MINOR: opentracing: transfer of context names without prefix
In order to enable the assignment of a context name, and yet exclude the
use of that name (prefix in this case) when extracting the context from
the HTTP header, a special character '-' has been added, which can be
specified at the beginning of the prefix.
So let's say if we look at examples of the fe-be configuration, we can
transfer the context via an HTTP header without a prefix like this:
fe/ot.cfg:
..
span "HAProxy session"
inject "" use-headers
event on-backend-http-request
Such a context can be read in another process using a name that has a
special '-' sign at the beginning:
be/ot.cfg:
ot-scope frontend_http_request
extract "-ot-ctx" use-headers
span "HAProxy session" child-of "-ot-ctx" root
..
This means that the context name will be '-ot-ctx' but it will not be
used when extracting data from HTTP headers.
Of course, if the context does not have a prefix set, all HTTP headers
will be inserted into the OpenTracing library as context. All of the
above will only work correctly if that library can figure out what is
relevant to the context and what is not.
diff --git a/addons/ot/include/parser.h b/addons/ot/include/parser.h
index 5e7b298..75a39cc 100644
--- a/addons/ot/include/parser.h
+++ b/addons/ot/include/parser.h
@@ -38,6 +38,7 @@
#define FLT_OT_PARSE_SPAN_REF_CHILD "child-of"
#define FLT_OT_PARSE_SPAN_REF_FOLLOWS "follows-from"
#define FLT_OT_PARSE_CTX_AUTONAME "-"
+#define FLT_OT_PARSE_CTX_IGNORE_NAME '-'
#define FLT_OT_PARSE_CTX_USE_HEADERS "use-headers"
#define FLT_OT_PARSE_CTX_USE_VARS "use-vars"
#define FLT_OT_PARSE_OPTION_HARDERR "hard-errors"
diff --git a/addons/ot/src/http.c b/addons/ot/src/http.c
index 72b31b7..4a12ed8 100644
--- a/addons/ot/src/http.c
+++ b/addons/ot/src/http.c
@@ -99,6 +99,19 @@
if (chn == NULL)
FLT_OT_RETURN(retptr);
+ /*
+ * The keyword 'inject' allows you to define the name of the OpenTracing
+ * context without using a prefix. In that case all HTTP headers are
+ * transferred because it is not possible to separate them from the
+ * OpenTracing context (this separation is usually done via a prefix).
+ *
+ * When using the 'extract' keyword, the context name must be specified.
+ * To allow all HTTP headers to be extracted, the first character of
+ * that name must be set to FLT_OT_PARSE_CTX_IGNORE_NAME.
+ */
+ if (FLT_OT_STR_ISVALID(prefix) && (*prefix == FLT_OT_PARSE_CTX_IGNORE_NAME))
+ prefix_len = 0;
+
htx = htxbuf(&(chn->buf));
for (pos = htx_get_first(htx); pos != -1; pos = htx_get_next(htx, pos)) {