<chapter id="ctrl-channel">
<title>Management API</title>
- <para>A classic approach to the daemon configuration assumes that
+ <para>A classic approach to daemon configuration assumes that
the server's configuration is stored in the configuration files
and when the configuration is changed, the daemon is restarted.
- This approach has significant disadvantage of introducing periods
- of downtime, where client traffic is not handled. Another risk
+ This approach has the significant disadvantage of introducing periods
+ of downtime, when client traffic is not handled. Another risk
is that if the new configuration is invalid for whatever reason,
the server may refuse to start, which will further extend the
downtime period, until the issue is resolved.</para>
<para>To avoid such problems, both DHCPv4 and DHCPv6 servers
- support introduced support for a mechanism that will allow
+ introduced support for a mechanism that will allow
on-line reconfiguration, without requiring server shutdown.
Both servers can be instructed to open control sockets, which
is a communication channel. The server is able to receive
<section id="ctrl-channel-syntax">
<title>Data syntax</title>
- <para>Communication over Control Channel is conducted using JSON
+ <para>Communication over control channel is conducted using JSON
structures. If configured, Kea will open a socket and will listen
for any incoming connections. A process connecting to this socket
is expected to send JSON commands structured as follows:
}
</screen>
<command>result</command> indicates the outcome of the command. A value of 0
- means a success while any non-zero value designates an error. Currently 1 is
+ means success while any non-zero value designates an error. Currently 1 is
used as a generic error, but additional error codes may be added in the
future.<command>text</command> field typically appears when result is
- non-zero and contains description of the error encountered, but it may also
- appear for success results. That's command specific.
+ non-zero and contains a description of the error encountered, but it may
+ also appear for successful results. That's command specific.
<command>arguments</command> is a map of additional data values returned by
- the server, specific to the command issue. The map is always present, even
+ the server, specific to the command issued. The map is always present, even
if it contains no data values.</para>
</section>
<para>ISC does not provide a client for using control channel. The primary
reason for that is the expectation is that the entity using control channel
is typically an IPAM or similar network management/monitoring software which
- may have quite varied expectations regarding the client and even likely to
+ may have quite varied expectations regarding the client and is even likely to
be written in languages different than C or C++. Therefore we only provide
examples how one can take advantage of the API.</para>
<para>The easiest way is to use a tool called <command>socat</command>,
a tool available from <ulink url="http://www.dest-unreach.org/socat/">socat
- homepage</ulink>, but is also widely available in Linux and BSD
+ homepage</ulink>, but it is also widely available in Linux and BSD
distributions. Once Kea is started, one could connect to the control
interface using the following command:
<screen>
$ socat UNIX:/path/to/the/kea/socket -
</screen>
-where <command>/path/to/the/kea/socket</command> is the path specified in
-<command>Dhcp4/control-socket/socket-name</command> parameter in Kea
+where <command>/path/to/the/kea/socket</command> is the path specified in the
+<command>Dhcp4/control-socket/socket-name</command> parameter in the Kea
configuration file.</para>
<para>It is also easy to open UNIX socket programmatically. An example of
- such simplistic client written in C is available in the Kea Developer's
+ such a simplistic client written in C is available in the Kea Developer's
Guide, chapter Control Channel Overview, section Using Control Channel.</para>
</section>
<para>
<emphasis>list-commands</emphasis> command retrieves a list of all
- supported commands by the server. It does not take any arguments.
+ commands supported by the server. It does not take any arguments.
An example command may look like this:
<screen>
{
</para>
<para>
The server will respond with a list of all supported commands. The
- arguments element will be a list strings. Each string will convey
+ arguments element will be a list of strings. Each string will convey
one supported command.
</para>
</section> <!-- end of command-list-commands -->
<para>
<emphasis>shutdown</emphasis> command instructs the server to initiate
- its shutdown procedure. It is an equivalent of sending SIGTERM singal
+ its shutdown procedure. It is the equivalent of sending a SIGTERM singal
to the process. This command does not take any arguments. An example
command may look like this:
<screen>
<title>Statistics Overview</title>
<para>Both Kea DHCP servers support statistics gathering since
- 0.9.2-beta version. Working DHCP server encounters various events
- that can influence certain statistics to be collected. For
+ 0.9.2-beta version. A working DHCP server encounters various events
+ that can cause certain statistics to be collected. For
example, a DHCPv4 server may receive a packet (pkt4-received
- statistic increased by one) that after parsing was identifier as
- DHCPDISCOVER (pkt4-discover-received). Server processed it and
+ statistic increases by one) that after parsing was identifier as
+ DHCPDISCOVER (pkt4-discover-received). The Server processed it and
decided to send DHCPOFFER representing its answer (pkt4-offer-sent
- and pkt4-sent statistics increased by one). Such events happen
+ and pkt4-sent statistics increase by one). Such events happen
frequently, so it is not uncommon for the statistics to have
values in high thousands. They can serve as an easy and powerful
- tool for observing server's and network's health. For example,
+ tool for observing a server's and network's health. For example,
if pkt4-received statistic stops growing, it means that the
clients' packets are not reaching the server.</para>
</listitem>
<listitem>
<simpara><emphasis>duration</emphasis> - this type is intended for
- recoding time periods. It uses boost::posix_time::time_duration type,
+ recording time periods. It uses boost::posix_time::time_duration type,
which stores hours, minutes, seconds and microseconds.</simpara>
</listitem>
<listitem>
<simpara><emphasis>string</emphasis> - this type is intended for
- recoding statistics in textual forma. It uses std::string C++ type.
+ recording statistics in textual forma. It uses std::string C++ type.
</simpara>
</listitem>
</itemizedlist>
<para>
During normal operation, DHCPv4 and DHCPv6 servers gather statistics.
- For a DHCPv4 and DHCPv6 list of statistics, see <xref
+ For a list of DHCPv4 and DHCPv6 statistics, see <xref
linkend="dhcp4-stats"/> and <xref linkend="dhcp6-stats"/>, respectively.
</para>
<para>
To extract data from the statistics module, the control channel can be
used. See <xref linkend="ctrl-channel" /> for details. It is possible to
- retrieve a single statistic, all statistics, reset (i.e. set to neutral
+ retrieve a single or all statistics, reset statistics (i.e. set to neutral
value, typically zero) or even remove completely a single or all
statistics. See section <xref linkend="command-stats"/> for a list of
statistic oriented commands.
<section id="stats-lifecycle">
<title>Statistics Lifecycle</title>
<para>
- It is useful to understand how Statistics Manager module is working. When
+ It is useful to understand how the Statistics Manager module works. When
the server starts operation, the manager is empty and does not have any
statistics. When <command>statistic-get-all</command> is executed, an
empty list is returned. Once the server performs an operation that causes
- statistic change, related statistic will be created. In a general case
- once a statistic is recorded even once, it is kept in the manager, until
+ a statistic to change, the related statistic will be created. In the general
+ case once a statistic is recorded even once, it is kept in the manager, until
explicitly removed, by <command>statistic-remove</command> or
- <command>statistic-remove-all</command> is called or the server is shut
+ <command>statistic-remove-all</command> being called or the server is shut
down. Per subnet statistics are explicitly removed when reconfiguration
takes place.
</para>
</para>
<para>
Removing a statistic that is updated frequently makes little sense as it
- will be re-added when the server code records a given statistic the next
- time. <command>statistic-remove</command> and
+ will be re-added when the server code next records that statistic.
+ The <command>statistic-remove</command> and
<command>statistic-remove-all</command> commands are intended to remove
- statistics that is not expected to be observed in the near future. For
+ statistics that are not expected to be observed in the near future. For
example, a misconfigured device in a network may cause clients to report
duplicate addresses, so the server will report increasing values of
pkt4-decline-received. Once the problem is found and the device is
- removed, system administrator may want to remove pkt4-decline-received
- statistic, so it won't be reported anymore. If duplicate address is
- detected ever again, the server will add this statistic back.
+ removed, the system administrator may want to remove the
+ pkt4-decline-received statistic, so it won't be reported anymore. If a
+ duplicate address is detected ever again, the server will add this
+ statistic back.
</para>
</section>
<section id="command-stats">
- <title>Commands for manipulating statistics</title>
+ <title>Commands for Manipulating Statistics</title>
<para>
There are several commands defined that can be used for accessing (-get),
resetting to zero or neutral value (-reset) or even removing a statistic
completely (-remove). The difference between reset and remove is somewhat
- subtle. Reset command sets value of the statistic to zero or neutral
- value. After this operation, statistic will have value of 0 (integer), 0.0
- (float), 0h0m0s0us (duration) or "" (string). When asked for, statistic
+ subtle. The reset command sets the value of the statistic to zero or neutral
+ value. After this operation, the statistic will have a value of 0 (integer),
+ 0.0 (float), 0h0m0s0us (duration) or "" (string). When asked for, a statistic
with the values metioned will be returned. Remove removes a statistic
completely, so the statistic will not be reported anymore. Please note
that
</screen>
</para>
<para>
- The server will respond with details of requested statistic, with result
- set to 0 indicates success and specified statistic as the value of
- "arguments" parameter. If requested statistic is not found, the response
+ The server will respond with details of the requested statistic, with result
+ set to 0 indicating success and the specified statistic as the value of
+ "arguments" parameter. If the requested statistic is not found, the response
will contain an empty map, i.e. only { } as argument, but the status
code will still be set to success (0).
</para>
<title>statistic-reset command</title>
<para>
- <emphasis>statistic-reset</emphasis> command sets specified statistic to
- its neutral value: 0 for integer, 0.0 for float, 0h0m0s0us for time
+ <emphasis>statistic-reset</emphasis> command sets the specified statistic
+ to its neutral value: 0 for integer, 0.0 for float, 0h0m0s0us for time
duration and "" for string type. It takes a single string parameter
called <command>name</command> that specifies the statistic name. An
example command may look like this:
</screen>
</para>
<para>
- If specific statistic is found and reset was successful,
- the server will respond with status of 0, indicating success and empty
- parameters field. If error is encountered (e.g. requested statistic
- was not found), the server will return status code of 1 (error)
- and text field will contain the error description.
+ If the specific statistic is found and reset was successful, the
+ server will respond with a status of 0, indicating success and an empty
+ parameters field. If an error is encountered (e.g. requested statistic
+ was not found), the server will return a status code of 1 (error)
+ and the text field will contain the error description.
</para>
</section> <!-- end of command-statistic-reset -->
<title>statistic-remove command</title>
<para>
- <emphasis>statistic-remove</emphasis> command attempt to delete a single
+ <emphasis>statistic-remove</emphasis> command attempts to delete a single
statistic. It takes a single string parameter called
<command>name</command> that specifies the statistic name. An example
command may look like this:
</screen>
</para>
<para>
- If specific statistic is found and its removal was successful,
- the server will respond with status of 0, indicating success and empty
- parameters field. If error is encountered (e.g. requested statistic
- was not found), the server will return status code of 1 (error)
- and text field will contain the error description.
+ If the specific statistic is found and its removal was successful, the
+ server will respond with a status of 0, indicating success and an empty
+ parameters field. If an error is encountered (e.g. requested statistic
+ was not found), the server will return a status code of 1 (error)
+ and the text field will contain the error description.
</para>
</section> <!-- end of command-statistic-reset -->
</screen>
</para>
<para>
- If the operation is successful, the server will respond with status of
- 0, indicating success and empty parameters field. If error is
- encountered, the server will return status code of 1 (error) and text
+ If the operation is successful, the server will respond with a status of
+ 0, indicating success and an empty parameters field. If an error is
+ encountered, the server will return a status code of 1 (error) and the text
field will contain the error description.
</para>
</section> <!-- end of command-statistic-reset-all -->
<title>statistic-remove-all command</title>
<para>
- <emphasis>statistic-remove-all</emphasis> command attempt to delete all
+ <emphasis>statistic-remove-all</emphasis> command attempts to delete all
statistics. An example command may look like this:
<screen>
{
</screen>
</para>
<para>
- If removal of all statistics was successful, the server will respond
- with status of 0, indicating success and empty parameters field. If
- error is encountered, the server will return status code of 1 (error)
- and text field will contain the error description.
+ If the removal of all statistics was successful, the server will respond
+ with a status of 0, indicating success and an empty parameters field. If
+ an error is encountered, the server will return a status code of 1 (error)
+ and the text field will contain the error description.
</para>
</section> <!-- end of command-statistic-remove-all -->
projects / thirdparty / kea.git / commitdiff
