这篇文章的主要目的是告诉大家如何配置 Prometheus，使得它可以从指定的 Web Api 接口采集指标数据。文章中用到的案例是 NGINX 的采集配置，从设定了用户名和密码的 NGINX 数据指标页中采集数据，因此这篇文章的副标题可能是 nginx 的 prometheus 采集配置或者prometheus 采集 basic auth 的 nginx。
上图是配置完成后，在 Grafana 配置了模板的效果。
使用过 Prometheus 的朋友想必都知道如何配置 address:port 类服务，例如收集某个 Redis 的相关信息时，配置可以这么写：
- job_name: 'redis'
static_configs:
- targets: ['11.22.33.58:6087']
注释：以上案例中假设 Redis Exporter 的 地址和端口是 11.22.33.58:6087。
这种是最简单，也是最为人熟知的办法。但是如果要监控指定的 Web API，可就不能这么写了。如果你没有看到这篇文章，你可能会在搜索引擎里面这么搜：
- Prometheus 监控 Web
- Prometheus scrape Web
- Prometheus 监控接口
- Prometheus 监控指定 API
- Prometheus API 配置
- Prometheus 域名 配置
- Prometheus basic auth
- Prometheus 接口 用户名 密码
但很不幸的是，搜不到什么有效信息（现在是 2021 年 03 月），能找到的基本上都是坑。
条件假设
假设我们现在需要从地址为 www.weishidong.com//status/for… 的接口收集相关的 Prometheus 监控指标，并且这个接口使用了 basic auth（假定用户名为 weishidong，密码为 0099887kk）进行基本的权限校验。
配置实践操作
按照之前见到的 Prometheus 配置填写的话，很有可能把配置写成这样：
- job_name: 'web'
static_configs:
- targets: ['http://www.weishidong.com/status/format/prometheus']
basic_auth:
username: weishidong
password: 0099887kk
保存配置文件并重启服务后你就会发现，这样是收集不到数据的，简直糟糕。
官方配置指南
刚才的操作真的是糟糕透了，遇到不懂的问题时，我们当然是去翻官方文档了->Prometheus Configuration。阅读时推荐自上而下，不过如果你比较着急，可以直接来到 采集配置 这个部分。官方给出的示例如下（内容太多，这里只保留跟本文相关的部分，建议大家去看原文）：
# The job name assigned to scraped metrics by default.
job_name: <job_name>
# How frequently to scrape targets from this job.
[ scrape_interval: <duration> | default = <global_config.scrape_interval> ]
# Per-scrape timeout when scraping this job.
[ scrape_timeout: <duration> | default = <global_config.scrape_timeout> ]
# The HTTP resource path on which to fetch metrics from targets.
[ metrics_path: <path> | default = /metrics ]
# honor_labels controls how Prometheus handles conflicts between labels that are
# already present in scraped data and labels that Prometheus would attach
# server-side ("job" and "instance" labels, manually configured target
# labels, and labels generated by service discovery implementations).
#
# If honor_labels is set to "true", label conflicts are resolved by keeping label
# values from the scraped data and ignoring the conflicting server-side labels.
#
# If honor_labels is set to "false", label conflicts are resolved by renaming
# conflicting labels in the scraped data to "exported_<original-label>" (for
# example "exported_instance", "exported_job") and then attaching server-side
# labels.
#
# Setting honor_labels to "true" is useful for use cases such as federation and
# scraping the Pushgateway, where all labels specified in the target should be
# preserved.
#
# Note that any globally configured "external_labels" are unaffected by this
# setting. In communication with external systems, they are always applied only
# when a time series does not have a given label yet and are ignored otherwise.
[ honor_labels: <boolean> | default = false ]
# honor_timestamps controls whether Prometheus respects the timestamps present
# in scraped data.
#
# If honor_timestamps is set to "true", the timestamps of the metrics exposed
# by the target will be used.
#
# If honor_timestamps is set to "false", the timestamps of the metrics exposed
# by the target will be ignored.
[ honor_timestamps: <boolean> | default = true ]
# Configures the protocol scheme used for requests.
[ scheme: <scheme> | default = http ]
# Optional HTTP URL parameters.
params:
[ <string>: [<string>, ...] ]
# Sets the `Authorization` header on every scrape request with the
# configured username and password.
# password and password_file are mutually exclusive.
basic_auth:
[ username: <string> ]
[ password: <secret> ]
[ password_file: <string> ]
# Sets the `Authorization` header on every scrape request with
# the configured bearer token. It is mutually exclusive with `bearer_token_file`.
[ bearer_token: <secret> ]
# Sets the `Authorization` header on every scrape request with the bearer token
# read from the configured file. It is mutually exclusive with `bearer_token`.
[ bearer_token_file: <filename> ]
如果你认真看的话，应该会关注到几个关键信息： metrics_path 和 basic_auth。其中，metrics_path 用于指定 HTTP 类指标信息采集时的路由地址，默认值是 /metrics；字段 basic_auth 则是用来进行权限验证的，而且密码这里可以指定密码文件，而不是直接填写明文（一般来说，指定密码文件的安全性稍高与明文）。
有效的配置
根据官方文档的指引，我们很快便可以推导出正确的配置写法：
- job_name: 'web'
metrics_path: /status/format/prometheus
static_configs:
- targets: ['www.weishidong.com']
basic_auth:
username: weishidong
password: 0099887kk
要注意的是，这里并不需要填写 http:// 字样，因为 Prometheus 默认的 Scheme 就是 http。如果地址的 Scheme 是 https 的话，按照文档指引，我们需要添加 scheme 字段，对应的配置为：
- job_name: 'web'
metrics_path: /status/format/prometheus
static_configs:
- targets: ['www.weishidong.com']
scheme: https
basic_auth:
username: weishidong
password: 0099887kk
配置完成后，Prometheus 应该就能顺利的采集到数据了，配上 Grafana，就能够看到开篇给出的监控效果图。