ceph/doc/radosgw/lua-scripting.rst

   1 =============
   2 Lua Scripting
   3 =============
   4
   5 .. versionadded:: Pacific
   6
   7 .. contents::
   8
   9 This feature allows users to upload Lua scripts to different context in the radosgw. The two supported context are "preRequest" that will execute a script before the
  10 operation was taken, and "postRequest" that will execute after each operation is taken. Script may be uploaded to address requests for users of a specific tenant.
  11 The script can access fields in the request and modify some fields. All Lua language features can be used in the script.
  12
  13 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:
  14
  15   - 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
  16   - 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
  17   - 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.
  18     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.
  19     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`)
  20
  21
  22 .. toctree::
  23    :maxdepth: 1
  24
  25
  26 Script Management via CLI
  27 -------------------------
  28
  29 To upload a script:
  30
  31 ::
  32
  33    # radosgw-admin script put --infile={lua-file} --context={preRequest|postRequest} [--tenant={tenant-name}]
  34
  35
  36 To print the content of the script to standard output:
  37
  38 ::
  39
  40    # radosgw-admin script get --context={preRequest|postRequest} [--tenant={tenant-name}]
  41
  42
  43 To remove the script:
  44
  45 ::
  46
  47    # radosgw-admin script rm --context={preRequest|postRequest} [--tenant={tenant-name}]
  48
  49
  50 Package Management via CLI
  51 --------------------------
  52
  53 To add a package to the allowlist:
  54
  55 ::
  56
  57   # radosgw-admin script-package add --package={package name} [--allow-compilation]
  58
  59
  60 To add a specific version of a package to the allowlist:
  61
  62 ::
  63
  64   # radosgw-admin script-package add --package='{package name} {package version}' [--allow-compilation]
  65
  66
  67 * When adding a different version of a package which already exists in the list, the newly
  68   added version will override the existing one.
  69
  70 * When adding a package without a version specified, the latest version of the package
  71   will be added.
  72
  73
  74 To remove a package from the allowlist:
  75
  76 ::
  77
  78   # radosgw-admin script-package rm --package={package name}
  79
  80
  81 To remove a specific version of a package from the allowlist:
  82
  83 ::
  84
  85   # radosgw-admin script-package rm --package='{package name} {package version}'
  86
  87
  88 * When removing a package without a version specified, any existing versions of the
  89   package will be removed.
  90
  91
  92 To print the list of packages in the allowlist:
  93
  94 ::
  95
  96   # radosgw-admin script-package list
  97
  98
  99 Context Free Functions
 100 ----------------------
 101 Debug Log
 102 ~~~~~~~~~
 103 The ``RGWDebugLog()`` function accepts a string and prints it to the debug log with priority 20.
 104 Each log message is prefixed ``Lua INFO:``. This function has no return value.
 105
 106 Request Fields
 107 -----------------
 108
 109 .. warning:: This feature is experimental. Fields may be removed or renamed in the future.
 110
 111 .. note::
 112
 113     - Although Lua is a case-sensitive language, field names provided by the radosgw are case-insensitive. Function names remain case-sensitive.
 114     - Fields marked "optional" can have a nil value.
 115     - Fields marked as "iterable" can be used by the pairs() function and with the # length operator.
 116     - All table fields can be used with the bracket operator ``[]``.
 117     - ``time`` fields are strings with the following format: ``%Y-%m-%d %H:%M:%S``.
 118
 119
 120 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 121 | Field                                              | Type     | Description                                                  | Iterable | Writeable | Optional |
 122 +====================================================+==========+==============================================================+==========+===========+==========+
 123 | ``Request.RGWOp``                                  | string   | radosgw operation                                            | no       | no        | no       |
 124 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 125 | ``Request.DecodedURI``                             | string   | decoded URI                                                  | no       | no        | no       |
 126 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 127 | ``Request.ContentLength``                          | integer  | size of the request                                          | no       | no        | no       |
 128 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 129 | ``Request.GenericAttributes``                      | table    | string to string generic attributes map                      | yes      | no        | no       |
 130 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 131 | ``Request.Response``                               | table    | response to the request                                      | no       | no        | no       |
 132 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 133 | ``Request.Response.HTTPStatusCode``                | integer  | HTTP status code                                             | no       | yes       | no       |
 134 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 135 | ``Request.Response.HTTPStatus``                    | string   | HTTP status text                                             | no       | yes       | no       |
 136 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 137 | ``Request.Response.RGWCode``                       | integer  | radosgw error code                                           | no       | yes       | no       |
 138 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 139 | ``Request.Response.Message``                       | string   | response message                                             | no       | yes       | no       |
 140 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 141 | ``Request.SwiftAccountName``                       | string   | swift account name                                           | no       | no        | yes      |
 142 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 143 | ``Request.Bucket``                                 | table    | info on the bucket                                           | no       | no        | yes      |
 144 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 145 | ``Request.Bucket.Tenant``                          | string   | tenant of the bucket                                         | no       | no        | no       |
 146 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 147 | ``Request.Bucket.Name``                            | string   | bucket name                                                  | no       | no        | no       |
 148 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 149 | ``Request.Bucket.Marker``                          | string   | bucket marker (initial id)                                   | no       | no        | no       |
 150 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 151 | ``Request.Bucket.Id``                              | string   | bucket id                                                    | no       | no        | no       |
 152 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 153 | ``Request.Bucket.Count``                           | integer  | number of objects in the bucket                              | no       | no        | no       |
 154 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 155 | ``Request.Bucket.Size``                            | integer  | total size of objects in the bucket                          | no       | no        | no       |
 156 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 157 | ``Request.Bucket.ZoneGroupId``                     | string   | zone group of the bucket                                     | no       | no        | no       |
 158 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 159 | ``Request.Bucket.CreationTime``                    | time     | creation time of the bucket                                  | no       | no        | no       |
 160 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 161 | ``Request.Bucket.MTime``                           | time     | modification time of the bucket                              | no       | no        | no       |
 162 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 163 | ``Request.Bucket.Quota``                           | table    | bucket quota                                                 | no       | no        | no       |
 164 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 165 | ``Request.Bucket.Quota.MaxSize``                   | integer  | bucket quota max size                                        | no       | no        | no       |
 166 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 167 | ``Request.Bucket.Quota.MaxObjects``                | integer  | bucket quota max number of objects                           | no       | no        | no       |
 168 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 169 | ``Reques.Bucket.Quota.Enabled``                    | boolean  | bucket quota is enabled                                      | no       | no        | no       |
 170 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 171 | ``Request.Bucket.Quota.Rounded``                   | boolean  | bucket quota is rounded to 4K                                | no       | no        | no       |
 172 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 173 | ``Request.Bucket.PlacementRule``                   | table    | bucket placement rule                                        | no       | no        | no       |
 174 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 175 | ``Request.Bucket.PlacementRule.Name``              | string   | bucket placement rule name                                   | no       | no        | no       |
 176 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 177 | ``Request.Bucket.PlacementRule.StorageClass``      | string   | bucket placement rule storage class                          | no       | no        | no       |
 178 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 179 | ``Request.Bucket.User``                            | table    | bucket owner                                                 | no       | no        | no       |
 180 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 181 | ``Request.Bucket.User.Tenant``                     | string   | bucket owner tenant                                          | no       | no        | no       |
 182 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 183 | ``Request.Bucket.User.Id``                         | string   | bucket owner id                                              | no       | no        | no       |
 184 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 185 | ``Request.Object``                                 | table    | info on the object                                           | no       | no        | yes      |
 186 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 187 | ``Request.Object.Name``                            | string   | object name                                                  | no       | no        | no       |
 188 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 189 | ``Request.Object.Instance``                        | string   | object version                                               | no       | no        | no       |
 190 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 191 | ``Request.Object.Id``                              | string   | object id                                                    | no       | no        | no       |
 192 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 193 | ``Request.Object.Size``                            | integer  | object size                                                  | no       | no        | no       |
 194 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 195 | ``Request.Object.MTime``                           | time     | object mtime                                                 | no       | no        | no       |
 196 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 197 | ``Request.CopyFrom``                               | table    | information on copy operation                                | no       | no        | yes      |
 198 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 199 | ``Request.CopyFrom.Tenant``                        | string   | tenant of the object copied from                             | no       | no        | no       |
 200 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 201 | ``Request.CopyFrom.Bucket``                        | string   | bucket of the object copied from                             | no       | no        | no       |
 202 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 203 | ``Request.CopyFrom.Object``                        | table    | object copied from. See: ``Request.Object``                  | no       | no        | yes      |
 204 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 205 | ``Request.ObjectOwner``                            | table    | object owner                                                 | no       | no        | no       |
 206 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 207 | ``Request.ObjectOwner.DisplayName``                | string   | object owner display name                                    | no       | no        | no       |
 208 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 209 | ``Request.ObjectOwner.User``                       | table    | object user. See: ``Request.Bucket.User``                    | no       | no        | no       |
 210 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 211 | ``Request.ZoneGroup.Name``                         | string   | name of zone group                                           | no       | no        | no       |
 212 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 213 | ``Request.ZoneGroup.Endpoint``                     | string   | endpoint of zone group                                       | no       | no        | no       |
 214 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 215 | ``Request.UserAcl``                                | table    | user ACL                                                     | no       | no        | no       |
 216 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 217 | ``Request.UserAcl.Owner``                          | table    | user ACL owner. See: ``Request.ObjectOwner``                 | no       | no        | no       |
 218 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 219 | ``Request.UserAcl.Grants``                         | table    | user ACL map of string to grant                              | yes      | no        | no       |
 220 |                                                    |          | note: grants without an Id are not presented when iterated   |          |           |          |
 221 |                                                    |          | and only one of them can be accessed via brackets            |          |           |          |
 222 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 223 | ``Request.UserAcl.Grants["<name>"]``               | table    | user ACL grant                                               | no       | no        | no       |
 224 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 225 | ``Request.UserAcl.Grants["<name>"].Type``          | integer  | user ACL grant type                                          | no       | no        | no       |
 226 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 227 | ``Request.UserAcl.Grants["<name>"].User``          | table    | user ACL grant user                                          | no       | no        | no       |
 228 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 229 | ``Request.UserAcl.Grants["<name>"].User.Tenant``   | table    | user ACL grant user tenant                                   | no       | no        | no       |
 230 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 231 | ``Request.UserAcl.Grants["<name>"].User.Id``       | table    | user ACL grant user id                                       | no       | no        | no       |
 232 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 233 | ``Request.UserAcl.Grants["<name>"].GroupType``     | integer  | user ACL grant group type                                    | no       | no        | no       |
 234 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 235 | ``Request.UserAcl.Grants["<name>"].Referer``       | string   | user ACL grant referer                                       | no       | no        | no       |
 236 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 237 | ``Request.BucketAcl``                              | table    | bucket ACL. See: ``Request.UserAcl``                         | no       | no        | no       |
 238 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 239 | ``Request.ObjectAcl``                              | table    | object ACL. See: ``Request.UserAcl``                         | no       | no        | no       |
 240 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 241 | ``Request.Environment``                            | table    | string to string environment map                             | yes      | no        | no       |
 242 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 243 | ``Request.Policy``                                 | table    | policy                                                       | no       | no        | yes      |
 244 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 245 | ``Request.Policy.Text``                            | string   | policy text                                                  | no       | no        | no       |
 246 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 247 | ``Request.Policy.Id``                              | string   | policy Id                                                    | no       | no        | yes      |
 248 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 249 | ``Request.Policy.Statements``                      | table    | list of string statements                                    | yes      | no        | no       |
 250 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 251 | ``Request.UserPolicies``                           | table    | list of user policies                                        | yes      | no        | no       |
 252 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 253 | ``Request.UserPolicies[<index>]``                  | table    | user policy. See: ``Request.Policy``                         | no       | no        | no       |
 254 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 255 | ``Request.RGWId``                                  | string   | radosgw host id: ``<host>-<zone>-<zonegroup>``               | no       | no        | no       |
 256 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 257 | ``Request.HTTP``                                   | table    | HTTP header                                                  | no       | no        | no       |
 258 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 259 | ``Request.HTTP.Parameters``                        | table    | string to string parameter map                               | yes      | no        | no       |
 260 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 261 | ``Request.HTTP.Resources``                         | table    | string to string resource map                                | yes      | no        | no       |
 262 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 263 | ``Request.HTTP.Metadata``                          | table    | string to string metadata map                                | yes      | yes       | no       |
 264 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 265 | ``Request.HTTP.StorageClass``                      | string   | storage class                                                | no       | yes       | yes      |
 266 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 267 | ``Request.HTTP.Host``                              | string   | host name                                                    | no       | no        | no       |
 268 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 269 | ``Request.HTTP.Method``                            | string   | HTTP method                                                  | no       | no        | no       |
 270 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 271 | ``Request.HTTP.URI``                               | string   | URI                                                          | no       | no        | no       |
 272 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 273 | ``Request.HTTP.QueryString``                       | string   | HTTP query string                                            | no       | no        | no       |
 274 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 275 | ``Request.HTTP.Domain``                            | string   | domain name                                                  | no       | no        | no       |
 276 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 277 | ``Request.Time``                                   | time     | request time                                                 | no       | no        | no       |
 278 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 279 | ``Request.Dialect``                                | string   | "S3" or "Swift"                                              | no       | no        | no       |
 280 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 281 | ``Request.Id``                                     | string   | request Id                                                   | no       | no        | no       |
 282 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 283 | ``Request.TransactionId``                          | string   | transaction Id                                               | no       | no        | no       |
 284 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 285 | ``Request.Tags``                                   | table    | object tags map                                              | yes      | no        | no       |
 286 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 287 | ``Request.User``                                   | table    | user that triggered the request                              | no       | no        | no       |
 288 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 289 | ``Request.User.Tenant``                            | string   | triggering user tenant                                       | no       | no        | no       |
 290 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 291 | ``Request.User.Id``                                | string   | triggering user id                                           | no       | no        | no       |
 292 +----------------------------------------------------+----------+--------------------------------------------------------------+----------+-----------+----------+
 293
 294 Request Functions
 295 --------------------
 296 Operations Log
 297 ~~~~~~~~~~~~~~
 298 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.
 299
 300 Lua Code Samples
 301 ----------------
 302 - Print information on source and destination objects in case of copy:
 303
 304 .. code-block:: lua
 305
 306   function print_object(object)
 307     RGWDebugLog("  Name: " .. object.Name)
 308     RGWDebugLog("  Instance: " .. object.Instance)
 309     RGWDebugLog("  Id: " .. object.Id)
 310     RGWDebugLog("  Size: " .. object.Size)
 311     RGWDebugLog("  MTime: " .. object.MTime)
 312   end
 313
 314   if Request.CopyFrom and Request.Object and Request.CopyFrom.Object then
 315     RGWDebugLog("copy from object:")
 316     print_object(Request.CopyFrom.Object)
 317     RGWDebugLog("to object:")
 318     print_object(Request.Object)
 319   end
 320
 321 - Print ACLs via a "generic function":
 322
 323 .. code-block:: lua
 324
 325   function print_owner(owner)
 326     RGWDebugLog("Owner:")
 327     RGWDebugLog("  Display Name: " .. owner.DisplayName)
 328     RGWDebugLog("  Id: " .. owner.User.Id)
 329     RGWDebugLog("  Tenant: " .. owner.User.Tenant)
 330   end
 331
 332   function print_acl(acl_type)
 333     index = acl_type .. "ACL"
 334     acl = Request[index]
 335     if acl then
 336       RGWDebugLog(acl_type .. "ACL Owner")
 337       print_owner(acl.Owner)
 338       RGWDebugLog("  there are " .. #acl.Grants .. " grant for owner")
 339       for k,v in pairs(acl.Grants) do
 340         RGWDebugLog("    Grant Key: " .. k)
 341         RGWDebugLog("    Grant Type: " .. v.Type)
 342         RGWDebugLog("    Grant Group Type: " .. v.GroupType)
 343         RGWDebugLog("    Grant Referer: " .. v.Referer)
 344         RGWDebugLog("    Grant User Tenant: " .. v.User.Tenant)
 345         RGWDebugLog("    Grant User Id: " .. v.User.Id)
 346       end
 347     else
 348       RGWDebugLog("no " .. acl_type .. " ACL in request: " .. Request.Id)
 349     end
 350   end
 351
 352   print_acl("User")
 353   print_acl("Bucket")
 354   print_acl("Object")
 355
 356 - Use of operations log only in case of errors:
 357
 358 .. code-block:: lua
 359
 360   if Request.Response.HTTPStatusCode ~= 200 then
 361     RGWDebugLog("request is bad, use ops log")
 362     rc = Request.Log()
 363     RGWDebugLog("ops log return code: " .. rc)
 364   end
 365
 366 - Set values into the error message:
 367
 368 .. code-block:: lua
 369
 370   if Request.Response.HTTPStatusCode == 500 then
 371     Request.Response.Message = "<Message> something bad happened :-( </Message>"
 372   end
 373
 374 - Add metadata to objects that was not originally sent by the client:
 375
 376 In the `preRequest` context we should add:
 377
 378 .. code-block:: lua
 379
 380   if Request.RGWOp == 'put_obj' then
 381     Request.HTTP.Metadata["x-amz-meta-mydata"] = "my value"
 382   end
 383
 384 In the `postRequest` context we look at the metadata:
 385
 386 .. code-block:: lua
 387
 388   RGWDebugLog("number of metadata entries is: " .. #Request.HTTP.Metadata)
 389   for k, v in pairs(Request.HTTP.Metadata) do
 390     RGWDebugLog("key=" .. k .. ", " .. "value=" .. v)
 391   end
 392
 393 - Use modules to create Unix socket based, JSON encoded, "access log":
 394
 395 First we should add the following packages to the allowlist:
 396
 397 ::
 398
 399   # radosgw-admin script-package add --package=luajson
 400   # radosgw-admin script-package add --package=luasocket --allow-compilation
 401
 402
 403 Then, do a restart for the radosgw and upload the following script to the `postRequest` context:
 404
 405 .. code-block:: lua
 406
 407   if Request.RGWOp == "get_obj" then
 408     local json = require("json")
 409     local socket = require("socket")
 410     local unix = require("socket.unix")
 411     local s = assert(unix())
 412     E = {}
 413
 414     msg = {bucket = (Request.Bucket or (Request.CopyFrom or E).Bucket).Name,
 415       time = Request.Time,
 416       operation = Request.RGWOp,
 417       http_status = Request.Response.HTTPStatusCode,
 418       error_code = Request.Response.HTTPStatus,
 419       object_size = Request.Object.Size,
 420       trans_id = Request.TransactionId}
 421
 422     assert(s:connect("/tmp/socket"))
 423     assert(s:send(json.encode(msg).."\n"))
 424     assert(s:close())
 425   end
 426