HAProxy Enterprise Documentation 2.2r1

prepare acl

Start a transaction made up of multiple acl changes.

Description

If you need to make multiple changes to an acl file, and you need them to be applied all at the same time in one atomic change, submit them in a transaction using the prepare acl and commit acl commands.

This command cannot be used if the reference <acl> is a file also used as a map. In this case, the prepare map command must be used instead.

The workflow is as follows:

  • Use prepare acl to initiate the transaction.

  • Use add acl and clear acl as needed to make acl changes.

  • Use show acl to review the temporary version.

  • Use commit acl to commit the changes and make them active in runtime memory.

The prepare acl command starts the transaction by allocating a new version number for an acl ID or filename returned by show acl. The acl ID or filename argument is passed to the prepare acl command. The command responds with the new version number in the "New version created:" statement.

You can use the version number in the add acl, clear acl, and show acl commands.

There is no impact of allocating new versions, as unused versions will automatically be removed once a more recent version is committed. Version numbers are unsigned 32-bit values which wrap at the end, so care must be taken when comparing them in an external program.

The prepare acl operation creates an empty version of the acl file. Consequently, committing the version without first adding any entries effectively clears the acl file in runtime memory.

Examples

In this example, we start a new transaction for acl file /etc/hapee-2.2/paths.acl.

$ echo "prepare acl /etc/hapee-2.2/paths.acl" | \
   sudo socat stdio unix-connect:/var/run/hapee-2.2/hapee-lb.sock
New version created: 1

Contextual Example

This operation can be performed as part of a series of commands used to manage ACL files. The example in this section demonstrates how to modify ACLs in HAProxy Enterprise's running configuration. The ACLs are not persisted to files on disk. Any changes you make via the Runtime API are lost when the proxy halts.

An ACL is split into four parts:

  • a name for the ACL, which you choose

  • a fetch to collect information from the client's session

  • optional flags

  • a value to match against

In the example proxy configuration fragment below, we mark these parts:

frontend www
   bind :80
   #   name        fetch  flags       value
   acl static_url  path   -i -m beg   /images/

This ACL expression checks whether the requested URL path begins with /images/:

  1. Display a list of defined ACLs by calling show acl:

    $ echo "show acl" | \
   sudo socat stdio unix-connect:/var/run/hapee-2.2/hapee-lb.sock
    # id (file) description
0 () acl 'path' file '/etc/hapee-2.2/hapee-lb.cfg' line 51

  2. Display detail for the ACL by calling show acl:

    $ echo "show acl #0" | \
   sudo socat stdio unix-connect:/var/run/hapee-2.2/hapee-lb.sock
    0x563d5dcc40a0 /images/

  3. Use add acl to add the value /scripts/. Specify the ID of the ACL:

    $ echo "add acl #0 /scripts/" | \
   sudo socat stdio unix-connect:/var/run/hapee-2.2/hapee-lb.sock

    This updates the ACL so that it represents this expression:

    frontend www
   bind :80
   acl static_url path -i -m beg /images/ /scripts/

  4. Use del acl to remove the value /images/. Specify the ID of the ACL:

    $ echo "del acl #0 /images/" | \
   sudo socat stdio unix-connect:/var/run/hapee-2.2/hapee-lb.sock

    This updates the ACL so that it represents this expression:

    frontend www
   bind :80
   acl static_url path -i -m beg /scripts/

  5. Confirm the changes:

    $ echo "show acl #0" | \
   sudo socat stdio unix-connect:/var/run/hapee-2.2/hapee-lb.sock
    0x560024702060 /scripts/

See also

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