| Message ID | 1344354826-10375-36-git-send-email-lcapitulino@redhat.com |
|---|---|
| State | New |
| Headers | show |
On 08/07/2012 05:53 PM, Luiz Capitulino wrote: > Add information about the new error format and improve the text a bit. > > Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com> > --- > docs/writing-qmp-commands.txt | 47 +++++++++++++++++++++++++------------------ > 1 file changed, 27 insertions(+), 20 deletions(-) > > diff --git a/docs/writing-qmp-commands.txt b/docs/writing-qmp-commands.txt > index 0ad51aa..10ecd97 100644 > --- a/docs/writing-qmp-commands.txt > +++ b/docs/writing-qmp-commands.txt > @@ -210,19 +210,17 @@ if you don't see these strings, then something went wrong. > === Errors === > > QMP commands should use the error interface exported by the error.h header > -file. The basic function used to set an error is the error_set() one. > +file. Basically, errors are set by calling the error_set() function. > > Let's say we don't accept the string "message" to contain the word "love". If > -it does contain it, we want the "hello-world" command to the return the > -InvalidParameter error. > - > -Only one change is required, and it's in the C implementation: > +it does contain it, we want the "hello-world" command to return an error: > > void qmp_hello_world(bool has_message, const char *message, Error **errp) > { > if (has_message) { > if (strstr(message, "love")) { > - error_set(errp, QERR_INVALID_PARAMETER, "message"); > + error_set(errp, ERROR_CLASS_GENERIC_ERROR, > + "the word 'love' is not allowed"); > return; > } > printf("%s\n", message); > @@ -231,30 +229,40 @@ void qmp_hello_world(bool has_message, const char *message, Error **errp) > } > } > > -Let's test it. Build qemu, run it as defined in the "Testing" section, and > -then issue the following command: > +The first argument to the error_set() function is the Error pointer to pointer, > +which is passed to all QMP functions. The second argument is a ErrorClass > +value, which should be ERROR_CLASS_GENERIC_ERROR most of the time (more > +details about error classes are given below). The third argument is a human > +description of the error, this is a free-form printf-like string. > + > +Let's test the example above. Build qemu, run it as defined in the "Testing" > +section, and then issue the following command: > > -{ "execute": "hello-world", "arguments": { "message": "we love qemu" } } > +{ "execute": "hello-world", "arguments": { "message": "all you need is love" } } > > The QMP server's response should be: > > { > "error": { > - "class": "InvalidParameter", > - "desc": "Invalid parameter 'message'", > - "data": { > - "name": "message" > - } > + "class": "GenericError", you have here trailing white-space ^ > + "desc": "the word 'love' is not allowed" > } > } > > -Which is the InvalidParameter error. > +As a general rule, all QMP errors should use ERROR_CLASS_GENERIC_ERROR. There > +are two exceptions to this rule: > + > + 1. A non-generic ErrorClass value exists* for the failure you want to report > + (eg. DeviceNotFound) > + > + 2. Management applications have to take special action on the failure you > + want to report, hence you have to add a new ErrorClass value so that they > + can check for it > > -When you have to return an error but you're unsure what error to return or > -which arguments an error takes, you should look at the qerror.h file. Note > -that you might be required to add new errors if needed. > +If the failure you want to report doesn't fall in one of the two cases above, > +just report ERROR_CLASS_GENERIC_ERROR. > > -FIXME: describe better the error API and how to add new errors. > + * All existing ErrorClass values are defined in the qapi-schema.json file > > === Command Documentation === > > @@ -275,7 +283,6 @@ here goes "hello-world"'s new entry for the qapi-schema.json file: > # @message: #optional string to be printed > # > # Returns: Nothing on success. > -# If @message contains "love", InvalidParameter > # > # Notes: if @message is not provided, the "Hello, world" string will > # be printed instead
On Wed, 08 Aug 2012 14:35:23 +0200 Pavel Hrdina <phrdina@redhat.com> wrote: > On 08/07/2012 05:53 PM, Luiz Capitulino wrote: > > Add information about the new error format and improve the text a bit. > > > > Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com> > > --- > > docs/writing-qmp-commands.txt | 47 +++++++++++++++++++++++++------------------ > > 1 file changed, 27 insertions(+), 20 deletions(-) > > > > diff --git a/docs/writing-qmp-commands.txt b/docs/writing-qmp-commands.txt > > index 0ad51aa..10ecd97 100644 > > --- a/docs/writing-qmp-commands.txt > > +++ b/docs/writing-qmp-commands.txt > > @@ -210,19 +210,17 @@ if you don't see these strings, then something went wrong. > > === Errors === > > > > QMP commands should use the error interface exported by the error.h header > > -file. The basic function used to set an error is the error_set() one. > > +file. Basically, errors are set by calling the error_set() function. > > > > Let's say we don't accept the string "message" to contain the word "love". If > > -it does contain it, we want the "hello-world" command to the return the > > -InvalidParameter error. > > - > > -Only one change is required, and it's in the C implementation: > > +it does contain it, we want the "hello-world" command to return an error: > > > > void qmp_hello_world(bool has_message, const char *message, Error **errp) > > { > > if (has_message) { > > if (strstr(message, "love")) { > > - error_set(errp, QERR_INVALID_PARAMETER, "message"); > > + error_set(errp, ERROR_CLASS_GENERIC_ERROR, > > + "the word 'love' is not allowed"); > > return; > > } > > printf("%s\n", message); > > @@ -231,30 +229,40 @@ void qmp_hello_world(bool has_message, const char *message, Error **errp) > > } > > } > > > > -Let's test it. Build qemu, run it as defined in the "Testing" section, and > > -then issue the following command: > > +The first argument to the error_set() function is the Error pointer to pointer, > > +which is passed to all QMP functions. The second argument is a ErrorClass > > +value, which should be ERROR_CLASS_GENERIC_ERROR most of the time (more > > +details about error classes are given below). The third argument is a human > > +description of the error, this is a free-form printf-like string. > > + > > +Let's test the example above. Build qemu, run it as defined in the "Testing" > > +section, and then issue the following command: > > > > -{ "execute": "hello-world", "arguments": { "message": "we love qemu" } } > > +{ "execute": "hello-world", "arguments": { "message": "all you need is love" } } > > > > The QMP server's response should be: > > > > { > > "error": { > > - "class": "InvalidParameter", > > - "desc": "Invalid parameter 'message'", > > - "data": { > > - "name": "message" > > - } > > + "class": "GenericError", > > you have here trailing white-space ^ I've fixed it for v3, thanks. > > > + "desc": "the word 'love' is not allowed" > > } > > } > > > > -Which is the InvalidParameter error. > > +As a general rule, all QMP errors should use ERROR_CLASS_GENERIC_ERROR. There > > +are two exceptions to this rule: > > + > > + 1. A non-generic ErrorClass value exists* for the failure you want to report > > + (eg. DeviceNotFound) > > + > > + 2. Management applications have to take special action on the failure you > > + want to report, hence you have to add a new ErrorClass value so that they > > + can check for it > > > > -When you have to return an error but you're unsure what error to return or > > -which arguments an error takes, you should look at the qerror.h file. Note > > -that you might be required to add new errors if needed. > > +If the failure you want to report doesn't fall in one of the two cases above, > > +just report ERROR_CLASS_GENERIC_ERROR. > > > > -FIXME: describe better the error API and how to add new errors. > > + * All existing ErrorClass values are defined in the qapi-schema.json file > > > > === Command Documentation === > > > > @@ -275,7 +283,6 @@ here goes "hello-world"'s new entry for the qapi-schema.json file: > > # @message: #optional string to be printed > > # > > # Returns: Nothing on success. > > -# If @message contains "love", InvalidParameter > > # > > # Notes: if @message is not provided, the "Hello, world" string will > > # be printed instead >
diff --git a/docs/writing-qmp-commands.txt b/docs/writing-qmp-commands.txt index 0ad51aa..10ecd97 100644 --- a/docs/writing-qmp-commands.txt +++ b/docs/writing-qmp-commands.txt @@ -210,19 +210,17 @@ if you don't see these strings, then something went wrong. === Errors === QMP commands should use the error interface exported by the error.h header -file. The basic function used to set an error is the error_set() one. +file. Basically, errors are set by calling the error_set() function. Let's say we don't accept the string "message" to contain the word "love". If -it does contain it, we want the "hello-world" command to the return the -InvalidParameter error. - -Only one change is required, and it's in the C implementation: +it does contain it, we want the "hello-world" command to return an error: void qmp_hello_world(bool has_message, const char *message, Error **errp) { if (has_message) { if (strstr(message, "love")) { - error_set(errp, QERR_INVALID_PARAMETER, "message"); + error_set(errp, ERROR_CLASS_GENERIC_ERROR, + "the word 'love' is not allowed"); return; } printf("%s\n", message); @@ -231,30 +229,40 @@ void qmp_hello_world(bool has_message, const char *message, Error **errp) } } -Let's test it. Build qemu, run it as defined in the "Testing" section, and -then issue the following command: +The first argument to the error_set() function is the Error pointer to pointer, +which is passed to all QMP functions. The second argument is a ErrorClass +value, which should be ERROR_CLASS_GENERIC_ERROR most of the time (more +details about error classes are given below). The third argument is a human +description of the error, this is a free-form printf-like string. + +Let's test the example above. Build qemu, run it as defined in the "Testing" +section, and then issue the following command: -{ "execute": "hello-world", "arguments": { "message": "we love qemu" } } +{ "execute": "hello-world", "arguments": { "message": "all you need is love" } } The QMP server's response should be: { "error": { - "class": "InvalidParameter", - "desc": "Invalid parameter 'message'", - "data": { - "name": "message" - } + "class": "GenericError", + "desc": "the word 'love' is not allowed" } } -Which is the InvalidParameter error. +As a general rule, all QMP errors should use ERROR_CLASS_GENERIC_ERROR. There +are two exceptions to this rule: + + 1. A non-generic ErrorClass value exists* for the failure you want to report + (eg. DeviceNotFound) + + 2. Management applications have to take special action on the failure you + want to report, hence you have to add a new ErrorClass value so that they + can check for it -When you have to return an error but you're unsure what error to return or -which arguments an error takes, you should look at the qerror.h file. Note -that you might be required to add new errors if needed. +If the failure you want to report doesn't fall in one of the two cases above, +just report ERROR_CLASS_GENERIC_ERROR. -FIXME: describe better the error API and how to add new errors. + * All existing ErrorClass values are defined in the qapi-schema.json file === Command Documentation === @@ -275,7 +283,6 @@ here goes "hello-world"'s new entry for the qapi-schema.json file: # @message: #optional string to be printed # # Returns: Nothing on success. -# If @message contains "love", InvalidParameter # # Notes: if @message is not provided, the "Hello, world" string will # be printed instead
Add information about the new error format and improve the text a bit. Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com> --- docs/writing-qmp-commands.txt | 47 +++++++++++++++++++++++++------------------ 1 file changed, 27 insertions(+), 20 deletions(-)