boothd - Man Page

The Booth Cluster Ticket Manager.

Synopsis

boothd daemon [-SD] [-c config] [-l lockfile]

booth list [-s site] [-c config]

booth grant [-s site] [-c config] [-FCw] ticket

booth revoke [-s site] [-c config] [-w] ticket

booth peers [-s site] [-c config]

booth status [-D] [-c config]

Booth manages tickets which authorizes one of the cluster sites located in geographically dispersed distances to run certain resources. It is designed to be extend Pacemaker to support geographically distributed clustering.

It is based on the RAFT protocol, see eg. https://ramcloud.stanford.edu/wiki/download/attachments/11370504/raft.pdf for details.

Short Examples

# boothd daemon -D

# booth list

# booth grant ticket-nfs

# booth revoke ticket-nfs

Options

-c configfile

Configuration to use.

Can be a full path to a configuration file, or a short name; in the latter case, the directory /etc/booth and suffix .conf are added. Per default booth is used, which results in the path /etc/booth/booth.conf.

The configuration name also determines the name of the PID file - for the defaults, /var/run/booth/booth.pid.

-s

Site address or name.

The special value other can be used to specify the other site. Obviously, in that case, the booth configuration must have exactly two sites defined.

-F

immediate grant: Don’t wait for unreachable sites to relinquish the ticket. See the Booth ticket management section below for more details. For manual tickets this option allows one to grant a ticket which is currently granted. See the Manual tickets section below for more details.

This option may be DANGEROUS. It makes booth grant the ticket even though it cannot ascertain that unreachable sites don’t hold the same ticket. It is up to the user to make sure that unreachable sites don’t have this ticket as granted.

-w

wait for the request outcome: The client waits for the final outcome of grant or revoke request.

-C

wait for ticket commit to CIB: The client waits for the ticket commit to CIB (only for grant requests). If one or more sites are unreachable, this takes the ticket expire time (plus, if defined, the acquire-after time).

-h, --help

Give a short usage output.

--version

Report version information.

-S

systemd mode: don’t fork. Disables daemonizing, the process will remain in the foreground.

-D

Increases the debug output level.

-l lockfile

Use another lock file. By default, the lock file name is inferred from the configuration file name. Normally not needed.

Commands

Whether the binary is called as boothd or booth doesn’t matter; the first argument determines the mode of operation.

daemon

Tells boothd to serve a site. The locally configured interfaces are searched for an IP address that is defined in the configuration. booth then runs in either /arbitrator/ or /site/ mode.

client

Booth clients can list the ticket information (see also crm_ticket -L), and revoke or grant tickets to a site.

The grant and, under certain circumstances, revoke operations may take a while to return a definite operation’s outcome. The client will wait up to the network timeout value (by default 5 seconds) for the result. Unless the -w option was set, in which case the client waits indefinitely.

In this mode the configuration file is searched for an IP address that is locally reachable, ie. matches a configured subnet. This allows one to run the client commands on another node in the same cluster, as long as the config file and the service IP is locally reachable.

For instance, if the booth service IP is 192.168.55.200, and the local node has 192.168.55.15 configured on one of its network interfaces, it knows which site it belongs to.

Use -s to direct client to connect to a different site.

status

boothd looks for the (locked) PID file and the UDP socket, prints some output to stdout (for use in shell scripts) and returns an OCF-compatible return code. With -D, a human-readable message is printed to STDERR as well.

peers

List the other boothd servers we know about.

In addition to the type, name (IP address), and the last time the server was heard from, network statistics are also printed. The statistics are split into two rows, the first one consists of counters for the sent packets and the second one for the received packets. The first counter is the total number of packets and descriptions of the other counters follows:

resends: Packets which had to be resent because the recipient didn’t acknowledge a message. This usually means that either the message or the acknowledgement got lost. The number of resends usually reflect the network reliability.
error: Packets which either couldn’t be sent, got truncated, or were badly formed. Should be zero.
invalid: These packets contain either invalid or non-existing ticket name or refer to a non-existing ticket leader. Should be zero.
authfail: Packets which couldn’t be authenticated. Should be zero.

Configuration File

The configuration file must be identical on all sites and arbitrators.

A minimal file may look like this:

site="192.168.201.100"
site="192.168.202.100"
arbitrator="192.168.203.100"
ticket="ticket-db8"

Comments start with a hash-sign ('#'). Whitespace at the start and end of the line, and around the '=', are ignored.

The following key/value pairs are defined:

port

The UDP/TCP port to use. Default is 9929.

transport

The transport protocol to use for Raft exchanges. Currently only UDP is supported.

Clients use TCP to communicate with a daemon; Booth will always bind and listen to both UDP and TCP ports.

authfile

File containing the authentication key. The key can be either binary or text. If the latter, then both leading and trailing white space, including new lines, is ignored. This key is a shared secret and used to authenticate both clients and servers. The key must be between 8 and 64 characters long and be readable only by the file owner.

maxtimeskew

As protection against replay attacks, packets contain generation timestamps. Such a timestamp is not allowed to be too old. Just how old can be specified with this parameter. The value is in seconds and the default is 600 (10 minutes). If clocks vary more than this default between sites and nodes (which is definitely something you should fix) then set this parameter to a higher value. The time skew test is performed only in concert with authentication.

debug

Specifies the debug output level. Alternative to command line argument. Effective only for daemon mode of operation.

site

Defines a site Raft member with the given IP. Sites can acquire tickets. The sites' IP should be managed by the cluster.

arbitrator

Defines an arbitrator Raft member with the given IP. Arbitrators help reach consensus in elections and cannot hold tickets.

Booth needs at least three members for normal operation. Odd number of members provides more redundancy.

site-user, site-group, arbitrator-user, arbitrator-group

These define the credentials boothd will be running with.

On a (Pacemaker) site the booth process will have to call crm_ticket, so the default is to use hacluster:'haclient'; for an arbitrator this user and group might not exists, so there we default to nobody:'nobody'.

ticket

Registers a ticket. Multiple tickets can be handled by single Booth instance.

Use the special ticket name __defaults__ to modify the defaults. The __defaults__ stanza must precede all the other ticket specifications.

All times are in seconds.

expire

The lease time for a ticket. After that time the ticket can be acquired by another site if the ticket holder is not reachable.

The default is 600.

acquire-after

Once a ticket is lost, wait this time in addition before acquiring the ticket.

This is to allow for the site that lost the ticket to relinquish the resources, by either stopping them or fencing a node.

A typical delay might be 60 seconds, but ultimately it depends on the protected resources and the fencing configuration.

The default is 0.

renewal-freq

Set the ticket renewal frequency period.

If the network reliability is often reduced over prolonged periods, it is advisable to try to renew more often.

Before every renewal, if defined, the command or commands specified in before-acquire-handler is run. In that case the renewal-freq parameter is effectively also the local cluster monitoring interval.

timeout

After that time booth will re-send packets if there was an insufficient number of replies. This should be long enough to allow packets to reach other members.

The default is 5.

retries

Defines how many times to retry sending packets before giving up waiting for acks from other members.

Default is 10. Values lower than 3 are illegal.

Ticket renewals should allow for this number of retries. Hence, the total retry time must be shorter than the renewal time (either half the expire time or renewal-freq):

timeout*(retries+1) < renewal

weights

A comma-separated list of integers that define the weight of individual Raft members, in the same order as the site and arbitrator lines.

Default is 0 for all; this means that the order in the configuration file defines priority for conflicting requests.

before-acquire-handler

If set, this parameter specifies either a file containing a program to be run or a directory where a number of programs can reside. They are invoked before boothd tries to acquire or renew a ticket. If any of them exits with a code other than 0, boothd relinquishes the ticket.

Thus it is possible to ensure whether the services and its dependencies protected by the ticket are in good shape at this site. For instance, if a service in the dependency-chain has a failcount of INFINITY on all available nodes, the service will be unable to run. In that case, it is of no use to claim the ticket.

One or more arguments may follow the program or directory location. Typically, there is at least the name of one of the resources which depend on this ticket.

See below for details about booth specific environment variables. The distributed service-runnable script is an example which may be used to test whether a pacemaker resource can be started.

attr-prereq

Sites can have GEO attributes managed with the geostore(8) program. Attributes are within ticket’s scope and may be tested by boothd for additional control of ticket failover (automatic) or ticket acquire (manual).

Attributes are typically used to convey extra information about resources, for instance database replication status. The attributes are commonly updated by resource agents.

Attribute values are referenced in expressions and may be tested for equality with the eq binary operator or inequality with the ne operator. The usage is as follows:

attr-prereq = <grant_type> <name> <op> <value>

<grant_type>: "auto" | "manual"
<name>:       attribute name
<op>:         "eq" | "ne"
<value>:      attribute value

The two grant types are auto for ticket failover and manual for grants using the booth client. Only in case the expression evaluates to true can the ticket be granted.

It is not clear whether the manual grant type has any practical use because, obviously, this operation is anyway controlled by a human.

Note that there can be no guarantee on whether an attribute value is up to date, i.e. if it actually reflects the current state.

mode

Specifies if the ticket is manual or automatic.

By default all tickets are automatic (that is, they are fully controlled by Raft algorithm). Assign the strings "manual" or "MANUAL" to define the ticket as manually controlled.

One example of a booth configuration file:

transport = udp
port = 9930

# D-85774
site="192.168.201.100"
# D-90409
site="::ffff:192.168.202.100"
# A-1120
arbitrator="192.168.203.100"

ticket="ticket-db8"
    expire        = 600
    acquire-after = 60
    timeout       = 10
    retries       = 5
    renewal-freq  = 60
    before-acquire-handler = /usr/share/booth/service-runnable db8
    attr-prereq = auto repl_state eq ACTIVE

Booth Ticket Management

The booth cluster guarantees that every ticket is owned by only one site at the time.

Tickets must be initially granted with the booth client grant command. Once it gets granted, the ticket is managed by the booth cluster. Hence, only granted tickets are managed by booth.

If the ticket gets lost, i.e. that the other members of the booth cluster do not hear from the ticket owner in a sufficiently long time, one of the remaining sites will acquire the ticket. This is what is called ticket failover.

If the remaining members cannot form a majority, then the ticket cannot fail over.

A ticket may be revoked at any time with the booth client revoke command. For revoke to succeed, the site holding the ticket must be reachable.

Once the ticket is administratively revoked, it is not managed by the booth cluster anymore. For the booth cluster to start managing the ticket again, it must be again granted to a site.

The grant operation, in case not all sites are reachable, may get delayed for the ticket expire time (and, if defined, the acquire-after time). The reason is that the other booth members may not know if the ticket is currently granted at the unreachable site.

This delay may be disabled with the -F option. In that case, it is up to the administrator to make sure that the unreachable site is not holding the ticket.

When the ticket is managed by booth, it is dangerous to modify it manually using either crm_ticket command or crm site ticket. Neither of these tools is aware of booth and, consequently, booth itself may not be aware of any ticket status changes. A notable exception is setting the ticket to standby which is typically done before a planned failover.

Notes

Tickets are not meant to be moved around quickly, the default expire time is 600 seconds (10 minutes).

booth works with both IPv4 and IPv6 addresses.

booth renews a ticket before it expires, to account for possible transmission delays. The renewal time, unless explicitly set, is set to half the expire time.

Handlers

Currently, there’s only one external handler defined (see the before-acquire-handler configuration item above).

The following environment variables are exported to the handler:

BOOTH_TICKET: The ticket name, as given in the configuration file. (See ticket item above.)
BOOTH_LOCAL: The local site name, as defined in site.
BOOTH_CONF_PATH: The path to the active configuration file.
BOOTH_CONF_NAME: The configuration name, as used by the -c commandline argument.
BOOTH_TICKET_EXPIRES: When the ticket expires (in seconds since 1.1.1970), or 0.

The handler is invoked with positional arguments specified after it.

Files

/etc/booth/booth.conf: The default configuration file name. See also the -c argument.
/etc/booth/authkey: There is no default, but this is a typical location for the shared secret (authentication key).
/var/run/booth/: Directory that holds PID/lock files. See also the status command.

Raft Implementation

In essence, every ticket corresponds to a separate Raft cluster.

A ticket is granted to the Raft Leader which then owns (or keeps) the ticket.

Arbitrator Management

The booth daemon for an arbitrator which typically doesn’t run the cluster stack, may be started through systemd or with /etc/init.d/booth-arbitrator, depending on which init system the platform supports.

The SysV init script starts a booth arbitrator for every configuration file found in /etc/booth.

Platforms running systemd can enable and start every configuration separately using systemctl:

# systemctl enable booth@<configurationname>
# systemctl start  booth@<configurationname>

systemctl requires the configuration name, even for the default name booth.

MANUAL TICKETS

Manual tickets allow users to create and manage tickets which are subsequently handled by booth without using the Raft algorithm. Granting and revoking manual tickets is fully controlled by the administrator. It is possible to define a number of manual and normal tickets in one GEO cluster.

Automatic ticket management provided by Raft algorithm isn’t applied to manually controlled tickets. In particular, there is no elections, automatic failover procedures, and term expiration.

However, booth controls if a ticket is currently being granted to any site and warns the user approprietly.

Tickets which were manually granted to a site, will remain there until they are manually revoked. Even if a site becomes offline, the ticket will not be moved to another site. This behavior allows administrators to make sure that some services will remain in a particular site and will not be moved to another site, possibly located in a different geographical location.

Also, configuring only manual tickets in a GEO cluster, allows one to have just two sites in a cluster, without a need of having an arbitrator. This is possible because there is no automatic elections and no voting performed for manual tickets.

Manual tickets are defined in a configuration files by adding a mode ticket parameter and setting it to manual or MANUAL:

ticket="manual-ticket"
    [...]
    mode = manual
    [...]

Manual tickets can be granted and revoked by using normal grant and revoke commands, with the usual flags and parameters. The only difference is that specyfiyng -F flag during grant command, forced a site to become a leader of the specified ticket, even if the ticket is granted to another site.

Exit Status

0: Success. For the status command: Daemon running.
1 (PCMK_OCF_UNKNOWN_ERROR): General error code.
7 (PCMK_OCF_NOT_RUNNING): No daemon process for that configuration active.

Bugs

Booth is tested regularly. See the README-testing file for more information.

Please report any bugs either at GitHub: https://github.com/ClusterLabs/booth/issues

Or, if you prefer bugzilla, at openSUSE bugzilla (component "High Availability"): https://bugzilla.opensuse.org/enter_bug.cgi?product=openSUSE%20Factory

Author

boothd was originally written (mostly) by Jiaju Zhang.

In 2013 and 2014 Philipp Marek took over maintainership.

Since April 2014 it has been mainly developed by Dejan Muhamedagic.

Many people contributed (see the AUTHORS file).

2024-07-17