > > > from
> > > > > > public API.
> > > > > > If it not happens today, it may change tomorrow: one will be
> > removed,
> > > > > > another one will be added.
> > > > > >
> > > > > > >Nested exceptions are not forbidden to use. They can provide
> > > > additional
> > > > > > details on the error for debug purposes
> > > > > >
> > > > > > I see another issue, which is in the Ignite 2.x, but not attend
> > here.
> > > > We
> > > > > > can have a deep nested exception and use it for handling.
> > > > > > In the result, all time when we are handling an exception we use
> > > > > > pattern like this:
> > > > > > try{
> > > > > > ...
> > > > > > }
> > > > > > catch (Exception e) {
> > > > > > if (X.hasCause(e, TimeoutException.class))
> > > > > > throw e;
> > > > > >
> > > > > > if (X.hasCause(e, ConnectException.class,
> EOFException.class))
> > > > > > continue;
> > > > > >
> > > > > > if (X.hasCause(e, InterruptedException.class))
> > > > > > return false;
> > > > > > }
> > > > > >
> > > > > > If we have a pant to make only one exception to the client side,
> we
> > > can
> > > > > > also do it for an internal exception.
> > > > > >
> > > > > > On Wed, Apr 14, 2021 at 11:42 AM Alexei Scherbakov <
> > > > > > alexey.scherbak...@gmail.com> wrote:
> > > > > >
> > > > > > > Alexey,
> > > > > > >
> > > > > > > ср, 14 апр. 2021 г. в 01:52, Alexey Kukushkin <
> > > > > kukushkinale...@gmail.com
> > > > > > >:
> > > > > > >
> > > > > > > > Just some points looking questionable to me, although I
> realize
> > > the
> > > > > > error
> > > > > > > > handling style may be very opinionated:
> > > > > > > >
> > > > > > > > - Would it make sense splitting the proposed composite
> error
> > > > code
> > > > > > > > (TBL-0001) into separate numeric code (0001) and
> > > scope/category
> > > > > > > ("TBL")
> > > > > > > > to
> > > > > > > > avoid parsing the code when an error handler needs to
> > analyze
> > > > only
> > > > > > the
> > > > > > > > category or the code?
> > > > > > > >
> > > > > > >
> > > > > > > TBL-0001 is a *string representation* of the error. It is
> built
> > > > from
> > > > > 2
> > > > > > > byte scope id (mapped to name TBL) and 2 byte number (0001).
> Both
> > > > > > > internally packed in int. No any kind of parsing will be
> > necessary
> > > to
> > > > > > read
> > > > > > > scope/category.
> > > > > > >
> > > > > > >
> > > > > > > > - "*The cause - short string description of an issue,
> > readable
> > > > by
> > > > > > > > user.*".
> > > > > > > > This terminology sounds confusing to me since that "cause"
> > > > sounds
> > > > > > like
> > > > > > > > Java
> > > > > > > > Throwable's Message to me and the "Cause" is a lower level
> > > > > > exception.
> > > > > > > >
> > > > > > >
> > > > > > > The string describes the cause of error, so the name. I'm ok to
> > > > rename
> > > > > it
> > > > > > > to a message. It will be stored in IgniteException.message
> field
> > > > > anyway.
> > > > > > >
> > > > > > >
> > > > > > > > - "*The action - steps for a user to resolve error...*".
> The
> > > > > action
> > > > > > is
> > > > > > > > very important but do we want to make it part of the
> > > > > > IgniteException?
> > > > > > > I
> > > > > > > > do
> > > > > > > > not think the recovery action text should be part of the
> > > > > exception.
> > > > > > > > IgniteException may include a URL pointing to the
> > > corresponding
> > > > > > > > documentation - this is discussable.
> > > > > > > >
> > > > > > >
> > > > > > > This will not be the part of the exception. A user should visit
> > the
> > > > > > > documentation page and read the action section by corresponding
> > > error
> > > > > > code.
> > > > > > >
> > > > > > >
> > > > > > > > - "*All public methods throw only unchecked
> > IgniteException*"
> > > -
> > > > I
> > > > > > > assume
> > > > > > > > we still respect JCache specification and prefer using
> > > standard
> > > > > Java
> > > > > > > > exception to signal about invalid parameters.
> > > > > > > >
> > > > > > >
> > > > > > > Using standard java exceptions whenever possible makes sense.
> > > > > > >
> > > > > > >
> > > > > > > > - Why we do not follow the "classic" structured exception
> > > > handling
> > > > > > > > practices in Ignite:
> > > > > > > >
> > > > > > >
> > > > > > > Ignite 3 will be multi language, and other languages use other
> > > error
> > > > > > > processing models. SQL for example uses error codes.
> > > > > > > The single exception approach simplifies and unifies error
> > handling
> > > > > > across
> > > > > > > platforms for me.
> > > > > > >
> > > > > > >
> > > > > > > > - Why do we not allow using checked exceptions? It
> seems
> > to
> > > > me
> > > > > > > > sometimes forcing the user to handle an error serves
> as a
> > > > hint
> > > > > > and
> > > > > > > > thus
> > > > > > > > improves usability. For example, handling an
> > > > > > optimistic/pessimistic
> > > > > > > > transaction conflict/deadlock. Or handling a timeout
> for
> > > > > > operations
> > > > > > > > with
> > > > > > > > timeouts.
> > > > > > > >
> > > > > > >
> > > > > > > A valid point. Checked exceptions must be used for whose
> methods,
> > > > where
> > > > > > > error handling is enforced, for example tx optimistic failure.
> > > > > > > Such errors will also have corresponding error codes.
> > > > > > >
> > > > > > >
> > > > > > > > - Why single public IgniteException and no exception
> > > > hierarchy?
> > > > > > > Java
> > > > > > > > is optimized for structured exception handling instead
> of
> > > > using
> > > > > > > > IF-ELSE to
> > > > > > > > analyze the codes.
> > > > > > > >
> > > > > > >
> > > > > > > Exception hierarchy is not required when using error codes and
> > > > > applicable
> > > > > > > only to java API, so I would avoid spending efforts on it.
> > > > > > >
> > > > > > >
> > > > > > > > - Why no nested exceptions? Sometimes an error handler
> is
> > > > > > > interested
> > > > > > > > only in high level exceptions (like Invalid
> > Configuration)
> > > > and
> > > > > > > > sometimes
> > > > > > > > details are needed (like specific configuration parser
> > > > > > exceptions).
> > > > > > > >
> > > > > > >
> > > > > > > Nested exceptions are not forbidden to use. They can provide
> > > > additional
> > > > > > > details on the error for debug purposes, but not strictly
> > required,
> > > > > > because
> > > > > > > error code + message should provide enough information to the
> > user.
> > > > > > >
> > > > > > >
> > > > > > > > - For async methods returning a Future we may have a
> > universal
> > > > > rule
> > > > > > on
> > > > > > > > how to handle exceptions. For example, we may specify that
> > any
> > > > > async
> > > > > > > > method
> > > > > > > > can throw only invalid argument exceptions. All other
> errors
> > > are
> > > > > > > > reported
> > > > > > > > via the exceptionally(IgniteException -> {}) callback even
> > if
> > > > the
> > > > > > > async
> > > > > > > > method was executed synchronously.
> > > > > > > >
> > > > > > >
> > > > > > > This is ok to me.
> > > > > > >
> > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > > вт, 13 апр. 2021 г. в 12:08, Alexei Scherbakov <
> > > > > > > > alexey.scherbak...@gmail.com
> > > > > > > > >:
> > > > > > > >
> > > > > > > > > Igniters,
> > > > > > > > >
> > > > > > > > > I would like to start the discussion about error handling
> in
> > > > > Ignite 3
> > > > > > > and
> > > > > > > > > how we can improve it compared to Ignite 2.
> > > > > > > > >
> > > > > > > > > The error handling in Ignite 2 was not very good because of
> > > > generic
> > > > > > > > > CacheException thrown on almost any occasion, having deeply
> > > > nested
> > > > > > root
> > > > > > > > > cause and often containing no useful information on further
> > > steps
> > > > > to
> > > > > > > fix
> > > > > > > > > the issue.
> > > > > > > > >
> > > > > > > > > I aim to fix it by introducing some rules on error
> handling.
> > > > > > > > >
> > > > > > > > > *Public exception structure.*
> > > > > > > > >
> > > > > > > > > A public exception must have an error code, a cause, and an
> > > > action.
> > > > > > > > >
> > > > > > > > > * The code - the combination of 2 byte scope id and 2 byte
> > > error
> > > > > > number
> > > > > > > > > within the module. This allows up to 2^16 errors for each
> > > scope,
> > > > > > which
> > > > > > > > > should be enough. The error code string representation can
> > look
> > > > > like
> > > > > > > > > RFT-0001 or TBL-0001
> > > > > > > > > * The cause - short string description of an issue,
> readable
> > by
> > > > > user.
> > > > > > > > This
> > > > > > > > > can have dynamic parameters depending on the error type for
> > > > better
> > > > > > user
> > > > > > > > > experience, like "Can't write a snapshot, no space left on
> > > device
> > > > > > {0}"
> > > > > > > > > * The action - steps for a user to resolve error situation
> > > > > described
> > > > > > in
> > > > > > > > the
> > > > > > > > > documentation in the corresponding error section, for
> example
> > > > > "Clean
> > > > > > up
> > > > > > > > > disk space and retry the operation".
> > > > > > > > >
> > > > > > > > > Common errors should have their own scope, for example
> > IGN-0001
> > > > > > > > >
> > > > > > > > > All public methods throw only unchecked
> > > > > > > > > org.apache.ignite.lang.IgniteException containing
> > > aforementioned
> > > > > > > fields.
> > > > > > > > > Each public method must have a section in the javadoc with
> a
> > > list
> > > > > of
> > > > > > > all
> > > > > > > > > possible error codes for this method.
> > > > > > > > >
> > > > > > > > > A good example with similar structure can be found here [1]
> > > > > > > > >
> > > > > > > > > *Async timeouts.*
> > > > > > > > >
> > > > > > > > > Because almost all API methods in Ignite 3 are async, they
> > all
> > > > will
> > > > > > > have
> > > > > > > > a
> > > > > > > > > configurable default timeout and can complete with timeout
> > > error
> > > > > if a
> > > > > > > > > computation is not finished in time, for example if a
> > response
> > > > has
> > > > > > not
> > > > > > > > been
> > > > > > > > > yet received.
> > > > > > > > > I suggest to complete the async op future with
> > TimeoutException
> > > > in
> > > > > > this
> > > > > > > > > case to make it on par with synchronous execution using
> > > > future.get,
> > > > > > > which
> > > > > > > > > will throw java.util.concurrent.TimeoutException on
> timeout.
> > > > > > > > > For reference, see
> > > > java.util.concurrent.CompletableFuture#orTimeout
> > > > > > > > > No special error code should be used for this scenario.
> > > > > > > > >
> > > > > > > > > *Internal exceptions hierarchy.*
> > > > > > > > >
> > > > > > > > > All internal exceptions should extend
> > > > > > > > > org.apache.ignite.internal.lang.IgniteInternalException for
> > > > checked
> > > > > > > > > exceptions and
> > > > > > > > >
> > org.apache.ignite.internal.lang.IgniteInternalCheckedException
> > > > for
> > > > > > > > > unchecked exceptions.
> > > > > > > > >
> > > > > > > > > Thoughts ?
> > > > > > > > >
> > > > > > > > > [1]
> > > > > >
> https://docs.oracle.com/cd/B10501_01/server.920/a96525/preface.htm
> > > > > > > > >
> > > > > > > > > --
> > > > > > > > >
> > > > > > > > > Best regards,
> > > > > > > > > Alexei Scherbakov
> > > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > > --
> > > > > > > > Best regards,
> > > > > > > > Alexey
> > > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > --
> > > > > > >
> > > > > > > Best regards,
> > > > > > > Alexei Scherbakov
> > > > > > >
> > > > > >
> > > > > >
> > > > > > --
> > > > > > Vladislav Pyatkov
> > > > > >
> > > > >
> > > >
> > > >
> > > > --
> > > >
> > > > Best regards,
> > > > Alexei Scherbakov
> > > >
> > >
> > >
> > > --
> > > Best regards,
> > > Andrey V. Mashenkov
> > >
> >
> >
> > --
> >
> > Best regards,
> > Alexei Scherbakov
> >
>
--
Best regards,
Alexei Scherbakov
