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Server side storage for the client (aka browser) and server.<\/p>\n

The storage is tied to the sid<\/code> in the authentication token of the client. This sid<\/code> is unique and changed if the user\nlogs on or logs off.<\/p>\n

Model functions<\/h2>\n

model\/server_storage\/post\/key<\/code> store a key, with the value of in the payload of the message.<\/p>\n

model\/server_storage\/get\/key<\/code> - fetch a key.<\/p>\n

model\/server_storage\/get<\/code> - fetch all keys.<\/p>\n

model\/server_storage\/delete\/key<\/code> - delete a key.<\/p>\n

model\/server_storage\/delete<\/code> - delete all values from the server storage.<\/p>\n

Example in JavaScript from the client:<\/p>\n

cotonic.broker.publish("bridge\/origin\/model\/server_storage\/post\/foo", { "hello": "world" });\n\ncotonic.broker.call("bridge\/origin\/model\/server_storage\/get\/foo")\n       .then( (msg) => console.log(msg) );\n\n{\n    dup: false\n    packet_id: null\n    payload: {result: {hello: "world"}, status: "ok"}\n    properties: {content_type: "application\/json"}\n    qos: 0\n    retain: false\n    topic: "reply\/page-3-0.4080048813145437"\n    type: "publish"\n}\n<\/code><\/pre>\n
Example in a template:<\/p>\n
The hello key of foo is now: {{ m.server_storage.foo.hello|escape }}\n<\/code><\/pre>\n
Note that we must<\/strong> escape the value, as it originates from the client and contains arbitrary values, including HTML.<\/p>\n
Example in Erlang:<\/p>\n
m_server_storage:store(<<"foo">>, #{ <<"hello">> => <<"world">> }, Context),\n\ncase m_server_storage:lookup(<<"foo">>, Context) of\n    {ok, Value} ->  % Found the value\n    {error, no_session} -> % No session\n    {error, not_found} -> % There is a session but unknown key\nend.\n\nm_server_storage:delete(<<"foo">>, Context).\n<\/code><\/pre>\n
Storage of secret server data<\/h2>\n
Sometimes the server code wants to attach data to the specific client that is not accessible to the client itself. An\nexample is a secret during an OAuth handshake.<\/p>\n
For this there is a special, unlimited, storage API, which is only accessible using the Erlang API:<\/p>\n
m_server_storage:secure_store(<<"foo">>, #{ <<"my">> => <<"secret">> }, Context),\n\ncase m_server_storage:secure_lookup(<<"foo">>, Context) of\n    {ok, Value} ->  % Found the value\n    {error, no_session} -> % No session\n    {error, not_found} -> % There is a session but unknown key\nend.\n\nm_server_storage:secure_delete(<<"foo">>, Context).\n<\/code><\/pre>\n
The keys in the secure<\/em> storage are separate from the keys in the normal storage. There can be a key with the same name\nand different values in both storages.<\/p>\n
Storage process<\/h2>\n
If a value is stored in the server side storage then a process is started. This process holds all stored values, and\ntimes out after 900 seconds.<\/p>\n
Any HTTP request with the proper sid<\/code> will extend the lifetime of the storage process.<\/p>\n
The storage process holds at most 100 KB of data, above that it will respond with a full<\/code> error status.<\/p>\n
Configuration keys<\/h2>\n
There are two configuration keys, both need a number:<\/p>\n
  • mod_server_storage.storage_expire<\/code> The timeout in seconds of the storage process defaults to 900 seconds.<\/li>
  • mod_server_storage.storage_maxsize<\/code> The maximum stored size in bytes, both the keys and the values are counted. Default is 100 KB.<\/li><\/ul>\n
    Note that the storage is in-memory, so it is best to set the storage maxsize and expire as low as possible.<\/p>\n
    Accepted Events<\/h2>\n
    This module handles the following notifier callbacks:<\/p>\n
    • observe_request_context<\/code>: Periodic ping for the session, done by the client using m_server_storage:ping<\/code>.<\/li>
    • observe_server_storage<\/code>: Decoupling of server storage from other modules using m_server_storage:lookup<\/code>.<\/li><\/ul>","slug":"mod_server_storage","is_protected":false,"visible_for":0,"tz":"UTC","language":["en"],"doc_source_hash":"7d6381e40e11ef7a2abff28accc0c04b0cc0fc4e5a71e9ea63b22790df998878","is_featured":false,"content_group_id":{"id":2551,"is_a":["meta","content_group"],"name":"content_group_imported_docs","title":"Imported documentation","uri":"https:\/\/zotonic.com\/id\/content_group_imported_docs"},"category_id":{"id":320,"is_a":["meta","category"],"name":"module","title":"Modules","uri":"https:\/\/test.zotonic.com\/id\/320"},"doc_source_path":"apps\/zotonic_mod_server_storage\/src\/mod_server_storage.erl","publication_start":"2023-06-24T08:17:53Z","github_url":"https:\/\/github.com\/zotonic\/zotonic\/blob\/master\/apps\/zotonic_mod_server_storage\/src\/mod_server_storage.erl","pivot_location_lng":null,"doc_source_kind":"module","name":"doc_module_mod_server_storage","is_unfindable":false,"is_published":true,"pivot_geocode":null,"created":"2020-05-30T05:47:18Z","uri":null,"doc_status":"current","is_dependent":false,"erlang_app":"zotonic_mod_server_storage","publication_end":"9999-06-01T00:00:00Z","modifier_id":{"id":1,"is_a":["person"],"name":"administrator","title":"Site Administrator","uri":"https:\/\/zotonic.com\/id\/1"},"privacy":0,"doc_source_commit":"b8c4b2ccdc223257f311968fbd17b2d66f0c4156\n","creator_id":{"id":336,"is_a":["person","robot"],"name":"gitbot","title":"Git","uri":"https:\/\/zotonic.com\/id\/336"},"modified":"2026-09-30T09:39:38Z","title_slug":"mod_server_storage"},"uri":"https:\/\/zotonic.com\/id\/1307","uri_template":"https:\/\/zotonic.com\/id\/:id","websub":{"hub":"https:\/\/zotonic.com\/.zotonic\/websub","topic":"https:\/\/zotonic.com\/.zotonic\/websub\/topic\/1307"}},"status":"ok"}