freedev's questions

There is a limit to 5 public IP addresses (Elastic IPs) for each AWS Account and I have reached such limit.

Now I have many EC2 instances created without the "Auto-assign Public IP" attribute, which assign a public ip address at start.

This is good because we don't pay and consume valuable resources. On the other hand I cannot access directly via ssh, but only bridging between an instance that has a public ip address.

I would like to override the "Auto-assign Public IP" parameter set during instance launch, in order to restart the instances and allocate a public ip address when need. And, when the maintenance task is completed, reset the parameter and restart the instance again.

Is there any chance to change this behaviour or should assume is not possible?

Looking at solrhome/data directory in my solrcloud cluster I have found a lot of old snapshot directories like these:

snapshot.20150506003702765
snapshot.20150506003702760
snapshot.20150507002849492
snapshot.20150507002849473
snapshot.20150507002849459

or even a month older. These directories keep really a lot of space, 2 or 3 times the whole index.

May I delete these directories? If yes, is there a best practice, should I restart solrcloud?

On a remote server I have a file which is the mongodump output compressed, let me say a file called mongodb.tar.gz.

Inside mongodb.tar.gz there is a directory structure like this:

dump/dbname/
dump/dbname/blogs.bson
dump/dbname/blogs.metadata.json
dump/dbname/editors_choice.bson
dump/dbname/editors_choice.metadata.json
...

Is there anyway to restore this dump without download and uncompress entire file locally?

I mean something like:

curl http://remoteserver/mongodb.tar.gz | gunzip | mongorestore -d dbname 

I'm moving a big directory of images from an HTTP server to another and I cannot change any configuration.

I would like my user don't even suppose that a moving in progress. So I thought to add an Apache httpd server configured as reverse proxy in front of both the servers.

This reverse proxy when a resource is not found in the destination should try to get it in the origin server.

Is there any way to do this using mod_rewrite or some standard Apache httpd module?

The resources are not on the front-end server, but on two back-end servers.

I have this configuration:

mongos> db.adminCommand('getShardMap')
{
"map" : {
    "RS13" : "RS13/mongo09-02:27003,mongo09-01:27001",
    "RS13/mongo09-02:27003,mongo09-01:27001" : "RS13/mongo09-02:27003,mongo09-01:27001",
    "RS26" : "RS26/mongo09-04.de.prod:27008,mongo09-01:27002",
    "RS26/mongo09-04.de.prod:27008,mongo09-01:27002" : "RS26/mongo09-04.de.prod:27008,mongo09-01:27002",
    "RS45" : "RS45/mongo09-02:27004,mongo09-03:27005",
    "RS45/mongo09-02:27004,mongo09-03:27005" : "RS45/mongo09-02:27004,mongo09-03:27005",
    "RS67" : "RS67/mongo09-03:27006,mongo09-03.de.prod:27006,mongo09-04.de.prod:27007",
    "RS67/mongo09-03:27006,mongo09-03.de.prod:27006,mongo09-04.de.prod:27007" : "RS67/mongo09-03:27006,mongo09-03.de.prod:27006,mongo09-04.de.prod:27007",
    "config" : "mongo09-01:27011,mongo09-02:27012,mongo09-03:27013",
    "mongo09-01:27001" : "RS13/mongo09-02:27003,mongo09-01:27001",
    "mongo09-01:27002" : "RS26/mongo09-04.de.prod:27008,mongo09-01:27002",
    "mongo09-02:27003" : "RS13/mongo09-02:27003,mongo09-01:27001",
    "mongo09-02:27004" : "RS45/mongo09-02:27004,mongo09-03:27005",
    "mongo09-03.de.prod:27006" : "RS67/mongo09-03:27006,mongo09-03.de.prod:27006,mongo09-04.de.prod:27007",
    "mongo09-03:27005" : "RS45/mongo09-02:27004,mongo09-03:27005",
    "mongo09-03:27006" : "RS67/mongo09-03:27006,mongo09-03.de.prod:27006,mongo09-04.de.prod:27007",
    "mongo09-04.de.prod:27007" : "RS67/mongo09-03:27006,mongo09-03.de.prod:27006,mongo09-04.de.prod:27007",
    "mongo09-04.de.prod:27008" : "RS26/mongo09-04.de.prod:27008,mongo09-01:27002"
},
"ok" : 1
}

Actually mongo09-03 it seems to be duplicated:

    "mongo09-03.de.prod:27006" : "RS67/mongo09-03:27006,mongo09-03.de.prod:27006,mongo09-04.de.prod:27007",
    "mongo09-03:27006" : "RS67/mongo09-03:27006,mongo09-03.de.prod:27006,mongo09-04.de.prod:27007",

And please consider replica set RS67 is also part of a sharding cluster.

May I remove a mongodb replica set when it is into a sharding cluster ? And if yes, how?

Can I use rs.remove(hostname) ?

PHP lstat the full path many times before read the file is looking for. And this happens when in apache httpd configuration is specified PHP_ADMIN_VALUE open_basedir setting or if safe_mode is ON.

If I have a simple website with only phpinfo.php page and inside we have only "".

Consider we have latest version of httpd (2.2.15) and PHP (5.2.13 or 5.3.2).

If we specify safe_mode=on or PHP_ADMIN_VALUE open_basedir in Virtual host configuration:

<Directory "/usr/local/myspace/webspace/httpdocs">
                PHP_ADMIN_VALUE open_basedir "/usr/local/myspace/webspace"
</Directory>
<VirtualHost *:80>
        ServerName damorealt.xoom.it
        DocumentRoot "/usr/local/myspace/webspace/httpdocs"
    CustomLog   /var/log/httpd/damorealt/access_log   combined
    ErrorLog   /var/log/httpd/damorealt/error_log
</VirtualHost >

Calling page http://damorealt.xoom.it/phpinfo.php we can reproduce following behavior:

First check

25933 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs/phpinfo.php", {st_mode=S_IFREG|0644, st_size=16, ...}) = 0

Second check

25933 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs/phpinfo.php", {st_mode=S_IFREG|0644, st_size=16, ...}) = 0

Third check (incomplete)

25933 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0

Fifth check.

25933 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
25933 lstat("/usr/local/myspace/webspace/httpdocs/phpinfo.php", {st_mode=S_IFREG|0644, st_size=16, ...}) = 0

Read the file!

25933 open("/usr/local/myspace/webspace/httpdocs/phpinfo.php", O_RDONLY) = 16
25933 fstat(16, {st_mode=S_IFREG|0644, st_size=16, ...}) = 0
25933 read(16, "\n", 8192) = 16
25933 read(16, "", 8192)                = 0
25933 read(16, "", 8192)                = 0
25933 close(16)                         = 0

If PHP_ADMIN_VALUE open_basedir "/usr/local/myspace/webspace" is removed ::

First check

26235 time(NULL)                        = 1278696735
26235 lstat("/usr", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
26235 lstat("/usr/local", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
26235 lstat("/usr/local/myspace", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
26235 lstat("/usr/local/myspace/webspace", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
26235 lstat("/usr/local/myspace/webspace/httpdocs", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
26235 lstat("/usr/local/myspace/webspace/httpdocs/phpinfo.php", {st_mode=S_IFREG|0644, st_size=16, ...}) = 0

Read the file.

26235 open("/usr/local/myspace/webspace/httpdocs/phpinfo.php", O_RDONLY) = 16
26235 fstat(16, {st_mode=S_IFREG|0644, st_size=16, ...}) = 0
26235 read(16, "\n", 8192) = 16
26235 read(16, "", 8192)                = 0
26235 read(16, "", 8192)                = 0
26235 close(16)                         = 0
26235 uname({sys="Linux", node="svilpar4", ...}) = 0
26235 time(NULL)                        = 1278696735
26235 writev(15, [{"HTTP/1.1 200 OK\r\nDate: Fri, 09 J"..., 173},[...]
26235 chdir("/")                        = 0

Can someone explain me why PHP have such behavior?