Tcl Requires Chilkat v11.5.0+

Box: Poll User Events and Save a Checkpoint

See more Box Examples

Poll the authenticated user event stream in bounded batches. The local JSON checkpoint keeps processed event IDs and the next stream position. This single-process demonstration logs events; a production worker should commit its business action, deduplication record, and cursor transactionally and prune old IDs.

See the Box API guide for setup and the complete workflow.

Tcl

load ./chilkat.dll

set success 0

#  Requires Chilkat 11.5.0 or later and a previously unlocked Chilkat bundle.
#  See Global Unlock Sample.
#  Guide: Box API Guide.

set success 0

#  Supply an unexpired token obtained with one of the Box authentication examples.
#  A token represents a particular user or service account. IDs must be accessible to it.
set curl [new_CkHttpCurl]

CkHttpCurl_SetVar $curl "access_token" "BOX_ACCESS_TOKEN"

set state [new_CkJsonObject]

set files [new_CkFileAccess]

set statePath "qa_data/box_events_state.json"
if {[CkFileAccess_FileExists $files $statePath] == 1} then {
    set success [CkJsonObject_LoadFile $state $statePath]
    if {$success != 1} then {
        puts [CkJsonObject_lastErrorText $state]
        delete_CkHttpCurl $curl
        delete_CkJsonObject $state
        delete_CkFileAccess $files
        exit
    }

    if {[CkJsonObject_HasMember $state "position"] != 1} then {
        puts "Invalid checkpoint: position missing."
        delete_CkHttpCurl $curl
        delete_CkJsonObject $state
        delete_CkFileAccess $files
        exit
    }

} else {
    #  "now" starts a new subscription. It deliberately skips historical events.
    CkJsonObject_UpdateString $state "position" "now"
}

CkHttpCurl_SetVar $curl "position" [CkJsonObject_stringOf $state "position"]
set page [new_CkJsonObject]

set seenPath [new_CkStringBuilder]

set batch 0

set more 1
while {expr [$more == 1]  &&  [$batch < 20]} {
    CkHttpCurl_ClearTargetOutput $curl "*"
    set authorizedCommand1 [new_CkStringBuilder]

    CkStringBuilder_SetString $authorizedCommand1 "curl -X GET \"https://api.box.com/2.0/events?stream_type=all&stream_position={{position}}&limit=100\" -H \"Authorization: Bearer {{access_token}}\""
    set headerReplacement1 [CkStringBuilder_Replace $authorizedCommand1 "{{access_token}}" [CkHttpCurl_getVar $curl "access_token"]]
    set success [CkHttpCurl_DoYourThing $curl [CkStringBuilder_getAsString $authorizedCommand1]]
    if {expr [$success != 1]  ||  [[CkHttpCurl_get_StatusCode $curl] != 200]} then {
        puts "Box request failed. HTTP status: [CkHttpCurl_get_StatusCode $curl]"
        puts "Failure reason: [CkHttpCurl_get_FailReason $curl]"
        puts [CkHttpCurl_responseBodyStr $curl]
        delete_CkHttpCurl $curl
        delete_CkJsonObject $state
        delete_CkFileAccess $files
        delete_CkJsonObject $page
        delete_CkStringBuilder $seenPath
        delete_CkStringBuilder $authorizedCommand1
        exit
    }

    set success [CkHttpCurl_GetResponseJson $curl $page]
    if {$success != 1} then {
        puts [CkHttpCurl_lastErrorText $curl]
        delete_CkHttpCurl $curl
        delete_CkJsonObject $state
        delete_CkFileAccess $files
        delete_CkJsonObject $page
        delete_CkStringBuilder $seenPath
        delete_CkStringBuilder $authorizedCommand1
        exit
    }

    set count [CkJsonObject_SizeOfArray $page "entries"]
    set i 0
    while {$i < $count} {
        CkJsonObject_put_I $page $i
        set eventId [CkJsonObject_stringOf $page "entries[i].event_id"]
        if {$eventId == ""} then {
            puts "Event without an event_id; checkpoint not advanced."
            delete_CkHttpCurl $curl
            delete_CkJsonObject $state
            delete_CkFileAccess $files
            delete_CkJsonObject $page
            delete_CkStringBuilder $seenPath
            delete_CkStringBuilder $authorizedCommand1
            exit
        }

        CkStringBuilder_Clear $seenPath
        CkStringBuilder_Append $seenPath "seen."
        CkStringBuilder_Append $seenPath $eventId
        if {[CkJsonObject_HasMember $state [CkStringBuilder_getAsString $seenPath]] == 0} then {
            #  Replace this logging with your idempotent business operation.
            #  Record success only after that operation succeeds.
            puts "$eventId [CkJsonObject_stringOf $page {entries[i].event_type}] [CkJsonObject_stringOf $page {entries[i].source.id}]"
            CkJsonObject_UpdateBool $state [CkStringBuilder_getAsString $seenPath] 1
        }

        set i [expr $i + 1]
    }
    set nextPosition [CkJsonObject_stringOf $page "next_stream_position"]
    if {$nextPosition == ""} then {
        puts "Missing next_stream_position; checkpoint not advanced."
        delete_CkHttpCurl $curl
        delete_CkJsonObject $state
        delete_CkFileAccess $files
        delete_CkJsonObject $page
        delete_CkStringBuilder $seenPath
        delete_CkStringBuilder $authorizedCommand1
        exit
    }

    set more [expr [$count > 0]  &&  [$nextPosition != [CkHttpCurl_getVar $curl "position"]]]
    CkJsonObject_UpdateString $state "position" $nextPosition
    set success [CkJsonObject_WriteFile $state $statePath]
    if {$success != 1} then {
        puts [CkJsonObject_lastErrorText $state]
        delete_CkHttpCurl $curl
        delete_CkJsonObject $state
        delete_CkFileAccess $files
        delete_CkJsonObject $page
        delete_CkStringBuilder $seenPath
        delete_CkStringBuilder $authorizedCommand1
        exit
    }

    CkHttpCurl_SetVar $curl "position" $nextPosition
    set batch [expr $batch + 1]
}
puts "Checkpoint saved. Run again later to continue polling."

delete_CkHttpCurl $curl
delete_CkJsonObject $state
delete_CkFileAccess $files
delete_CkJsonObject $page
delete_CkStringBuilder $seenPath
delete_CkStringBuilder $authorizedCommand1