Notice

This document is for a development version of Ceph.

Lua Scripting

New in version Pacific.

This feature allows users to assign execution context to Lua scripts. The supported contexts are:

  • prerequest which will execute a script before each operation is performed

  • postrequest which will execute after each operation is performed

  • background which will execute within a specified time interval

  • getdata which will execute on objects’ data when objects are downloaded

  • putdata which will execute on objects’ data when objects are uploaded

A request (pre or post) or data (get or put) context script may be constrained to operations belonging to a specific tenant’s users. The request context script can also access fields in the request and modify certain fields, as well as the Global RGW Table. The data context script can access the content of the object as well as the request fields and the Global RGW Table. All Lua language features can be used in all contexts.

By default, all Lua standard libraries are available in the script, however, in order to allow for other Lua modules to be used in the script, we support adding packages to an allowlist:

  • All packages in the allowlist are being re-installed using the luarocks package manager on radosgw restart. Therefore a restart is needed for adding or removing of packages to take effect

  • To add a package that contains C source code that needs to be compiled, use the --allow-compilation flag. In this case a C compiler needs to be available on the host

  • Lua packages are installed in, and used from, a directory local to the radosgw. Meaning that Lua packages in the allowlist are separated from any Lua packages available on the host. By default, this directory would be /tmp/luarocks/<entity name>. Its prefix part (/tmp/luarocks/) could be set to a different location via the rgw_luarocks_location configuration parameter. Note that this parameter should not be set to one of the default locations where luarocks install packages (e.g. $HOME/.luarocks, /usr/lib64/lua, /usr/share/lua).

Script Management via CLI

To upload a script:

# radosgw-admin script put --infile={lua-file} --context={prerequest|postrequest|background|getdata|putdata} [--tenant={tenant-name}]
  • When uploading a script with the background context, a tenant name may not be specified.

To print the content of the script to standard output:

# radosgw-admin script get --context={prerequest|postrequest|background|getdata|putdata} [--tenant={tenant-name}]

To remove the script:

# radosgw-admin script rm --context={prerequest|postrequest|background|getdata|putdata} [--tenant={tenant-name}]

Package Management via CLI

To add a package to the allowlist:

# radosgw-admin script-package add --package={package name} [--allow-compilation]

To add a specific version of a package to the allowlist:

# radosgw-admin script-package add --package='{package name} {package version}' [--allow-compilation]
  • When adding a different version of a package which already exists in the list, the newly added version will override the existing one.

  • When adding a package without a version specified, the latest version of the package will be added.

To remove a package from the allowlist:

# radosgw-admin script-package rm --package={package name}

To remove a specific version of a package from the allowlist:

# radosgw-admin script-package rm --package='{package name} {package version}'
  • When removing a package without a version specified, any existing versions of the package will be removed.

To print the list of packages in the allowlist:

# radosgw-admin script-package list

Context Free Functions

Debug Log

The RGWDebugLog() function accepts a string and prints it to the debug log with priority 20. Each log message is prefixed Lua INFO:. This function has no return value.

Request Fields

Warning

This feature is experimental. Fields may be removed or renamed in the future.

Note

  • Although Lua is a case-sensitive language, field names provided by the radosgw are case-insensitive. Function names remain case-sensitive.

  • Fields marked “optional” can have a nil value.

  • Fields marked as “iterable” can be used by the pairs() function and with the # length operator.

  • All table fields can be used with the bracket operator [].

  • time fields are strings with the following format: %Y-%m-%d %H:%M:%S.

Field

Type

Description

Iterable

Writeable

Optional

Request.RGWOp

string

radosgw operation

no

no

no

Request.DecodedURI

string

decoded URI

no

no

no

Request.ContentLength

integer

size of the request

no

no

no

Request.GenericAttributes

table

string to string generic attributes map

yes

no

no

Request.Response

table

response to the request

no

no

no

Request.Response.HTTPStatusCode

integer

HTTP status code

no

yes

no

Request.Response.HTTPStatus

string

HTTP status text

no

yes

no

Request.Response.RGWCode

integer

radosgw error code

no

yes

no

Request.Response.Message

string

response message

no

yes

no

Request.SwiftAccountName

string

swift account name

no

no

yes

Request.Bucket

table

info on the bucket

no

no

no

Request.Bucket.Tenant

string

tenant of the bucket

no

no

yes

Request.Bucket.Name

string

bucket name (writeable only in prerequest context)

no

yes

no

Request.Bucket.Marker

string

bucket marker (initial id)

no

no

yes

Request.Bucket.Id

string

bucket id

no

no

yes

Request.Bucket.Count

integer

number of objects in the bucket

no

no

yes

Request.Bucket.Size

integer

total size of objects in the bucket

no

no

yes

Request.Bucket.ZoneGroupId

string

zone group of the bucket

no

no

yes

Request.Bucket.CreationTime

time

creation time of the bucket

no

no

yes

Request.Bucket.MTime

time

modification time of the bucket

no

no

yes

Request.Bucket.Quota

table

bucket quota

no

no

yes

Request.Bucket.Quota.MaxSize

integer

bucket quota max size

no

no

no

Request.Bucket.Quota.MaxObjects

integer

bucket quota max number of objects

no

no

no

Reques.Bucket.Quota.Enabled

boolean

bucket quota is enabled

no

no

no

Request.Bucket.Quota.Rounded

boolean

bucket quota is rounded to 4K

no

no

no

Request.Bucket.PlacementRule

table

bucket placement rule

no

no

yes

Request.Bucket.PlacementRule.Name

string

bucket placement rule name

no

no

no

Request.Bucket.PlacementRule.StorageClass

string

bucket placement rule storage class

no

no

no

Request.Bucket.User

table

bucket owner

no

no

yes

Request.Bucket.User.Tenant

string

bucket owner tenant

no

no

no

Request.Bucket.User.Id

string

bucket owner id

no

no

no

Request.Object

table

info on the object

no

no

yes

Request.Object.Name

string

object name

no

no

no

Request.Object.Instance

string

object version

no

no

no

Request.Object.Id

string

object id

no

no

no

Request.Object.Size

integer

object size

no

no

no

Request.Object.MTime

time

object mtime

no

no

no

Request.CopyFrom

table

information on copy operation

no

no

yes

Request.CopyFrom.Tenant

string

tenant of the object copied from

no

no

no

Request.CopyFrom.Bucket

string

bucket of the object copied from

no

no

no

Request.CopyFrom.Object

table

object copied from. See: Request.Object

no

no

yes

Request.ObjectOwner

table

object owner

no

no

no

Request.ObjectOwner.DisplayName

string

object owner display name

no

no

no

Request.ObjectOwner.User

table

object user. See: Request.Bucket.User

no

no

no

Request.ZoneGroup.Name

string

name of zone group

no

no

no

Request.ZoneGroup.Endpoint

string

endpoint of zone group

no

no

no

Request.UserAcl

table

user ACL

no

no

no

Request.UserAcl.Owner

table

user ACL owner. See: Request.ObjectOwner

no

no

no

Request.UserAcl.Grants

table

user ACL map of string to grant note: grants without an Id are not presented when iterated and only one of them can be accessed via brackets

yes

no

no

Request.UserAcl.Grants["<name>"]

table

user ACL grant

no

no

no

Request.UserAcl.Grants["<name>"].Type

integer

user ACL grant type

no

no

no

Request.UserAcl.Grants["<name>"].User

table

user ACL grant user

no

no

no

Request.UserAcl.Grants["<name>"].User.Tenant

table

user ACL grant user tenant

no

no

no

Request.UserAcl.Grants["<name>"].User.Id

table

user ACL grant user id

no

no

no

Request.UserAcl.Grants["<name>"].GroupType

integer

user ACL grant group type

no

no

no

Request.UserAcl.Grants["<name>"].Referer

string

user ACL grant referer

no

no

no

Request.BucketAcl

table

bucket ACL. See: Request.UserAcl

no

no

no

Request.ObjectAcl

table

object ACL. See: Request.UserAcl

no

no

no

Request.Environment

table

string to string environment map

yes

no

no

Request.Policy

table

policy

no

no

yes

Request.Policy.Text

string

policy text

no

no

no

Request.Policy.Id

string

policy Id

no

no

yes

Request.Policy.Statements

table

list of string statements

yes

no

no

Request.UserPolicies

table

list of user policies

yes

no

no

Request.UserPolicies[<index>]

table

user policy. See: Request.Policy

no

no

no

Request.RGWId

string

radosgw host id: <host>-<zone>-<zonegroup>

no

no

no

Request.HTTP

table

HTTP header

no

no

no

Request.HTTP.Parameters

table

string to string parameter map

yes

no

no

Request.HTTP.Resources

table

string to string resource map

yes

no

no

Request.HTTP.Metadata

table

string to string metadata map

yes

yes

no

Request.HTTP.StorageClass

string

storage class

no

yes

yes

Request.HTTP.Host

string

host name

no

no

no

Request.HTTP.Method

string

HTTP method

no

no

no

Request.HTTP.URI

string

URI

no

no

no

Request.HTTP.QueryString

string

HTTP query string

no

no

no

Request.HTTP.Domain

string

domain name

no

no

no

Request.Time

time

request time

no

no

no

Request.Dialect

string

“S3” or “Swift”

no

no

no

Request.Id

string

request Id

no

no

no

Request.TransactionId

string

transaction Id

no

no

no

Request.Tags

table

object tags map

yes

no

no

Request.User

table

user that triggered the request

no

no

no

Request.User.Tenant

string

triggering user tenant

no

no

no

Request.User.Id

string

triggering user id

no

no

no

Request.Trace

table

info on trace

no

no

no

Request.Trace.Enable

boolean

tracing is enabled

no

yes

no

Request Functions

Operations Log

The Request.Log() function prints the requests into the operations log. This function has no parameters. It returns 0 for success and an error code if it fails.

Tracing

Tracing functions can be used only in the postrequest context.

  • Request.Trace.SetAttribute(<key>, <value>) - sets the attribute for the request’s trace. The function takes two arguments: the first is the key, which should be a string, and the second is the value, which can either be a string or a number (integer or double). You may then locate specific traces by using this attribute.

  • Request.Trace.AddEvent(<name>, <attributes>) - adds an event to the first span of the request’s trace An event is defined by event name, event time, and zero or more event attributes. The function accepts one or two arguments: A string containing the event name should be the first argument, followed by the event attributes, which is optional for events without attributes. An event’s attributes must be a table of strings.

Background Context

The background context may be used for purposes that include analytics, monitoring, caching data for other context executions. - Background script execution default interval is 5 seconds.

Data Context

Both getdata and putdata contexts have the following fields: - Data which is read-only and iterable (byte by byte). In case that an object is uploaded or retrieved in multiple chunks, the Data field will hold data of one chunk at a time. - Offset which is holding the offset of the chunk within the entire object. - The Request fields and the background RGW table are also available in these contexts.

Global RGW Table

The RGW Lua table is accessible from all contexts and saves data written to it during execution so that it may be read and used later during other executions, from the same context of a different one. - Each RGW instance has its own private and ephemeral RGW Lua table that is lost when the daemon restarts. Note that background context scripts will run on every instance. - The maximum number of entries in the table is 100,000. Each entry has a string key a value with a combined length of no more than 1KB. A Lua script will abort with an error if the number of entries or entry size exceeds these limits. - The RGW Lua table uses string indices and can store values of type: string, integer, double and boolean

Increment/Decrement Functions

Since entries in the RGW table could be accessed from multiple places at the same time we need a way to atomically increment and decrement numeric values in it. For that the following functions should be used: - RGW.increment(<key>, [value]) would increment the value of key by value if value is provided or by 1 if not - RGW.decrement(<key>, [value]) would decrement the value of key by value if value is provided or by 1 if not - if the value of key is not numeric, the execution of the script would fail - if we try to increment or decrement by non-numeric values, the execution of the script would fail

Lua Code Samples

  • Print information on source and destination objects in case of copy:

function print_object(object)
  RGWDebugLog("  Name: " .. object.Name)
  RGWDebugLog("  Instance: " .. object.Instance)
  RGWDebugLog("  Id: " .. object.Id)
  RGWDebugLog("  Size: " .. object.Size)
  RGWDebugLog("  MTime: " .. object.MTime)
end

if Request.CopyFrom and Request.Object and Request.CopyFrom.Object then
  RGWDebugLog("copy from object:")
  print_object(Request.CopyFrom.Object)
  RGWDebugLog("to object:")
  print_object(Request.Object)
end
  • Print ACLs via a “generic function”:

function print_owner(owner)
  RGWDebugLog("Owner:")
  RGWDebugLog("  Display Name: " .. owner.DisplayName)
  RGWDebugLog("  Id: " .. owner.User.Id)
  RGWDebugLog("  Tenant: " .. owner.User.Tenant)
end

function print_acl(acl_type)
  index = acl_type .. "ACL"
  acl = Request[index]
  if acl then
    RGWDebugLog(acl_type .. "ACL Owner")
    print_owner(acl.Owner)
    RGWDebugLog("  there are " .. #acl.Grants .. " grant for owner")
    for k,v in pairs(acl.Grants) do
      RGWDebugLog("    Grant Key: " .. k)
      RGWDebugLog("    Grant Type: " .. v.Type)
      RGWDebugLog("    Grant Group Type: " .. v.GroupType)
      RGWDebugLog("    Grant Referer: " .. v.Referer)
      RGWDebugLog("    Grant User Tenant: " .. v.User.Tenant)
      RGWDebugLog("    Grant User Id: " .. v.User.Id)
    end
  else
    RGWDebugLog("no " .. acl_type .. " ACL in request: " .. Request.Id)
  end
end

print_acl("User")
print_acl("Bucket")
print_acl("Object")
  • Use of operations log only in case of errors:

if Request.Response.HTTPStatusCode ~= 200 then
  RGWDebugLog("request is bad, use ops log")
  rc = Request.Log()
  RGWDebugLog("ops log return code: " .. rc)
end
  • Set values into the error message:

if Request.Response.HTTPStatusCode == 500 then
  Request.Response.Message = "<Message> something bad happened :-( </Message>"
end
  • Add metadata to objects that was not originally sent by the client:

In the prerequest context we should add:

if Request.RGWOp == 'put_obj' then
  Request.HTTP.Metadata["x-amz-meta-mydata"] = "my value"
end

In the postrequest context we look at the metadata:

RGWDebugLog("number of metadata entries is: " .. #Request.HTTP.Metadata)
for k, v in pairs(Request.HTTP.Metadata) do
  RGWDebugLog("key=" .. k .. ", " .. "value=" .. v)
end
  • Use modules to create Unix socket based, JSON encoded, “access log”:

First we should add the following packages to the allowlist:

# radosgw-admin script-package add --package=luajson
# radosgw-admin script-package add --package=luasocket --allow-compilation

Then, do a restart for the radosgw and upload the following script to the postrequest context:

if Request.RGWOp == "get_obj" then
  local json = require("json")
  local socket = require("socket")
  local unix = require("socket.unix")
  local s = assert(unix())
  E = {}

  msg = {bucket = (Request.Bucket or (Request.CopyFrom or E).Bucket).Name,
    time = Request.Time,
    operation = Request.RGWOp,
    http_status = Request.Response.HTTPStatusCode,
    error_code = Request.Response.HTTPStatus,
    object_size = Request.Object.Size,
    trans_id = Request.TransactionId}

  assert(s:connect("/tmp/socket"))
  assert(s:send(json.encode(msg).."\n"))
  assert(s:close())
end
  • Trace only requests of specific bucket

Tracing is disabled by default, so we should enable tracing for this specific bucket

if Request.Bucket.Name == "my-bucket" then
    Request.Trace.Enable = true
end

If tracing is enabled on the RGW, the value of Request.Trace.Enable is true, so we should disable tracing for all other requests that do not match the bucket name. In the prerequest context:

if Request.Bucket.Name ~= "my-bucket" then
    Request.Trace.Enable = false
end

Note that changing Request.Trace.Enable does not change the tracer’s state, but disables or enables the tracing for the request only.

  • Add Information for requests traces

in postrequest context, we can add attributes and events to the request’s trace.

Request.Trace.AddEvent("lua script execution started")

Request.Trace.SetAttribute("HTTPStatusCode", Request.Response.HTTPStatusCode)

event_attrs = {}
for k,v in pairs(Request.GenericAttributes) do
  event_attrs[k] = v
end

Request.Trace.AddEvent("second event", event_attrs)
  • The entropy value of an object could be used to detect whether the object is encrypted. The following script calculates the entropy and size of uploaded objects and print to debug log

in the putdata context, add the following script

function object_entropy()
        local byte_hist = {}
        local byte_hist_size = 256
        for i = 1,byte_hist_size do
                byte_hist[i] = 0
        end
        local total = 0

        for i, c in pairs(Data)  do
                local byte = c:byte() + 1
                byte_hist[byte] = byte_hist[byte] + 1
                total = total + 1
        end

        entropy = 0

        for _, count in ipairs(byte_hist) do
                if count ~= 0 then
                        local p = 1.0 * count / total
                        entropy = entropy - (p * math.log(p)/math.log(byte_hist_size))
                end
        end

        return entropy
end

local full_name = Request.Bucket.Name.."\\"..Request.Object.Name
RGWDebugLog("entropy of chunk of: " .. full_name .. " at offset:" .. tostring(Offset)  ..  " is: " .. tostring(object_entropy()))
RGWDebugLog("payload size of chunk of: " .. full_name .. " is: " .. #Data)