Environment (Required on creation):

Camunda BPM 7.13

Description (Required on creation; please attach any relevant screenshots, stacktraces, log files, etc. to the ticket):

Proper request to history REST API may cause server to go down.

Steps to reproduce:

1. Create a lot of process-instances
2. Make an GET request to /engine-rest/history/process-instance without any parameters

Observed Behavior:

Server goes down.

Expected behavior:

Server successfully makes a response.

Root Cause

Almost all REST APIs has no default value for maxResults parameter, causing them to return all results by default. This can cause a huge response body for history API responses and, in some cases, for other APIs. Huge response body may lead to several java, http-server or http-protocol level errors causing engine service or the whole application eventually to go down.

Solution Ideas:

Provide reasonable default value for maxResults parameter in all REST APIs or make this parameter mandatory and return 400 if it is absent.