[TS-4834] Expose bad disk and disk access failures

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 7.1.0
• Component/s: Cache, Metrics
• Assignee: Gancho Tenev
• Reporter: Gancho Tenev
• Created: 08/Sep/16 22:06
• Updated: 22/Dec/16 16:45
• Resolved: 22/Dec/16 16:45

Description

We would like to monitor low-level disk access failures and disks marked by ATS as bad.

I have a patch that exposes that information through

proxy.process.cache.disk_error_count 10
proxy.process.cache.disk_bad_count 5

and the following tests/shows how it would work...

Start ATS with 2 disks and tail diags.log

$ cat etc/trafficserver/storage.config
/dev/sdb
/dev/sdc

$ tail -f var/log/trafficserver/diags.log
[Sep  8 12:18:48.149] Server {0x2b5f43db54c0} NOTE: traffic server running
[Sep  8 12:18:48.198] Server {0x2b5f44654700} NOTE: cache enabled

Check related metrics and observe all 0s

$ ./bin/traffic_ctl metric match "proxy.process.cache*.disk.*" "proxy.process.cache.*(read|write).failure" "proxy.process.http.cache_(read|write)_errors"
proxy.process.cache.disk_error_count 0
proxy.process.cache.disk_bad_count 0
proxy.process.cache.read.failure 0
proxy.process.cache.write.failure 0
proxy.process.cache.volume_0.read.failure 0
proxy.process.cache.volume_0.write.failure 0
proxy.process.http.cache_write_errors 0
proxy.process.http.cache_read_errors 0

Now using your favorite hard disk failure injection tool inject 10 failures, by setting both disks used by this setup /dev/sdb and /dev/sdc to fail all reads. And shoot 5 requests causing 10 failed reads.

$ for i in 1 2 3 4 5; do curl -x 127.0.0.1:80 http://example.com/1 -o /dev/null -s; done

$ tail -f var/log/trafficserver/diags.log
[Sep  8 12:19:09.758] Server {0x2aaab4302700} WARNING: cache disk operation failed READ -1 0
[Sep  8 12:19:09.759] Server {0x2aaac0100700} WARNING: cache disk operation failed READ -1 0
[Sep  8 12:19:09.764] Server {0x2b5f43db54c0} WARNING: Error accessing Disk /dev/sdb [1/10]
[Sep  8 12:19:09.769] Server {0x2b5f44654700} WARNING: Error accessing Disk /dev/sdb [2/10]
[Sep  8 12:19:09.785] Server {0x2aaac0100700} WARNING: cache disk operation failed READ -1 0
[Sep  8 12:19:09.786] Server {0x2aaab4302700} WARNING: cache disk operation failed READ -1 0
[Sep  8 12:19:09.791] Server {0x2b5f44654700} WARNING: Error accessing Disk /dev/sdb [3/10]
[Sep  8 12:19:09.796] Server {0x2b5f43db54c0} WARNING: Error accessing Disk /dev/sdb [4/10]
[Sep  8 12:19:09.812] Server {0x2aaab4100700} WARNING: cache disk operation failed READ -1 0
[Sep  8 12:19:09.813] Server {0x2aaacc100700} WARNING: cache disk operation failed READ -1 0
[Sep  8 12:19:09.817] Server {0x2b5f43db54c0} WARNING: Error accessing Disk /dev/sdb [5/10]
[Sep  8 12:19:09.823] Server {0x2b5f44654700} WARNING: Error accessing Disk /dev/sdb [6/10]
[Sep  8 12:19:09.843] Server {0x2aaacc302700} WARNING: cache disk operation failed READ -1 0
[Sep  8 12:19:09.844] Server {0x2aaad8100700} WARNING: cache disk operation failed READ -1 0
[Sep  8 12:19:09.847] Server {0x2b5f44654700} WARNING: Error accessing Disk /dev/sdb [7/10]
[Sep  8 12:19:09.854] Server {0x2b5f43db54c0} WARNING: Error accessing Disk /dev/sdb [8/10]
[Sep  8 12:19:09.874] Server {0x2aaacc302700} WARNING: cache disk operation failed READ -1 0
[Sep  8 12:19:09.875] Server {0x2aaad8100700} WARNING: cache disk operation failed READ -1 0
[Sep  8 12:19:09.880] Server {0x2b5f43db54c0} WARNING: Error accessing Disk /dev/sdb [9/10]
[Sep  8 12:19:09.887] Server {0x2b5f44654700} WARNING: too many errors accessing disk /dev/sdb [10/10]: declaring disk bad

We see 5 read failures which triggered 10 actually disk reads and marked the failing disk as a bad disk.

$ ./bin/traffic_ctl metric match "proxy.process.cache*.disk.*" "proxy.process.cache.*(read|write).failure" "proxy.process.http.cache_(read|write)_errors"
proxy.process.cache.disk_error_count 10
proxy.process.cache.disk_bad_count 1
proxy.process.cache.read.failure 5
proxy.process.cache.write.failure 5
proxy.process.cache.volume_0.read.failure 5
proxy.process.cache.volume_0.write.failure 5
proxy.process.http.cache_write_errors 0
proxy.process.http.cache_read_errors 0

Now shoot 5 requests causing 10 failed reads.

$ for i in 1 2 3 4 5; do curl -x 127.0.0.1:80 http://example.com/1 -o /dev/null -s; done

$ tail -f var/log/trafficserver/diags.log
[Sep  8 12:26:02.874] Server {0x2aaae4100700} WARNING: cache disk operation failed READ -1 0
[Sep  8 12:26:02.875] Server {0x2aaaf0302700} WARNING: cache disk operation failed READ -1 0
[Sep  8 12:26:02.876] Server {0x2b5f44654700} WARNING: Error accessing Disk /dev/sdc [1/10]
[Sep  8 12:26:02.885] Server {0x2b5f43db54c0} WARNING: Error accessing Disk /dev/sdc [2/10]
[Sep  8 12:26:02.902] Server {0x2aaaf0302700} WARNING: cache disk operation failed READ -1 0
[Sep  8 12:26:02.902] Server {0x2aaae4100700} WARNING: cache disk operation failed READ -1 0
[Sep  8 12:26:02.907] Server {0x2b5f43db54c0} WARNING: Error accessing Disk /dev/sdc [3/10]
[Sep  8 12:26:02.914] Server {0x2b5f44654700} WARNING: Error accessing Disk /dev/sdc [4/10]
[Sep  8 12:26:02.936] Server {0x2aaafc100700} WARNING: cache disk operation failed READ -1 0
[Sep  8 12:26:02.936] Server {0x2aab08100700} WARNING: cache disk operation failed READ -1 0
[Sep  8 12:26:02.940] Server {0x2b5f44654700} WARNING: Error accessing Disk /dev/sdc [5/10]
[Sep  8 12:26:02.946] Server {0x2b5f43db54c0} WARNING: Error accessing Disk /dev/sdc [6/10]
[Sep  8 12:26:02.971] Server {0x2aab08100700} WARNING: cache disk operation failed READ -1 0
[Sep  8 12:26:02.971] Server {0x2aaafc100700} WARNING: cache disk operation failed READ -1 0
[Sep  8 12:26:02.976] Server {0x2b5f43db54c0} WARNING: Error accessing Disk /dev/sdc [7/10]
[Sep  8 12:26:02.982] Server {0x2b5f44654700} WARNING: Error accessing Disk /dev/sdc [8/10]
[Sep  8 12:26:03.002] Server {0x2aaafc100700} WARNING: cache disk operation failed READ -1 0
[Sep  8 12:26:03.002] Server {0x2aab08100700} WARNING: cache disk operation failed READ -1 0
[Sep  8 12:26:03.006] Server {0x2b5f44654700} WARNING: Error accessing Disk /dev/sdc [9/10]
[Sep  8 12:26:03.012] Server {0x2b5f43db54c0} WARNING: too many errors accessing disk /dev/sdc [10/10]: declaring disk bad

We see 5 more read failures which triggered 10 more actual failed disk reads and marked the second disk as bad.

$ ./bin/traffic_ctl metric match "proxy.process.cache*.disk.*" "proxy.process.cache.*(read|write).failure" "proxy.process.http.cache_(read|write)_errors"
proxy.process.cache.disk_error_count 20
proxy.process.cache.disk_bad_count 2
proxy.process.cache.read.failure 10
proxy.process.cache.write.failure 10
proxy.process.cache.volume_0.read.failure 10
proxy.process.cache.volume_0.write.failure 10
proxy.process.http.cache_write_errors 0
proxy.process.http.cache_read_errors 0

After marking all the (2) disks as bad finally ATS disabled the cache and started going to origin on every requests.

$ tail -f var/log/trafficserver/diags.log
[Sep  8 12:26:03.012] Server {0x2b5f43db54c0} WARNING: All storage devices offline, cache disabled

Issue Links

• links to: GitHub Pull Request #996