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/*! @page error_handling Error handling
WiredTiger operations return a value of 0 on success and a non-zero
value on error. Error codes may be either positive or negative:
positive error codes are standard error codes as described for
POSIX-like systems (for example, \c EINVAL or \c EBUSY), negative error
codes are WiredTiger-specific (for example, \c WT_ROLLBACK).
@section error_ebusy EBUSY errors
WiredTiger returns \c EBUSY for operations requiring exclusive access, when
an object is not available for exclusive access. These operations include the
WT_SESSION::alter, WT_SESSION::drop, WT_SESSION::rename, WT_SESSION::salvage,
WT_SESSION::upgrade and WT_SESSION::verify methods, all of which will return
\c EBUSY and fail if there are open cursors on the target object. Internal
WiredTiger threads may temporarily open cursors on objects (for example,
threads performing operations like statistics logging), and in that case
operations may temporarily fail and return \c EBUSY when there are no
application cursors open on the object. In this case, simply retrying the
operation should be sufficient.
Additionally, unwritten data in the WiredTiger cache will prevent exclusive
access to objects. In this case, calling the WT_SESSION:checkpoint method to
perform a database checkpoint should resolve the problem, allowing a subsequent
retry of the operation requiring exclusive access to succeed. Further
failures imply other threads of control simultaneously updating the object
in cache. Repeatedly calling checkpoint will race with those threads,
and it's unspecified when or even if exclusive access to the object will be
granted. Generally, applications will not call WiredTiger methods requiring
exclusive access when the objects might be in active use by other threads.
@section error_list WiredTiger-specific errors
WiredTiger-specific error codes are allocated from -31,800 to -31,999,
inclusive. The following is a list of the WiredTiger-specific return values:
@if IGNORE_BUILT_BY_API_ERR_BEGIN
@endif
@par \c WT_ROLLBACK
This error is generated when an operation cannot be completed due to a conflict with concurrent
operations. The operation may be retried; if a transaction is in progress, it should be rolled back
and the operation retried in a new transaction.
@par \c WT_DUPLICATE_KEY
This error is generated when the application attempts to insert a record with the same key as an
existing record without the 'overwrite' configuration to WT_SESSION::open_cursor.
@par \c WT_ERROR
This error is returned when an error is not covered by a specific error return. The operation may be
retried; if a transaction is in progress, it should be rolled back and the operation retried in a
new transaction.
@par \c WT_NOTFOUND
This error indicates an operation did not find a value to return. This includes cursor search and
other operations where no record matched the cursor's search key such as WT_CURSOR::update or
WT_CURSOR::remove.
@par \c WT_PANIC
This error indicates an underlying problem that requires a database restart. The application may
exit immediately, no further WiredTiger calls are required (and further calls will themselves
immediately fail).
@par \c WT_RUN_RECOVERY
This error is generated when ::wiredtiger_open is configured to return an error if recovery is
required to use the database.
@par \c WT_CACHE_FULL
This error is generated when wiredtiger_open is configured to run in-memory, and a data modification
operation requires more than the configured cache size to complete. The operation may be retried; if
a transaction is in progress, it should be rolled back and the operation retried in a new
transaction.
@par \c WT_PREPARE_CONFLICT
This error is generated when the application attempts to read an updated record which is part of a
transaction that has been prepared but not yet resolved.
@par \c WT_TRY_SALVAGE
This error is generated when corruption is detected in an on-disk file. During normal operations,
this may occur in rare circumstances as a result of a system crash. The application may choose to
salvage the file or retry wiredtiger_open with the 'salvage=true' configuration setting.
@if IGNORE_BUILT_BY_API_ERR_END
@endif
@section error_translation Translating errors
The WT_SESSION::strerror and ::wiredtiger_strerror functions return the
standard text message associated with any WiredTiger, ISO C, or POSIX
standard API.
@snippet ex_all.c Display an error thread safe
@snippet ex_all.c Display an error
Note that ::wiredtiger_strerror is not thread-safe.
*/
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