Re: [PATCH] telemetry: support boolean type

[Bruce Richardson <bruce.richardson@intel.com>]

On Wed, Oct 19, 2022 at 04:28:58PM +0200, David Marchand wrote:
> On Wed, Oct 19, 2022 at 3:48 PM Bruce Richardson
> <bruce.richardson@intel.com> wrote:
> >
> > On Wed, Oct 19, 2022 at 09:37:02AM +0200, David Marchand wrote:
> > > Add the boolean type RTE_TEL_BOOL_VAL for values in arrays and dicts.
> > >
> > > Signed-off-by: David Marchand <david.marchand@redhat.com>
> > > ---
> >
> > This patch looks pretty good to me. Some very small comments inline below.
> > One thing I notice is that we are not supporting booleans except as part of
> > an array or dictionary. Is it likely that we will ever want to have a
> > telemetry command that just returns true/false alone? Don't see that being
> 
> I wondered too, but then I saw that only the "simple" type string was
> handled and others were not.
> So I decided to skip.
> 
> 
> > necessary just yet, so:
> >
> > Reviewed-by: Bruce Richardson <bruce.richardson@intel.com>
> > Acked-by: Bruce Richardson <bruce.richardson@intel.com>
> >
> > >  app/test/test_telemetry_data.c | 88 +++++++++++++++++++++++++++++++++-
> > >  lib/telemetry/rte_telemetry.h  | 36 ++++++++++++++
> > >  lib/telemetry/telemetry.c      | 24 +++++++++-
> > >  lib/telemetry/telemetry_data.c | 44 +++++++++++++++--
> > >  lib/telemetry/telemetry_data.h |  5 ++
> > >  lib/telemetry/telemetry_json.h | 34 +++++++++++++
> > >  lib/telemetry/version.map      |  5 ++
> > >  7 files changed, 228 insertions(+), 8 deletions(-)
> > >
> >
> > <snip>
> >
> > > diff --git a/lib/telemetry/rte_telemetry.h b/lib/telemetry/rte_telemetry.h
> > > index a0d21d6b7f..5d74212f17 100644
> > > --- a/lib/telemetry/rte_telemetry.h
> > > +++ b/lib/telemetry/rte_telemetry.h
> > > @@ -2,6 +2,7 @@
> > >   * Copyright(c) 2018 Intel Corporation
> > >   */
> > >
> > > +#include <stdbool.h>
> > >  #include <stdint.h>
> > >
> > >  #include <rte_compat.h>
> > > @@ -46,6 +47,7 @@ enum rte_tel_value_type {
> > >       RTE_TEL_INT_VAL,    /** a signed 32-bit int value */
> > >       RTE_TEL_U64_VAL,    /** an unsigned 64-bit int value */
> > >       RTE_TEL_CONTAINER, /** a container struct */
> > > +     RTE_TEL_BOOL_VAL,   /** a boolean value */
> > >  };
> > >
> > >  /**
> > > @@ -155,6 +157,22 @@ int
> > >  rte_tel_data_add_array_container(struct rte_tel_data *d,
> > >               struct rte_tel_data *val, int keep);
> > >
> > > +/**
> > > + * Add a boolean to an array.
> > > + * The array must have been started by rte_tel_data_start_array() with
> > > + * RTE_TEL_BOOL_VAL as the type parameter.
> > > + *
> > > + * @param d
> > > + *   The data structure passed to the callback
> > > + * @param x
> > > + *   The number to be returned in the array
> >
> > number -> boolean value
> >
> 
> Indeed..
> 
> > > + * @return
> > > + *   0 on success, negative errno on error
> > > + */
> > > +__rte_experimental
> > > +int
> > > +rte_tel_data_add_array_bool(struct rte_tel_data *d, bool x);
> > > +
> > >  /**
> > >   * Add a string value to a dictionary.
> > >   * The dict must have been started by rte_tel_data_start_dict().
> > > @@ -233,6 +251,24 @@ int
> > >  rte_tel_data_add_dict_container(struct rte_tel_data *d, const char *name,
> > >               struct rte_tel_data *val, int keep);
> > >
> > > +/**
> > > + * Add a boolean value to a dictionary.
> > > + * The dict must have been started by rte_tel_data_start_dict().
> > > + *
> > > + * @param d
> > > + *   The data structure passed to the callback
> > > + * @param name
> > > + *   The name the value is to be stored under in the dict
> > > + *   Must contain only alphanumeric characters or the symbols: '_' or '/'
> > > + * @param val
> > > + *   The number to be stored in the dict
> >
> > number -> boolean value
> >
> > > + * @return
> > > + *   0 on success, negative errno on error, E2BIG on string truncation of name.
> > > + */
> > > +__rte_experimental
> > > +int
> > > +rte_tel_data_add_dict_bool(struct rte_tel_data *d, const char *name, bool val);
> > > +
> > >  /**
> > >   * This telemetry callback is used when registering a telemetry command.
> > >   * It handles getting and formatting information to be returned to telemetry
> > > diff --git a/lib/telemetry/telemetry.c b/lib/telemetry/telemetry.c
> > <snip>
> > > diff --git a/lib/telemetry/telemetry_data.c b/lib/telemetry/telemetry_data.c
> > > index 5b319c18fb..4f81f71e03 100644
> > > --- a/lib/telemetry/telemetry_data.c
> > > +++ b/lib/telemetry/telemetry_data.c
> > > @@ -16,10 +16,11 @@ int
> > >  rte_tel_data_start_array(struct rte_tel_data *d, enum rte_tel_value_type type)
> > >  {
> > >       enum tel_container_types array_types[] = {
> > > -                     RTE_TEL_ARRAY_STRING, /* RTE_TEL_STRING_VAL = 0 */
> > > -                     RTE_TEL_ARRAY_INT,    /* RTE_TEL_INT_VAL = 1 */
> > > -                     RTE_TEL_ARRAY_U64,    /* RTE_TEL_u64_VAL = 2 */
> > > -                     RTE_TEL_ARRAY_CONTAINER, /* RTE_TEL_CONTAINER = 3 */
> > > +             [RTE_TEL_STRING_VAL] = RTE_TEL_ARRAY_STRING,
> > > +             [RTE_TEL_INT_VAL] = RTE_TEL_ARRAY_INT,
> > > +             [RTE_TEL_U64_VAL] = RTE_TEL_ARRAY_U64,
> > > +             [RTE_TEL_CONTAINER] = RTE_TEL_ARRAY_CONTAINER,
> > > +             [RTE_TEL_BOOL_VAL] = RTE_TEL_ARRAY_BOOL,
> > >       };
> >
> > Really like this change!
> 
> I don't remember if this form is related to some CXX standard... but I
> see that no compiler complained in the CI.
> 
> 
> >
> > >       d->type = array_types[type];
> > >       d->data_len = 0;
> > > @@ -80,6 +81,17 @@ rte_tel_data_add_array_u64(struct rte_tel_data *d, uint64_t x)
> > >       return 0;
> > >  }
> > >
> > > +int
> > > +rte_tel_data_add_array_bool(struct rte_tel_data *d, bool x)
> > > +{
> > > +     if (d->type != RTE_TEL_ARRAY_BOOL)
> > > +             return -EINVAL;
> > > +     if (d->data_len >= RTE_TEL_MAX_ARRAY_ENTRIES)
> > > +             return -ENOSPC;
> > > +     d->data.array[d->data_len++].boolval = x;
> > > +     return 0;
> > > +}
> > > +
> > >  int
> > >  rte_tel_data_add_array_container(struct rte_tel_data *d,
> > >               struct rte_tel_data *val, int keep)
> > <snip>
> > > diff --git a/lib/telemetry/telemetry_json.h b/lib/telemetry/telemetry_json.h
> > > index e3fae7c30d..c97da97366 100644
> > > --- a/lib/telemetry/telemetry_json.h
> > > +++ b/lib/telemetry/telemetry_json.h
> > > @@ -7,6 +7,7 @@
> > >
> > >  #include <inttypes.h>
> > >  #include <stdarg.h>
> > > +#include <stdbool.h>
> > >  #include <stdio.h>
> > >  #include <rte_common.h>
> > >  #include <rte_telemetry.h>
> > > @@ -159,6 +160,21 @@ rte_tel_json_add_array_u64(char *buf, const int len, const int used,
> > >       return ret == 0 ? used : end + ret;
> > >  }
> > >
> > > +/* Appends a boolean into the JSON array in the provided buffer. */
> > > +static inline int
> > > +rte_tel_json_add_array_bool(char *buf, const int len, const int used,
> > > +             bool val)
> > > +{
> > > +     int ret, end = used - 1; /* strip off final delimiter */
> > > +     if (used <= 2) /* assume empty, since minimum is '[]' */
> > > +             return __json_snprintf(buf, len, "[%s]",
> > > +                             val ? "true" : "false");
> > > +
> > > +     ret = __json_snprintf(buf + end, len - end, ",%s]",
> > > +                     val ? "true" : "false");
> >
> > Wonder if it's worthwhile doing a macro for this conditional, since the
> > same ternary-operator snippet appears 4 times in this code.
> 
> Err, naming it would be hard and I don't see for now how we could reuse it.
> 
Yes, and I see Morten has objected from a readability perspective, so
keeping as-is is fine. 

One final suggestion though might be to have an array with the strings as so:

const char *bool_str[2] = { "false", "true" };

and then in the code use "bool_str[val]" in place of ternary operator.
(From a quick check with godbolt is looks like bool params are clamped to 0
or 1 on function call, but if we want to be paranoid, we can lookup based
on [!!val])

However, ok to keep code as-is for this too.

/Bruce