6. Processed Dump Storage

Processed dumps are stored in two places: the relational database as well as in flat files within a file system. This forking of the storage scheme came from the realization that the infrequently used data within the database ‘dumps’ tables was causing performance problems within PostgreSQL. The ‘dumps’ tables took nearly eighty percent of the total storage, making replication and backup problematic. Since the ‘dumps’ table’s data is used only when a user requests a specific crash dump by uuid, most of the data is rarely, if ever, accessed.

We decided to migrate these dump into a file system storage outside the database.

In the file system, after processing, dumps are stored a gzip compressed JSON file format. This format echos a flattening of the ‘reports’, ‘extensions’ and the now deprecated ‘dumps’ tables within the database.

6.1. Directory Structure


Just as in the JsonDumpStorage scheme, there are two branches: ‘name’ and ‘date’

6.2. Access by Name

Most lookups of processed crash data happens by name. We use a radix storage technique where the first 4 characters of the file name are used for two levels of directory names. A file called aabbf9cb-395b-47e8-9600-4f20e2090331.jsonz would be found in the file system as .../aa/bb/aabbf9cb-395b-47e8-9600-4f20e2090331.jsonz

6.3. Access by Date

For the purposes of finding crashes that happened at specific date and time, a hierarchy of date directories offer quick lookup. The leaves of the date directories contain symbolic links to the locations of crash data.

6.4. JSON File Format


{"signature": "nsThread::ProcessNextEvent(int, int*)",
 "uuid": "aabbf9cb-395b-47e8-9600-4f20e2090331",
 "date_processed": "2009-03-31 14:45:09.215601",
 "install_age": 100113,
 "uptime": 7,
 "last_crash": 95113,
 "product": "SomeProduct",
 "version": "3.5.2",
 "build_id": "20090223121634",
 "branch": "1.9.1",
 "os_name": "Mac OS X",
 "os_version": "10.5.6 9G55",
 "cpu_name": "x86",
 "cpu_info":     "GenuineIntel family 6 model 15 stepping 6",
 "crash_address": "0xe9b246",
 "User Comments": "This thing crashed.\nHelp me Kirk.",
 "app_notes": "",
 "success": true,
 "truncated": false,
 "processor_notes": "",
 "distributor_version": "",
 "add-ons": [["{ABDE892B-13A8-4d1b-88E6-365A6E755758}", "1.0"], ["{b2e293ee-fd7e-4c71-a714-5f4750d8d7b7}", ""], ["{972ce4c6-7e08-4474-a285-3208198ce6fd}", "3.5.2"]],
 "dump":"OS|Mac OS X|10.5.6 9G55\\nCPU|x86|GenuineIntel family 6 model 15 stepping 6|2\\nCrash|EXC_BAD_ACCESS / KERN_PROTECTION_FAILURE|0x1558c095|0\\n

The “dump” component is the direct streamed output from the Breakpad “minidump_stackwalk” program. Unfortunately, that project does not give detailed documentation of the format.