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timeout interview questions

Top timeout frequently asked interview questions

Timeout on a Python function call

I'm calling a function in Python which I know may stall and force me to restart the script.

How do I call the function or what do I wrap it in so that if it takes longer than 5 seconds the script cancels it and does something else?


Source: (StackOverflow)

What is default session timeout in ASP.NET?

What is the default session timeout value in ASP.NET?


Source: (StackOverflow)

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WCF timeout exception detailed investigation

We have an application that has a WCF service (*.svc) running on IIS7 and various clients querying the service. The server is running Win 2008 Server. The clients are running either Windows 2008 Server or Windows 2003 server. I am getting the following exception, which I have seen can in fact be related to a large number of potential WCF issues.

System.TimeoutException: The request channel timed out while waiting for a reply after 00:00:59.9320000. Increase the timeout value passed to the call to Request or increase the SendTimeout value on the Binding. The time allotted to this operation may have been a portion of a longer timeout. ---> System.TimeoutException: The HTTP request to 'http://www.domain.com/WebServices/myservice.svc/gzip' has exceeded the allotted timeout of 00:01:00. The time allotted to this operation may have been a portion of a longer timeout. 

I have increased the timeout to 30min and the error still occurred. This tells me that something else is at play, because the quantity of data could never take 30min to upload or download.

The error comes and goes. At the moment, it is more frequent. It does not seem to matter if I have 3 clients running simultaneously or 100, it still occurs once in a while. Most of the time, there are no timeouts but I still get a few per hour. The error comes from any of the methods that are invoked. One of these methods does not have parameters and returns a bit of data. Another takes in lots of data as a parameter but executes asynchronously. The errors always originate from the client and never reference any code on the server in the stack trace. It always ends with:

 at System.Net.HttpWebRequest.GetResponse()
  at System.ServiceModel.Channels.HttpChannelFactory.HttpRequestChannel.HttpChannelRequest.WaitForReply(TimeSpan timeout)

On the server: I've tried (and currently have) the following binding settings:

maxBufferSize="2147483647" maxReceivedMessageSize="2147483647" maxBufferPoolSize="2147483647"

It does not seem to have an impact.

I've tried (and currently have) the following throttling settings:

<serviceThrottling maxConcurrentCalls="1500"   maxConcurrentInstances="1500"    maxConcurrentSessions="1500"/>

It does not seem to have an impact.

I currently have the following settings for the WCF service.

[ServiceBehavior(InstanceContextMode = InstanceContextMode.Single, ConcurrencyMode = ConcurrencyMode.Single)]

I ran with ConcurrencyMode.Multiple for a while, and the error still occurred.

I've tried restarting IIS, restarting my underlying SQL Server, restarting the machine. All of these don't seem to have an impact.

I've tried disabling the Windows firewall. It does not seem to have an impact.

On the client, I have these settings:

maxReceivedMessageSize="2147483647"

<system.net>
    <connectionManagement>
    <add address="*" maxconnection="16"/>
</connectionManagement> 
</system.net>

My client closes its connections:

var client = new MyClient();

try
{
    return client.GetConfigurationOptions();
}
finally
{
    client.Close();
}

I have changed the registry settings to allow more outgoing connections:

MaxConnectionsPerServer=24, MaxConnectionsPer1_0Server=32.

I have now just recently tried SvcTraceViewer.exe. I managed to catch one exception on the client end. I see that its duration is 1 minute. Looking at the server side trace, I can see that the server is not aware of this exception. The maximum duration I can see is 10 seconds.

I have looked at active database connections using exec sp_who on the server. I only have a few (2-3). I have looked at TCP connections from one client using TCPview. It usually is around 2-3 and I have seen up to 5 or 6.

Simply put, I am stumped. I have tried everything I could find, and must be missing something very simple that a WCF expert would be able to see. It is my gut feeling that something is blocking my clients at the low-level (TCP), before the server actually receives the message and/or that something is queuing the messages at the server level and never letting them process.

If you have any performance counters I should look at, please let me know. (please indicate what values are bad, as some of these counters are hard to decypher). Also, how could I log the WCF message size? Finally, are there any tools our there that would allow me to test how many connections I can establish between my client and server (independently from my application)

Thanks for your time!

Extra information added June 20th:

My WCF application does something similar to the following.

while (true)
{
   Step1GetConfigurationSettingsFromServerViaWCF(); // can change between calls
   Step2GetWorkUnitFromServerViaWCF();
   DoWorkLocally(); // takes 5-15minutes. 
   Step3SendBackResultsToServerViaWCF();
}

Using WireShark, I did see that when the error occurs, I have a five TCP retransmissions followed by a TCP reset later on. My guess is the RST is coming from WCF killing the connection. The exception report I get is from Step3 timing out.

I discovered this by looking at the tcp stream "tcp.stream eq 192". I then expanded my filter to "tcp.stream eq 192 and http and http.request.method eq POST" and saw 6 POSTs during this stream. This seemed odd, so I checked with another stream such as tcp.stream eq 100. I had three POSTs, which seems a bit more normal because I am doing three calls. However, I do close my connection after every WCF call, so I would have expected one call per stream (but I don't know much about TCP).

Investigating a bit more, I dumped the http packet load to disk to look at what these six calls where.

1) Step3
2) Step1
3) Step2
4) Step3 - corrupted
5) Step1
6) Step2

My guess is two concurrent clients are using the same connection, that is why I saw duplicates. However, I still have a few more issues that I can't comprehend:

a) Why is the packet corrupted? Random network fluke - maybe? The load is gzipped using this sample code: http://msdn.microsoft.com/en-us/library/ms751458.aspx - Could the code be buggy once in a while when used concurrently? I should test without the gzip library.

b) Why would I see step 1 & step 2 running AFTER the corrupted operation timed out? It seems to me as if these operations should not have occurred. Maybe I am not looking at the right stream because my understanding of TCP is flawed. I have other streams that occur at the same time. I should investigate other streams - a quick glance at streams 190-194 show that the Step3 POST have proper payload data (not corrupted). Pushing me to look at the gzip library again.


Source: (StackOverflow)

Android error: Failed to install *.apk on device *: timeout

I'm getting this error from time to time and don't know what causing this:
When trying to run/debug an Android app on a real device (Galaxy Samsung S in my case) I'm getting the following error in the Console:

Failed to install *.apk on device *:

timeout Launch canceled!

This is all the Console is telling me. LogCat doesn't provide any information. Eclipse Problems view is not showing any issues.

I tried the following steps with no success:
1. Cleaning the project (Project->Clean)
2. Restarting device, Eclipse, laptop, all of the above...
3. Moving the project to a location without spaces, according to Failed to install apk on device 'emulator-5554': timeout

The app has been debugged in the past on that device many times (app is live on Market), but this problem happens every so often, and is VERY FRUSTRATING...

Any help would be greatly appreciated! Thanks.


Source: (StackOverflow)

Timeouts WCF Services

How do the timeouts work in WCF? I know for example that you can configure sendTimeout and receiveTimeout for a clients binding. But how do they work?

MSDN describes sendTimeout as:

A TimeSpan value that specifies the interval of time provided for a send operation to complete. This value should be greater than or equal to Zero. The default is 00:01:00.

What are send operations/receive operations?


Source: (StackOverflow)

What is jQuery's ajax default timeout value?

Does anyone know what the default jQuery ajax timeout value is?


Source: (StackOverflow)

MySQL server has gone away - in exactly 60 seconds

I recently discovered that a sql query that was running fine earlier is now timing out after 60 seconds and throwing an error. The query is slow but runs as part of a nightly job so that's not a problem in itself (so please don't suggest I optimize it).

I'm able to reproduce the error consistently by running "select SLEEP(120);" from PHP as shown below. However, running the same statement from a MySQL client is successful (returns 0). I've tried adjusting wait_timeout (set to 28800), but have had no luck. I've also rebooted both the db server and machine itself.

The fact that it always times out at exactly 60 seconds suggests to me that it is likely to be a setting and not a limited resources issue.

I'm running:
Windows Server 2003
MySql 5.1.36-community
PHP 5.3

Below are my test code, the output and the results from SHOW VARIABLES

Thanks!

CODE:

set_error_handler("sqlErrorHandler");
set_time_limit(12000);


$link = mysql_connect("$MYSQL_Host","$MYSQL_User","$MYSQL_Pass");
mysql_select_db($MYSQL_db, $link);

echo "mysql_ping = " . (mysql_ping($link) ? "LIVE" : "DEAD") . "<br /><br />"; 

$sql = "SELECT SLEEP(120);";

$start = microtime(true);
mysql_query($sql, $link);

echo "**query done**<br />";
allDone();

function allDone(){
 global $start, $sql;

 $end = microtime(true);
 echo "sql : $sql<br />";
 echo "elapsed : " . ($end - $start) . "<br />";
 echo "<br />";
}

function sqlErrorHandler($errno, $errstr, $errfile, $errline){
 global $link;
 echo "Error : $errno<br />$errstr<br />";
 echo "mysql_ping : " . (mysql_ping($link) ? "LIVE" : "DEAD") . "<br />"; 
 echo "<br />";

 allDone();
}

OUTPUT :

mysql_ping = LIVE

Error : 2
mysql_query() [function.mysql-query]: MySQL server has gone away
mysql_ping : DEAD

sql : SELECT SLEEP(120);
elapsed : 60.051116943359

Error : 2
mysql_query() [function.mysql-query]: Error reading result set's header
mysql_ping : DEAD

sql : SELECT SLEEP(120);
elapsed : 60.0511469841

**query done**
sql : SELECT SLEEP(120);
elapsed : 60.051155090332

SHOW VARIABLES:

Variable_name=Value
auto_increment_increment=1
auto_increment_offset=1
autocommit=ON
automatic_sp_privileges=ON
back_log=50
basedir=C:\\Program Files\\MySQL\\MySQL Server 5.1\\
big_tables=OFF
binlog_cache_size=32768
binlog_format=STATEMENT
bulk_insert_buffer_size=8388608
character_set_client=utf8
character_set_connection=utf8
character_set_database=latin1
character_set_filesystem=binary
character_set_results=utf8
character_set_server=latin1
character_set_system=utf8
character_sets_dir=C:\\Program Files\\MySQL\\MySQL Server 5.1\\share\\charsets\\
collation_connection=utf8_general_ci
collation_database=latin1_swedish_ci
collation_server=latin1_swedish_ci
completion_type=0
concurrent_insert=1
connect_timeout=10
datadir=C:\\Documents and Settings\\All Users\\Application Data\\MySQL\\MySQL Server 5.1\\Data\\
date_format=%Y-%m-%d
datetime_format=%Y-%m-%d %H:%i:%s
default_week_format=0
delay_key_write=ON
delayed_insert_limit=100
delayed_insert_timeout=300
delayed_queue_size=1000
div_precision_increment=4
engine_condition_pushdown=ON
error_count=0
event_scheduler=OFF
expire_logs_days=0
flush=OFF
flush_time=1800
foreign_key_checks=ON
ft_boolean_syntax=+ -><()~*:""&|
ft_max_word_len=84
ft_min_word_len=4
ft_query_expansion_limit=20
ft_stopword_file=(built-in)
general_log=OFF
general_log_file=C:\\Documents and Settings\\All Users\\Application Data\\MySQL\\MySQL Server 5.1\\Data\\p1.log
group_concat_max_len=1024
have_community_features=YES
have_compress=YES
have_crypt=NO
have_csv=YES
have_dynamic_loading=YES
have_geometry=YES
have_innodb=YES
have_ndbcluster=NO
have_openssl=DISABLED
have_partitioning=YES
have_query_cache=YES
have_rtree_keys=YES
have_ssl=DISABLED
have_symlink=YES
identity=0
ignore_builtin_innodb=OFF
init_connect=
init_file=
init_slave=
innodb_adaptive_hash_index=ON
innodb_additional_mem_pool_size=2097152
innodb_autoextend_increment=8
innodb_autoinc_lock_mode=1
innodb_buffer_pool_size=96468992
innodb_checksums=ON
innodb_commit_concurrency=0
innodb_concurrency_tickets=500
innodb_data_file_path=ibdata1:10M:autoextend
innodb_data_home_dir=D:\\MySQL Datafiles\\
innodb_doublewrite=ON
innodb_fast_shutdown=1
innodb_file_io_threads=4
innodb_file_per_table=OFF
innodb_flush_log_at_trx_commit=1
innodb_flush_method=
innodb_force_recovery=0
innodb_lock_wait_timeout=50
innodb_locks_unsafe_for_binlog=OFF
innodb_log_buffer_size=1048576
innodb_log_file_size=19922944
innodb_log_files_in_group=2
innodb_log_group_home_dir=.\\
innodb_max_dirty_pages_pct=90
innodb_max_purge_lag=0
innodb_mirrored_log_groups=1
innodb_open_files=300
innodb_rollback_on_timeout=OFF
innodb_stats_on_metadata=ON
innodb_support_xa=ON
innodb_sync_spin_loops=20
innodb_table_locks=ON
innodb_thread_concurrency=8
innodb_thread_sleep_delay=10000
innodb_use_legacy_cardinality_algorithm=ON
insert_id=0
interactive_timeout=28800
join_buffer_size=131072
keep_files_on_create=OFF
key_buffer_size=50331648
key_cache_age_threshold=300
key_cache_block_size=1024
key_cache_division_limit=100
language=C:\\Program Files\\MySQL\\MySQL Server 5.1\\share\\english\\
large_files_support=ON
large_page_size=0
large_pages=OFF
last_insert_id=0
lc_time_names=en_US
license=GPL
local_infile=ON
log=OFF
log_bin=OFF
log_bin_trust_function_creators=OFF
log_bin_trust_routine_creators=OFF
log_error=C:\\Documents and Settings\\All Users\\Application Data\\MySQL\\MySQL Server 5.1\\Data\\p1.err
log_output=FILE
log_queries_not_using_indexes=OFF
log_slave_updates=OFF
log_slow_queries=OFF
log_warnings=1
long_query_time=10.000000
low_priority_updates=OFF
lower_case_file_system=ON
lower_case_table_names=1
max_allowed_packet=1048576
max_binlog_cache_size=4294963200
max_binlog_size=1073741824
max_connect_errors=10
max_connections=800
max_delayed_threads=20
max_error_count=64
max_heap_table_size=16777216
max_insert_delayed_threads=20
max_join_size=18446744073709551615
max_length_for_sort_data=1024
max_prepared_stmt_count=16382
max_relay_log_size=0
max_seeks_for_key=4294967295
max_sort_length=1024
max_sp_recursion_depth=0
max_tmp_tables=32
max_user_connections=0
max_write_lock_count=4294967295
min_examined_row_limit=0
multi_range_count=256
myisam_data_pointer_size=6
myisam_max_sort_file_size=107374182400
myisam_recover_options=OFF
myisam_repair_threads=1
myisam_sort_buffer_size=12582912
myisam_stats_method=nulls_unequal
myisam_use_mmap=OFF
named_pipe=OFF
net_buffer_length=16384
net_read_timeout=30
net_retry_count=10
net_write_timeout=80
new=OFF
old=OFF
old_alter_table=OFF
old_passwords=OFF
open_files_limit=2048
optimizer_prune_level=1
optimizer_search_depth=62
optimizer_switch=index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on
pid_file=C:\\Documents and Settings\\All Users\\Application Data\\MySQL\\MySQL Server 5.1\\Data\\p1.pid
plugin_dir=C:\\Program Files\\MySQL\\MySQL Server 5.1\\lib/plugin
port=3306
preload_buffer_size=32768
profiling=OFF
profiling_history_size=15
protocol_version=10
pseudo_thread_id=3230
query_alloc_block_size=8192
query_cache_limit=1048576
query_cache_min_res_unit=4096
query_cache_size=33554432
query_cache_type=ON
query_cache_wlock_invalidate=OFF
query_prealloc_size=8192
rand_seed1=
rand_seed2=
range_alloc_block_size=4096
read_buffer_size=65536
read_only=OFF
read_rnd_buffer_size=262144
relay_log=
relay_log_index=
relay_log_info_file=relay-log.info
relay_log_purge=ON
relay_log_space_limit=0
report_host=
report_password=
report_port=3306
report_user=
rpl_recovery_rank=0
secure_auth=OFF
secure_file_priv=
server_id=0
shared_memory=OFF
shared_memory_base_name=MYSQL
skip_external_locking=ON
skip_networking=OFF
skip_show_database=OFF
slave_compressed_protocol=OFF
slave_exec_mode=STRICT
slave_load_tmpdir=C:\\WINDOWS\\TEMP
slave_net_timeout=3600
slave_skip_errors=OFF
slave_transaction_retries=10
slow_launch_time=2
slow_query_log=OFF
slow_query_log_file=C:\\Documents and Settings\\All Users\\Application Data\\MySQL\\MySQL Server 5.1\\Data\\p1-slow.log
sort_buffer_size=262144
sql_auto_is_null=ON
sql_big_selects=ON
sql_big_tables=OFF
sql_buffer_result=OFF
sql_log_bin=ON
sql_log_off=OFF
sql_log_update=ON
sql_low_priority_updates=OFF
sql_max_join_size=18446744073709551615
sql_mode=
sql_notes=ON
sql_quote_show_create=ON
sql_safe_updates=OFF
sql_select_limit=18446744073709551615
sql_slave_skip_counter=
sql_warnings=OFF
ssl_ca=
ssl_capath=
ssl_cert=
ssl_cipher=
ssl_key=
storage_engine=InnoDB
sync_binlog=0
sync_frm=ON
system_time_zone=Eastern Daylight Time
table_definition_cache=256
table_lock_wait_timeout=50
table_open_cache=619
table_type=InnoDB
thread_cache_size=38
thread_handling=one-thread-per-connection
thread_stack=196608
time_format=%H:%i:%s
time_zone=SYSTEM
timed_mutexes=OFF
timestamp=1256827484
tmp_table_size=16777216
tmpdir=C:\\WINDOWS\\TEMP
transaction_alloc_block_size=8192
transaction_prealloc_size=4096
tx_isolation=REPEATABLE-READ
unique_checks=ON
updatable_views_with_limit=YES
version=5.1.36-community
version_comment=MySQL Community Server (GPL)
version_compile_machine=ia32
version_compile_os=Win32
wait_timeout=28800
warning_count=0

Source: (StackOverflow)

How to set HttpResponse timeout for Android in Java

I have created the following function for checking the connection status:

private void checkConnectionStatus() {
    HttpClient httpClient = new DefaultHttpClient();

    try {
      String url = "http://xxx.xxx.xxx.xxx:8000/GaitLink/"
                   + strSessionString + "/ConnectionStatus";
      Log.d("phobos", "performing get " + url);
      HttpGet method = new HttpGet(new URI(url));
      HttpResponse response = httpClient.execute(method);

      if (response != null) {
        String result = getResponse(response.getEntity());
        ...

When I shut down the server for testing the execution waits a long time at line

HttpResponse response = httpClient.execute(method);

Does anyone know how to set the timeout in order to avoid waiting too long?

Thanks!


Source: (StackOverflow)

Using module 'subprocess' with timeout

Here's the Python code to run an arbitrary command returning its stdout data, or raise an exception on non-zero exit codes:

proc = subprocess.Popen(
    cmd,
    stderr=subprocess.STDOUT,  # Merge stdout and stderr
    stdout=subprocess.PIPE,
    shell=True)

communicate is used to wait for the process to exit:

stdoutdata, stderrdata = proc.communicate()

The subprocess module does not support timeout--ability to kill a process running for more than X number of seconds--therefore, communicate may take forever to run.

What is the simplest way to implement timeouts in a Python program meant to run on Windows and Linux?


Source: (StackOverflow)

How to timeout a thread

I want to run a thread for some fixed amount of time. If it is not completed within that time, I want to either kill it, throw some exception, or handle it in some way. How can it be done?

One way of doing it as I figured out from this thread is to use a TimerTask inside the run() method of the Thread.

Are there any better solutions for this?

 
EDIT: Adding a bounty as I needed a clearer answer. The ExecutorService code given below does not address my problem. Why should I sleep() after executing (some code - I have no handle over this piece of code)? If the code is completed and the sleep() is interrupted, how can that be a timeOut?

The task that needs to be executed is not in my control. It can be any piece of code. The problem is this piece of code might run into an infinite loop. I don't want that to happen. So, I just want to run that task in a separate thread. The parent thread has to wait till that thread finishes and needs to know the status of the task (i.e whether it timed out or some exception occured or if its a success). If the task goes into an infinite loop, my parent thread keeps on waiting indefinitely, which is not an ideal situation.


Source: (StackOverflow)

Timeout a command in bash without unnecessary delay

This answer to Command line command to auto-kill a command after a certain amount of time

proposes a 1-line method to timeout a long-running command from the bash command line:

( /path/to/slow command with options ) & sleep 5 ; kill $!

But it's possible that a given "long-running" command may finish earlier than the timeout. (Let's call it a "typically-long-running-but-sometimes-fast" command, or tlrbsf for fun.)

So this nifty 1-liner approach has a couple of problems. First, the sleep isn't conditional, so that sets an undesirable lower bound on the time taken for the sequence to finish. Consider 30s or 2m or even 5m for the sleep, when the tlrbsf command finishes in 2 seconds — highly undesirable. Second, the kill is unconditional, so this sequence will attempt to kill a non-running process and whine about it.

So...

Is there a way to timeout a typically-long-running-but-sometimes-fast ("tlrbsf") command that

  • has a bash implementation (the other question already has Perl and C answers)
  • will terminate at the earlier of the two: tlrbsf program termination, or timeout elapsed
  • will not kill non-existing/non-running processes (or, optionally: will not complain about a bad kill)
  • doesn't have to be a 1-liner
  • can run under Cygwin or Linux

... and, for bonus points, runs the tlrbsf command in the foreground and any 'sleep' or extra process in the background, such that the stdin/stdout/stderr of the tlrbsf command can be redirected, same as if it had been run directly?

If so, please share your code. If not, please explain why.

I have spent awhile trying to hack the aforementioned example but I'm hitting the limit of my bash skills.


Source: (StackOverflow)

How to put a delay on AngularJS instant search?

I am new to AngularJS, and I have a performance issue that I can't seem to address. I have instant search but it's somewhat laggy, since it starts searching on each keyup().

JS:

var App = angular.module('App', []);

App.controller('DisplayController', function($scope, $http) {
$http.get('data.json').then(function(result){
    $scope.entries = result.data;
});
});

HTML:

<input id="searchText" type="search" placeholder="live search..." ng-model="searchText" />
<div class="entry" ng-repeat="entry in entries | filter:searchText">
<span>{{entry.content}}</span>
</div>

The JSON data isn't even that large, 300KB only, I think what I need to accomplish is to put a delay of ~1 sec on the search to wait for the user to finish typing, instead of performing the action on each keystroke. AngularJS does this internally, and after reading docs and other topics on here I couldn't find a specific answer.

I would appreciate any pointers on how I can delay the instant search. Thanks.


Source: (StackOverflow)

Timeout jQuery effects

I am trying to have an element fade in, then in 5000 ms fade back out again. I know I can do something like:

setTimeout(function () { $(".notice").fadeOut(); }, 5000);

But that will only control the fade out, would I add the above on the callback?


Source: (StackOverflow)

Setting Curl's Timeout in PHP

I'm running a curl request on an eXist database through php. The dataset is very large, and as a result, the database consistently takes a long amount of time to return an XML response. To fix that, we set up a curl request, with what is supposed to be a long timeout.

$ch = curl_init();
$headers["Content-Length"] = strlen($postString);
$headers["User-Agent"] = "Curl/1.0";

curl_setopt($ch, CURLOPT_URL, $requestUrl);
curl_setopt($ch, CURLOPT_HEADER, false);
curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_USERPWD, 'admin:');
curl_setopt($ch,CURLOPT_TIMEOUT,1000);
$response = curl_exec($ch);
curl_close($ch);

However, the curl request consistently ends before the request is completed (<1000 when requested via a browser). Does anyone know if this is the proper way to set timeouts in curl?


Source: (StackOverflow)

Change Volley timeout duration

I use the new Volley framework for Android to do a request to my server. But it timeouts before getting the response, although it does respond.

I tried adding this code:

HttpConnectionParams.setConnectionTimeout(httpParams, 5000);
HttpConnectionParams.setSoTimeout(httpParams, timeoutMs);

in HttpClientStack of the Volley framework to a different integer (50000), but it still times out before 50 seconds.

Is there a way to change the timeout to a long value?


Source: (StackOverflow)