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52c2ec3202
Since commit 3a4bedccc ("MEDIUM: vars: replace the global name index with
a hash") the names of HAProxy variables are no longer saved, ie their
64-bit hashes are saved instead.
This is very convenient for the HAProxy itself, but for the OpenTracing
module it is a problem because the names of the variables are important
when transferring the OpenTracing context. Namely, this context consists
of an unknown amount of data stored in a key-value format. The number
of these data (and the name of the variable used for this purpose) is
determined with the configuration of the OpenTracing filter, as well as
with the tracer used. The two previous sentences seem to be in conflict,
but that is only so at first glance. The function in the OpenTracing
filter used to read the context does not really know this, neither their
number nor its name. The only thing that function actually knows is the
prefix of the variable names used for context transfer, and by that it
could find all the necessary data. Of course, until the application of
the above-mentioned commit.
The problem is solved in a very simple way: in a common variable that
the filter always knows its name, the names of all variables that are the
product of the OpenTracing context are saved. The names of these context
variables can only be added to that common variable. When that variable
is no longer needed (when we no longer need context), it is deleted.
The format for saving data to this common variable is as follows:
+-----+---------------+-- .. --+-----+---------------+
| len | variable name | | len | variable name |
+-----+---------------+-- .. --+-----+---------------+
The amount of memory space used to store the length of the name is 1 byte,
with a sign (the minus sign is provided for inactive records, but this is
not currently used). This means that the maximum length of the variable
name to be saved is 127 characters, which is quite enough for use in the
filter. The buffer size for such data storage is global.tune.bufsize.
This patch must be backported in 2.5.
56 lines
2.0 KiB
C
56 lines
2.0 KiB
C
/***
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* Copyright 2020 HAProxy Technologies
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*
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* This file is part of the HAProxy OpenTracing filter.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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#ifndef _OPENTRACING_VARS_H_
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#define _OPENTRACING_VARS_H_
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#define FLT_OT_VARS_SCOPE "txn"
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#define FLT_OT_VAR_CTX_SIZE int8_t
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#define FLT_OT_VAR_CHAR_DASH 'D'
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#define FLT_OT_VAR_CHAR_SPACE 'S'
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struct flt_ot_ctx {
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char value[BUFSIZ];
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int value_len;
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};
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typedef int (*flt_ot_ctx_loop_cb)(struct sample *, size_t, const char *, const char *, const char *, FLT_OT_VAR_CTX_SIZE, char **, void *);
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#ifndef DEBUG_OT
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# define flt_ot_vars_dump(...) while (0)
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#else
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void flt_ot_vars_dump(struct stream *s);
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#endif
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int flt_ot_var_register(const char *scope, const char *prefix, const char *name, char **err);
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int flt_ot_var_set(struct stream *s, const char *scope, const char *prefix, const char *name, const char *value, uint opt, char **err);
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int flt_ot_vars_unset(struct stream *s, const char *scope, const char *prefix, uint opt, char **err);
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struct otc_text_map *flt_ot_vars_get(struct stream *s, const char *scope, const char *prefix, uint opt, char **err);
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#endif /* _OPENTRACING_VARS_H_ */
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/*
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* Local variables:
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* c-indent-level: 8
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* c-basic-offset: 8
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* End:
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*
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* vi: noexpandtab shiftwidth=8 tabstop=8
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*/
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