1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
|
/*
*
* Copyright 2015-2016, Google Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
* * Neither the name of Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
#include <grpc/census.h>
#include <grpc/support/alloc.h>
#include <grpc/support/log.h>
#include <grpc/support/port_platform.h>
#include <grpc/support/useful.h>
#include <stdbool.h>
#include <string.h>
#include "src/core/support/string.h"
// Functions in this file support the public context API, including
// encoding/decoding as part of context propagation across RPC's. The overall
// requirements (in approximate priority order) for the
// context representation:
// 1. Efficient conversion to/from wire format
// 2. Minimal bytes used on-wire
// 3. Efficient context creation
// 4. Efficient lookup of tag value for a key
// 5. Efficient iteration over tags
// 6. Minimal memory footprint
//
// Notes on tradeoffs/decisions:
// * tag includes 1 byte length of key, as well as nil-terminating byte. These
// are to aid in efficient parsing and the ability to directly return key
// strings. This is more important than saving a single byte/tag on the wire.
// * The wire encoding uses only single byte values. This eliminates the need
// to handle endian-ness conversions. It also means there is a hard upper
// limit of 255 for both CENSUS_MAX_TAG_KV_LEN and CENSUS_MAX_PROPAGATED_TAGS.
// * Keep all tag information (keys/values/flags) in a single memory buffer,
// that can be directly copied to the wire.
// * Binary tags share the same structure as, but are encoded separately from,
// non-binary tags. This is primarily because non-binary tags are far more
// likely to be repeated across multiple RPC calls, so are more efficiently
// cached and compressed in any metadata schemes.
// Structure representing a set of tags. Essentially a count of number of tags
// present, and pointer to a chunk of memory that contains the per-tag details.
struct tag_set {
int ntags; // number of tags.
int ntags_alloc; // ntags + number of deleted tags (total number of tags
// in all of kvm). This will always be == ntags, except during the process
// of building a new tag set.
size_t kvm_size; // number of bytes allocated for key/value storage.
size_t kvm_used; // number of bytes of used key/value memory
char *kvm; // key/value memory. Consists of repeated entries of:
// Offset Size Description
// 0 1 Key length, including trailing 0. (K)
// 1 1 Value length. (V)
// 2 1 Flags
// 3 K Key bytes
// 3 + K V Value bytes
//
// We refer to the first 3 entries as the 'tag header'. If extra values are
// introduced in the header, you will need to modify the TAG_HEADER_SIZE
// constant, the raw_tag structure (and everything that uses it) and the
// encode/decode functions appropriately.
};
// Number of bytes in tag header.
#define TAG_HEADER_SIZE 3 // key length (1) + value length (1) + flags (1)
// Offsets to tag header entries.
#define KEY_LEN_OFFSET 0
#define VALUE_LEN_OFFSET 1
#define FLAG_OFFSET 2
// raw_tag represents the raw-storage form of a tag in the kvm of a tag_set.
struct raw_tag {
uint8_t key_len;
uint8_t value_len;
uint8_t flags;
char *key;
char *value;
};
// Use a reserved flag bit for indication of deleted tag.
#define CENSUS_TAG_DELETED CENSUS_TAG_RESERVED
#define CENSUS_TAG_IS_DELETED(flags) (flags & CENSUS_TAG_DELETED)
// Primary (external) representation of a context. Composed of 3 underlying
// tag_set structs, one for each of the binary/printable propagated tags, and
// one for everything else. This is to efficiently support tag
// encoding/decoding.
struct census_context {
struct tag_set tags[3];
census_context_status status;
};
// Indices into the tags member of census_context
#define PROPAGATED_TAGS 0
#define PROPAGATED_BINARY_TAGS 1
#define LOCAL_TAGS 2
// Extract a raw tag given a pointer (raw) to the tag header. Allow for some
// extra bytes in the tag header (see encode/decode functions for usage: this
// allows for future expansion of the tag header).
static char *decode_tag(struct raw_tag *tag, char *header, int offset) {
tag->key_len = (uint8_t)(*header++);
tag->value_len = (uint8_t)(*header++);
tag->flags = (uint8_t)(*header++);
header += offset;
tag->key = header;
header += tag->key_len;
tag->value = header;
return header + tag->value_len;
}
// Make a copy (in 'to') of an existing tag_set.
static void tag_set_copy(struct tag_set *to, const struct tag_set *from) {
memcpy(to, from, sizeof(struct tag_set));
to->kvm = gpr_malloc(to->kvm_size);
memcpy(to->kvm, from->kvm, from->kvm_used);
}
// Delete a tag from a tag_set, if it exists (returns true if it did).
static bool tag_set_delete_tag(struct tag_set *tags, const char *key,
size_t key_len) {
char *kvp = tags->kvm;
for (int i = 0; i < tags->ntags_alloc; i++) {
uint8_t *flags = (uint8_t *)(kvp + FLAG_OFFSET);
struct raw_tag tag;
kvp = decode_tag(&tag, kvp, 0);
if (CENSUS_TAG_IS_DELETED(tag.flags)) continue;
if ((key_len == tag.key_len) && (memcmp(key, tag.key, key_len) == 0)) {
*flags |= CENSUS_TAG_DELETED;
tags->ntags--;
return true;
}
}
return false;
}
// Delete a tag from a context, return true if it existed.
static bool context_delete_tag(census_context *context, const census_tag *tag,
size_t key_len) {
return (
tag_set_delete_tag(&context->tags[LOCAL_TAGS], tag->key, key_len) ||
tag_set_delete_tag(&context->tags[PROPAGATED_TAGS], tag->key, key_len) ||
tag_set_delete_tag(&context->tags[PROPAGATED_BINARY_TAGS], tag->key,
key_len));
}
// Add a tag to a tag_set. Return true on success, false if the tag could
// not be added because of constraints on tag set size. This function should
// not be called if the tag may already exist (in a non-deleted state) in
// the tag_set, as that would result in two tags with the same key.
static bool tag_set_add_tag(struct tag_set *tags, const census_tag *tag,
size_t key_len) {
if (tags->ntags == CENSUS_MAX_PROPAGATED_TAGS) {
return false;
}
const size_t tag_size = key_len + tag->value_len + TAG_HEADER_SIZE;
if (tags->kvm_used + tag_size > tags->kvm_size) {
// allocate new memory if needed
tags->kvm_size += 2 * CENSUS_MAX_TAG_KV_LEN + TAG_HEADER_SIZE;
char *new_kvm = gpr_malloc(tags->kvm_size);
memcpy(new_kvm, tags->kvm, tags->kvm_used);
gpr_free(tags->kvm);
tags->kvm = new_kvm;
}
char *kvp = tags->kvm + tags->kvm_used;
*kvp++ = (char)key_len;
*kvp++ = (char)tag->value_len;
// ensure reserved flags are not used.
*kvp++ = (char)(tag->flags & (CENSUS_TAG_PROPAGATE | CENSUS_TAG_STATS |
CENSUS_TAG_BINARY));
memcpy(kvp, tag->key, key_len);
kvp += key_len;
memcpy(kvp, tag->value, tag->value_len);
tags->kvm_used += tag_size;
tags->ntags++;
tags->ntags_alloc++;
return true;
}
// Add/modify/delete a tag to/in a context. Caller must validate that tag key
// etc. are valid.
static void context_modify_tag(census_context *context, const census_tag *tag,
size_t key_len) {
// First delete the tag if it is already present.
bool deleted = context_delete_tag(context, tag, key_len);
// Determine if we need to add it back.
bool call_add = tag->value != NULL && tag->value_len != 0;
bool added = false;
if (call_add) {
if (CENSUS_TAG_IS_PROPAGATED(tag->flags)) {
if (CENSUS_TAG_IS_BINARY(tag->flags)) {
added = tag_set_add_tag(&context->tags[PROPAGATED_BINARY_TAGS], tag,
key_len);
} else {
added = tag_set_add_tag(&context->tags[PROPAGATED_TAGS], tag, key_len);
}
} else {
added = tag_set_add_tag(&context->tags[LOCAL_TAGS], tag, key_len);
}
}
if (deleted) {
if (call_add) {
context->status.n_modified_tags++;
} else {
context->status.n_deleted_tags++;
}
} else {
if (added) {
context->status.n_added_tags++;
} else {
context->status.n_ignored_tags++;
}
}
}
// Remove memory used for deleted tags from a tag set. Basic algorithm:
// 1) Walk through tag set to find first deleted tag. Record where it is.
// 2) Find the next not-deleted tag. Copy all of kvm from there to the end
// "over" the deleted tags
// 3) repeat #1 and #2 until we have seen all tags
// 4) if we are still looking for a not-deleted tag, then all the end portion
// of the kvm is deleted. Just reduce the used amount of memory by the
// appropriate amount.
static void tag_set_flatten(struct tag_set *tags) {
if (tags->ntags == tags->ntags_alloc) return;
bool found_deleted = false; // found a deleted tag.
char *kvp = tags->kvm;
char *dbase = NULL; // record location of deleted tag
for (int i = 0; i < tags->ntags_alloc; i++) {
struct raw_tag tag;
char *next_kvp = decode_tag(&tag, kvp, 0);
if (found_deleted) {
if (!CENSUS_TAG_IS_DELETED(tag.flags)) {
ptrdiff_t reduce = kvp - dbase; // #bytes in deleted tags
GPR_ASSERT(reduce > 0);
ptrdiff_t copy_size = tags->kvm + tags->kvm_used - kvp;
GPR_ASSERT(copy_size > 0);
memmove(dbase, kvp, (size_t)copy_size);
tags->kvm_used -= (size_t)reduce;
next_kvp -= reduce;
found_deleted = false;
}
} else {
if (CENSUS_TAG_IS_DELETED(tag.flags)) {
dbase = kvp;
found_deleted = true;
}
}
kvp = next_kvp;
}
if (found_deleted) {
GPR_ASSERT(dbase > tags->kvm);
tags->kvm_used = (size_t)(dbase - tags->kvm);
}
tags->ntags_alloc = tags->ntags;
}
census_context *census_context_create(const census_context *base,
const census_tag *tags, int ntags,
census_context_status const **status) {
census_context *context = gpr_malloc(sizeof(census_context));
// If we are given a base, copy it into our new tag set. Otherwise set it
// to zero/NULL everything.
if (base == NULL) {
memset(context, 0, sizeof(census_context));
} else {
tag_set_copy(&context->tags[PROPAGATED_TAGS], &base->tags[PROPAGATED_TAGS]);
tag_set_copy(&context->tags[PROPAGATED_BINARY_TAGS],
&base->tags[PROPAGATED_BINARY_TAGS]);
tag_set_copy(&context->tags[LOCAL_TAGS], &base->tags[LOCAL_TAGS]);
memset(&context->status, 0, sizeof(context->status));
}
// Walk over the additional tags and, for those that aren't invalid, modify
// the context to add/replace/delete as required.
for (int i = 0; i < ntags; i++) {
const census_tag *tag = &tags[i];
size_t key_len = strlen(tag->key) + 1;
// ignore the tag if it is too long/short.
if (key_len != 1 && key_len <= CENSUS_MAX_TAG_KV_LEN &&
tag->value_len <= CENSUS_MAX_TAG_KV_LEN) {
context_modify_tag(context, tag, key_len);
} else {
context->status.n_invalid_tags++;
}
}
// Remove any deleted tags, update status if needed, and return.
tag_set_flatten(&context->tags[PROPAGATED_TAGS]);
tag_set_flatten(&context->tags[PROPAGATED_BINARY_TAGS]);
tag_set_flatten(&context->tags[LOCAL_TAGS]);
context->status.n_propagated_tags = context->tags[PROPAGATED_TAGS].ntags;
context->status.n_propagated_binary_tags =
context->tags[PROPAGATED_BINARY_TAGS].ntags;
context->status.n_local_tags = context->tags[LOCAL_TAGS].ntags;
if (status) {
*status = &context->status;
}
return context;
}
const census_context_status *census_context_get_status(
const census_context *context) {
return &context->status;
}
void census_context_destroy(census_context *context) {
gpr_free(context->tags[PROPAGATED_TAGS].kvm);
gpr_free(context->tags[PROPAGATED_BINARY_TAGS].kvm);
gpr_free(context->tags[LOCAL_TAGS].kvm);
gpr_free(context);
}
void census_context_initialize_iterator(const census_context *context,
census_context_iterator *iterator) {
iterator->context = context;
iterator->index = 0;
if (context->tags[PROPAGATED_TAGS].ntags != 0) {
iterator->base = PROPAGATED_TAGS;
iterator->kvm = context->tags[PROPAGATED_TAGS].kvm;
} else if (context->tags[PROPAGATED_BINARY_TAGS].ntags != 0) {
iterator->base = PROPAGATED_BINARY_TAGS;
iterator->kvm = context->tags[PROPAGATED_BINARY_TAGS].kvm;
} else if (context->tags[LOCAL_TAGS].ntags != 0) {
iterator->base = LOCAL_TAGS;
iterator->kvm = context->tags[LOCAL_TAGS].kvm;
} else {
iterator->base = -1;
}
}
int census_context_next_tag(census_context_iterator *iterator,
census_tag *tag) {
if (iterator->base < 0) {
return 0;
}
struct raw_tag raw;
iterator->kvm = decode_tag(&raw, iterator->kvm, 0);
tag->key = raw.key;
tag->value = raw.value;
tag->value_len = raw.value_len;
tag->flags = raw.flags;
if (++iterator->index == iterator->context->tags[iterator->base].ntags) {
do {
if (iterator->base == LOCAL_TAGS) {
iterator->base = -1;
return 1;
}
} while (iterator->context->tags[++iterator->base].ntags == 0);
iterator->index = 0;
iterator->kvm = iterator->context->tags[iterator->base].kvm;
}
return 1;
}
// Find a tag in a tag_set by key. Return true if found, false otherwise.
static bool tag_set_get_tag(const struct tag_set *tags, const char *key,
size_t key_len, census_tag *tag) {
char *kvp = tags->kvm;
for (int i = 0; i < tags->ntags; i++) {
struct raw_tag raw;
kvp = decode_tag(&raw, kvp, 0);
if (key_len == raw.key_len && memcmp(raw.key, key, key_len) == 0) {
tag->key = raw.key;
tag->value = raw.value;
tag->value_len = raw.value_len;
tag->flags = raw.flags;
return true;
}
}
return false;
}
int census_context_get_tag(const census_context *context, const char *key,
census_tag *tag) {
size_t key_len = strlen(key) + 1;
if (key_len == 1) {
return 0;
}
if (tag_set_get_tag(&context->tags[PROPAGATED_TAGS], key, key_len, tag) ||
tag_set_get_tag(&context->tags[PROPAGATED_BINARY_TAGS], key, key_len,
tag) ||
tag_set_get_tag(&context->tags[LOCAL_TAGS], key, key_len, tag)) {
return 1;
}
return 0;
}
// Context encoding and decoding functions.
//
// Wire format for tag_set's on the wire:
//
// First, a tag set header:
//
// offset bytes description
// 0 1 version number
// 1 1 number of bytes in this header. This allows for future
// expansion.
// 2 1 number of bytes in each tag header.
// 3 1 ntags value from tag set.
//
// This is followed by the key/value memory from struct tag_set.
#define ENCODED_VERSION 0 // Version number
#define ENCODED_HEADER_SIZE 4 // size of tag set header
// Encode a tag set. Returns 0 if buffer is too small.
static size_t tag_set_encode(const struct tag_set *tags, char *buffer,
size_t buf_size) {
if (buf_size < ENCODED_HEADER_SIZE + tags->kvm_used) {
return 0;
}
buf_size -= ENCODED_HEADER_SIZE;
*buffer++ = (char)ENCODED_VERSION;
*buffer++ = (char)ENCODED_HEADER_SIZE;
*buffer++ = (char)TAG_HEADER_SIZE;
*buffer++ = (char)tags->ntags;
if (tags->ntags == 0) {
return ENCODED_HEADER_SIZE;
}
memcpy(buffer, tags->kvm, tags->kvm_used);
return ENCODED_HEADER_SIZE + tags->kvm_used;
}
char *census_context_encode(const census_context *context, char *buffer,
size_t buf_size, size_t *print_buf_size,
size_t *bin_buf_size) {
*print_buf_size =
tag_set_encode(&context->tags[PROPAGATED_TAGS], buffer, buf_size);
if (*print_buf_size == 0) {
return NULL;
}
char *b_buffer = buffer + *print_buf_size;
*bin_buf_size = tag_set_encode(&context->tags[PROPAGATED_BINARY_TAGS],
b_buffer, buf_size - *print_buf_size);
if (*bin_buf_size == 0) {
return NULL;
}
return b_buffer;
}
// Decode a tag set.
static void tag_set_decode(struct tag_set *tags, const char *buffer,
size_t size) {
uint8_t version = (uint8_t)(*buffer++);
uint8_t header_size = (uint8_t)(*buffer++);
uint8_t tag_header_size = (uint8_t)(*buffer++);
tags->ntags = tags->ntags_alloc = (int)(*buffer++);
if (tags->ntags == 0) {
tags->ntags_alloc = 0;
tags->kvm_size = 0;
tags->kvm_used = 0;
tags->kvm = NULL;
return;
}
if (header_size != ENCODED_HEADER_SIZE) {
GPR_ASSERT(version != ENCODED_VERSION);
GPR_ASSERT(ENCODED_HEADER_SIZE < header_size);
buffer += (header_size - ENCODED_HEADER_SIZE);
}
tags->kvm_used = size - header_size;
tags->kvm_size = tags->kvm_used + CENSUS_MAX_TAG_KV_LEN;
tags->kvm = gpr_malloc(tags->kvm_size);
if (tag_header_size != TAG_HEADER_SIZE) {
// something new in the tag information. I don't understand it, so
// don't copy it over.
GPR_ASSERT(version != ENCODED_VERSION);
GPR_ASSERT(tag_header_size > TAG_HEADER_SIZE);
char *kvp = tags->kvm;
for (int i = 0; i < tags->ntags; i++) {
memcpy(kvp, buffer, TAG_HEADER_SIZE);
kvp += header_size;
struct raw_tag raw;
buffer =
decode_tag(&raw, (char *)buffer, tag_header_size - TAG_HEADER_SIZE);
memcpy(kvp, raw.key, (size_t)raw.key_len + raw.value_len);
kvp += raw.key_len + raw.value_len;
}
} else {
memcpy(tags->kvm, buffer, tags->kvm_used);
}
}
census_context *census_context_decode(const char *buffer, size_t size,
const char *bin_buffer, size_t bin_size) {
census_context *context = gpr_malloc(sizeof(census_context));
memset(&context->tags[LOCAL_TAGS], 0, sizeof(struct tag_set));
if (buffer == NULL) {
memset(&context->tags[PROPAGATED_TAGS], 0, sizeof(struct tag_set));
} else {
tag_set_decode(&context->tags[PROPAGATED_TAGS], buffer, size);
}
if (bin_buffer == NULL) {
memset(&context->tags[PROPAGATED_BINARY_TAGS], 0, sizeof(struct tag_set));
} else {
tag_set_decode(&context->tags[PROPAGATED_BINARY_TAGS], bin_buffer,
bin_size);
}
memset(&context->status, 0, sizeof(context->status));
context->status.n_propagated_tags = context->tags[PROPAGATED_TAGS].ntags;
context->status.n_propagated_binary_tags =
context->tags[PROPAGATED_BINARY_TAGS].ntags;
// TODO(aveitch): check that BINARY flag is correct for each type.
return context;
}
|