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51 lines
2.2 KiB
ReStructuredText
51 lines
2.2 KiB
ReStructuredText
Prometheus plugin
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=================
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Provides a Prometheus exporter to pass on Ceph performance counters
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from the collection point in ceph-mgr. Ceph-mgr receives MMgrReport
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messages from all MgrClient processes (mons and OSDs, for instance)
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with performance counter schema data and actual counter data, and keeps
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a circular buffer of the last N samples. This plugin creates an HTTP
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endpoint (like all Prometheus exporters) and retrieves the latest sample
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of every counter when polled (or "scraped" in Prometheus terminology).
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The HTTP path and query parameters are ignored; all extant counters
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for all reporting entities are returned in text exposition format.
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(See the Prometheus `documentation <https://prometheus.io/docs/instrumenting/exposition_formats/#text-format-details>`_.)
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Enabling
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--------
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The *prometheus* module is enabled with::
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ceph mgr module enable prometheus
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Configuration
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-------------
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By default the module will accept HTTP requests on port ``9283`` on all
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IPv4 and IPv6 addresses on the host. The port and listen address are both
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configurable with ``ceph config-key set``, with keys
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``mgr/prometheus/server_addr`` and ``mgr/prometheus/server_port``.
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This port is registered with Prometheus's `registry <https://github.com/prometheus/prometheus/wiki/Default-port-allocations>`_.
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Notes
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-----
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Counters and gauges are exported; currently histograms and long-running
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averages are not. It's possible that Ceph's 2-D histograms could be
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reduced to two separate 1-D histograms, and that long-running averages
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could be exported as Prometheus' Summary type.
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The names of the stats are exactly as Ceph names them, with
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illegal characters ``.`` and ``-`` translated to ``_``. There is one
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label applied, ``daemon``, and its value is the daemon.id for the
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daemon in question (e.g. ``{daemon=mon.hosta}`` or ``{daemon=osd.11}``).
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Timestamps, as with many Prometheus exporters, are established by
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the server's scrape time (Prometheus expects that it is polling the
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actual counter process synchronously). It is possible to supply a
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timestamp along with the stat report, but the Prometheus team strongly
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advises against this. This means that timestamps will be delayed by
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an unpredictable amount; it's not clear if this will be problematic,
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but it's worth knowing about.
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