404-solution / includes / diagnostics / EncodedTableResponseSize.php

EncodedTableResponseSize.php in 404 Solution trunk, at includes/diagnostics/EncodedTableResponseSize.php

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1	<?php
2
3	if (!defined('ABSPATH')) {
4	exit;
5	}
6
7	/**
8	* How many bytes the server actually encoded for a browser session's most
9	* recent completed admin-table response.
10	*
11	* The one question that needs BOTH durable journals and can be answered by
12	* neither alone. The stage trace owns the session-to-request join; the
13	* checkpoint journal owns the exact post-json_encode byte count. Joining them
14	* is a distinct responsibility from reading either channel for the support
15	* payload, which is why it lives here rather than inside
16	* ABJ_404_Solution_CheckpointJournalReader: that class answers "what does this
17	* journal say", and this one answers a question about the site.
18	*
19	* Consumed once, by the size_target canary step, so the ladder's size probes
20	* are calibrated against the real failing response rather than a default.
21	*
22	* Every absence is NAMED rather than collapsed into one word. Support report
23	* 2026-08-27 (Azure App Service, plugin 4.3.4) shipped
24	* `{bytes: null, source: "unavailable"}` for a session the browser definitely
25	* had, and nothing in the payload could separate "the client sent no session"
26	* from "the trace journal names no table request for it" (what actually
27	* happened -- the trace writer was never armed) from "the table request ran and
28	* journaled no size". A fabricated size is never returned in any of the three.
29	*/
30	final class ABJ_404_Solution_EncodedTableResponseSize {
31
32	/**
33	* The size for one browser session, or a named absence.
34	*
35	* Scans the bounded/rotated journals and the live pending spools of both
36	* channels. Missing, malformed, foreign-session, non-table and zero-byte
37	* records all resolve to a named absence rather than to a number.
38	*
39	* An absence here is not the end of the ladder's size axis: the step falls
40	* through to a live measurement
41	* (ABJ_404_Solution_MeasuredTableResponseSize) and carries this channel's
42	* own answer alongside it as `realResponseRecordedSource`, so the reason
43	* the recorded number was unavailable survives even when a measured one
44	* replaces it. Naming the absence precisely is what makes that pair
45	* readable; see ABJ_404_Solution_AjaxCanaryStepRunner::resolveSizeTarget().
46	*
47	* @return array{bytes: int\|null, source: string, request_id: string}
48	*/
49	public static function forSession(string $sessionId): array {
50	// Guarded before the reads, not inside fromLines(), so the no-session
51	// case still costs no journal I/O the way it always has.
52	if (substr($sessionId, 0, 64) === '') {
53	return self::noEncodedSize('unavailable');
54	}
55	try {
56	$traceSource = ABJ_404_Solution_AjaxTraceJournal::supportCollectionSource();
57	$source = ABJ_404_Solution_CheckpointJournalReader::supportCollectionSource();
58	return self::fromLines(
59	ABJ_404_Solution_DiagnosticJournalExcerpt::readAllLines($traceSource['paths']),
60	ABJ_404_Solution_DiagnosticJournalExcerpt::readAllLines($source['paths']),
61	$sessionId
62	);
63	} catch (Throwable $e) {
64	// Unconditional; abj404_logPhpFallback() is defined at plugin
65	// entry, before any class here can be autoloaded.
66	abj404_logPhpFallback(
67	'ajax-checkpoint', 'Encoded table response-size lookup failed: ' . $e->getMessage());
68	return self::noEncodedSize('journal_error');
69	}
70	}
71
72	/**
73	* The same answer built from journal lines a caller already holds.
74	*
75	* Exists so a caller that reads the checkpoint journal for its own reasons
76	* can join against the EXACT lines it read. Two independent reads of the
77	* same growing file can straddle a concurrent append, which pairs a record
78	* from one instant with a record from another and reports a comparison
79	* neither read actually saw. ABJ_404_Solution_ResponseBodyDeliveryEvidence
80	* is that caller: it reads the checkpoint journal to find delivery records
81	* and needs the emitted size drawn from the same snapshot.
82	*
83	* The trace and checkpoint journals stay separate parameters because they
84	* are separate files answering separate halves of the join; only the
85	* checkpoint half is shared with that caller.
86	*
87	* @param array<int, string> $traceLines
88	* @param array<int, string> $checkpointLines
89	* @return array{bytes: int\|null, source: string, request_id: string}
90	*/
91	public static function fromLines(array $traceLines, array $checkpointLines, string $sessionId): array {
92	$sessionId = substr($sessionId, 0, 64);
93	if ($sessionId === '') {
94	return self::noEncodedSize('unavailable');
95	}
96	$tableRequestIds = self::tableRequestIdsInSession($traceLines, $sessionId);
97	if ($tableRequestIds === array()) {
98	return self::noEncodedSize('session_not_traced');
99	}
100	return self::latestEncodedSizeForRequests(
101	$checkpointLines, $tableRequestIds, self::noEncodedSize('no_encoded_size_recorded'));
102	}
103
104	/**
105	* The no-size answer, carrying the reason it is the answer.
106	*
107	* @return array{bytes: int\|null, source: string, request_id: string}
108	*/
109	private static function noEncodedSize(string $reason): array {
110	return array('bytes' => null, 'source' => $reason, 'request_id' => '');
111	}
112
113	/**
114	* @param array<int, string> $traceLines
115	* @return array<string, bool>
116	*/
117	private static function tableRequestIdsInSession(array $traceLines, string $sessionId): array {
118	$requestIds = array();
119	foreach ($traceLines as $line) {
120	if (strpos($line, 'ajaxUpdatePaginationLinks') === false
121	\|\| strpos($line, $sessionId) === false) {
122	continue;
123	}
124	$record = json_decode($line, true);
125	if (!is_array($record)) {
126	continue;
127	}
128	$action = is_scalar($record['action'] ?? null) ? (string)$record['action'] : '';
129	$part = is_scalar($record['part'] ?? null) ? (string)$record['part'] : '';
130	$recordSessionId = is_scalar($record['session_id'] ?? null) ? (string)$record['session_id'] : '';
131	if ($action !== 'ajaxUpdatePaginationLinks' \|\| $part !== 'table'
132	\|\| $recordSessionId !== $sessionId) {
133	continue;
134	}
135	$requestId = is_scalar($record['request_id'] ?? null)
136	? (string)$record['request_id'] : '';
137	if (preg_match('/^[A-Za-z0-9]{8,64}$/', $requestId) === 1) {
138	$requestIds[$requestId] = true;
139	}
140	}
141	return $requestIds;
142	}
143
144	/**
145	* @param array<int, string> $checkpointLines
146	* @param array<string, bool> $requestIds
147	* @param array{bytes: int\|null, source: string, request_id: string} $unavailable
148	* @return array{bytes: int\|null, source: string, request_id: string}
149	*/
150	private static function latestEncodedSizeForRequests(
151	array $checkpointLines,
152	array $requestIds,
153	array $unavailable
154	): array {
155	$latest = $unavailable;
156	foreach ($checkpointLines as $line) {
157	if (strpos($line, '"event":"json_encode"') === false) {
158	continue;
159	}
160	$record = json_decode($line, true);
161	if (!is_array($record)) {
162	continue;
163	}
164	$event = is_scalar($record['event'] ?? null) ? (string)$record['event'] : '';
165	$requestId = is_scalar($record['request_id'] ?? null)
166	? (string)$record['request_id'] : '';
167	$bytes = is_numeric($record['bytes'] ?? null) ? (int)$record['bytes'] : 0;
168	if ($event !== 'json_encode' \|\| !isset($requestIds[$requestId]) \|\| $bytes <= 0) {
169	continue;
170	}
171	$latest = array(
172	'bytes' => $bytes,
173	'source' => 'session_json_encode',
174	'request_id' => $requestId,
175	);
176	}
177	return $latest;
178	}
179	}
180