{"id":38965,"date":"2019-10-31T22:27:03","date_gmt":"2019-10-31T19:27:03","guid":{"rendered":"https:\/\/prohoster.info\/blog\/liveness-probes-v-kubernetes-mogut-byt-opasny\/"},"modified":"2019-10-31T22:27:03","modified_gmt":"2019-10-31T19:27:03","slug":"liveness-probes-v-kubernetes-mogut-byt-opasny","status":"publish","type":"post","link":"https:\/\/prohoster.info\/cs\/blog\/administrirovanie\/liveness-probes-v-kubernetes-mogut-byt-opasny","title":{"rendered":"Liveness probes v Kubernetes mohou b\u00fdt nebezpe\u010dn\u00e9","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"<p><i><b>Pozn. p\u0159ek.<\/b>: Hlavn\u00ed in\u017een\u00fdr spole\u010dnosti Zalando, Henning Jacobs, si n\u011bkolikr\u00e1t v\u0161iml u u\u017eivatel\u016f Kubernetes probl\u00e9my s pochopen\u00edm \u00fa\u010delu liveness (a readiness) probes a jejich spr\u00e1vn\u00e9 aplikace. Proto shrom\u00e1\u017edil sv\u00e9 my\u0161lenky v t\u00e9to stru\u010dn\u00e9 pozn\u00e1mce, kter\u00e1 se \u010dasem stane sou\u010d\u00e1st\u00ed dokumentace K8s.<\/i><\/p>\n<p><img decoding=\"async\" alt=\"Liveness probes v Kubernetes mohou b\u00fdt nebezpe\u010dn\u00e9\" src=\"\/wp-content\/uploads\/2019\/10\/b246e18dadd582889382f306508135a8.jpg\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\nKontroln\u00ed mechanismy, zn\u00e1m\u00e9 v Kubernetes jako <i>liveness probes<\/i> <i>(tj. doslova \u201etesty \u017eivotaschopnosti\u201c \u2014 pozn. p\u0159ekl.)<\/i>, mohou b\u00fdt pom\u011brn\u011b nebezpe\u010dn\u00e9. Doporu\u010duji se jim vyhnout, pokud je to mo\u017en\u00e9: v\u00fdjimkou jsou pouze p\u0159\u00edpady, kdy jsou skute\u010dn\u011b nezbytn\u00e9 a vy pln\u011b rozum\u00edte specifik\u016fm a d\u016fsledk\u016fm jejich pou\u017eit\u00ed. V tomto p\u0159\u00edsp\u011bvku se budeme zab\u00fdvat liveness a readiness kontrolami a tak\u00e9 se dozv\u00edte, kdy <i>je vhodn\u00e9<\/i> a nen\u00ed vhodn\u00e9 je pou\u017e\u00edvat.<noindex><a rel=\"nofollow\" name=\"habracut\"><\/a><\/noindex><\/p>\n<p>M\u016fj kolega Sandor se ned\u00e1vno pod\u011blil na Twitteru o nej\u010dast\u011bj\u0161\u00ed chyby, kter\u00e9 se mu objevuj\u00ed, v\u010detn\u011b t\u011bch spojen\u00fdch s pou\u017eit\u00edm readiness\/liveness probes:<\/p>\n<p><noindex><a rel=\"nofollow\" href=\"https:\/\/twitter.com\/sszuecs\/status\/1175377157343907840\"><img decoding=\"async\" alt=\"Liveness probes v Kubernetes mohou b\u00fdt nebezpe\u010dn\u00e9\" src=\"\/wp-content\/uploads\/2019\/10\/8bc2e834e77e2b51baf06d2465a97b4f.jpg\" style=\"display:block;margin: 0 auto;\" \/><\/a><\/noindex><\/p>\n<p>\u0160patn\u011b nastaven\u00e1 <code>livenessProbe<\/code> m\u016f\u017ee zhor\u0161it situace s vysok\u00fdm zat\u00ed\u017een\u00edm (lavinov\u00e9 vyp\u00edn\u00e1n\u00ed + potenci\u00e1ln\u011b dlouh\u00e9 spu\u0161t\u011bn\u00ed kontejneru\/aplikace) a v\u00e9st k dal\u0161\u00edm negativn\u00edm n\u00e1sledk\u016fm, jako je p\u00e1d z\u00e1vislost\u00ed <i>(viz tak\u00e9 <noindex><a rel=\"nofollow\" href=\"https:\/\/srcco.de\/posts\/k3s-outage-traefik-acme-lets-encrypt-local-path.html\">m\u016fj ned\u00e1vn\u00fd \u010dl\u00e1nek<\/a><\/noindex> o omezen\u00ed po\u010dtu po\u017eadavk\u016f v kombinaci K3s+ACME)<\/i>Je\u0161t\u011b hor\u0161\u00ed je, kdy\u017e je liveness probe kombinov\u00e1na se zdravotn\u00ed kontrolou z\u00e1vislosti (health check), kdy hraje roli extern\u00ed datab\u00e1ze: <b>jedin\u00fd v\u00fdpadek DB restartuje v\u0161echny va\u0161e kontejnery<\/b>!<\/p>\n<p>Obecn\u00e9 poselstv\u00ed <i>\u201eNepou\u017e\u00edvejte liveness probes\u201c<\/i> v tomto p\u0159\u00edpad\u011b moc nepom\u00e1h\u00e1, proto se pod\u00edvejme, k \u010demu slou\u017e\u00ed readiness a liveness kontroly. <\/p>\n<p><i>Pozn\u00e1mka: v\u011bt\u0161ina n\u00ed\u017ee uveden\u00e9ho testu byla p\u016fvodn\u011b zahrnuta do intern\u00ed dokumentace pro v\u00fdvoj\u00e1\u0159e spole\u010dnosti Zalando.<\/i><\/p>\n<h2>Kontroly Readiness a Liveness<\/h2>\n<p>\nKubernetes poskytuje dva d\u016fle\u017eit\u00e9 mechanismy, naz\u00fdvan\u00e9 <noindex><a rel=\"nofollow\" href=\"https:\/\/kubernetes.io\/docs\/tasks\/configure-pod-container\/configure-liveness-readiness-probes\/\">liveness probes a readiness probes<\/a><\/noindex>. Ty pravideln\u011b prov\u00e1d\u011bj\u00ed n\u011bjakou akci \u2014 nap\u0159\u00edklad pos\u00edlaj\u00ed HTTP po\u017eadavek, otev\u00edraj\u00ed TCP spojen\u00ed nebo vykon\u00e1vaj\u00ed p\u0159\u00edkaz v kontejneru \u2014 aby potvrdily, \u017ee aplikace funguje spr\u00e1vn\u011b.<\/p>\n<p>Kubernetes pou\u017e\u00edv\u00e1 <b>readiness probes<\/b>, aby bylo jasn\u00e9, kdy je kontejner p\u0159ipraven p\u0159ij\u00edmat provoz. Pod se pova\u017euje za p\u0159ipraven\u00fd, pokud jsou v\u0161echny jeho kontejnery p\u0159ipraven\u00e9. Jeden z \u00fa\u010del\u016f tohoto mechanismu spo\u010d\u00edv\u00e1 v kontrole, kter\u00e9 pody jsou pou\u017e\u00edv\u00e1ny jako backendy pro slu\u017eby Kubernetes (a zejm\u00e9na Ingress).<\/p>\n<p><b>Zdravotn\u00ed kontroly<\/b> pom\u00e1haj\u00ed Kubernetes pochopit, kdy je \u010das restartovat kontejner. Nap\u0159\u00edklad takov\u00e1 kontrola umo\u017e\u0148uje zachytit deadlock, kdy se aplikace \u201ezasekne\u201c na jednom m\u00edst\u011b. Restart kontejneru v takov\u00e9m stavu pom\u00e1h\u00e1 posunout aplikaci z mrtv\u00e9ho bodu, i p\u0159es chyby, m\u016f\u017ee v\u0161ak tak\u00e9 v\u00e9st k kask\u00e1dov\u00fdm selh\u00e1n\u00edm (viz n\u00ed\u017ee).<\/p>\n<p>Pokud se pokus\u00edte prov\u00e9st nasazen\u00ed aktualizace aplikace, kter\u00e9 sel\u017ee v kontrol\u00e1ch zdrav\u00ed\/p\u0159ipravenosti, jeho nasazen\u00ed se zastav\u00ed, proto\u017ee Kubernetes bude \u010dekat na status <code>Ready<\/code> ze v\u0161ech pod\u016f.<\/p>\n<h2>P\u0159\u00edklad<\/h2>\n<p>\nZde je p\u0159\u00edklad kontroly p\u0159ipravenosti, kter\u00e1 kontroluje cestu <code>\/health<\/code> p\u0159es HTTP s v\u00fdchoz\u00edmi nastaven\u00edmi (<i>interval<\/i>: 10 sekund, <i>timeout<\/i>: 1 sekunda, <i>\u00fasp\u011b\u0161n\u00fd pr\u00e1h<\/i>: 1, <i>nespr\u00e1vn\u00fd pr\u00e1h<\/i>: 3):<\/p>\n<pre><code class=\"plaintext\"># \u0447\u0430\u0441\u0442\u044c \u043e\u0431\u0449\u0435\u0433\u043e \u043e\u043f\u0438\u0441\u0430\u043d\u0438\u044f deployment'\u0430\/\u0441\u0442\u0435\u043a\u0430\npodTemplate:\n  spec:\n    containers:\n    - name: my-container\n      # ...\n      readinessProbe:\n        httpGet:\n          path: \/health\n          port: 8080<\/code><\/pre>\n<p><\/p>\n<h2>Doporu\u010den\u00ed<\/h2>\n<p><\/p>\n<ol>\n<li> Pro mikroslu\u017eby s HTTP endpointem (REST atd.) <b>v\u017edy ur\u010dete kontrolu p\u0159ipravenosti<\/b>, kter\u00e1 ov\u011b\u0159uje, zda je aplikace (pod) p\u0159ipravena p\u0159ij\u00edmat provoz.<\/li>\n<li> Zajist\u011bte, aby kontrola p\u0159ipravenosti <b>pokryla p\u0159ipravenost skute\u010dn\u00e9ho portu webov\u00e9ho serveru<\/b>:\n<ul>\n<li> pou\u017e\u00edvaj\u00edc\u00ed porty pro administrativn\u00ed pot\u0159eby, naz\u00fdvan\u00e9 \u201eadmin\u201c nebo \u201emanagement\u201c (nap\u0159\u00edklad 9090), pro <code>readinessProbe<\/code>, zajist\u011bte, aby endpoint vracel OK pouze v p\u0159\u00edpad\u011b, \u017ee je hlavn\u00ed HTTP port (nap\u0159\u00edklad 8080) p\u0159ipraven p\u0159ij\u00edmat provoz*;\n<p><i>* V\u00edm alespo\u0148 o jednom p\u0159\u00edpad\u011b v Zalando, kdy se to nestalo, tedy <code>readinessProbe<\/code> zkontroloval port \u201emanagement\u201c, ale samotn\u00fd server se v\u016fbec neza\u010dal na\u010d\u00edtat kv\u016fli probl\u00e9m\u016fm s na\u010d\u00edt\u00e1n\u00edm cache.<\/i><\/li>\n<li> p\u0159id\u00e1n\u00ed readiness probe na samostatn\u00fd port m\u016f\u017ee v\u00e9st k tomu, \u017ee p\u0159et\u00ed\u017een\u00ed na hlavn\u00edm portu nebude reflektov\u00e1no ve zdravotn\u00ed kontrole (to znamen\u00e1, \u017ee fronta vl\u00e1ken na serveru je pln\u00e1, ale zdravotn\u00ed kontrola st\u00e1le ukazuje, \u017ee v\u0161e je v po\u0159\u00e1dku).<\/li>\n<\/ul>\n<\/li>\n<li> Ujist\u011bte se, \u017ee <b>kontrola p\u0159ipravenosti zahrnuje inicializaci\/migraci datab\u00e1ze<\/b>;\n<ul>\n<li> nejjednodu\u0161\u0161\u00ed zp\u016fsob, jak toho dos\u00e1hnout, je volat HTTP server a\u017e po dokon\u010den\u00ed inicializace (nap\u0159\u00edklad migrace DB s <noindex><a rel=\"nofollow\" href=\"https:\/\/flywaydb.org\/\">Flyway<\/a><\/noindex> atd.); to znamen\u00e1 m\u00edsto toho, abyste m\u011bnili stav zdravotn\u00ed kontroly, jednodu\u0161e nespou\u0161t\u011bjte webov\u00fd server, dokud nebude migrace datab\u00e1ze dokon\u010dena*.\n<p><i>* Tak\u00e9 je mo\u017en\u00e9 spou\u0161t\u011bt migrace datab\u00e1ze z init-kontejner\u016f mimo pod. St\u00e1le jsem p\u0159\u00edznivcem samostatn\u00fdch (self-contained) aplikac\u00ed, tedy t\u011bch, v nich\u017e kontejner aplikace bez extern\u00ed koordinace v\u00ed, jak uvede datab\u00e1zi do po\u017eadovan\u00e9ho stavu.<\/i><\/li>\n<\/ul>\n<\/li>\n<li> Pou\u017eijte <code>httpGet<\/code> pro readiness kontroly prost\u0159ednictv\u00edm typick\u00fdch endpoint\u016f zdravotn\u00edch kontrol (nap\u0159\u00edklad, <code>\/health<\/code>).<\/li>\n<li> <b>Zjist\u011bte parametry kontrol, kter\u00e9 jsou nastaveny jako v\u00fdchoz\u00ed.<\/b> (<code>interval: 10s<\/code>, <code>timeout: 1s<\/code>, <code>successThreshold: 1<\/code>, <code>failureThreshold: 3<\/code>):\n<ul>\n<li> v\u00fdchoz\u00ed parametry znamenaj\u00ed, \u017ee pod se stane <i>not-ready<\/i> p\u0159ibli\u017en\u011b za 30 sekund (3 ne\u00fasp\u011b\u0161n\u00e9 kontroly provozuschopnosti).<\/li>\n<\/ul>\n<\/li>\n<li> Pou\u017eijte samostatn\u00fd port pro \u201eadmin\u201c nebo \u201emanagement\u201c, pokud technologick\u00fd stack (nap\u0159\u00edklad Java\/Spring) to umo\u017e\u0148uje, abyste odd\u011blili spr\u00e1vu \u201ezdrav\u00ed\u201c a metriky od b\u011b\u017en\u00e9ho provozu:\n<ul>\n<li> ale nezapome\u0148te na bod 2.<\/li>\n<\/ul>\n<\/li>\n<li> Pokud je to nutn\u00e9, m\u016f\u017eete readiness probe pou\u017e\u00edt k vyh\u0159\u00e1t\u00ed\/z\u00e1t\u011b\u017eov\u00e1n\u00ed cache a vracet stavov\u00fd k\u00f3d 503, dokud se kontejner ne \u201evyh\u0159eje\u201c:\n<ul>\n<li> tak\u00e9 doporu\u010duji se sezn\u00e1mit s novou kontrolou <code>startupProbe<\/code>, <noindex><a rel=\"nofollow\" href=\"https:\/\/sysdig.com\/blog\/whats-new-kubernetes-1-16\/\">kter\u00e1 se objevila ve verzi 1.16<\/a><\/noindex> <i>(psali jsme o n\u00ed v ru\u0161tin\u011b, <noindex><a rel=\"nofollow\" href=\"https:\/\/habr.com\/ru\/company\/flant\/blog\/467477\/\">zde<\/a><\/noindex> \u2014 pozn. p\u0159ekl.)<\/i>.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n<p><\/p>\n<h2>Upozorn\u011bn\u00ed<\/h2>\n<p><\/p>\n<ol>\n<li> <b>Nespol\u00e9hejte se na vn\u011bj\u0161\u00ed z\u00e1vislosti<\/b> (nap\u0159\u00edklad datov\u00e9 \u00falo\u017ei\u0161t\u011b) p\u0159i prov\u00e1d\u011bn\u00ed test\u016f na readiness\/liveness \u2014 to m\u016f\u017ee v\u00e9st k kask\u00e1dov\u00fdm poruch\u00e1m:\n<ul>\n<li> jako p\u0159\u00edklad vezm\u011bme stateful slu\u017ebu REST s 10 pody z\u00e1visl\u00fdmi na jedn\u00e9 datab\u00e1zi Postgres: kdy\u017e kontrola z\u00e1vis\u00ed na funk\u010dn\u00edm p\u0159ipojen\u00ed k datab\u00e1zi, v\u0161echny 10 pody mohou selhat, pokud dojde k prodlev\u011b v s\u00edti\/nebo na stran\u011b datab\u00e1ze \u2014 obvykle to v\u0161e kon\u010d\u00ed h\u016f\u0159e, ne\u017e by mohlo;<\/li>\n<li> v\u0161imn\u011bte si, \u017ee Spring Data ve v\u00fdchoz\u00edm nastaven\u00ed kontroluje p\u0159ipojen\u00ed k datab\u00e1zi*;\n<p><i>* Takov\u00e9 je chov\u00e1n\u00ed v\u00fdchoz\u00edho nastaven\u00ed Spring Data Redis (alespo\u0148 tak bylo p\u0159edt\u00edm, ne\u017e jsem naposledy kontroloval), co\u017e vedlo k \u201ekatastrofick\u00e9mu\u201c selh\u00e1n\u00ed: kdy\u017e byl Redis kr\u00e1tce nedostupn\u00fd, v\u0161echny pody \u201eselhaly\u201c.<\/i><\/li>\n<li> v tomto smyslu tak\u00e9 m\u016f\u017ee znamenat dal\u0161\u00ed pody stejn\u00e9 aplikace, tak\u017ee ide\u00e1ln\u011b by kontrola nem\u011bla z\u00e1viset na stavu dal\u0161\u00edch pod\u016f ve stejn\u00e9m clusteru, aby se p\u0159ede\u0161lo kask\u00e1dov\u00fdm selh\u00e1n\u00edm:\n<ul>\n<li> v\u00fdsledky se mohou li\u0161it pro aplikace s distribuovan\u00fdm stavem (nap\u0159\u00edklad in-memory caching v podech).<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<li> <b>Nepou\u017e\u00edvejte liveness probe<\/b> pro pod (s v\u00fdjimkou p\u0159\u00edpad\u016f, kdy jsou skute\u010dn\u011b nezbytn\u00e9 a vy si pln\u011b uv\u011bdomujete specifika a d\u016fsledky jejich pou\u017eit\u00ed):\n<ul>\n<li> liveness probe m\u016f\u017ee pomoci obnovit \u201ezamrzl\u00e9\u201c kontejnery, ale proto\u017ee m\u00e1te plnou kontrolu nad svou aplikac\u00ed, takov\u00e9 v\u011bci, jako jsou \u201ezamrzl\u00e9\u201c procesy a deadlocky, by se ide\u00e1ln\u011b nem\u011bly vyskytovat: lep\u0161\u00ed alternativou je z\u00e1m\u011brn\u00fd p\u00e1d aplikace a jej\u00ed n\u00e1vrat do p\u0159edchoz\u00edho stabiln\u00edho stavu;<\/li>\n<li> ne\u00fasp\u011b\u0161n\u00e1 liveness probe povede k restartu kontejneru, co\u017e m\u016f\u017ee potenci\u00e1ln\u011b zhor\u0161it d\u016fsledky chyb spojen\u00fdch s na\u010d\u00edt\u00e1n\u00edm: restart kontejneru zp\u016fsob\u00ed prostoje (alespo\u0148 po dobu spu\u0161t\u011bn\u00ed aplikace, \u0159ekn\u011bme, v\u00edce ne\u017e 30 sekund), co\u017e vyvol\u00e1 nov\u00e9 chyby, zvy\u0161uje z\u00e1t\u011b\u017e na dal\u0161\u00ed kontejnery a zvy\u0161uje pravd\u011bpodobnost jejich selh\u00e1n\u00ed, atd.;<\/li>\n<li> liveness kontroly v kombinaci s extern\u00edmi z\u00e1vislostmi jsou nejhor\u0161\u00ed mo\u017en\u00e1 kombinace, hroz\u00edc\u00ed kask\u00e1dov\u00fdmi selh\u00e1n\u00edmi: drobn\u00e9 zpo\u017ed\u011bn\u00ed na stran\u011b datab\u00e1ze povede k restartu v\u0161ech va\u0161ich kontejner\u016f!<\/li>\n<\/ul>\n<\/li>\n<li> Parametry liveness a readiness kontrol <b>by m\u011bly b\u00fdt odli\u0161n\u00e9<\/b>:\n<ul>\n<li> liveness probe lze pou\u017e\u00edt se stejn\u00fdm health checkem, ale s vy\u0161\u0161\u00edm prahov\u00fdm hodnotou spou\u0161t\u011bn\u00ed (<code>failureThreshold<\/code>), nap\u0159\u00edklad p\u0159i\u0159adit stav <i>not-ready<\/i> po 3 pokusech a pova\u017eovat, \u017ee liveness probe selhala po 10 pokusech;<\/li>\n<\/ul>\n<\/li>\n<li> <b>Nepou\u017e\u00edvejte exec kontroly<\/b>, proto\u017ee s nimi souvisej\u00ed zn\u00e1m\u00e9 probl\u00e9my, kter\u00e9 vedou k vzniku zombie proces\u016f:\n<ul>\n<li> podrobnosti: viz <noindex><a rel=\"nofollow\" href=\"https:\/\/www.youtube.com\/watch?v=QKI-JRs2RIE\">v\u00fdstup specialist\u016f spole\u010dnosti Datadog<\/a><\/noindex>.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n<p><\/p>\n<h2>Shrnut\u00ed<\/h2>\n<p><\/p>\n<ul>\n<li> Pou\u017e\u00edvejte readiness probes, abyste ur\u010dili, kdy je pod p\u0159ipraven k p\u0159ij\u00edm\u00e1n\u00ed provozu.<\/li>\n<li> Pou\u017e\u00edvejte liveness probes pouze tehdy, kdy\u017e jsou skute\u010dn\u011b pot\u0159ebn\u00e9.<\/li>\n<li> Nespr\u00e1vn\u00e9 pou\u017eit\u00ed readiness\/liveness probes m\u016f\u017ee v\u00e9st ke sn\u00ed\u017een\u00ed dostupnosti a kask\u00e1dov\u00fdm selh\u00e1n\u00edm.<\/li>\n<\/ul>\n<p>\n<noindex><a rel=\"nofollow\" href=\"https:\/\/twitter.com\/sszuecs\/status\/1175655221382529025\"><img decoding=\"async\" alt=\"Liveness probes v Kubernetes mohou b\u00fdt nebezpe\u010dn\u00e9\" src=\"\/wp-content\/uploads\/2019\/10\/8c212c41d6e69cd515a85d2b6100aaed.jpg\" style=\"display:block;margin: 0 auto;\" \/><\/a><\/noindex><\/p>\n<h2>Dal\u0161\u00ed materi\u00e1ly k t\u00e9matu<\/h2>\n<p><\/p>\n<ul>\n<li> <noindex><a rel=\"nofollow\" href=\"https:\/\/kubernetes.io\/docs\/tasks\/configure-pod-container\/configure-liveness-readiness-probes\/\">Dokumentace Kubernetes: Konfigurace liveness a readiness kontrol<\/a><\/noindex>;<\/li>\n<li> <noindex><a rel=\"nofollow\" href=\"https:\/\/blog.colinbreck.com\/kubernetes-liveness-and-readiness-probes-revisited-how-to-avoid-shooting-yourself-in-the-other-foot\/\">Kubernetes Liveness a Readiness Probes Znovu Zv\u00e1\u017een\u00e9: Jak se vyhnout zran\u011bn\u00ed p\u0159i vlastn\u00edm sm\u011b\u0159ov\u00e1n\u00ed.<\/a><\/noindex>;<\/li>\n<li> <noindex><a rel=\"nofollow\" href=\"https:\/\/keepingitclassless.net\/2018\/12\/december-4-nre-labs-outage-post-mortem\/\">NRE Labs V\u00fdpadek Post-Mortem<\/a><\/noindex> (vypr\u00e1v\u00ed tak\u00e9 o livenessProbe).<\/li>\n<\/ul>\n<p><\/p>\n<h2>Aktualizace \u010d. 1 ze dne 2019-09-29<\/h2>\n<p>\n<noindex><a rel=\"nofollow\" href=\"https:\/\/twitter.com\/BarrWill1\/status\/1178144162526453760\">O init-kontejnerech pro migraci datab\u00e1ze<\/a><\/noindex>: p\u0159id\u00e1na pozn\u00e1mka.<\/p>\n<p><noindex><a rel=\"nofollow\" href=\"https:\/\/twitter.com\/ejc3\/status\/1178077779293683713\">EJ mi p\u0159ipomn\u011bl<\/a><\/noindex> o PDB: jedn\u00edm z probl\u00e9m\u016f liveness check\u016f je nedostatek koordinace mezi pody. V Kubernetes existuje <noindex><a rel=\"nofollow\" href=\"https:\/\/kubernetes.io\/docs\/tasks\/run-application\/configure-pdb\/\">Pod Disruption Budgets (PDB)<\/a><\/noindex> k omezen\u00ed po\u010dtu paraleln\u00edch selh\u00e1n\u00ed, kter\u00e9 m\u016f\u017ee aplikace za\u017e\u00edt, ale kontroly nezohled\u0148uj\u00ed PDB. Ide\u00e1ln\u011b bychom mohli na\u0159\u00eddit K8s: \"Restartuj jeden pod, pokud jeho kontrola sel\u017ee, ale neopakuj je v\u0161echny, abychom to nezhor\u0161ili.\"<\/p>\n<p><noindex><a rel=\"nofollow\" href=\"https:\/\/twitter.com\/bboreham\/status\/1178083887991398400\">Bryan to skv\u011ble formuloval<\/a><\/noindex>: \u201ePou\u017eijte liveness probe, kdy\u017e si jste jisti, \u017ee <b>to nejlep\u0161\u00ed, co m\u016f\u017eete ud\u011blat, je \u201ezab\u00edt\u201c aplikaci<\/b>\u201c (op\u011bt, p\u0159\u00edli\u0161 to nep\u0159eh\u00e1n\u011bjte).<\/p>\n<p><noindex><a rel=\"nofollow\" href=\"https:\/\/twitter.com\/bboreham\/status\/1178207929540972544\"><img decoding=\"async\" alt=\"Liveness probes v Kubernetes mohou b\u00fdt nebezpe\u010dn\u00e9\" src=\"\/wp-content\/uploads\/2019\/10\/524122a63bd4acd950bf9fc8aeeb45be.jpg\" style=\"display:block;margin: 0 auto;\" \/><\/a><\/noindex><\/p>\n<h2>Aktualizace \u010d. 2 z 29. 9. 2019<\/h2>\n<p>\n<noindex><a rel=\"nofollow\" href=\"https:\/\/twitter.com\/Guillaume_Swiss\/status\/1178258781152563200\">Co se t\u00fd\u010de \u010dten\u00ed dokumentace p\u0159ed pou\u017eit\u00edm<\/a><\/noindex>: vytvo\u0159il jsem odpov\u00eddaj\u00edc\u00ed \u017e\u00e1dost (<noindex><a rel=\"nofollow\" href=\"https:\/\/github.com\/kubernetes\/website\/issues\/16607\">feature request<\/a><\/noindex>) na dopln\u011bn\u00ed dokumentace o liveness probes.<\/p>\n<h2>P.S. od p\u0159ekladatele<\/h2>\n<p>\nP\u0159e\u010dt\u011bte si tak\u00e9 n\u00e1\u0161 blog:<\/p>\n<ul>\n<li> \u00ab<noindex><a rel=\"nofollow\" href=\"https:\/\/habr.com\/ru\/company\/flant\/blog\/415393\/\">Kubernetes: \u017eivot podu<\/a><\/noindex>\u00bb;<\/li>\n<li> \u00ab<noindex><a rel=\"nofollow\" href=\"https:\/\/habr.com\/ru\/company\/flant\/blog\/425085\/\">7 nejlep\u0161\u00edch praktik pro provoz kontejner\u016f podle Google<\/a><\/noindex>\u00bb;<\/li>\n<li> \u00ab<noindex><a rel=\"nofollow\" href=\"https:\/\/habr.com\/ru\/company\/flant\/blog\/353272\/\">7 princip\u016f n\u00e1vrhu aplikac\u00ed zalo\u017een\u00fdch na kontejnerech<\/a><\/noindex>\u00bb.<\/li>\n<\/ul>\n<p>Zdroj: <a content=\"nofollow\" rel=\"nofollow\" href=\"https:\/\/habr.com\/ru\/company\/flant\/blog\/470958\/\">habr.com<\/a><\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"<p>\u041f\u0440\u0438\u043c. \u043f\u0435\u0440\u0435\u0432.: \u0412\u0435\u0434\u0443\u0449\u0438\u0439 \u0438\u043d\u0436\u0435\u043d\u0435\u0440 \u0438\u0437 \u043a\u043e\u043c\u043f\u0430\u043d\u0438\u0438 Zalando \u2014 Henning Jacobs \u2014 \u043d\u0435 \u0440\u0430\u0437 \u0437\u0430\u043c\u0435\u0447\u0430\u043b \u0443 \u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u0442\u0435\u043b\u0435\u0439 Kubernetes \u043f\u0440\u043e\u0431\u043b\u0435\u043c\u044b \u0432 \u043f\u043e\u043d\u0438\u043c\u0430\u043d\u0438\u0438 \u043f\u0440\u0435\u0434\u043d\u0430\u0437\u043d\u0430\u0447\u0435\u043d\u0438\u044f liveness (\u0438 readiness) probes \u0438 \u0438\u0445 \u043a\u043e\u0440\u0440\u0435\u043a\u0442\u043d\u043e\u0433\u043e \u043f\u0440\u0438\u043c\u0435\u043d\u0435\u043d\u0438\u044f. \u041f\u043e\u0441\u0435\u043c\u0443 \u043e\u043d \u0441\u043e\u0431\u0440\u0430\u043b \u0441\u0432\u043e\u0438 \u043c\u044b\u0441\u043b\u0438 \u0432 \u044d\u0442\u0443 \u0451\u043c\u043a\u0443\u044e \u0437\u0430\u043c\u0435\u0442\u043a\u0443, \u043a\u043e\u0442\u043e\u0440\u0430\u044f \u0441\u043e \u0432\u0440\u0435\u043c\u0435\u043d\u0435\u043c \u0441\u0442\u0430\u043d\u0435\u0442 \u0447\u0430\u0441\u0442\u044c\u044e \u0434\u043e\u043a\u0443\u043c\u0435\u043d\u0442\u0430\u0446\u0438\u0438 K8s. \u041f\u0440\u043e\u0432\u0435\u0440\u043a\u0438 \u0441\u043e\u0441\u0442\u043e\u044f\u043d\u0438\u044f, \u0438\u0437\u0432\u0435\u0441\u0442\u043d\u044b\u0435 \u0432 Kubernetes \u043a\u0430\u043a liveness probes (\u0442.\u0435., \u0434\u043e\u0441\u043b\u043e\u0432\u043d\u043e, [&hellip;]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":29232,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[688],"tags":[],"class_list":["post-38965","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-administrirovanie"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 5.0.3 - aioseo.com -->\n\t<meta name=\"description\" content=\"\u041f\u0440\u0438\u043c. \u043f\u0435\u0440\u0435\u0432.: \u0412\u0435\u0434\u0443\u0449\u0438\u0439 \u0438\u043d\u0436\u0435\u043d\u0435\u0440 \u0438\u0437 \u043a\u043e\u043c\u043f\u0430\u043d\u0438\u0438 Zalando \u2014 Henning Jacobs \u2014 \u043d\u0435 \u0440\u0430\u0437 \u0437\u0430\u043c\u0435\u0447\u0430\u043b \u0443 \u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u0442\u0435\u043b\u0435\u0439 Kubernetes \u043f\u0440\u043e\u0431\u043b\u0435\u043c\u044b \u0432 \u043f\u043e\u043d\u0438\u043c\u0430\u043d\u0438\u0438 \u043f\u0440\u0435\u0434\u043d\u0430\u0437\u043d\u0430\u0447\u0435\u043d\u0438\u044f liveness (\u0438 readiness) probes \u0438 \u0438\u0445 \u043a\u043e\u0440\u0440\u0435\u043a\u0442\u043d\u043e\u0433\u043e \u043f\u0440\u0438\u043c\u0435\u043d\u0435\u043d\u0438\u044f.\" \/>\n\t<meta name=\"robots\" content=\"max-image-preview:large\" \/>\n\t<meta name=\"author\" content=\"Yuri Gagarin\"\/>\n\t<link rel=\"canonical\" href=\"https:\/\/prohoster.info\/cs\/blog\/administrirovanie\/liveness-probes-v-kubernetes-mogut-byt-opasny\" \/>\n\t\t<meta name=\"generator\" content=\"All in One SEO (AIOSEO) 5.0.3\" \/>\n\t\t<meta property=\"og:locale\" content=\"cs_CZ\" \/>\n\t\t<meta property=\"og:site_name\" content=\"ProHoster | \u041a\u0443\u043f\u0438\u0442\u044c \u043d\u0430\u0434\u0435\u0436\u043d\u044b\u0439 \u0445\u043e\u0441\u0442\u0438\u043d\u0433 \u0434\u043b\u044f \u0441\u0430\u0439\u0442\u043e\u0432 \u0441 \u0437\u0430\u0449\u0438\u0442\u043e\u0439 \u043e\u0442 DDoS, VPS VDS \u0441\u0435\u0440\u0432\u0435\u0440\u044b\" \/>\n\t\t<meta property=\"og:type\" content=\"article\" \/>\n\t\t<meta property=\"og:title\" content=\"\ud83e\udd47Liveness probes \u0432 Kubernetes \u043c\u043e\u0433\u0443\u0442 \u0431\u044b\u0442\u044c \u043e\u043f\u0430\u0441\u043d\u044b | ProHoster\" \/>\n\t\t<meta property=\"og:description\" content=\"\u041f\u0440\u0438\u043c. \u043f\u0435\u0440\u0435\u0432.: \u0412\u0435\u0434\u0443\u0449\u0438\u0439 \u0438\u043d\u0436\u0435\u043d\u0435\u0440 \u0438\u0437 \u043a\u043e\u043c\u043f\u0430\u043d\u0438\u0438 Zalando \u2014 Henning Jacobs \u2014 \u043d\u0435 \u0440\u0430\u0437 \u0437\u0430\u043c\u0435\u0447\u0430\u043b \u0443 \u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u0442\u0435\u043b\u0435\u0439 Kubernetes \u043f\u0440\u043e\u0431\u043b\u0435\u043c\u044b \u0432 \u043f\u043e\u043d\u0438\u043c\u0430\u043d\u0438\u0438 \u043f\u0440\u0435\u0434\u043d\u0430\u0437\u043d\u0430\u0447\u0435\u043d\u0438\u044f liveness (\u0438 readiness) probes \u0438 \u0438\u0445 \u043a\u043e\u0440\u0440\u0435\u043a\u0442\u043d\u043e\u0433\u043e \u043f\u0440\u0438\u043c\u0435\u043d\u0435\u043d\u0438\u044f.\" \/>\n\t\t<meta property=\"og:url\" content=\"https:\/\/prohoster.info\/cs\/blog\/administrirovanie\/liveness-probes-v-kubernetes-mogut-byt-opasny\" \/>\n\t\t<meta property=\"og:image\" content=\"https:\/\/prohoster.info\/wp-content\/uploads\/2021\/11\/logo-350.jpg\" \/>\n\t\t<meta property=\"og:image:secure_url\" content=\"https:\/\/prohoster.info\/wp-content\/uploads\/2021\/11\/logo-350.jpg\" \/>\n\t\t<meta property=\"og:image:width\" content=\"350\" \/>\n\t\t<meta property=\"og:image:height\" content=\"350\" \/>\n\t\t<meta property=\"article:published_time\" content=\"2019-10-31T19:27:03+00:00\" \/>\n\t\t<meta property=\"article:modified_time\" content=\"2019-10-31T19:27:03+00:00\" \/>\n\t\t<meta property=\"article:publisher\" content=\"https:\/\/www.facebook.com\/prohoster\" \/>\n\t\t<meta property=\"article:author\" content=\"https:\/\/www.facebook.com\/prohoster\" \/>\n\t\t<!-- All in One SEO -->\n\n","aioseo_head_json":{"title":"\ud83e\udd47Liveness probes v Kubernetes mohou b\u00fdt nebezpe\u010dn\u00e9 | ProHoster","description":"Pozn. p\u0159ekl.: Veden\u00ed in\u017een\u00fdr ze spole\u010dnosti Zalando \u2014 Henning Jacobs \u2014 n\u011bkolikr\u00e1t zaznamenal u u\u017eivatel\u016f Kubernetes probl\u00e9my s porozum\u011bn\u00edm \u00fa\u010delu liveness (a readiness) probes a jejich spr\u00e1vn\u00e9mu pou\u017eit\u00ed.","canonical_url":"https:\/\/prohoster.info\/cs\/blog\/administrirovanie\/liveness-probes-v-kubernetes-mogut-byt-opasny","robots":"max-image-preview:large","keywords":"","webmasterTools":{"miscellaneous":""},"schema":null,"og:locale":"cs_CZ","og:site_name":"ProHoster | \u041a\u0443\u043f\u0438\u0442\u044c \u043d\u0430\u0434\u0435\u0436\u043d\u044b\u0439 \u0445\u043e\u0441\u0442\u0438\u043d\u0433 \u0434\u043b\u044f \u0441\u0430\u0439\u0442\u043e\u0432 \u0441 \u0437\u0430\u0449\u0438\u0442\u043e\u0439 \u043e\u0442 DDoS, VPS VDS \u0441\u0435\u0440\u0432\u0435\u0440\u044b","og:type":"article","og:title":"\ud83e\udd47Liveness probes \u0432 Kubernetes \u043c\u043e\u0433\u0443\u0442 \u0431\u044b\u0442\u044c \u043e\u043f\u0430\u0441\u043d\u044b | ProHoster","og:description":"\u041f\u0440\u0438\u043c. \u043f\u0435\u0440\u0435\u0432.: \u0412\u0435\u0434\u0443\u0449\u0438\u0439 \u0438\u043d\u0436\u0435\u043d\u0435\u0440 \u0438\u0437 \u043a\u043e\u043c\u043f\u0430\u043d\u0438\u0438 Zalando \u2014 Henning Jacobs \u2014 \u043d\u0435 \u0440\u0430\u0437 \u0437\u0430\u043c\u0435\u0447\u0430\u043b \u0443 \u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u0442\u0435\u043b\u0435\u0439 Kubernetes \u043f\u0440\u043e\u0431\u043b\u0435\u043c\u044b \u0432 \u043f\u043e\u043d\u0438\u043c\u0430\u043d\u0438\u0438 \u043f\u0440\u0435\u0434\u043d\u0430\u0437\u043d\u0430\u0447\u0435\u043d\u0438\u044f liveness (\u0438 readiness) probes \u0438 \u0438\u0445 \u043a\u043e\u0440\u0440\u0435\u043a\u0442\u043d\u043e\u0433\u043e \u043f\u0440\u0438\u043c\u0435\u043d\u0435\u043d\u0438\u044f.","og:url":"https:\/\/prohoster.info\/cs\/blog\/administrirovanie\/liveness-probes-v-kubernetes-mogut-byt-opasny","og:image":"https:\/\/prohoster.info\/wp-content\/uploads\/2021\/11\/logo-350.jpg","og:image:secure_url":"https:\/\/prohoster.info\/wp-content\/uploads\/2021\/11\/logo-350.jpg","og:image:width":350,"og:image:height":350,"article:published_time":"2019-10-31T19:27:03+00:00","article:modified_time":"2019-10-31T19:27:03+00:00","article:publisher":"https:\/\/www.facebook.com\/prohoster","article:author":"https:\/\/www.facebook.com\/prohoster"},"aioseo_meta_data":{"post_id":"38965","title":null,"description":null,"keywords":null,"keyphrases":null,"primary_term":null,"canonical_url":null,"og_title":null,"og_description":null,"og_object_type":"default","og_image_type":"default","og_image_url":null,"og_image_width":null,"og_image_height":null,"og_image_custom_url":null,"og_image_custom_fields":null,"og_video":null,"og_custom_url":null,"og_article_section":null,"og_article_tags":null,"twitter_use_og":false,"twitter_card":"default","twitter_image_type":"default","twitter_image_url":null,"twitter_image_custom_url":null,"twitter_image_custom_fields":null,"twitter_title":null,"twitter_description":null,"schema":{"blockGraphs":[],"customGraphs":[],"default":{"data":{"Article":[],"Course":[],"Dataset":[],"FAQPage":[],"Movie":[],"Person":[],"Product":[],"ProductReview":[],"Car":[],"Recipe":[],"Service":[],"SoftwareApplication":[],"WebPage":[]},"graphName":"","isEnabled":true},"graphs":[]},"schema_type":null,"schema_type_options":null,"pillar_content":false,"robots_default":true,"robots_noindex":false,"robots_noarchive":false,"robots_nosnippet":false,"robots_nofollow":false,"robots_noimageindex":false,"robots_noodp":false,"robots_notranslate":false,"robots_max_snippet":null,"robots_max_videopreview":null,"robots_max_imagepreview":"large","priority":null,"frequency":null,"local_seo":null,"seo_analyzer_scan_date":"2026-01-24 00:10:22","breadcrumb_settings":null,"limit_modified_date":false,"reviewed_by":null,"ai":null,"created":"2021-03-01 00:59:27","updated":"2026-01-24 00:10:22","focus_keyword":null,"additional_keywords":null,"truseo_locale":null},"gt_translate_keys":[{"key":"link","format":"url"}],"_links":{"self":[{"href":"https:\/\/prohoster.info\/cs\/wp-json\/wp\/v2\/posts\/38965","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/prohoster.info\/cs\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/prohoster.info\/cs\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/prohoster.info\/cs\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/prohoster.info\/cs\/wp-json\/wp\/v2\/comments?post=38965"}],"version-history":[{"count":0,"href":"https:\/\/prohoster.info\/cs\/wp-json\/wp\/v2\/posts\/38965\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/prohoster.info\/cs\/wp-json\/wp\/v2\/media\/29232"}],"wp:attachment":[{"href":"https:\/\/prohoster.info\/cs\/wp-json\/wp\/v2\/media?parent=38965"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/prohoster.info\/cs\/wp-json\/wp\/v2\/categories?post=38965"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/prohoster.info\/cs\/wp-json\/wp\/v2\/tags?post=38965"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}