[COUCHDB-1393] badmatch on big binary

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Won't Fix
• Assignee: Unassigned
• Reporter: Jan Lehnardt
• Created: 25/Jan/12 09:53
• Updated: 02/Sep/18 06:36
• Resolved: 02/Sep/18 06:36

Description

via dev@ by Peta Bogdan <[e-mail]>

Hello,

I have a small database around 120 MB with approximately 16,000 documents.

However, it happens (also from futon) that I get this error:

[Tue, 17 Jan 2012 07:22:01 GMT] [error] [<0.185.0>] {error_report,<0.30.0>,
{<0.185.0>,crash_report,
[[{initial_call,{couch_file,init,['Argument__1']}},

{pid,<0.185.0>}

,

{registered_name,[]},
{error_info,
{exit,
{{badmatch,
{ok,
9_MEGABYTES_BINARY}},
[{couch_file,read_raw_iolist_int,3},
{couch_file,maybe_read_more_iolist,4},
{couch_file,handle_call,3},
{gen_server,handle_msg,5},
{proc_lib,init_p_do_apply,3}]},
[{gen_server,terminate,6},
{proc_lib,init_p_do_apply,3}]}},
{ancestors,[<0.184.0>]},
{messages,
[{'$gen_call',
{<0.10840.18>,#Ref<0.0.3.20907>},
bytes}]},
{links,[<0.190.0>]},
{dictionary,[]},
{trap_exit,true},
{status,running},
{heap_size,1597},
{stack_size,24},
{reductions,65666}],
[{neighbour,
[{pid,<0.190.0>},
{registered_name,[]}

,
{initial_call,
{couch_ref_counter,init,['Argument__1']}},
{current_function,{gen_server,loop,6}},

{ancestors,[<0.188.0>,<0.187.0>,<0.184.0>]}

,

{messages,[]}

,

{links,[<0.185.0>]}

,

{dictionary,[]}

,

{trap_exit,false}

,

{status,waiting}

,

{heap_size,610}

,

{stack_size,9}

,

{reductions,362}

]}]]}}

If this error occurs to frequently causes couch_server to reach its max
restart frequency causing the entire supervision tree to shutdown and hence
the database server instance disappears.

The function couch_file:read_raw_iolist_int/3 calls file:pread which
returns

{ok, Binary}

. This Binary has almost 9 megabytes in size, which is
very strange.
I think this does mean that the function file:pread/3 is instructed to read
from wrong position.

The only reason I can think of is that the value of 'TotalBytes' from line
(1) doesn't match the value of 'TotalBytes' from line (2)

(1) TotalBytes = calculate_total_read_len(BlockOffset, Len),
(2)

{ok, <<RawBin:TotalBytes/binary>>}

= file:pread(Fd, Pos, TotalBytes),

The possible answer would be that in certain conditions the function
calculate_total_read_len/2 doesn't return the expected value.

Server: CouchDB/1.1.1 (Erlang OTP/R14B04)
OS: OpenBSD 5.0 GENERIC.MP#63 amd64

Now, the trouble is how to circumvent this situation.

Thank you in advance,

Bogdan