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DOC: management: document the <tgid>/<fd> form of show fd

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Add the syntax description, including the wildcard forms and the
note that <tgid> is currently parsed but ignored pending future
support for per-thread-group fd tables.
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Maxime Henrion 2026-05-08 10:35:53 -04:00 committed by Olivier Houchard
parent 4f9b8574d2
commit a9f38c19b4
1 changed files with 33 additions and 30 deletions
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doc/management.txt
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@ -3095,37 +3095,40 @@ show events [<sink>] [-w] [-n] [-0]
delimited by a line feed character ('\n' or 10 or 0x0A). It is possible to
change this to the NUL character ('\0' or 0) by passing the "-0" argument.
show fd [-!plcfbsd]* [<fd>]
show fd [-!plcfbsd]* [[<tgid>]/[<fd>] | <fd>]
Dump the list of either all open file descriptors or just the one number <fd>
if specified. A set of flags may optionally be passed to restrict the dump
only to certain FD types or to omit certain FD types. When '-' or '!' are
encountered, the selection is inverted for the following characters in the
same argument. The inversion is reset before each argument word delimited by
white spaces. Selectable FD types include 'p' for pipes, 'l' for listeners,
'c' for connections (any type), 'f' for frontend connections, 'b' for backend
connections (any type), 's' for connections to servers, 'd' for connections
to the "dispatch" address or the backend's transparent address. With this,
'b' is a shortcut for 'sd' and 'c' for 'fb' or 'fsd'. 'c!f' is equivalent to
'b' ("any connections except frontend connections" are indeed backend
connections). This is only aimed at developers who need to observe internal
states in order to debug complex issues such as abnormal CPU usages. One fd
is reported per lines, and for each of them, its state in the poller using
upper case letters for enabled flags and lower case for disabled flags, using
"P" for "polled", "R" for "ready", "A" for "active", the events status using
"H" for "hangup", "E" for "error", "O" for "output", "P" for "priority" and
"I" for "input", a few other flags like "N" for "new" (just added into the fd
cache), "U" for "updated" (received an update in the fd cache), "L" for
"linger_risk", "C" for "cloned", then the cached entry position, the pointer
to the internal owner, the pointer to the I/O callback and its name when
known. When the owner is a connection, the connection flags, and the target
are reported (frontend, proxy or server). When the owner is a listener, the
listener's state and its frontend are reported. There is no point in using
this command without a good knowledge of the internals. It's worth noting
that the output format may evolve over time so this output must not be parsed
by tools designed to be durable. Some internal structure states may look
suspicious to the function listing them, in this case the output line will be
suffixed with an exclamation mark ('!'). This may help find a starting point
when trying to diagnose an incident.
if specified. The form "<tgid>/<fd>" is also accepted, where either side may
be empty as a wildcard ("/<fd>" for fd <fd> across thread groups, "<tgid>/"
for all fds of <tgid>). The <tgid> is currently parsed but ignored, pending
future support for per-thread-group fd tables. A set of flags may optionally
be passed to restrict the dump only to certain FD types or to omit certain FD
types. When '-' or '!' are encountered, the selection is inverted for the
following characters in the same argument. The inversion is reset before each
argument word delimited by white spaces. Selectable FD types include 'p' for
pipes, 'l' for listeners, 'c' for connections (any type), 'f' for frontend
connections, 'b' for backend connections (any type), 's' for connections to
servers, 'd' for connections to the "dispatch" address or the backend's
transparent address. With this, 'b' is a shortcut for 'sd' and 'c' for 'fb' or
'fsd'. 'c!f' is equivalent to 'b' ("any connections except frontend
connections" are indeed backend connections). This is only aimed at developers
who need to observe internal states in order to debug complex issues such as
abnormal CPU usages. One fd is reported per lines, and for each of them, its
state in the poller using upper case letters for enabled flags and lower case
for disabled flags, using "P" for "polled", "R" for "ready", "A" for "active",
the events status using "H" for "hangup", "E" for "error", "O" for "output",
"P" for "priority" and "I" for "input", a few other flags like "N" for "new"
(just added into the fd cache), "U" for "updated" (received an update in the
fd cache), "L" for "linger_risk", "C" for "cloned", then the cached entry
position, the pointer to the internal owner, the pointer to the I/O callback
and its name when known. When the owner is a connection, the connection flags,
and the target are reported (frontend, proxy or server). When the owner is a
listener, the listener's state and its frontend are reported. There is no
point in using this command without a good knowledge of the internals. It's
worth noting that the output format may evolve over time so this output must
not be parsed by tools designed to be durable. Some internal structure states
may look suspicious to the function listing them, in this case the output line
will be suffixed with an exclamation mark ('!'). This may help find a starting
point when trying to diagnose an incident.
show info [typed|json] [desc] [float]
Dump info about haproxy status on current process. If "typed" is passed as an