Knowledge base
spool-directorydirectiveDirectory the engine watches for message files, reading each one and publishing it as a job.storage-addressdirectiveConnection string for an external store holding message bodies, so that jobs travelling through the broker carry only a key.storage-ttldirectiveSeconds a body is kept in the store before it expires.download-cacheWritten by the HubdirectiveStore for downloaded resources, so the same image is not fetched for every message.download-ttlWritten by the HubdirectiveSeconds a downloaded resource is served from the cache before being fetched again.spool-delaydirectiveSeconds a file must sit untouched before it is read, so half-written files are not published.spool-fail-directorydirectiveDirectory that receives spooled files the engine could not parse.spool-open-filesdirectiveHow many spooled files the engine holds open simultaneously.spool-removedirectiveWhether a spooled file is deleted once it has been published.spool-threadsdirectiveHow many threads read and publish spooled files in parallel.storage-policydirectiveWhether outgoing, incoming, all or no message bodies are placed in the external store.storage-rescheduledirectiveSeconds before a message whose body could not be fetched is tried again.storage-threadsdirectiveHow many connections to the store the engine keeps for fetching and writing bodies.storage-timeoutdirectiveSeconds to wait for the store to return a body before treating the fetch as failed.Three places a message body can be, and what each costsmechanismA body travels inside the job through the broker, or sits in an external store addressed by a key, or arrives as a file in a watched directory — and each choice moves the bottleneck somewhere else.keymessage propertyIdentifier of a body held in the external message store, used instead of an inline mime.The body could not be fetcheddelivery stateThe external message store could not return the body in time.