NullPointerException in disk usage data metric

Jenkins and plugins versions report

Environment

```text Jenkins: 2.452.1 OS: Linux - 5.14.0-362.24.1.el9_3.x86_64 Java: 17.0.11 - Eclipse Adoptium (OpenJDK 64-Bit Server VM) --- Parameterized-Remote-Trigger:3.2.0 ansicolor:1.0.4 ant:497.v94e7d9fffa_b_9 antisamy-markup-formatter:162.v0e6ec0fcfcf6 apache-httpcomponents-client-4-api:4.5.14-208.v438351942757 apache-httpcomponents-client-5-api:5.3.1-1.0 artifactory:4.0.6 asm-api:9.7-33.v4d23ef79fcc8 authentication-tokens:1.113.v81215a_241826 authorize-project:1.7.1 blueocean:1.27.12 blueocean-bitbucket-pipeline:1.27.12 blueocean-commons:1.27.12 blueocean-config:1.27.12 blueocean-core-js:1.27.12 blueocean-dashboard:1.27.12 blueocean-display-url:2.4.2 blueocean-events:1.27.12 blueocean-git-pipeline:1.27.12 blueocean-github-pipeline:1.27.12 blueocean-i18n:1.27.12 blueocean-jira:1.27.12 blueocean-jwt:1.27.12 blueocean-personalization:1.27.12 blueocean-pipeline-api-impl:1.27.12 blueocean-pipeline-editor:1.27.12 blueocean-pipeline-scm-api:1.27.12 blueocean-rest:1.27.12 blueocean-rest-impl:1.27.12 blueocean-web:1.27.12 bootstrap5-api:5.3.3-1 bouncycastle-api:2.30.1.78.1-233.vfdcdeb_0a_08a_a_ branch-api:2.1169.va_f810c56e895 build-monitor-plugin:1.14-883.vf620a_44eb_ec1 build-timeout:1.32 caffeine-api:3.1.8-133.v17b_1ff2e0599 checks-api:2.2.0 claim:554.va_f9b_58b_0a_088 cloud-stats:336.v788e4055508b_ cloudbees-bitbucket-branch-source:886.v44cf5e4ecec5 cloudbees-disk-usage-simple:203.v3f46a_7462b_1a_ cloudbees-folder:6.928.v7c780211d66e command-launcher:107.v773860566e2e commons-lang3-api:3.13.0-62.v7d18e55f51e2 commons-text-api:1.11.0-109.vfe16c66636eb_ compact-columns:1.185.vf3851b_4d31fe config-file-provider:973.vb_a_80ecb_9a_4d0 configuration-as-code:1810.v9b_c30a_249a_4c configuration-as-code-groovy:1.1 console-column-plugin:252.v0b_8fa_0e33b_72 content-replace:1.8.2 credentials:1337.v60b_d7b_c7b_c9f credentials-binding:677.vdc9d38cb_254d cucumber-reports:5.8.1 dark-theme:439.vdef09f81f85e data-tables-api:2.0.7-1 dependency-track:5.0.0 display-url-api:2.204.vf6fddd8a_8b_e9 docker-commons:439.va_3cb_0a_6a_fb_29 docker-java-api:3.3.6-90.ve7c5c7535ddd docker-plugin:1.6.1 docker-workflow:580.vc0c340686b_54 downstream-buildview:69.v16da_b_2c36f6c durable-task:555.v6802fe0f0b_82 echarts-api:5.5.0-1 eddsa-api:0.3.0-4.v84c6f0f4969e email-ext:1814.v404722f34263 extended-read-permission:53.v6499940139e5 external-monitor-job:215.v2e88e894db_f8 extra-columns:1.26 favorite:2.208.v91d65b_7792a_c file-leak-detector:1.13 flyway-api:9.22.3-75.vfdfb_f75a_a_9b_e flyway-runner:122.v004b_965a_cd08 font-awesome-api:6.5.2-1 gatling:1.3.0 git:5.2.2 git-client:4.7.0 git-parameter:0.9.19 git-server:126.v0d945d8d2b_39 github:1.39.0 github-api:1.318-461.v7a_c09c9fa_d63 github-branch-source:1789.v5b_0c0cea_18c3 gitlab-plugin:1.8.1 global-build-stats:293.vd7b_d6e361475 gradle:2.12 groovy-events-listener-plugin:2.210.v8a_4107f66127 gson-api:2.11.0-41.v019fcf6125dc handy-uri-templates-2-api:2.1.8-30.v7e777411b_148 hashicorp-vault-plugin:368.v48134f694db_f htmlpublisher:1.34 instance-identity:185.v303dc7c645f9 ionicons-api:74.v93d5eb_813d5f jackson2-api:2.17.0-379.v02de8ec9f64c jacoco:3.3.6 jakarta-activation-api:2.1.3-1 jakarta-mail-api:2.1.3-1 javadoc:243.vb_b_503b_b_45537 javax-activation-api:1.2.0-7 javax-mail-api:1.6.2-10 jaxb:2.3.9-1 jdk-tool:73.vddf737284550 jenkins-design-language:1.27.12 jersey2-api:2.42-147.va_28a_44603b_d5 jira:3.13 jjwt-api:0.11.5-112.ve82dfb_224b_a_d job-dsl:1.87 joda-time-api:2.12.7-29.v5a_b_e3a_82269a_ jquery3-api:3.7.1-2 jsch:0.2.16-86.v42e010d9484b_ json-api:20240303-41.v94e11e6de726 json-path-api:2.9.0-58.v62e3e85b_a_655 junit:1265.v65b_14fa_f12f0 kubernetes:4238.v41b_3ef14a_5d8 kubernetes-client-api:6.10.0-240.v57880ce8b_0b_2 kubernetes-credentials:174.va_36e093562d9 kubernetes-pipeline-devops-steps:1.6 ldap:725.v3cb_b_711b_1a_ef lockable-resources:1255.vf48745da_35d0 mailer:472.vf7c289a_4b_420 mapdb-api:1.0.9-40.v58107308b_7a_7 matrix-auth:3.2.2 matrix-project:831.v084e85a_b_4ea_d maven-plugin:3.23 metrics:4.2.21-451.vd51df8df52ec mina-sshd-api-common:2.12.1-101.v85b_e08b_780dd mina-sshd-api-core:2.12.1-101.v85b_e08b_780dd monitoring:1.99.0 naginator:1.449.ve19751d70eb_0 nested-view:1.33 next-executions:327.v136ff959e97b_ notification:1.17 oic-auth:4.269.va_7526f34f306 okhttp-api:4.11.0-172.vda_da_1feeb_c6e pam-auth:1.11 pipeline-build-step:540.vb_e8849e1a_b_d8 pipeline-github-lib:61.v629f2cc41d83 pipeline-graph-analysis:216.vfd8b_ece330ca_ pipeline-groovy-lib:710.v4b_94b_077a_808 pipeline-input-step:495.ve9c153f6067b_ pipeline-milestone-step:119.vdfdc43fc3b_9a_ pipeline-model-api:2.2198.v41dd8ef6dd56 pipeline-model-definition:2.2198.v41dd8ef6dd56 pipeline-model-extensions:2.2198.v41dd8ef6dd56 pipeline-rest-api:2.34 pipeline-stage-step:312.v8cd10304c27a_ pipeline-stage-tags-metadata:2.2198.v41dd8ef6dd56 pipeline-stage-view:2.34 pipeline-utility-steps:2.16.2 plain-credentials:182.v468b_97b_9dcb_8 plugin-usage-plugin:4.4 plugin-util-api:4.1.0 prism-api:1.29.0-15 progress-bar-column-plugin:11.vdef198c2d6c1 prometheus:770.ve5e758db_606e pubsub-light:1.18 role-strategy:727.vd344b_eec783d run-condition:1.7 scm-api:690.vfc8b_54395023 script-security:1341.va_2819b_414686 slack:715.v1cfed1b_9c63c snakeyaml-api:2.2-111.vc6598e30cc65 sonar:2.17.2 sse-gateway:1.26 ssh-agent:367.vf9076cd4ee21 ssh-credentials:337.v395d2403ccd4 ssh-slaves:2.968.v6f8823c91de4 sshd:3.322.v159e91f6a_550 structs:337.v1b_04ea_4df7c8 support-core:1449.v261d6f7b_f9f3 theme-manager:215.vc1ff18d67920 thinBackup:2.0 timestamper:1.27 token-macro:400.v35420b_922dcb_ trilead-api:2.147.vb_73cc728a_32e uno-choice:2.8.3 variant:60.v7290fc0eb_b_cd view-job-filters:377.v66f4b_796e5fa_ workflow-aggregator:596.v8c21c963d92d workflow-api:1316.v33eb_726c50b_a_ workflow-basic-steps:1058.vcb_fc1e3a_21a_9 workflow-cps:3894.3896.vca_2c931e7935 workflow-durable-task-step:1353.v1891a_b_01da_18 workflow-job:1400.v7fd111b_ec82f workflow-multibranch:783.va_6eb_ef636fb_d workflow-scm-step:427.v4ca_6512e7df1 workflow-step-api:657.v03b_e8115821b_ workflow-support:907.v6713a_ed8a_573 ```

What Operating System are you using (both controller, and any agents involved in the problem)?

Docker image: jenkins/jenkins:2.452.1

Reproduction steps

Every time the metrics are fetched by kuberntes, teh exception is thrown.

Expected Results

The Metric should not fail

Actual Results

2024-06-05 06:04:57.163+0000 [id=5899]  WARNING o.j.p.p.DiskUsageCollector#collect: Failed to get disk usage data due to an unexpected error.
java.lang.NullPointerException: Cannot invoke "java.lang.Long.longValue()" because the return value of "com.cloudbees.simplediskusage.DiskItem.getCount()" is null
    at org.jenkinsci.plugins.prometheus.collectors.disk.DiskUsageFileCountGauge.calculateMetric(DiskUsageFileCountGauge.java:35)
    at org.jenkinsci.plugins.prometheus.collectors.disk.DiskUsageFileCountGauge.calculateMetric(DiskUsageFileCountGauge.java:9)
    at org.jenkinsci.plugins.prometheus.DiskUsageCollector.lambda$collectDiskUsage$0(DiskUsageCollector.java:64)
    at java.base/java.util.ArrayList.forEach(Unknown Source)
    at org.jenkinsci.plugins.prometheus.DiskUsageCollector.lambda$collectDiskUsage$1(DiskUsageCollector.java:64)
    at java.base/java.util.concurrent.CopyOnWriteArrayList.forEach(Unknown Source)
    at org.jenkinsci.plugins.prometheus.DiskUsageCollector.collectDiskUsage(DiskUsageCollector.java:61)
    at org.jenkinsci.plugins.prometheus.DiskUsageCollector.collect(DiskUsageCollector.java:36)
    at io.prometheus.client.Collector.collect(Collector.java:45)
    at io.prometheus.client.CollectorRegistry$MetricFamilySamplesEnumeration.findNextElement(CollectorRegistry.java:204)
    at io.prometheus.client.CollectorRegistry$MetricFamilySamplesEnumeration.nextElement(CollectorRegistry.java:219)
    at io.prometheus.client.CollectorRegistry$MetricFamilySamplesEnumeration.nextElement(CollectorRegistry.java:152)
    at java.base/java.util.Enumeration$1.next(Unknown Source)
    at org.jenkinsci.plugins.prometheus.config.disabledmetrics.FilteredMetricEnumeration.filterList(FilteredMetricEnumeration.java:21)
    at org.jenkinsci.plugins.prometheus.config.disabledmetrics.FilteredMetricEnumeration.<init>(FilteredMetricEnumeration.java:15)
    at org.jenkinsci.plugins.prometheus.service.DefaultPrometheusMetrics.collectMetrics(DefaultPrometheusMetrics.java:53)
    at org.jenkinsci.plugins.prometheus.service.PrometheusAsyncWorker.execute(PrometheusAsyncWorker.java:41)
    at hudson.model.AsyncPeriodicWork.lambda$doRun$0(AsyncPeriodicWork.java:102)
    at java.base/java.lang.Thread.run(Unknown Source)

Anything else?

No response

Are you interested in contributing a fix?

No response

jenkinsci / prometheus-plugin