Emit Prometheus 0.0.4 format version in /metrics Content-Type

[jantman]

Fixes #26.

Problem

/metrics returned Content-Type: text/plain; charset=utf-8, with no exposition format version. Prometheus v2 tolerated that and silently fell back to the 0.0.4 text format; Prometheus v3 fails the scrape outright when the Content-Type names no recognized format version.

Change

kiosk_show_replacement/metrics.py now responds with text/plain; version=0.0.4; charset=utf-8, held in a new module-level PROMETHEUS_CONTENT_TYPE constant.

Two deviations from the fix sketched in the issue, both deliberate:

• No prometheus_client dependency. The issue suggested Response(generate_latest(registry), mimetype=CONTENT_TYPE_LATEST). This module hand-builds its exposition text and has no prometheus_client registry at all, so generate_latest() does not apply without rewriting the whole collector — well beyond what the issue asks for. Adding a runtime dependency solely to import a string constant did not seem worth it, so the value is defined locally with a comment recording that it is identical to CONTENT_TYPE_LATEST.
• content_type= instead of mimetype=. Werkzeug appends its own charset to a mimetype, so passing the full value there duplicates the parameter. Worth noting: the previous code hit this too and was actually emitting text/plain; charset=utf-8; charset=utf-8.

Verification

• New unit test asserts the exact header value.

• Full backend suite: 687 passed, 1 skipped.

• nox -s format / lint / type_check all clean (mypy: no issues in 36 files).

• Checked against a running dev server:

  $ curl -si http://127.0.0.1:5000/metrics | head -4
  HTTP/1.1 200 OK
  Server: Werkzeug/3.1.5 Python/3.14.7
  Date: Sun, 20 Sep 2026 15:16:38 GMT
  Content-Type: text/plain; version=0.0.4; charset=utf-8
  

Not covered here

The issue's remaining two checkboxes are dm-puppet changes and live-infrastructure steps that belong in that repository, not this one:

• release a new image and bump the dmpuppet::internals::kiosk_show tag
• drop fallback_scrape_protocol: PrometheusText0.0.4 from the kiosk job in prometheus.yml, then confirm the target still scrapes on Prometheus v3

Those should follow once this merges and an image is cut.

🤖 Generated with Claude Code

https://claude.ai/code/session_019XAhg2bNjxS9PMFUtTVT1J

[github-actions]

Coverage Report

File	Stmts	Miss	Cover	Missing
__init__.py	10	0	100%
app.py	138	31	77%	35, 75, 193, 235–236, 238–239, 241–244, 256–258, 261, 263, 273, 275, 278–279, 282–285, 289–292, 295–296, 299
database_utils.py	170	130	23%	30–36, 41–47, 57, 59–61, 64–65, 67–69, 72–74, 77, 79, 88, 90–93, 95, 116, 118, 121–123, 126, 129, 131–132, 134–135, 137–139, 142–146, 159, 161–164, 167, 177, 186–187, 190, 219, 247, 250, 283–284, 286–287, 289–292, 301, 303, 308, 310, 315, 318–319, 324, 326, 333, 336–337, 339–340, 347–348, 356, 361, 384–387, 390, 393–396, 399–401, 404–406, 408–409, 411–413, 426–429, 431–433, 436, 439, 442, 445–447, 449–450, 452–454
db_resilience.py	122	3	97%	186, 256, 280
exceptions.py	110	0	100%
health.py	112	16	85%	81–83, 86–87, 98, 119–120, 134, 147, 158–160, 170–172
ical_parser.py	113	6	94%	85, 120, 124, 127, 134, 197
ical_service.py	170	18	89%	80, 82–85, 87, 127–128, 130, 233, 342, 368–369, 375, 382, 454, 456, 460
logging_config.py	81	3	96%	110, 112, 190
metrics.py	237	6	97%	433–434, 478–479, 489–490
middleware.py	36	6	83%	77, 95–96, 109–110, 117
migration_utils.py	73	73	0%	8–9, 11–12, 15, 18–19, 26–32, 34–35, 46–48, 50–55, 57–58, 68–70, 72–77, 79–80, 90–96, 98–99, 105–108, 110–111, 117–120, 122–123, 133–138, 141, 144, 151, 153–154, 156, 161–162
sse.py	167	58	65%	45, 47–48, 50–51, 53–54, 57–59, 61–62, 65–66, 68, 118, 120–122, 204, 210–211, 213–214, 218, 225, 227–228, 230, 232, 234, 309, 322, 324, 332, 335–336, 338, 341, 345–346, 348, 352–353, 355, 358–359, 361, 365, 369–370, 372, 383, 395–398, 449
storage.py	331	49	85%	88–90, 156–157, 163, 168, 259–261, 489–491, 512, 526, 573–576, 580, 604–606, 617–619, 675–676, 680, 701–703, 743–746, 774–775, 777–783, 785, 832–833, 860
storage_resilience.py	163	53	67%	68–69, 203–204, 211, 213–219, 266–270, 303–305, 334, 347–348, 352–358, 362–364, 382, 384–389, 391–401, 403, 405
validation.py	138	17	87%	221, 223, 229, 263, 265–266, 268–269, 337–342, 348, 376, 413
api
__init__.py	10	2	80%	27, 38
helpers.py	77	20	74%	170, 179, 222, 230, 235, 243, 248, 256, 261, 270, 275, 283–286, 293, 301–304
v1.py	1576	645	59%	89, 177–179, 219, 225, 231, 240, 262, 290–292, 304, 341, 345, 361–364, 455, 488, 492, 495, 515–516, 519, 529, 533, 537, 656–658, 661, 675, 679, 683, 687, 752, 755–756, 761–762, 765–766, 768–769, 772–773, 776, 789, 800, 823–826, 842, 846, 850, 876–879, 889, 893, 897, 901, 905, 926, 933–935, 952–957, 975, 979, 998–1002, 1025, 1040–1042, 1057, 1064–1066, 1080, 1089–1091, 1108, 1119–1121, 1131, 1135, 1140, 1145, 1150, 1170–1171, 1187–1190, 1200, 1204, 1208–1210, 1220, 1224, 1228, 1244–1245, 1249, 1262, 1319–1322, 1329–1332, 1334–1336, 1338–1340, 1343–1344, 1347–1350, 1353–1354, 1357, 1365–1366, 1368, 1371, 1382, 1387, 1390, 1394–1398, 1401, 1411, 1415, 1426–1429, 1441–1444, 1446–1448, 1450–1451, 1453–1454, 1456, 1459, 1461–1464, 1471–1474, 1476–1478, 1480–1481, 1483–1485, 1487, 1490, 1492–1495, 1512, 1540–1542, 1549–1551, 1553, 1555–1557, 1576, 1578–1581, 1584, 1587–1592, 1595, 1598, 1600, 1602–1606, 1618–1621, 1623, 1626, 1628, 1630–1632, 1639–1642, 1644–1646, 1649–1650, 1653, 1656–1657, 1660, 1673–1674, 1676, 1679, 1683–1693, 1700–1703, 1705–1707, 1709–1710, 1712, 1714–1716, 1723–1726, 1728–1730, 1732–1733, 1735–1737, 1740, 1742, 1749–1751, 1753–1766, 1768–1769, 1771, 1774, 1776–1786, 1793–1796, 1798–1800, 1802–1803, 1805–1807, 1809, 1812, 1814–1817, 1828–1831, 1833–1835, 1837–1839, 1841–1842, 1844–1845, 1848–1850, 1852, 1855, 1857–1862, 1865, 1872–1875, 1877–1879, 1881–1882, 1884–1887, 1889–1891, 1893–1894, 1897–1899, 1901–1905, 1908, 1910–1911, 1914, 1916–1917, 1919–1920, 1922, 1924, 1928, 1935, 1939–1942, 1984, 2064–2066, 2069–2070, 2078, 2084, 2092, 2101, 2122, 2126, 2156–2158, 2160–2162, 2170, 2180, 2184, 2223–2225, 2227–2229, 2237, 2264, 2272, 2316–2318, 2320–2322, 2324–2326, 2330, 2357, 2377, 2387, 2405–2407, 2409–2411, 2419, 2457–2459, 2467, 2482, 2490, 2514, 2522, 2534–2536, 2546, 2550, 2554, 2559, 2564–2565, 2570, 2586, 2598–2600, 2642, 2650, 2677–2679, 2689, 2700–2701, 2709–2711, 2736, 2738, 2741, 2745, 2747, 2749–2754, 2760, 2762–2764, 2767, 2772–2773, 2775, 2779, 2781–2783, 2799, 2801, 2803, 2807, 2813–2814, 2816–2822, 2825–2826, 2829–2837, 2840–2848, 2850–2851, 2854–2855, 2858–2859, 2862–2868, 2872, 2874, 2876–2877, 2880, 2896, 2950–2952, 2959–2960, 2962–2964, 2966–2968, 2971, 2980, 2982, 2986, 2996–2998, 3021, 3050–3052, 3172–3173, 3180–3181, 3183–3185, 3187–3189, 3191, 3194, 3197, 3200–3202, 3204–3211, 3213–3214, 3216–3221, 3223, 3226–3227, 3229–3230, 3243, 3246–3247, 3251, 3253–3254, 3266–3267, 3271, 3275, 3286–3288, 3291
auth
__init__.py	4	0	100%
decorators.py	48	12	75%	54, 106, 122, 132–134, 136, 148–149, 151, 153–154
views.py	83	18	78%	73, 75–77, 120–121, 162–163, 165–166, 172, 240–241, 244–245, 254, 258, 267
cli
__init__.py	1	0	100%
init_db.py	85	67	21%	41–46, 48–49, 52–55, 57–58, 61–62, 65–66, 68, 73, 75–79, 81–82, 85–92, 94, 96, 100, 102–103, 141–142, 145, 148–151, 153–157, 159, 162, 171–173, 176–177, 179–183, 185, 187–188
main.py	35	15	57%	17, 28, 30–32, 41, 43–44, 53–54, 56, 58–59, 61, 66
config
__init__.py	58	0	100%
dashboard
__init__.py	2	0	100%
views.py	56	17	69%	88–91, 151, 153–157, 159, 161, 163, 165, 177, 188–189
display
__init__.py	2	0	100%
views.py	151	47	68%	31, 33, 38, 53, 171–172, 187, 195, 230–231, 239, 273, 275–276, 278, 280–281, 283, 285, 306–308, 311–312, 314, 325, 333–334, 343, 354, 356–357, 364, 366, 368, 375, 388, 391, 410, 413, 415–416, 423, 425, 427, 433, 444
main
__init__.py	17	17	0%	10, 12, 14, 17, 20–21, 30, 33–35, 42, 45, 52, 55–56, 63, 69
models
__init__.py	479	43	91%	126, 141, 263, 405, 407, 414, 431, 559, 584, 592, 594, 601, 609, 617, 725, 792, 799, 827, 885, 890, 924–927, 930, 1096, 1112, 1115, 1117, 1165–1166, 1168–1173, 1179, 1181, 1200, 1203, 1210, 1213
slideshow
__init__.py	50	34	32%	43, 46, 52–54, 56–58, 61–64, 66, 73–77, 80–82, 84, 90–91, 97, 103, 105, 107–112, 114
static
__init__.py	0	0	100%
templates
__init__.py	0	0	100%
utils
__init__.py	52	35	32%	43–46, 49–52, 65, 67–69, 71–72, 75–79, 92–97, 110–111, 121, 135–137, 140, 143–144, 146
TOTAL	4957	1441	70%

Tests	Skipped	Failures	Errors	Time
688	1 💤	0 ❌	0 🔥	56.401s ⏱️

[github-actions]

Claude Code review
_{From Claude, via the Claude PR Review workflow -- hence github-actions[bot].}

This PR fixes /metrics to emit Content-Type: text/plain; version=0.0.4; charset=utf-8 (via a new PROMETHEUS_CONTENT_TYPE constant and content_type= instead of mimetype=) so Prometheus v3 accepts the scrape, and adds a unit test asserting the exact header value. Four independent review passes (two CLAUDE.md compliance, two bug/security/logic) found no issues — the change is small, correct, and well-tested.

No issues found. Checked for bugs and CLAUDE.md compliance.

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_{🔎 2m 17s · 11 turns · $0.6320 · run log}