I am trying to solve why I am getting on docker / nginx container error 502 with connect() failed (111: Connection refused) when I setup properly the ssl , but I got this issue . I dont see clerly where it comes from . how can I fix this? upstream web_server {     server web:8000; }  server {      listen 80;     server_name demo.io www.demo.io;      access_log /var/log/nginx/demo.io.log;     error_log /var/log/nginx/demo.io.log;      location / {         rewrite ^ https://$host$request_uri? permanent;         proxy_pass http://web_server;         proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;         proxy_set_header Host $host;         proxy_redirect off;     }      location /static/ {         alias /home/app/web/static/;     } } #https://demo.io server {     listen 443 ssl http2;     listen [::]:443 ssl http2;     server_name demo.io;      server_tokens off;      ssl_certificate /etc/letsencrypt/live/demo.io/fullchain.pem;     ssl_certificate_key /etc/letsencrypt/live/demo.io/privkey.pem;      ssl_buffer_size 8k;      ssl_dhparam /etc/ssl/certs/ssl-dhparams.pem;      ssl_protocols TLSv1.2 TLSv1.1 TLSv1;     ssl_prefer_server_ciphers on;      ssl_ciphers ECDH+AESGCM:ECDH+AES256:ECDH+AES128:DH+3DES:!ADH:!AECDH:!MD5;      ssl_ecdh_curve secp384r1;     ssl_session_tickets off;      # OCSP stapling     ssl_stapling on;     ssl_stapling_verify on;     resolver 8.8.8.8;      location / {         proxy_pass https://web;         proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;         proxy_set_header Host $host;         proxy_redirect off;     } }
This is a  about Connection Refused    We see a lot of questions to the effect      When I try to connect to a system I get a message      Connection refused      Why is this ?
Knowing which java.exe process to kill on a windows machine When a java based application starts to misbehave on a windows machine, you want to be able to kill the process in the task manager if you can't quit the application normally. Most of the time, there's more than one java based application running on my machine. Is there a better way than just randomly killing java.exe processes in hope that you'll hit the correct application eventually?  EDIT: Thank you to all the people who pointed me to Sysinternal's Process Explorer - Exactly what I'm looking for! Why didn't the Emperor realize that torturing Luke to death in front of Vader might be a bad idea? Any examples of life forms on Earth that could have survived on Mars or Moon? Do we know of any living forms on Earth that could continue to live on Mars? How can one expand the function $f_1(x) = x$ on $(−π, π)$in terms of the functions $\cos nx, n = 0, 1, 2, ...$ and $\sin nx, n = 1, 2, ...,$ in a way so that $$f_2(x) = a_0 + \sum_{n=1}^{\infty}(a_n \cos nx + b_n \sin nx)$$ is the expansion of the $f_1$, how is that? I have asked  related to the same issue but didn't get full answer, I have been told that this is a standard application of Fourier series, $f_1$ and $f_2$ are equivalent in the sense that $f_1(x)=f_2(x)$ for all $x∈(−π,π)$. For any $x$ in this interval, the Fourier series will converge to $f(x)$, but I didn't get any rigorous proof  with elaborate explanation. So, plz provide rigorous proof of $f_1=f_2$ with elaborate explanation as I am new to the subject. Thanks You. I have attached the excerpt below - Is there evidence of "think tank" meaning "the brain"? The  Random House Dictionary defines the expression  as:         a research institute or organization employed to solve complex problems or predict or plan future developments, as in military, political, or social areas.      According to  the above connotation  is an extention of an earliar sense  which referred to "the brain":        also think-tank, 1959 as "research institute" (first reference is to Center for Behavioral Sciences, Palo Alto, Calif.); it had been colloquial for "the brain" since 1905.      : shows usage of "think tank" only from the late '50s.  Is there evidence  of earlier usages of "think tank" meaning "the brain"? Despite  its colloquial   usage I assume  the expression was quite widespread before it was adopted by the Stanford University. Why can't I install iOS 9.3? I saw an update for my iOS 9.2.1 device to iOS 9.3.  However, it said that the update cannot be verified, although it was downloaded.  I even deleted all data and applications from the device, but I still cannot update the device to 9.3; it just says "Your software is up to date" on iOS 9.2.1.  Can you force an update to 9.3? Prove $ \forall c \in \mathbb{R^{+}}, \forall B \in \mathbb{N}, \exists n \in \mathbb{N}, (n \geq B) \wedge (\sqrt{2n} > c \ln(n+2)) $? Books about matroids Could you recommend any approachable books/papers/texts about matroids (maybe a chapter from somewhere)? The ideal reference would contain multiple examples, present some intuitions and keep formalism to a necessary minimum.  I would appreciate any hints or appropriate sources. Boot stuck at logo screen after upgrading to 14.10 Manually calculated $R^2$ doesn't match up with randomForest() $R^2$ for testing new data I know this is a fairly specific R question, but I may be thinking about proportion variance explained, $R^2$, incorrectly. Here goes.  I'm trying to use the R package randomForest. I have some training data and testing data. When I fit a random forest model, the randomForest function allows you to input new testing data to test. It then tells you the percentage of variance explained in this new data. When I look at this, I get one number.  When I use the predict() function to predict the outcome value of the testing data based on the model fit from the training data, and I take the squared correlation coefficient between these values and the actual outcome values for the testing data, I get a different number. These values don't match up.   Here's some R code to demonstrate the problem.  # use the built in iris data data(iris)  #load the randomForest library library(randomForest)  # split the data into training and testing sets index &lt;- 1:nrow(iris) trainindex &lt;- sample(index, trunc(length(index)/2)) trainset &lt;- iris[trainindex, ] testset &lt;- iris[-trainindex, ]  # fit a model to the training set (column 1, Sepal.Length, will be the outcome) set.seed(42) model &lt;- randomForest(x=trainset[ ,-1],y=trainset[ ,1])  # predict values for the testing set (the first column is the outcome, leave it out) predicted &lt;- predict(model, testset[ ,-1])  # what's the squared correlation coefficient between predicted and actual values? cor(predicted, testset[, 1])^2  # now, refit the model using built-in x.test and y.test set.seed(42) randomForest(x=trainset[ ,-1], y=trainset[ ,1], xtest=testset[ ,-1], ytest=testset[ ,1]) Let $(X,\mathcal{M},\mu)$ be a measure space and $\{f\}$ be a sequence of functions on $X$, each of which is integrable over $X$. Show that $\{f_n\}$ is uniformly integrable if and only if for each $\varepsilon \gt 0$, there is a $\delta \gt 0$ such that for any natural number $n$ and measurable subset $E$ of $X$, if $\mu(E) \lt \delta$, $$ \left|\int_E f_n~d\mu\right| \lt \epsilon.$$     I think one direction $(\Rightarrow)$ is clear. Since $f_n$ being uniformly integrable imply that for every $\varepsilon\gt 0,~\exists \delta \gt 0$ such that for any $E\in \mathcal{M},~\mu(E)\lt \delta$, $\int_E |f_n|~d\mu$ for every natural $n$. But then   $$ \left|\int_E f_n~d\mu\right|\le \int_E|f_n|~d\mu \lt \varepsilon.$$    Any suggestions for the other direction?   Edit:  Following Davide's suggestions, I have   $$ \begin{align*} \int_E |f_n|~d\mu &amp; \le \int_{E\cap [f_n \ge 0]} f_n~d\mu + \int_{E\cap [f_n \lt 0]} (-f_n)~d\mu\\ &amp; = \left| \int_{E\cap [f_n \ge 0]} f_n~d\mu \right| + \left| \int_{E\cap [f_n \lt 0]}f_n~d\mu \right| \\ &amp; \lt \varepsilon + \varepsilon = 2\varepsilon. \end{align*} $$ Suppose the proper length of a train is longer than that of a bridge, and the bridge can't bear the total weight of the train but can bear it partially. As the train goes very fast, it becomes shorter than the bridge and it can be entirely on the bridge. As a result, the bridge will collapse. However, in the train's frame, the train is even longer than the bridge, and it is only partially on the bridge; so the bridge will not collapse. What is the solution to this paradox? Does it matter what I choose for serialVersionUID when extending Serializable classes in Java? What are imaginary numbers? At school, I really struggled to understand the concept of imaginary numbers.  My teacher told us that an imaginary number is a number that has something to do with the square root of $-1$.  When I tried to calculate the square root of $-1$ on my calculator, it gave me an error.  To this day I still do not understand imaginary numbers.  It makes no sense to me at all.  Is there someone here who totally gets it and can explain it?  Why is the concept even useful? I see that Stack&nbsp;Overflow is very Linux specific. Doesn't Unix &amp; Linux and Ask&nbsp;Ubuntu cover much of the same ground? I see that Unix &amp; Linux and Server&nbsp;Fault also cater to many Linux server questions. Similarly, Ask&nbsp;Ubuntu and Super&nbsp;User seems to contain most like questions. Why can't we downvote our own posts? Once in a blue moon, I've wanted the ability to downvote my own answer to some question.  ()  Obviously upvoting one's own posts is out of the question.  But down is different.  Voting my own answer down can help me improve the site by pushing my answer lower in the ranking than another answer with a better or more situation-appropriate alternative.  It's not something I'd do often, but I would use this feature if it were available.  If implemented, I'd expect this feature to operate just like downvotes on other user's posts.  That is:   I get a few seconds to undo the downvote;  I get to remove the downvote after an edit to the post;  I lose a point for placing the downvote (CW excepted); I lose two points for receiving the downvote (CW excepted).   If you're noticing that I'd lose 3 points for downvoting my own non-CW post, congratulations! You can add!  I can think of a couple of potential downsides to this change.  The first one may be a dealbreaker; the second is probably not that big a deal.   Strategic downvoting of oneself: since you can undo the vote after an edit, and you can always edit your own posts, someone could downvote themselves soon after posting (especially on a FGITW answer) to garner extra sympathy upvotes. Badge collecting: the Peer Pressure badge just got easier, because if you have a -2 score on an answer, just downvote and delete for an instant badge. How to check if a service is running on Android? How do I check if a background service is running?  I want an Android activity that toggles the state of the service -- it lets me turn it on if it is off and off if it is on. In cricket how does someone become an umpire at international level? Is there some procedure for this? How are they selected and what is the criteria for this? Short story where the Earth has been kept inside a force field for millennia How to run Wireshark on Ubuntu 17.10 I used to run wireshark on ubuntu 17.04 with  ~/$ sudo wireshark   but now (just after update to 17.10) when I write the same I get an error  ~/$ sudo wireshark      QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'     Invalid MIT-MAGIC-COOKIE-1 keyQXcbConnection: Could not connect to display :0