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POC: New beresp.error VCL variable #4097

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POC: New beresp.error VCL variable #4097

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a3c515b
vcc_expr: Remove vcc_expr_tostring() fmt argument
dridi Apr 29, 2024
b4c5cb1
vcc_expr: Allow STRING <cmp> STRANDS comparison
dridi Apr 29, 2024
d3a7348
POC: vcc: Introduce an error type
dridi Apr 29, 2024
20bc748
POC: vrt: Expose a new beresp.error variable
dridi Apr 29, 2024
9f1b8c1
POC: builtin.vcl: Display beresp.error when present
dridi Apr 29, 2024
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8 changes: 7 additions & 1 deletion bin/varnishd/builtin.vcl
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Original file line number Diff line number Diff line change
Expand Up @@ -266,7 +266,13 @@ sub vcl_builtin_backend_error {
</head>
<body>
<h1>Error "} + beresp.status + " " + beresp.reason + {"</h1>
<p>"} + beresp.reason + {"</p>
<p>"};
if (beresp.error) {
set beresp.body += beresp.error;
} else {
set beresp.body += beresp.reason;
}
set beresp.body += {"</p>
<h3>Guru Meditation:</h3>
<p>XID: "} + bereq.xid + {"</p>
<hr>
Expand Down
1 change: 1 addition & 0 deletions bin/varnishd/cache/cache.h
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Expand Up @@ -442,6 +442,7 @@ struct busyobj {

uint16_t err_code;
const char *err_reason;
const char *err_resp;

const char *client_identity;
};
Expand Down
8 changes: 5 additions & 3 deletions bin/varnishd/cache/cache_backend.c
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Expand Up @@ -49,6 +49,7 @@
#include "cache_vcl.h"
#include "http1/cache_http1.h"
#include "proxy/cache_proxy.h"
#include "vrt_obj.h"

#include "VSC_vbe.h"

Expand All @@ -60,7 +61,7 @@ static struct lock backends_mtx;

/*--------------------------------------------------------------------*/

void
const char *
VBE_Connect_Error(struct VSC_vbe *vsc, int err)
{

Expand All @@ -81,7 +82,7 @@ VBE_Connect_Error(struct VSC_vbe *vsc, int err)
break;
case ECONNREFUSED:
vsc->fail_econnrefused++;
break;
return (VRT_c_error_connection_refused());
case ENETUNREACH:
vsc->fail_enetunreach++;
break;
Expand All @@ -91,6 +92,7 @@ VBE_Connect_Error(struct VSC_vbe *vsc, int err)
default:
vsc->fail_other++;
}
return (NULL);
}

/*--------------------------------------------------------------------*/
Expand Down Expand Up @@ -158,7 +160,7 @@ vbe_dir_getfd(VRT_CTX, struct worker *wrk, VCL_BACKEND dir, struct backend *bp,
pfd = VCP_Get(bp->conn_pool, tmod, wrk, force_fresh, &err);
if (pfd == NULL) {
Lck_Lock(bp->director->mtx);
VBE_Connect_Error(bp->vsc, err);
bo->err_resp = VBE_Connect_Error(bp->vsc, err);
Lck_Unlock(bp->director->mtx);
VSLb(bo->vsl, SLT_FetchError,
"backend %s: fail errno %d (%s)",
Expand Down
2 changes: 1 addition & 1 deletion bin/varnishd/cache/cache_backend.h
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Expand Up @@ -82,5 +82,5 @@ void VBP_Insert(struct backend *b, struct vrt_backend_probe const *p,
void VBP_Remove(struct backend *b);
void VBP_Control(const struct backend *b, int stop);
void VBP_Status(struct vsb *, const struct backend *, int details, int json);
void VBE_Connect_Error(struct VSC_vbe *, int err);
const char * VBE_Connect_Error(struct VSC_vbe *, int err);

11 changes: 11 additions & 0 deletions bin/varnishd/cache/cache_vrt_var.c
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Expand Up @@ -623,6 +623,17 @@ VRT_r_beresp_backend(VRT_CTX)

/*--------------------------------------------------------------------*/

VCL_STRING
VRT_r_beresp_error(VRT_CTX)
{

CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
CHECK_OBJ_NOTNULL(ctx->bo, BUSYOBJ_MAGIC);
return (ctx->bo->err_resp);
}

/*--------------------------------------------------------------------*/

VCL_VOID
VRT_u_bereq_body(VRT_CTX)
{
Expand Down
10 changes: 10 additions & 0 deletions bin/varnishtest/tests/v00019.vtc
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Expand Up @@ -69,6 +69,16 @@ varnish v1 -errvcl {Comparison of different types: STRING '==' INT} {
}
}

varnish v1 -vcl {
import debug;
backend be none;
sub vcl_recv {
if ("string" == debug.return_strands("string")) {
return (fail("should compile"));
}
}
}

varnish v1 -errvcl {Symbol not found: 'req.http.req.http.foo'} {
backend b { .host = "${localhost}"; }
sub vcl_recv {
Expand Down
20 changes: 20 additions & 0 deletions bin/varnishtest/tests/v00072.vtc
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@@ -0,0 +1,20 @@
varnishtest "VCL error messages"

# Instead of adding coverage for all errors here, we should probably add
# error.* coverage to existing test cases.

server s1 "" -start -break

varnish v1 -vcl+backend {
sub vcl_backend_error {
if (beresp.error != error.connection_refused) {
return (abandon);
}
}
} -start

client c1 {
txreq
rxresp
expect resp.body ~ "<p>Connection refused by the backend</p>"
} -run
22 changes: 22 additions & 0 deletions doc/sphinx/reference/vcl_var.rst
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Expand Up @@ -1149,6 +1149,15 @@ beresp.filters
``beresp.do_*`` switches is a VCL error.


beresp.error

Type: STRING

Readable from: vcl_backend_error

TODO: description (change type to ERROR?)


.. _beresp.grace:

beresp.grace
Expand Down Expand Up @@ -1899,3 +1908,16 @@ storage.<name>.used_space
Used space in the named stevedore. Only available for the malloc
stevedore.

Error messages
--------------

TODO: general introduction.

error.connection_refused

Type: ERROR

Error message: Connection refused by the backend

TODO: description (maybe mention ECONNREFUSED etc)

1 change: 1 addition & 0 deletions include/vrt.h
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Expand Up @@ -386,6 +386,7 @@ typedef unsigned VCL_BOOL;
typedef int64_t VCL_BYTES;
typedef vtim_dur VCL_DURATION;
typedef const char * VCL_ENUM;
typedef const char * VCL_ERROR;
typedef const struct gethdr_s * VCL_HEADER;
typedef struct http * VCL_HTTP;
typedef void VCL_INSTANCE;
Expand Down
12 changes: 11 additions & 1 deletion lib/libvcc/generate.py
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Expand Up @@ -183,7 +183,12 @@ def emit_var(self):
fo.write('\tsym->rname = "HDR_')
fo.write(self.nam.split(".")[0].upper())
fo.write('";\n')
elif self.rd and self.typ != "HEADER":
elif self.typ == "ERROR":
emsg = " ".join(self.wr)
self.wr = []
fo.write('\tsym->rname = "VRT_c_%s()";\n' % cnam)
fh.write("#define VRT_c_%s() \"%s\"\n" % (cnam, emsg))
elif self.rd and self.typ != "HEADER" and self.typ != "ERROR":
fo.write('\tsym->rname = "VRT_r_%s(ctx)";\n' % cnam)
varproto("VCL_" + self.typ + " VRT_r_%s(VRT_CTX)" % cnam)
fo.write("\tsym->r_methods =\n")
Expand Down Expand Up @@ -266,6 +271,11 @@ def parse_var(ln):
for i in j[2:]:
vu.append(i.strip(",."))
continue
if j[0] == "Error" and j[1] == "message:":
vt = "ERROR"
vr = ["all"]
vw = j[2:] # stash error message in write permissions
continue
if j[0] == "Alias" and j[1] == "of:":
va = j[2]
continue
Expand Down
21 changes: 12 additions & 9 deletions lib/libvcc/vcc_expr.c
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Expand Up @@ -288,19 +288,18 @@ vcc_expr_tobool(struct vcc *tl, struct expr **e)
*/

static void
vcc_expr_tostring(struct vcc *tl, struct expr **e, vcc_type_t fmt)
vcc_expr_tostring(struct vcc *tl, struct expr **e)
{
const char *p;
uint8_t constant = EXPR_VAR;

CHECK_OBJ_NOTNULL(*e, EXPR_MAGIC);
assert(fmt == STRINGS || fmt->stringform);
assert(fmt != (*e)->fmt);
assert((*e)->fmt != STRINGS);

p = (*e)->fmt->tostring;
if (p != NULL) {
AN(*p);
*e = vcc_expr_edit(tl, fmt, p, *e, NULL);
*e = vcc_expr_edit(tl, STRINGS, p, *e, NULL);
(*e)->constant = constant;
(*e)->nstr = 1;
} else {
Expand Down Expand Up @@ -816,7 +815,7 @@ vcc_expr5(struct vcc *tl, struct expr **e, vcc_type_t fmt)
ERRCHK(tl);
/* Unless asked for a HEADER, fold to string here */
if (*e && fmt != HEADER && (*e)->fmt == HEADER) {
vcc_expr_tostring(tl, e, STRINGS);
vcc_expr_tostring(tl, e);
ERRCHK(tl);
}
return;
Expand Down Expand Up @@ -1071,9 +1070,9 @@ vcc_expr_add(struct vcc *tl, struct expr **e, vcc_type_t fmt)
} else if (tk->tok == '+' &&
((*e)->fmt == STRINGS || fmt == STRINGS)) {
if ((*e)->fmt != STRINGS)
vcc_expr_tostring(tl, e, STRINGS);
vcc_expr_tostring(tl, e);
if (e2->fmt != STRINGS)
vcc_expr_tostring(tl, &e2, STRINGS);
vcc_expr_tostring(tl, &e2);
if (vcc_islit(*e) && vcc_isconst(e2)) {
lit = vcc_islit(e2);
*e = vcc_expr_edit(tl, STRINGS,
Expand Down Expand Up @@ -1187,6 +1186,10 @@ cmp_string(struct vcc *tl, struct expr **e, const struct cmps *cp)
tk = tl->t;
vcc_NextToken(tl);
vcc_expr_add(tl, &e2, STRINGS);
if (e2->fmt != STRINGS && e2->fmt->stringform) {
/* NB: no concatenation processed by vcc_expr_add() */
vcc_expr_tostring(tl, &e2);
}
ERRCHK(tl);
if (e2->fmt != STRINGS) {
VSB_printf(tl->sb,
Expand Down Expand Up @@ -1420,7 +1423,7 @@ vcc_expr0(struct vcc *tl, struct expr **e, vcc_type_t fmt)
return;

if ((*e)->fmt != STRINGS && fmt->stringform)
vcc_expr_tostring(tl, e, STRINGS);
vcc_expr_tostring(tl, e);

if ((*e)->fmt->stringform) {
VSB_printf(tl->sb, "Cannot convert type %s(%s) to %s(%s)\n",
Expand All @@ -1431,7 +1434,7 @@ vcc_expr0(struct vcc *tl, struct expr **e, vcc_type_t fmt)
}

if (fmt == BODY && !(*e)->fmt->bodyform)
vcc_expr_tostring(tl, e, STRINGS);
vcc_expr_tostring(tl, e);

if (fmt == BODY && (*e)->fmt->bodyform) {
if ((*e)->fmt == STRINGS)
Expand Down
7 changes: 7 additions & 0 deletions lib/libvcc/vcc_types.c
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Expand Up @@ -114,6 +114,13 @@ const struct type ENUM[1] = {{
.tostring = "",
}};

const struct type ERROR[1] = {{
.magic = TYPE_MAGIC,
.name = "ERROR",
.stringform = 1,
.tostring = "(\v1)",
}};

const struct type HEADER[1] = {{
.magic = TYPE_MAGIC,
.name = "HEADER",
Expand Down