monitoring system. Such status page will be exported on a network port
and will be encoded in JSON (simple text) over HTTP.
-The choice of json is obvious as we already depend on it in Ganeti and
+The choice of JSON is obvious as we already depend on it in Ganeti and
thus we don't need to add extra libraries to use it, as opposed to what
would happen for XML or some other markup format.
- Node OS resources report (memory, CPU, network interfaces)
- Information from a plugin system
+Format of the report
+--------------------
+
+The report of the will be in JSON format, and it will present an array
+of report objects.
+Each report object will be produced by a specific data collector.
+Each report object includes some mandatory fields, to be provided by all
+the data collectors:
+
+``name``
+ The name of the data collector that produced this part of the report.
+ It is supposed to be unique inside a report.
+
+``version``
+ The version of the data collector that produces this part of the
+ report. Built-in data collectors (as opposed to those implemented as
+ plugins) should have "B" as the version number.
+
+``formatVersion``
+ The format of what is represented in the "data" field for each data
+ collector might change over time. Every time this happens, the
+ format_version should be changed, so that who reads the report knows
+ what format to expect, and how to correctly interpret it.
+
+``timestamp``
+ The time when the reported data were gathered. Is has to be expressed
+ in nanoseconds since the unix epoch (0:00:00 January 01, 1970). If not
+ enough precision is available (or needed) it can be padded with
+ zeroes. If a report object needs multiple timestamps, it can add more
+ and/or override this one inside its own "data" section.
+
+``category``
+ A collector can belong to a given category of collectors (e.g.: storage
+ collectors, daemon collector). This means that it will have to provide a
+ minumum set of prescribed fields, as documented for each category.
+ This field will contain the name of the category the collector belongs to,
+ if any, or just the ``null`` value.
+
+``kind``
+ Two kinds of collectors are possible:
+ `Performance reporting collectors`_ and `Status reporting collectors`_.
+ The respective paragraphs will describe them and the value of this field.
+
+``data``
+ This field contains all the data generated by the specific data collector,
+ in its own independently defined format. The monitoring agent could check
+ this syntactically (according to the JSON specifications) but not
+ semantically.
+
+Here follows a minimal example of a report::
+
+ [
+ {
+ "name" : "TheCollectorIdentifier",
+ "version" : "1.2",
+ "formatVersion" : 1,
+ "timestamp" : 1351607182000000000,
+ "category" : null,
+ "kind" : 0,
+ "data" : { "plugin_specific_data" : "go_here" }
+ },
+ {
+ "name" : "AnotherDataCollector",
+ "version" : "B",
+ "formatVersion" : 7,
+ "timestamp" : 1351609526123854000,
+ "category" : "storage",
+ "kind" : 1,
+ "data" : { "status" : { "code" : 1,
+ "message" : "Error on disk 2"
+ },
+ "plugin_specific" : "data",
+ "some_late_data" : { "timestamp" : 1351609526123942720,
+ ...
+ }
+ }
+ }
+ ]
+
+Performance reporting collectors
+++++++++++++++++++++++++++++++++
+
+These collectors only provide data about some component of the system, without
+giving any interpretation over their meaning.
+
+The value of the ``kind`` field of the report will be ``0``.
+
+Status reporting collectors
++++++++++++++++++++++++++++
+
+These collectors will provide information about the status of some
+component of ganeti, or managed by ganeti.
+
+The value of their ``kind`` field will be ``1``.
+
+The rationale behind this kind of collectors is that there are some situations
+where exporting data about the underlying subsystems would expose potential
+issues. But if Ganeti itself is able (and going) to fix the problem, conflicts
+might arise between Ganeti and something/somebody else trying to fix the same
+problem.
+Also, some external monitoring systems might not be aware of the internals of a
+particular subsystem (e.g.: DRBD) and might only exploit the high level
+response of its data collector, alerting an administrator if anything is wrong.
+Still, completely hiding the underlying data is not a good idea, as they might
+still be of use in some cases. So status reporting plugins will provide two
+output modes: one just exporting a high level information about the status,
+and one also exporting all the data they gathered.
+The default output mode will be the status-only one. Through a command line
+parameter (for stand-alone data collectors) or through the HTTP request to the
+monitoring agent
+(when collectors are executed as part of it) the verbose output mode providing
+all the data can be selected.
+
+When exporting just the status each status reporting collector will provide,
+in its ``data`` section, at least the following field:
+
+``status``
+ summarizes the status of the component being monitored and consists of two
+ subfields:
+
+ ``code``
+ It assumes a numeric value, encoded in such a way to allow using a bitset
+ to easily distinguish which states are currently present in the whole cluster.
+ If the bitwise OR of all the ``status`` fields is 0, the cluster is
+ completely healty.
+ The status codes are as follows:
+
+ ``0``
+ The collector can determine that everything is working as
+ intended.
+
+ ``1``
+ Something is temporarily wrong but it is being automatically fixed by
+ Ganeti.
+ There is no need of external intervention.
+
+ ``2``
+ The collector can determine that something is wrong and Ganeti has no
+ way to fix it autonomously. External intervention is required.
+
+ ``4``
+ The collector has failed to understand whether the status is good or
+ bad. Further analysis is required. Interpret this status as a
+ potentially dangerous situation.
+
+ ``message``
+ A message to better explain the reason of the status.
+ The exact format of the message string is data collector dependent.
+
+ The field is mandatory, but the content can be ``null`` if the code is
+ ``0`` (working as intended) or ``1`` (being fixed automatically).
+
+ If the status code is ``2``, the message should specify what has gone
+ wrong.
+ If the status code is ``4``, the message shoud explain why it was not
+ possible to determine a proper status.
+
+The ``data`` section will also contain all the fields describing the gathered
+data, according to a collector-specific format.
+
Instance status
+++++++++++++++
system, which then will export those themselves.
Monitoring and auditing systems can then use the reason to understand
-the cause of an instance status, and they can use the object version to
+the cause of an instance status, and they can use the timestamp to
understand the freshness of their data even in the absence of an atomic
cross-node reporting: for example if they see an instance "up" on a node
after seeing it running on a previous one, they can compare these values
upon.
The instance status will be on each node, for the instances it is
-primary for and will contain at least:
+primary for, and its ``data`` section of the report will contain a list
+of instances, with at least the following fields for each instance:
+
+``name``
+ The name of the instance.
+
+``uuid``
+ The UUID of the instance (stable on name change).
+
+``admin_state``
+ The status of the instance (up/down/offline) as requested by the admin.
-- The instance name
-- The instance UUID (stable on name change)
-- The instance running status (up or down)
-- The timestamp of last known change
-- The timestamp of when the status was last checked (see caching, below)
-- The last known reason for change, if any
+``actual_state``
+ The actual status of the instance. It can be ``up``, ``down``, or
+ ``hung`` if the instance is up but it appears to be completely stuck.
-More information about all the fields and their type will be available
-in the "Format of the report" section.
+``uptime``
+ The uptime of the instance (if it is up, "null" otherwise).
+
+``mtime``
+ The timestamp of the last known change to the instance state.
+
+``state_reason``
+ The last known reason for state change, described according to the
+ following subfields:
+
+ ``text``
+ Either a user-provided reason (if any), or the name of the command that
+ triggered the state change, as a fallback.
+
+ ``jobID``
+ The ID of the job that caused the state change.
+
+ ``source``
+ Where the state change was triggered (RAPI, CLI).
+
+``status``
+ It represents the status of the instance, and its format is the same as that
+ of the ``status`` field of `Status reporting collectors`_.
+
+Each hypervisor should provide its own instance status data collector, possibly
+with the addition of more, specific, fields.
+The ``category`` field of all of them will be ``instance``.
+The ``kind`` field will be ``1``.
Note that as soon as a node knows it's not the primary anymore for an
instance it will stop reporting status for it: this means the instance
will either disappear, if it has been deleted, or appear on another
node, if it's been moved.
-Instance Disk status
-++++++++++++++++++++
+The ``code`` of the ``status`` field of the report of the Instance status data
+collector will be:
-As for the instance status Ganeti has now only partial information about
-its instance disks: in particular each node is unaware of the disk to
-instance mapping, that exists only on the master.
+``0``
+ if ``status`` is ``0`` for all the instances it is reporting about.
-For this design doc we plan to fix this by changing all RPCs that create
-a backend storage or that put an already existing one in use and passing
-the relevant instance to the node. The node can then export these to the
-status reporting tool.
+``1``
+ otherwise.
+
+Storage status
+++++++++++++++
+
+The storage status collectors will be a series of data collectors
+(drbd, rbd, plain, file) that will gather data about all the storage types
+for the current node (this is right now hardcoded to the enabled storage
+types, and in the future tied to the enabled storage pools for the nodegroup).
+
+The ``name`` of each of these collector will reflect what storage type each of
+them refers to.
+
+The ``category`` field of these collector will be ``storage``.
+
+The ``kind`` field will be ``1`` (`Status reporting collectors`_).
+
+The ``data`` section of the report will provide at least the following fields:
+
+``free``
+ The amount of free space (in KBytes).
+
+``used``
+ The amount of used space (in KBytes).
+
+``total``
+ The total visible space (in KBytes).
+
+Each specific storage type might provide more type-specific fields.
+
+In case of error, the ``message`` subfield of the ``status`` field of the
+report of the instance status collector will disclose the nature of the error
+as a type specific information. Examples of these are "backend pv unavailable"
+for lvm storage, "unreachable" for network based storage or "filesystem error"
+for filesystem based implementations.
+
+DRBD status
+***********
+
+This data collector will run only on nodes where DRBD is actually
+present and it will gather information about DRBD devices.
+
+Its ``kind`` in the report will be ``1`` (`Status reporting collectors`_).
+
+Its ``category`` field in the report will contain the value ``storage``.
+
+When executed in verbose mode, the ``data`` section of the report of this
+collector will provide the following fields:
+
+``versionInfo``
+ Information about the DRBD version number, given by a combination of
+ any (but at least one) of the following fields:
+
+ ``version``
+ The DRBD driver version.
+
+ ``api``
+ The API version number.
+
+ ``proto``
+ The protocol version.
+
+ ``srcversion``
+ The version of the source files.
+
+ ``gitHash``
+ Git hash of the source files.
+
+ ``buildBy``
+ Who built the binary, and, optionally, when.
+
+``device``
+ A list of structures, each describing a DRBD device (a minor) and containing
+ the following fields:
+
+ ``minor``
+ The device minor number.
+
+ ``connectionState``
+ The state of the connection. If it is "Unconfigured", all the following
+ fields are not present.
+
+ ``localRole``
+ The role of the local resource.
+
+ ``remoteRole``
+ The role of the remote resource.
+
+ ``localState``
+ The status of the local disk.
+
+ ``remoteState``
+ The status of the remote disk.
+
+ ``replicationProtocol``
+ The replication protocol being used.
+
+ ``ioFlags``
+ The input/output flags.
+
+ ``perfIndicators``
+ The performance indicators. This field will contain the following
+ sub-fields:
+
+ ``networkSend``
+ KiB of data sent on the network.
+
+ ``networkReceive``
+ KiB of data received from the network.
+
+ ``diskWrite``
+ KiB of data written on local disk.
+
+ ``diskRead``
+ KiB of date read from the local disk.
+
+ ``activityLog``
+ Number of updates of the activity log.
+
+ ``bitMap``
+ Number of updates to the bitmap area of the metadata.
+
+ ``localCount``
+ Number of open requests to the local I/O subsystem.
+
+ ``pending``
+ Number of requests sent to the partner but not yet answered.
+
+ ``unacknowledged``
+ Number of requests received by the partner but still to be answered.
+
+ ``applicationPending``
+ Num of block input/output requests forwarded to DRBD but that have not yet
+ been answered.
+
+ ``epochs``
+ (Optional) Number of epoch objects. Not provided by all DRBD versions.
+
+ ``writeOrder``
+ (Optional) Currently used write ordering method. Not provided by all DRBD
+ versions.
+
+ ``outOfSync``
+ (Optional) KiB of storage currently out of sync. Not provided by all DRBD
+ versions.
+
+ ``syncStatus``
+ (Optional) The status of the synchronization of the disk. This is present
+ only if the disk is being synchronized, and includes the following fields:
+
+ ``percentage``
+ The percentage of synchronized data.
+
+ ``progress``
+ How far the synchronization is. Written as "x/y", where x and y are
+ integer numbers expressed in the measurement unit stated in
+ ``progressUnit``
+
+ ``progressUnit``
+ The measurement unit for the progress indicator.
+
+ ``timeToFinish``
+ The expected time before finishing the synchronization.
+
+ ``speed``
+ The speed of the synchronization.
+
+ ``want``
+ The desiderd speed of the synchronization.
+
+ ``speedUnit``
+ The measurement unit of the ``speed`` and ``want`` values. Expressed
+ as "size/time".
+
+ ``instance``
+ The name of the Ganeti instance this disk is associated to.
-While we haven't implemented these RPC changes yet, we'll use confd to
-fetch this information in the data collector.
-
-Since Ganeti supports many type of disks for instances (drbd, rbd,
-plain, file) we will export both a "generic" status which will work for
-any type of disk and will be very opaque (at minimum just an "healthy"
-or "error" state, plus perhaps some human readable comment and a
-"per-type" status which will explain more about the internal details but
-will not be compatible between different storage types (and will for
-example export the drbd connection status, sync, and so on).
-
-Status of storage for instances
-+++++++++++++++++++++++++++++++
-
-The node will also be reporting on all storage types it knows about for
-the current node (this is right now hardcoded to the enabled storage
-types, and in the future tied to the enabled storage pools for the
-nodegroup). For this kind of information also we will report both a
-generic health status (healthy or error) for each type of storage, and
-some more generic statistics (free space, used space, total visible
-space). In addition type specific information can be exported: for
-example, in case of error, the nature of the error can be disclosed as a
-type specific information. Examples of these are "backend pv
-unavailable" for lvm storage, "unreachable" for network based storage or
-"filesystem error" for filesystem based implementations.
Ganeti daemons status
+++++++++++++++++++++
-Ganeti will report what information it has about its own daemons: this
-includes memory usage, uptime, CPU usage. This should allow identifying
-possible problems with the Ganeti system itself: for example memory
-leaks, crashes and high resource utilization should be evident by
-analyzing this information.
+Ganeti will report what information it has about its own daemons.
+This should allow identifying possible problems with the Ganeti system itself:
+for example memory leaks, crashes and high resource utilization should be
+evident by analyzing this information.
+
+The ``kind`` field will be ``1`` (`Status reporting collectors`_).
+
+Each daemon will have its own data collector, and each of them will have
+a ``category`` field valued ``daemon``.
+
+When executed in verbose mode, their data section will include at least:
+
+``memory``
+ The amount of used memory.
+
+``size_unit``
+ The measurement unit used for the memory.
+
+``uptime``
+ The uptime of the daemon.
-Ganeti daemons will also be able to export extra internal information to
-the status reporting, through the plugin system (see below).
+``CPU usage``
+ How much cpu the daemon is using (percentage).
+
+Any other daemon-specific information can be included as well in the ``data``
+section.
Hypervisor resources report
+++++++++++++++++++++++++++
specific" way. Each hypervisor can then add extra specific information
that is not generic enough be abstracted.
+The ``kind`` field will be ``0`` (`Performance reporting collectors`_).
+
+Each of the hypervisor data collectory will be of ``category``: ``hypervisor``.
+
Node OS resources report
++++++++++++++++++++++++
Since Ganeti assumes it's running on Linux, it's useful to export some
-basic information as seen by the host system. This includes number and
-status of CPUs, memory, filesystems and network intefaces as well as the
-version of components Ganeti interacts with (Linux, drbd, hypervisor,
-etc).
+basic information as seen by the host system.
+
+The ``category`` field of the report will be ``null``.
+
+The ``kind`` field will be ``0`` (`Performance reporting collectors`_).
+
+The ``data`` section will include:
+
+``cpu_number``
+ The number of available cpus.
+
+``cpus``
+ A list with one element per cpu, showing its average load.
+
+``memory``
+ The current view of memory (free, used, cached, etc.)
+
+``filesystem``
+ A list with one element per filesystem, showing a summary of the
+ total/available space.
+
+``NICs``
+ A list with one element per network interface, showing the amount of
+ sent/received data, error rate, IP address of the interface, etc.
+
+``versions``
+ A map using the name of a component Ganeti interacts (Linux, drbd,
+ hypervisor, etc) as the key and its version number as the value.
Note that we won't go into any hardware specific details (e.g. querying a
node RAID is outside the scope of this, and can be implemented as a
plugin) but we can easily just report the information above, since it's
standard enough across all systems.
-Plugin system
-+++++++++++++
+Format of the query
+-------------------
-The monitoring system will be equipped with a plugin system that can
-export specific local information through it. The plugin system will be
-in the form of either scripts whose output will be inserted in the
-report, plain text files which will be inserted into the report, or
-local unix or network sockets from which the information has to be read.
-This should allow most flexibility for implementing an efficient system,
-while being able to keep it as simple as possible.
+The queries to the monitoring agent will be HTTP GET requests on port 1815.
+The answer will be encoded in JSON format and will depend on the specific
+accessed resource.
-The plugin system is expected to be used by local installations to
-export any installation specific information that they want to be
-monitored, about either hardware or software on their systems.
+If a request is sent to a non-existing resource, a 404 error will be returned by
+the HTTP server.
+The following paragraphs will present the existing resources supported by the
+current protocol version, that is version 1.
-Format of the query
--------------------
+``/``
++++++
+The root resource. It will return the list of the supported protocol version
+numbers.
-The query will be an HTTP GET request on a particular port. At the
-beginning it will only be possible to query the full status report.
+Currently, this will include only version 1.
+``/1``
+++++++
+Not an actual resource per-se, it is the root of all the resources of protocol
+version 1.
-Format of the report
---------------------
+If requested through GET, the null JSON value will be returned.
+
+``/1/list/collectors``
+++++++++++++++++++++++
+Returns a list of tuples (kind, category, name) showing all the collectors
+available in the system.
+
+``/1/report/all``
++++++++++++++++++
+A list of the reports of all the data collectors, as described in the section
+`Format of the report`_.
-TBD (this part needs to be completed with the format of the JSON and the
-types of the various variables exported, as they get evaluated and
-decided)
+`Status reporting collectors`_ will provide their output in non-verbose format.
+The verbose format can be requested by adding the parameter ``verbose=1`` to the
+request.
+``/1/report/[category]/[collector_name]``
++++++++++++++++++++++++++++++++++++++++++
+Returns the report of the collector ``[collector_name]`` that belongs to the
+specified ``[category]``.
+
+If a collector does not belong to any category, ``collector`` will be used as
+the value for ``[category]``.
+
+`Status reporting collectors`_ will provide their output in non-verbose format.
+The verbose format can be requested by adding the parameter ``verbose=1`` to the
+request.
+
+Instance disk status propagation
+--------------------------------
+
+As for the instance status Ganeti has now only partial information about
+its instance disks: in particular each node is unaware of the disk to
+instance mapping, that exists only on the master.
+
+For this design doc we plan to fix this by changing all RPCs that create
+a backend storage or that put an already existing one in use and passing
+the relevant instance to the node. The node can then export these to the
+status reporting tool.
+
+While we haven't implemented these RPC changes yet, we'll use Confd to
+fetch this information in the data collectors.
+
+Plugin system
+-------------
+
+The monitoring system will be equipped with a plugin system that can
+export specific local information through it.
+
+The plugin system is expected to be used by local installations to
+export any installation specific information that they want to be
+monitored, about either hardware or software on their systems.
+
+The plugin system will be in the form of either scripts or binaries whose output
+will be inserted in the report.
+
+Eventually support for other kinds of plugins might be added as well, such as
+plain text files which will be inserted into the report, or local unix or
+network sockets from which the information has to be read. This should allow
+most flexibility for implementing an efficient system, while being able to keep
+it as simple as possible.
Data collectors
---------------
In order to ease testing as well as to make it simple to reuse this
subsystem it will be possible to run just the "data collectors" on each
-node without passing through the agent daemon. Each data collector will
-report specific data about its subsystem and will be documented
-separately.
+node without passing through the agent daemon.
+If a data collector is run independently, it should print on stdout its
+report, according to the format corresponding to a single data collector
+report object, as described in the previous paragraphs.
Mode of operation
-----------------
can use adaptively to query a certain resource faster or slower
depending on those two parameters.
+When run as stand-alone binaries, the data collector will not using any
+caching system, and just fetch and return the data immediately.
Implementation place
--------------------
The libekg library should be looked at for easily providing metrics in
json format.
-
Implementation order
--------------------
We will implement the agent system in this order:
-- initial example data collectors (eg. for drbd and instance status)
-- initial daemon for exporting data
+- initial example data collectors (eg. for drbd and instance status).
+- initial daemon for exporting data, integrating the existing collectors
+- plugin system
- RPC updates for instance status reasons and disk to instance mapping
+- cache layer for the daemon
- more data collectors
-- cache layer for the daemon (if needed)
Future work
projects / ganeti-local / blobdiff